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Wong OL, Yuan J, Poon DMC, Chiu ST, Yang B, Chiu G, Yu SK, Cheung KY. Prostate diffusion-weighted imaging (DWI) in MR-guided radiotherapy: Reproducibility assessment on 1.5 T MR-Linac and 1.5 T MR-simulator. Magn Reson Imaging 2024; 111:47-56. [PMID: 38513789 DOI: 10.1016/j.mri.2024.03.020] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2024] [Revised: 03/11/2024] [Accepted: 03/16/2024] [Indexed: 03/23/2024]
Abstract
PURPOSE Diffusion-weighted imaging (DWI) holds promise for image-guided radiotherapy (MRgRT) in prostate cancer. However, challenges persist due to image distortion, artifacts, and apparent diffusion coefficient (ADC) reproducibility issues. This study aimed to assess DWI image quality and ADC reproducibility on both a 1.5 T MR-simulator and a 1.5 T MR-Linac, employing measurements from both an ACR MRI phantom and prostate cancer patients undergoing MRgRT. METHODS DW-MRI scans were conducted on 19 patients (mean age = 69 ± 8 years, with 23 MR-visible intra-prostatic lesions) and an ACR MRI phantom using a 1.5 T MR-simulator (b-values = 0, 800, 1400s/mm2) and a 1.5 T MR-Linac (b-values = 50, 500, 800 s/mm2). ADC homogeneity in the phantom was evaluated via 1D profile flatness (FL) in three directions. Image quality was assessed through qualitative 5-point Likert scale ratings and quantitative ADC and signal-to-noise ratio (SNR) measurements. Intra-observer reproducibility of image quality scores was evaluated using ICC(1, 2). Geometric distortion was measured by comparing landmark sizes on the ACR phantom against the ground truth. Mean ADC and reproducibility were assessed using Bland-Altman plots. RESULTS Both MR-simulator and MR-Linac demonstrated high ADC homogeneity (FL > 87.5% - MR-simulator: 97.23 ± 0.62%, MR-Linac: 94.75 ± 0.62%, p < 0.05) in the phantom. Image quality scores revealed acceptable ratings (≥3) for capsule demarcation, image artifacts, and geometric distortion in patients. However, intra-prostatic lesions were barely discernible in b800 images for both MR-simulator (average score = 2.37 ± 1.33) and MR-Linac (average score = 2.16 ± 1.28). While MR-Linac DWI scans exhibited significantly more severe geometric distortion than MR-simulator scans (p < 0.01), most phantom measurements fell within the image in-plane resolution of 3 mm. Significant differences were noted in MR-simulator ADC (CTV: 1.20 ± 0.14 × 10-3 mm2/s (MR-simulator) vs 1.06 ± 0.10 × 10-3 mm2/s (MR-Linac); GTV: 1.05 ± 0.21 × 10-3 mm2/s vs 0.91 ± 0.16 × 10 mm2/s, all p < 0.05), with a small non-zero bias observed in the Bland-Altman analysis (CTV: 12.3%; GTV: 14.5%). CONCLUSION The significantly larger MR-simulator ADC and the small non-zero bias hint at potential systematic differences in ADC values acquired from an MR-simulator and an MR-Linac, both at 1.5 T. Although acceptable ADC homogeneity was noted, caution is warranted in interpreting MR-Linac DWI images due to occasional severe artifacts. Further studies are essential to validate DWI and ADC as reliable imaging markers in prostate cancer MRgRT.
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Affiliation(s)
- Oi Lei Wong
- Research Department, Hong Kong Sanatorium & Hospital, Happy Valley, Hong Kong SAR, China.
| | - Jing Yuan
- Research Department, Hong Kong Sanatorium & Hospital, Happy Valley, Hong Kong SAR, China
| | - Darren M C Poon
- Comprehensive Oncology Center, Hong Kong Sanatorium & Hospital, Happy Valley, Hong Kong SAR, China
| | - Sin Ting Chiu
- Department of Radiotherapy, Hong Kong Sanatorium & Hospital, Happy Valley, Hong Kong SAR, China
| | - Bin Yang
- Medical Physics Department, Hong Kong Sanatorium & Hospital, Happy Valley, Hong Kong SAR, China
| | - George Chiu
- Department of Radiotherapy, Hong Kong Sanatorium & Hospital, Happy Valley, Hong Kong SAR, China
| | - Siu Ki Yu
- Medical Physics Department, Hong Kong Sanatorium & Hospital, Happy Valley, Hong Kong SAR, China
| | - Kin Yin Cheung
- Medical Physics Department, Hong Kong Sanatorium & Hospital, Happy Valley, Hong Kong SAR, China
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Poon DMC, Yuan J, Wong OL, Yang B, Tse MY, Lau KK, Chiu ST, Chiu PKF, Ng CF, Chui KL, Kwong YM, Ma WK, Cheung KY, Chiu G, Yu SK. One-year clinical outcomes of MR-guided stereotactic body radiation therapy with rectal spacer for patients with localized prostate cancer. World J Urol 2024; 42:97. [PMID: 38393414 PMCID: PMC10891188 DOI: 10.1007/s00345-024-04784-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2023] [Accepted: 01/10/2024] [Indexed: 02/25/2024] Open
Abstract
BACKGROUND AND PURPOSE This prospective study aimed to investigate adaptive magnetic resonance (MR)-guided stereotactic body radiation therapy (MRgSBRT) with rectal spacer for localized prostate cancer (PC) and report 1-year clinical outcomes. MATERIALS AND METHODS Thirty-four consecutive patients with low- to high-risk localized PC that underwent 5-fraction adaptive MRgSBRT with rectal spacer were enrolled. The dosimetric comparison was performed on a risk- and age-matched cohort treated with MRgSBRT but without a spacer at a similar timepoint. Clinician-reported outcomes were based on Common Terminology Criteria for Adverse Events. Patient-reported outcomes were based on the Expanded Prostate Cancer Index Composite (EPIC) questionnaire at baseline, acute (1-3 months), subacute (4-12 months), and late (> 12 months) phases. RESULTS The median follow-up was 390 days (range 28-823) and the median age was 70 years (range 58-82). One patient experienced rectal bleeding soon after spacer insertion that subsided before MRgSBRT. The median distance between the midline of the prostate midgland and the rectum after spacer insertion measured 7.8 mm (range 2.6-15.3), and the median length of the spacer was 45.9 mm (range 16.8-62.9) based on T2-weighted MR imaging. The use of spacer resulted in significant improvements in target coverage (V100% > 95% = 98.6% [range 93.4-99.8] for spacer vs. 97.8% [range 69.6-99.7] for non-spacer) and rectal sparing (V95% < 3 cc = 0.7 cc [range 0-4.6] for spacer vs. 4.9 cc [range 0-12.5] for non-spacer). Nine patients (26.5%) experienced grade 1 gastrointestinal toxicities, and no grade ≥ 2 toxicities were observed. During the 1-year follow-up period, EPIC scores for the bowel domain remained stable and were the highest among all other domains. CONCLUSIONS MRgSBRT with rectal spacer for localized PC showed exceptional tolerability with minimal gastrointestinal toxicities and satisfactory patient-reported outcomes. Improvements in dosimetry, rectal sparing, and target coverage were achieved with a rectal spacer. Randomized trials are warranted for further validation.
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Affiliation(s)
- Darren M C Poon
- Comprehensive Oncology Centre, 11/F, HKSH Eastern Building, 3 Tung Wong Roade Road, Shau Kei Wan, Hong Kong SAR.
| | - Jing Yuan
- Research Department, Hong Kong Sanatorium and Hospital, Happy Valley, Hong Kong, Hong Kong SAR
| | - Oi Lei Wong
- Research Department, Hong Kong Sanatorium and Hospital, Happy Valley, Hong Kong, Hong Kong SAR
| | - Bin Yang
- Medical Physics Department, Hong Kong Sanatorium and Hospital, Happy Valley, Hong Kong, Hong Kong SAR
| | - Mei Yan Tse
- Medical Physics Department, Hong Kong Sanatorium and Hospital, Happy Valley, Hong Kong, Hong Kong SAR
| | - Ka Ki Lau
- Medical Physics Department, Hong Kong Sanatorium and Hospital, Happy Valley, Hong Kong, Hong Kong SAR
| | - Sin Ting Chiu
- Department of Radiotherapy, Hong Kong Sanatorium and Hospital, Happy Valley, Hong Kong, Hong Kong SAR
| | - Peter Ka-Fung Chiu
- SH Ho Urology Centre, Department of Surgery, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong SAR
| | - Chi Fai Ng
- SH Ho Urology Centre, Department of Surgery, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong SAR
| | - Ka Lun Chui
- SH Ho Urology Centre, Department of Surgery, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong SAR
| | - Yiu Ming Kwong
- Urology Centre, Hong Kong Sanatorium and Hospital, Happy Valley, Hong Kong, Hong Kong SAR
| | - Wai Kit Ma
- Hong Kong Urology Clinic, Hong Kong, Hong Kong SAR
| | - Kin Yin Cheung
- Medical Physics Department, Hong Kong Sanatorium and Hospital, Happy Valley, Hong Kong, Hong Kong SAR
| | - George Chiu
- Department of Radiotherapy, Hong Kong Sanatorium and Hospital, Happy Valley, Hong Kong, Hong Kong SAR
| | - Siu Ki Yu
- Medical Physics Department, Hong Kong Sanatorium and Hospital, Happy Valley, Hong Kong, Hong Kong SAR
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Law MWK, Tse MY, Ho LCC, Lau KK, Wong OL, Yuan J, Cheung KY, Yu SK. A study of Bayesian deep network uncertainty and its application to synthetic CT generation for MR-only radiotherapy treatment planning. Med Phys 2024; 51:1244-1262. [PMID: 37665783 DOI: 10.1002/mp.16666] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2022] [Revised: 06/05/2023] [Accepted: 07/20/2023] [Indexed: 09/06/2023] Open
Abstract
BACKGROUND The use of synthetic computed tomography (CT) for radiotherapy treatment planning has received considerable attention because of the absence of ionizing radiation and close spatial correspondence to source magnetic resonance (MR) images, which have excellent tissue contrast. However, in an MR-only environment, little effort has been made to examine the quality of synthetic CT images without using the original CT images. PURPOSE To estimate synthetic CT quality without referring to original CT images, this study established the relationship between synthetic CT uncertainty and Bayesian uncertainty, and proposed a new Bayesian deep network for generating synthetic CT images and estimating synthetic CT uncertainty for MR-only radiotherapy treatment planning. METHODS AND MATERIALS A novel deep Bayesian network was formulated using probabilistic network weights. Two mathematical expressions were proposed to quantify the Bayesian uncertainty of the network and synthetic CT uncertainty, which was closely related to the mean absolute error (MAE) in Hounsfield Unit (HU) of synthetic CT. These uncertainties were examined to demonstrate the accuracy of representing the synthetic CT uncertainty using a Bayesian counterpart. We developed a hybrid Bayesian architecture and a new data normalization scheme, enabling the Bayesian network to generate both accurate synthetic CT and reliable uncertainty information when probabilistic weights were applied. The proposed method was evaluated in 59 patients (13/12/32/2 for training/validation/testing/uncertainty visualization) diagnosed with prostate cancer, who underwent same-day pelvic CT- and MR-acquisitions. To assess the relationship between Bayesian and synthetic CT uncertainties, linear and non-linear correlation coefficients were calculated on per-voxel, per-tissue, and per-patient bases. For accessing the accuracy of the CT number and dosimetric accuracy, the proposed method was compared with a commercially available atlas-based method (MRCAT) and a U-Net conditional-generative adversarial network (UcGAN). RESULTS The proposed model exhibited 44.33 MAE, outperforming UcGAN 52.51 and MRCAT 54.87. The gamma rate (2%/2 mm dose difference/distance to agreement) of the proposed model was 98.68%, comparable to that of UcGAN (98.60%) and MRCAT (98.56%). The per-patient and per-tissue linear correlation coefficients between the Bayesian and synthetic CT uncertainties ranged from 0.53 to 0.83, implying a moderate to strong linear correlation. Per-voxel correlation coefficients varied from -0.13 to 0.67 depending on the regions-of-interest evaluated, indicating tissue-dependent correlation. The R2 value for estimating MAE solely using Bayesian uncertainty was 0.98, suggesting that the uncertainty of the proposed model was an ideal candidate for predicting synthetic CT error, without referring to the original CT. CONCLUSION This study established a relationship between the Bayesian model uncertainty and synthetic CT uncertainty. A novel Bayesian deep network was proposed to generate a synthetic CT and estimate its uncertainty. Various metrics were used to thoroughly examine the relationship between the uncertainties of the proposed Bayesian model and the generated synthetic CT. Compared with existing approaches, the proposed model showed comparable CT number and dosimetric accuracies. The experiments showed that the proposed Bayesian model was capable of producing accurate synthetic CT, and was an effective indicator of the uncertainty and error associated with synthetic CT in MR-only workflows.
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Affiliation(s)
- Max Wai-Kong Law
- Medical Physics Department, Hong Kong Sanatorium and Hospital, Hong Kong SAR, China
| | - Mei-Yan Tse
- Medical Physics Department, Hong Kong Sanatorium and Hospital, Hong Kong SAR, China
| | - Leon Chin-Chak Ho
- Medical Physics Department, Hong Kong Sanatorium and Hospital, Hong Kong SAR, China
| | - Ka-Ki Lau
- Medical Physics Department, Hong Kong Sanatorium and Hospital, Hong Kong SAR, China
| | - Oi Lei Wong
- Research Department, Hong Kong Sanatorium and Hospital, Hong Kong SAR, China
| | - Jing Yuan
- Research Department, Hong Kong Sanatorium and Hospital, Hong Kong SAR, China
| | - Kin Yin Cheung
- Medical Physics Department, Hong Kong Sanatorium and Hospital, Hong Kong SAR, China
| | - Siu Ki Yu
- Medical Physics Department, Hong Kong Sanatorium and Hospital, Hong Kong SAR, China
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Zhou Y, Yuan J, Xue C, Poon DMC, Yang B, Yu SK, Cheung KY. A pilot study of MRI radiomics for high-risk prostate cancer stratification in 1.5 T MR-guided radiotherapy. Magn Reson Med 2023; 89:2088-2099. [PMID: 36572990 DOI: 10.1002/mrm.29564] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2022] [Revised: 11/09/2022] [Accepted: 12/09/2022] [Indexed: 12/28/2022]
Abstract
PURPOSE To investigate the potential value of MRI radiomics obtained from a 1.5 T MRI-guided linear accelerator (MR-LINAC) for D'Amico high-risk prostate cancer (PC) classification in MR-guided radiotherapy (MRgRT). METHODS One hundred seventy-six consecutive PC patients underwent 1.5 T MRgRT treatment were retrospectively enrolled. Each patient received one or two pretreatment T2 -weighted MRI scans on a 1.5 T MR-LINAC. The endpoint was to differentiate high-risk from low/intermediate-risk PC based on D'Amico criteria using MRI-radiomics. Totally 1023 features were extracted from clinical target volume (CTV) and planning target volume (PTV). Intraclass correlation coefficient of scan-rescan repeatability, feature correlation, and recursive feature elimination were used for feature dimension reduction. Least absolute shrinkage and selection operator regression was employed for model construction. Receiver operating characteristic area under the curve (AUC) analysis was used for model performance assessment in both training and testing data. RESULTS One hundred and eleven patients fulfilled all criteria were finally included: 76 for training and 35 for testing. The constructed MRI-radiomics models extracted from CTV and PTV achieved the AUC of 0.812 and 0.867 in the training data, without significant difference (P = 0.083). The model performances remained in the testing. The sensitivity, specificity, and accuracy were 85.71%, 64.29%, and 77.14% for the PTV-based model; and 71.43%, 71.43%, and 71.43% for the CTV-based model. The corresponding AUCs were 0.718 and 0.750 (P = 0.091) for CTV- and PTV-based models. CONCLUSION MRI-radiomics obtained from a 1.5 T MR-LINAC showed promising results in D'Amico high-risk PC stratification, potentially helpful for the future PC MRgRT. Prospective studies with larger sample sizes and external validation are warranted for further verification.
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Affiliation(s)
- Yihang Zhou
- Research Department, Hong Kong Sanatorium & Hospital, Hong Kong, People's Republic of China
| | - Jing Yuan
- Research Department, Hong Kong Sanatorium & Hospital, Hong Kong, People's Republic of China
| | - Cindy Xue
- Research Department, Hong Kong Sanatorium & Hospital, Hong Kong, People's Republic of China
| | - Darren M C Poon
- Comprehensive Oncology Center, Hong Kong Sanatorium & Hospital, Hong Kong, People's Republic of China
| | - Bin Yang
- Medical Physics Department, Hong Kong Sanatorium & Hospital, Hong Kong, People's Republic of China
| | - Siu Ki Yu
- Medical Physics Department, Hong Kong Sanatorium & Hospital, Hong Kong, People's Republic of China
| | - Kin Yin Cheung
- Medical Physics Department, Hong Kong Sanatorium & Hospital, Hong Kong, People's Republic of China
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Huang CY, Yang B, Lam WW, Geng H, Cheung KY, Yu SK. Magnetic field induced dose effects in radiation therapy using MR-linacs. Med Phys 2023. [PMID: 36975016 DOI: 10.1002/mp.16397] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2021] [Revised: 03/20/2023] [Accepted: 03/20/2023] [Indexed: 03/29/2023] Open
Abstract
MR-guided radiotherapy (MRgRT) is one of the most significant advances in radiotherapy in recent years. The hybrid systems were designed to visualize patient anatomical and physiological changes during the course of radiotherapy, enabling more precise treatment. However, before MR-linacs reach their full potential in delivering safe and accurate treatments to patients, the radiotherapy team must understand how a magnetic field alters the dosimetric properties of the radiation beam and its potential impact on treatment quality and clinical outcomes. This review aims to provide an in-depth description of the magnetic field induced dose effects for the two widely available systems, the 0.35 T and the 1.5 T MR-linacs. In MR-linac treatments, the primary photon beam passes through MR components that never exist in conventional linacs, which alter both in-field and out-of-field doses. More importantly, the interplay between the always-on magnetic field and the secondary electrons is not negligible. This interplay affects dose deposition in the patient, resulting in reduced in-field skin dose due to purged-out contaminant electrons, shortened build-up distance and a shifted crossline profile owing to asymmetric dose kernel. Especially two effects, namely electron return effect (ERE) and electron stream effect (ESE), are not seen in conventional radiotherapy. This review also summarizes the clinical observations on the site-specific treatments influenced mostly by the magnetic field. In MR-linac treatment, the head and neck region is one of the most challenging sites as ERE occurs at low and high density tissue interfaces and around air cavities, generating hot and cold spots. In breast cancer treatment, consideration should be given to the increased in-field skin dose induced by ERE and the increased out-of-field dose caused by ESE for regions such as the ears, chin, and neck. In lung cancer treatments, tissue inhomogeneity combined with ERE will exacerbate target dose heterogeneity and increase or decrease interface dose. Lastly, treatment in the abdomen and pelvic region will be affected by the presence of gas pockets near the target. The review provides practical recommendations to mitigate these effects. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- Chen-Yu Huang
- Medical Physics Department, Hong Kong Sanatorium and Hospital, Hong Kong, SAR, China
| | - Bin Yang
- Medical Physics Department, Hong Kong Sanatorium and Hospital, Hong Kong, SAR, China
| | - Wai Wang Lam
- Medical Physics Department, Hong Kong Sanatorium and Hospital, Hong Kong, SAR, China
| | - Hui Geng
- Medical Physics Department, Hong Kong Sanatorium and Hospital, Hong Kong, SAR, China
| | - Kin Yin Cheung
- Medical Physics Department, Hong Kong Sanatorium and Hospital, Hong Kong, SAR, China
| | - Siu Ki Yu
- Medical Physics Department, Hong Kong Sanatorium and Hospital, Hong Kong, SAR, China
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Xue C, Chu WCW, Yuan J, Poon DMC, Yang B, Zhou Y, Yu SK, Cheung KY. Determining the reliable feature change in longitudinal radiomics studies: A methodological approach using the reliable change index. Med Phys 2023; 50:958-969. [PMID: 36251320 DOI: 10.1002/mp.16046] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2022] [Revised: 07/28/2022] [Accepted: 09/30/2022] [Indexed: 11/07/2022] Open
Abstract
PURPOSE Determination of reliable change of radiomics feature over time is essential and vital in delta-radiomics, but has not yet been rigorously examined. This study attempts to propose a methodological approach using reliable change index (RCI), a statistical metric to determine the reliability of quantitative biomarker changes by accounting for the baseline measurement standard error, in delta-radiomics. The use of RCI was demonstrated with the MRI data acquired from a group of prostate cancer (PCa) patients treated by 1.5 T MRI-guided radiotherapy (MRgRT). METHODS Fifty consecutive PCa patients who underwent five-fractionated MRgRT were retrospectively included, and 1023 radiomics features were extracted from the clinical target volume (CTV) and planning target volume (PTV). The two MRI datasets acquired at the first fraction (MRI11 and MRI21) were used to calculate the baseline feature reliability against image acquisition using intraclass correlation coefficient (ICC). The RCI was constructed based on the baseline feature measurement standard deviation, ICC, and feature value differences at two time points between the fifth (MRI51) and the first fraction MRI (MRI11). The reliable change of features was determined in each patient only if the calculated RCI was over 1.96 or smaller than -1.96. The feature changes between MRI51 and MRI11 were correlated to two patient-reported quality-of-life clinical endpoints of urinary domain summary score (UDSS) and bowel domain summary score (BDSS) in 35 patients using the Spearman correlation test. Only the significant correlations between a feature that was reliably changed in ≥7 patients (20%) by RCI and an endpoint were considered as true significant correlations. RESULTS The 352 (34.4%) and 386 (37.7%) features among all 1023 features were determined by RCI to be reliably changed in more than five (10%) patients in the CTV and PTV, respectively. Nineteen features were found reliably changed in the CTV and 31 features in the PTV, respectively, in 10 (20%) or more patients. These features were not necessarily associated with significantly different longitudinal feature values (group p-value < 0.05). Most reliably changed features in more than 10 patients had excellent or good baseline test-retest reliability ICC, while none showed poor reliability. The RCI method ruled out the features to be reliably changed when substantial feature measurement bias was presented. After applying the RCI criterion, only four and five true significant correlations were confirmed with UDSS and BDSS in the CTV, respectively, with low true significance correlation rates of 10.8% (4/37) and 17.9% (5/28). No true significant correlations were found in the PTV. CONCLUSIONS The RCI method was proposed for delta-radiomics and demonstrated using PCa MRgRT data. The RCI has advantages over some other statistical metrics commonly used in the previous delta-radiomics studies, and is useful to reliably identify the longitudinal radiomics feature change on an individual basis. This proposed RCI method should be helpful for the development of essential feature selection methodology in delta-radiomics.
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Affiliation(s)
- Cindy Xue
- Research Department, Hong Kong Sanatorium & Hospital, Happy Valley, Hong Kong SAR, China.,Department of Imaging and Interventional Radiology, Prince of Wales Hospital, The Chinese University of Hong Kong, Hong Kong SAR, China
| | - Winnie C W Chu
- Department of Imaging and Interventional Radiology, Prince of Wales Hospital, The Chinese University of Hong Kong, Hong Kong SAR, China
| | - Jing Yuan
- Research Department, Hong Kong Sanatorium & Hospital, Happy Valley, Hong Kong SAR, China
| | - Darren M C Poon
- Comprehensive Oncology Center, Hong Kong Sanatorium & Hospital, Happy Valley, Hong Kong SAR, China
| | - Bin Yang
- Medical Physics Department, Hong Kong Sanatorium & Hospital, Happy Valley, Hong Kong SAR, China
| | - Yihang Zhou
- Research Department, Hong Kong Sanatorium & Hospital, Happy Valley, Hong Kong SAR, China
| | - Siu Ki Yu
- Medical Physics Department, Hong Kong Sanatorium & Hospital, Happy Valley, Hong Kong SAR, China
| | - Kin Yin Cheung
- Medical Physics Department, Hong Kong Sanatorium & Hospital, Happy Valley, Hong Kong SAR, China
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Poon DMC, Yang B, Geng H, Wong OL, Chiu ST, Cheung KY, Yu SK, Chiu G, Yuan J. Analysis of online plan adaptation for 1.5T magnetic resonance-guided stereotactic body radiotherapy (MRgSBRT) of prostate cancer. J Cancer Res Clin Oncol 2023; 149:841-850. [PMID: 35199189 PMCID: PMC8866042 DOI: 10.1007/s00432-022-03950-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2022] [Accepted: 02/06/2022] [Indexed: 12/11/2022]
Abstract
PURPOSE To analyze and characterize the online plan adaptation of 1.5T magnetic resonance-guided stereotactic body radiotherapy (MRgSBRT) of prostate cancer (PC). METHODS PC patients (n = 107) who received adaptive 1.5 Tesla MRgSBRT were included. Online plan adaptation was implemented by either the adapt-to-position (ATP) or adapt-to-shape (ATS) methods. Patients were assigned to the ATS group if they underwent ≥ 1 ATS fraction (n = 51); the remainder were assigned to the ATP group (n = 56). The online plan adaptation records of 535 (107 × 5) fractions were retrospectively reviewed. Rationales for ATS decision-making were determined and analyzed using predefined criteria. Statistics of ATS fractions were summarized. Associations of patient characteristics and clinical factors with ATS utilization were investigated. RESULTS There were 87 (16.3%) ATS fractions and 448 ATP fractions (83.7%). The numbers of ATS adoptions in fractions 1-5 were 29 (29/107, 27.1%), 18 (16.8%), 15 (14.0%), 16 (15.0%), and 9 (8.4%), respectively, with significant differences in adoption frequency between fractions (p = 0.007). Other baseline patient characteristics and clinical factors were not significantly associated with ATS classification (all p > 0.05). Underlying criteria for the determination of ATS implementation comprised anatomical changes (77 fractions in 50 patients) and discrete multiple targets (15 fractions in 3 patients). No ATS utilization was determined using dosimetric or online quality assurance criteria. CONCLUSIONS This study contributes to facilitating the establishment of a standardized protocol for online MR-guided adaptive radiotherapy in PC.
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Affiliation(s)
- Darren M. C. Poon
- grid.414329.90000 0004 1764 7097Comprehensive Oncology Centre, Hong Kong Sanatorium and Hospital, Happy Valley, Hong Kong, Hong Kong SAR China
| | - Bin Yang
- grid.414329.90000 0004 1764 7097Medical Physics Department, Hong Kong Sanatorium and Hospital, Happy Valley, Hong Kong, Hong Kong SAR China
| | - Hui Geng
- grid.414329.90000 0004 1764 7097Medical Physics Department, Hong Kong Sanatorium and Hospital, Happy Valley, Hong Kong, Hong Kong SAR China
| | - Oi Lei Wong
- grid.414329.90000 0004 1764 7097Research Department, Hong Kong Sanatorium and Hospital, Happy Valley, Hong Kong, Hong Kong SAR China
| | - Sin Ting Chiu
- grid.414329.90000 0004 1764 7097Department of Radiotherapy, Hong Kong Sanatorium and Hospital, Happy Valley, Hong Kong, Hong Kong SAR China
| | - Kin Yin Cheung
- grid.414329.90000 0004 1764 7097Medical Physics Department, Hong Kong Sanatorium and Hospital, Happy Valley, Hong Kong, Hong Kong SAR China
| | - Siu Ki Yu
- grid.414329.90000 0004 1764 7097Medical Physics Department, Hong Kong Sanatorium and Hospital, Happy Valley, Hong Kong, Hong Kong SAR China
| | - George Chiu
- grid.414329.90000 0004 1764 7097Department of Radiotherapy, Hong Kong Sanatorium and Hospital, Happy Valley, Hong Kong, Hong Kong SAR China
| | - Jing Yuan
- grid.414329.90000 0004 1764 7097Research Department, Hong Kong Sanatorium and Hospital, Happy Valley, Hong Kong, Hong Kong SAR China
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Yang B, Geng H, Chang TYA, Tse MY, Lam WW, Huang CY, Wu T, Lau KK, Cheung KY, Chiu G, Yu SK. Clinical implementation of kVCT-guided tomotherapy with ClearRT. Phys Eng Sci Med 2022; 45:915-924. [PMID: 35925545 DOI: 10.1007/s13246-022-01162-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2022] [Accepted: 07/07/2022] [Indexed: 10/16/2022]
Abstract
A helical fan-beam kilovoltage computed tomography (kVCT) was recently introduced into Tomotherapy units. This study aims to share the initial experience of kVCT in clinical workflow, compare its performance with that of the existing megavoltage computed tomography (MVCT), and explore its potential in adaptive planning. We retrospectively enrolled 23 patients who underwent both MVCT and kVCT scans. The clinical performance data regarding image acquisition time, nominal dose length product (DLP), registration time and registration corrections were extracted and compared. Image quality was scored by six experienced radiation therapists and quantified based on phantom measurements. CT number stability and the implementation of adaptive radiotherapy were dosimetrically evaluated by performing the dose recalculation on kVCT. Compared to MVCT, kVCT significantly reduced DLP (except the highest kVp protocol), image acquisition and registration time. KVCT obtained higher scores than MVCT on all criteria except artifacts. Phantom measurements also revealed a better image performance characterization of kVCT except for image uniformity. The CT number variation could lead to a dose difference of 0.5% for D95% of target and Dmean of organ-at-risk. For the treatment planning with kVCT, a systematic dose difference (> 1%) in PTV dose metrics was observed at regions with large longitudinal density discontinuities compared to the reference plans. The new kVCT imaging provides enhanced soft-tissue visualization. The improved efficiency with kVCT-guided treatment will allow more patients to be treated each day. In most cases, the dose calculation accuracy of kVCT images is acceptable except for regions with severe artifacts.
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Affiliation(s)
- Bin Yang
- Medical Physics Department, Hong Kong Sanatorium & Hospital, 2 Village Road, Happy Valley, Hong Kong, China.
| | - Hui Geng
- Medical Physics Department, Hong Kong Sanatorium & Hospital, 2 Village Road, Happy Valley, Hong Kong, China
| | - Tien Yee Amy Chang
- Comprehensive Oncology Centre, Hong Kong Sanatorium & Hospital, 2 Village Road, Happy Valley, Hong Kong, China
| | - Mei Yan Tse
- Medical Physics Department, Hong Kong Sanatorium & Hospital, 2 Village Road, Happy Valley, Hong Kong, China
| | - Wai Wang Lam
- Medical Physics Department, Hong Kong Sanatorium & Hospital, 2 Village Road, Happy Valley, Hong Kong, China
| | - Chen-Yu Huang
- Medical Physics Department, Hong Kong Sanatorium & Hospital, 2 Village Road, Happy Valley, Hong Kong, China
| | - Tungho Wu
- TMU Proton Center, Taipei Medical University Hospital, 252 Wuxing Street, Xinyi District, Taipei, Taiwan
| | - Ka Ki Lau
- Medical Physics Department, Hong Kong Sanatorium & Hospital, 2 Village Road, Happy Valley, Hong Kong, China
| | - Kin Yin Cheung
- Medical Physics Department, Hong Kong Sanatorium & Hospital, 2 Village Road, Happy Valley, Hong Kong, China
| | - George Chiu
- Department of Radiotherapy, Hong Kong Sanatorium & Hospital, 2 Village Road, Happy Valley, Hong Kong, China
| | - Siu Ki Yu
- Medical Physics Department, Hong Kong Sanatorium & Hospital, 2 Village Road, Happy Valley, Hong Kong, China
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Yang B, Yuan J, Poon DM, Geng H, Lam WW, Cheung KY, Yu SK. Assessment of planning target volume margins in 1.5 T magnetic resonance‐guided stereotactic body radiation therapy for localized prostate cancer. Precision Radiation Oncology 2022. [DOI: 10.1002/pro6.1155] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Affiliation(s)
- Bin Yang
- Medical Physics Department Hong Kong Sanatorium & Hospital Happy Valley Hong Kong China
| | - Jing Yuan
- Research Department Hong Kong Sanatorium & Hospital Happy Valley Hong Kong China
| | - Darren M.C. Poon
- Comprehensive Oncology Centre Hong Kong Sanatorium & Hospital Happy Valley Hong Kong China
| | - Hui Geng
- Medical Physics Department Hong Kong Sanatorium & Hospital Happy Valley Hong Kong China
| | - Wai Wang Lam
- Medical Physics Department Hong Kong Sanatorium & Hospital Happy Valley Hong Kong China
| | - Kin Yin Cheung
- Medical Physics Department Hong Kong Sanatorium & Hospital Happy Valley Hong Kong China
| | - Siu Ki Yu
- Medical Physics Department Hong Kong Sanatorium & Hospital Happy Valley Hong Kong China
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10
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Tabakov S, Goh J, Cheung KY. IUPESM milestone developments and achievements during 1980-2022-a tribute to the contributors. Health Technol (Berl) 2022; 12:609-612. [PMID: 35474737 PMCID: PMC9023040 DOI: 10.1007/s12553-022-00667-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2022] [Accepted: 04/05/2022] [Indexed: 10/25/2022]
Abstract
During 2020 the International Union for Physical and Engineering Sciences in Medicine (IUPESM) celebrated its 40th anniversary. At that time a paper was prepared tracing the main steps for the creation of the IUPESM (the Union formed of IOMP and IFMBE) and its very important activities for the global recognition of the professions [1]. The current paper, prepared by the IUPESM President, Vice-President and Past President, presents a chronology of the IUPESM Milestone Developments and Achievements and pays tribute to the main contributors for these achievements. Supplementary information The online version contains supplementary material available at 10.1007/s12553-022-00667-6.
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Affiliation(s)
| | - J Goh
- Department of Biomedical Engineering, National University of Singapore, Queenstown, Singapore
| | - K Y Cheung
- Hong Kong Sanatorium & Hospital, HKSH Eastern Medical Centre, Shau Kei Wan, Hong Kong
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11
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Xue C, Yuan J, Zhou Y, Wong OL, Cheung KY, Yu SK. Acquisition repeatability of MRI radiomics features in the head and neck: a dual-3D-sequence multi-scan study. Vis Comput Ind Biomed Art 2022; 5:10. [PMID: 35359245 PMCID: PMC8971276 DOI: 10.1186/s42492-022-00106-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2021] [Accepted: 02/23/2022] [Indexed: 02/08/2023] Open
Abstract
Radiomics has increasingly been investigated as a potential biomarker in quantitative imaging to facilitate personalized diagnosis and treatment of head and neck cancer (HNC), a group of malignancies associated with high heterogeneity. However, the feature reliability of radiomics is a major obstacle to its broad validity and generality in application to the highly heterogeneous head and neck (HN) tissues. In particular, feature repeatability of radiomics in magnetic resonance imaging (MRI) acquisition, which is considered a crucial confounding factor of radiomics feature reliability, is still sparsely investigated. This study prospectively investigated the acquisition repeatability of 93 MRI radiomics features in ten HN tissues of 15 healthy volunteers, aiming for potential magnetic resonance-guided radiotherapy (MRgRT) treatment of HNC. Each subject underwent four MRI acquisitions with MRgRT treatment position and immobilization using two pulse sequences of 3D T1-weighed turbo spin-echo and 3D T2-weighed turbo spin-echo on a 1.5 T MRI simulator. The repeatability of radiomics feature acquisition was evaluated in terms of the intraclass correlation coefficient (ICC), whereas within-subject acquisition variability was evaluated in terms of the coefficient of variation (CV). The results showed that MRI radiomics features exhibited heterogeneous acquisition variability and uncertainty dependent on feature types, tissues, and pulse sequences. Only a small fraction of features showed excellent acquisition repeatability (ICC > 0.9) and low within-subject variability. Multiple MRI scans improved the accuracy and confidence of the identification of reliable features concerning MRI acquisition compared to simple test-retest repeated scans. This study contributes to the literature on the reliability of radiomics features with respect to MRI acquisition and the selection of reliable radiomics features for use in modeling in future HNC MRgRT applications.
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Affiliation(s)
- Cindy Xue
- Research Department, Hong Kong Sanatorium & Hospital, Hong Kong, China
| | - Jing Yuan
- Research Department, Hong Kong Sanatorium & Hospital, Hong Kong, China.
| | - Yihang Zhou
- Research Department, Hong Kong Sanatorium & Hospital, Hong Kong, China
| | - Oi Lei Wong
- Research Department, Hong Kong Sanatorium & Hospital, Hong Kong, China
| | - Kin Yin Cheung
- Medical Physics Department, Hong Kong Sanatorium & Hospital, Hong Kong, China
| | - Siu Ki Yu
- Medical Physics Department, Hong Kong Sanatorium & Hospital, Hong Kong, China
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12
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Poon DMC, Wu S, Ho L, Cheung KY, Yu B. Proton Therapy for Prostate Cancer: Challenges and Opportunities. Cancers (Basel) 2022; 14:cancers14040925. [PMID: 35205673 PMCID: PMC8870339 DOI: 10.3390/cancers14040925] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2021] [Revised: 02/10/2022] [Accepted: 02/11/2022] [Indexed: 01/02/2023] Open
Abstract
Simple Summary Reported clinical outcomes of proton therapy (PT) for localized prostate cancer are similar to photon-based external beam radiotherapy. Apparently, the dosimetric advantages of PT have yet to be translated to clinical benefits. The suboptimal clinical outcomes of PT might be attributable to inadequate dose prescription, as indicated by the ASCENDE-RT trial. Moreover, uncertainties involved in the treatment planning and delivery processes, as well as technological limitations in PT treatment systems, may lead to discrepancies between planned doses and actual doses delivered to patients. In this article, we reviewed the current status of PT for prostate cancer and discussed different clinical implementations that could potentially improve the clinical outcome of PT for prostate cancer. Various technological advancements under which uncertainties in dose calculations can be minimized, including MRI-guided PT, dual-energy photon-counting CT and high-resolution Monte Carlo-based treatment planning systems, are highlighted. Abstract The dosimetric advantages of proton therapy (PT) treatment plans are demonstrably superior to photon-based external beam radiotherapy (EBRT) for localized prostate cancer, but the reported clinical outcomes are similar. This may be due to inadequate dose prescription, especially in high-risk disease, as indicated by the ASCENDE-RT trial. Alternatively, the lack of clinical benefits with PT may be attributable to improper dose delivery, mainly due to geometric and dosimetric uncertainties during treatment planning, as well as delivery procedures that compromise the dose conformity of treatments. Advanced high-precision PT technologies, and treatment planning and beam delivery techniques are being developed to address these uncertainties. For instance, external magnetic resonance imaging (MRI)-guided patient setup rooms are being developed to improve the accuracy of patient positioning for treatment. In-room MRI-guided patient positioning systems are also being investigated to improve the geometric accuracy of PT. Soon, high-dose rate beam delivery systems will shorten beam delivery time to within one breath hold, minimizing the effects of organ motion and patient movements. Dual-energy photon-counting computed tomography and high-resolution Monte Carlo-based treatment planning systems are available to minimize uncertainties in dose planning calculations. Advanced in-room treatment verification tools such as prompt gamma detector systems will be used to verify the depth of PT. Clinical implementation of these new technologies is expected to improve the accuracy and dose conformity of PT in the treatment of localized prostate cancers, and lead to better clinical outcomes. Improvement in dose conformity may also facilitate dose escalation, improving local control and implementation of hypofractionation treatment schemes to improve patient throughput and make PT more cost effective.
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Affiliation(s)
- Darren M. C. Poon
- Comprehensive Oncology Centre, Hong Kong Sanatorium & Hospital, Hong Kong 999077, China;
| | - Stephen Wu
- Medical Physics Department, Hong Kong Sanatorium & Hospital, Hong Kong 999077, China; (L.H.); (K.Y.C.); (B.Y.)
- Correspondence: ; Tel.: +852-29171413
| | - Leon Ho
- Medical Physics Department, Hong Kong Sanatorium & Hospital, Hong Kong 999077, China; (L.H.); (K.Y.C.); (B.Y.)
| | - Kin Yin Cheung
- Medical Physics Department, Hong Kong Sanatorium & Hospital, Hong Kong 999077, China; (L.H.); (K.Y.C.); (B.Y.)
| | - Ben Yu
- Medical Physics Department, Hong Kong Sanatorium & Hospital, Hong Kong 999077, China; (L.H.); (K.Y.C.); (B.Y.)
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13
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Yuan J, Poon DMC, Lo G, Wong OL, Cheung KY, Yu SK. A narrative review of MRI acquisition for MR-guided-radiotherapy in prostate cancer. Quant Imaging Med Surg 2022; 12:1585-1607. [PMID: 35111651 PMCID: PMC8739116 DOI: 10.21037/qims-21-697] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2021] [Accepted: 08/20/2021] [Indexed: 08/24/2023]
Abstract
Magnetic resonance guided radiotherapy (MRgRT), enabled by the clinical introduction of the integrated MRI and linear accelerator (MR-LINAC), is a novel technique for prostate cancer (PCa) treatment, promising to further improve clinical outcome and reduce toxicity. The role of prostate MRI has been greatly expanded from the traditional PCa diagnosis to also PCa screening, treatment and surveillance. Diagnostic prostate MRI has been relatively familiar in the community, particularly with the development of Prostate Imaging - Reporting and Data System (PI-RADS). But, on the other hand, the use of MRI in the emerging clinical practice of PCa MRgRT, which is substantially different from that in PCa diagnosis, has been so far sparsely presented in the medical literature. This review attempts to give a comprehensive overview of MRI acquisition techniques currently used in the clinical workflows of PCa MRgRT, from treatment planning to online treatment guidance, in order to promote MRI practice and research for PCa MRgRT. In particular, the major differences in the MRI acquisition of PCa MRgRT from that of diagnostic prostate MRI are demonstrated and explained. Limitations in the current MRI acquisition for PCa MRgRT are analyzed. The future developments of MRI in the PCa MRgRT are also discussed.
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Affiliation(s)
- Jing Yuan
- Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, Hong Kong, China
| | - Darren M. C. Poon
- Comprehensive Oncology Centre, Hong Kong Sanatorium & Hospital, Hong Kong, China
| | - Gladys Lo
- Department of Diagnostic & Interventional Radiology, Hong Kong Sanatorium & Hospital, Hong Kong, China
| | - Oi Lei Wong
- Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, Hong Kong, China
| | - Kin Yin Cheung
- Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, Hong Kong, China
| | - Siu Ki Yu
- Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, Hong Kong, China
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14
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Wong OL, Poon DM, Kam MK, Lo GG, Fung WW, Man SY, Xue C, Yu SK, Cheung KY, Yuan J. 3D‐T2W‐TSE radiotherapy treatment planning MRI using compressed sensing acceleration for prostate cancer: Image quality and delineation value. Asia Pac J Clin Oncol 2022; 18:e369-e377. [DOI: 10.1111/ajco.13752] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2021] [Accepted: 12/13/2021] [Indexed: 11/29/2022]
Affiliation(s)
- Oi Lei Wong
- Research Department Hong Kong Sanatorium and Hospital Hong Kong Hong Kong SAR
| | - Darren M.C. Poon
- Comprehensive Oncology Centre Hong Kong Sanatorium and Hospital Hong Kong Hong Kong SAR
| | - Miachael K.M. Kam
- Comprehensive Oncology Centre Hong Kong Sanatorium and Hospital Hong Kong Hong Kong SAR
| | - Gladys G. Lo
- Department of Diagnostic and Interventional Radiology Hong Kong Sanatorium and Hospital Hong Kong Hong Kong SAR
| | - Winky W.K. Fung
- Department of Radiotherapy Hong Kong Sanatorium and Hospital Hong Kong Hong Kong SAR
| | - Shei Yee Man
- Department of Radiotherapy Hong Kong Sanatorium and Hospital Hong Kong Hong Kong SAR
| | - Cindy Xue
- Research Department Hong Kong Sanatorium and Hospital Hong Kong Hong Kong SAR
| | - Siu Ki Yu
- Medical Physics Department Hong Kong Sanatorium and Hospital Hong Kong Hong Kong SAR
| | - Kin Yin Cheung
- Medical Physics Department Hong Kong Sanatorium and Hospital Hong Kong Hong Kong SAR
| | - Jing Yuan
- Research Department Hong Kong Sanatorium and Hospital Hong Kong Hong Kong SAR
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15
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Law MWL, Yuan J, Wong OL, Ying AD, Zhou Y, Cheung KY, Yu SK. Phantom assessment of three-dimensional geometric distortion of a dedicated wide-bore MR-simulator for radiotherapy. Biomed Phys Eng Express 2021; 8. [PMID: 34874313 DOI: 10.1088/2057-1976/ac3f4f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2021] [Accepted: 12/02/2021] [Indexed: 11/11/2022]
Abstract
This study evaluated the machine-dependent three-dimensional geometric distortion images acquired from a 1.5T 700mm-wide bore MR-simulator based on a large geometric accuracy phantom. With the consideration of radiation therapy (RT) application requirements, every sequence was examined in various combinations of acquisition-orientations and receiver-bandwidths with console-integrated distortion correction enabled. Distortion was repeatedly measured over a six-month period. The distortion measured from the images acquired at the beginning of this period was employed to retrospectively correct the distortion in the subsequent acquisitions. Geometric distortion was analyzed within the largest field-of-view allowed. Six sequences were examined for comprehensive distortion analysis - VIBE, SPACE, TSE, FLASH, BLADE and PETRA. Based on optimal acquisition parameters, their diameter-sphere-volumes (DSVs) of CT-comparable geometric fidelity (where 1mm distortion was allowed) were 333.6mm, 315.1mm, 316.0mm, 318.9mm, 306.2mm and 314.5mm respectively. This was a significant increase from 254.0mm, 245.5mm, 228.9mm, 256.6mm, 230.8mm and 254.2mm DSVs respectively, when images were acquired using un-optimized parameters. The longitudinal stability of geometric distortion and the efficacy of retrospective correction of console-corrected images, based on prior distortion measurements, were inspected using VIBE and SPACE. The retrospectively corrected images achieved over 500mm DSVs with 1mm distortion allowed. The median distortion was below 1mm after retrospective correction, proving that obtaining prior distortion map for subsequent retrospective distortion correction is beneficial. The systematic evaluation of distortion using various combinations of sequence-type, acquisition-orientation and receiver-bandwidth in a six-month time span would be a valuable guideline for optimizing sequence for various RT applications.
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Affiliation(s)
- Max W L Law
- Medical Physics Department, Hong Kong Sanatorium and Hospital, 2nd Village Road, Happy Valley, Hong Kong Island, Hong Kong, 000, HONG KONG
| | - Jing Yuan
- Research Department, Hong Kong Sanatorium and Hospital, 2nd Village Road, Happy Valley, Hong Kong Island, Hong Kong, 000, HONG KONG
| | - Oi Lei Wong
- Research Department, Hong Kong Sanatorium and Hospital, 2nd Village Road, Happy Valley, Hong Kong Island, Hong Kong, NA, 000, HONG KONG
| | - Abby D Ying
- Medical Physics Department, Hong Kong Sanatorium and Hospital, Hong Kong Sanatorium and Hospital, Hong Kong, HONG KONG
| | - Yihang Zhou
- Research Department, Hong Kong Sanatorium and Hospital, 2nd Village Road, Happy Valley, Hong Kong Island, Hong Kong, 000, HONG KONG
| | - Kin Yin Cheung
- Medical Physics Department, Hong Kong Sanatorium and Hospital, 2nd Village Road, Happy Valley, Hong Kong Island, Hong Kong, 000, HONG KONG
| | - Siu Ki Yu
- Medical Physics Department, Hong Kong Sanatorium and Hospital, 2nd Village Road, Happy Valley, Hong Kong Island, Hong Kong, 000, HONG KONG
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16
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Yang B, Tang KK, Huang CY, Geng H, Lam WW, Wong YS, Tse MY, Lau KK, Cheung KY, Yu SK. Out-of-field dose and its constituent components for a 1.5 T MR-Linac. Phys Med Biol 2021; 66. [PMID: 34700308 DOI: 10.1088/1361-6560/ac3346] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2021] [Accepted: 10/26/2021] [Indexed: 11/11/2022]
Abstract
This study aims to quantify the relative contributions of phantom scatter, collimator scatter and head leakage to the out-of-field doses (OFDs) of both static fields and clinical intensity-modulated radiation therapy (IMRT) treatments in a 1.5 T MR-Linac. The OFDs of static fields were measured at increasing distances from the field edge in an MR-conditional water phantom. Inline scans at depths of dmax (14 mm), 50 and 100 mm were performed for static fields of 5 × 5, 10 × 10 and 15 × 15 cm2under three different conditions: full scatter, with phantom scatter prevented, and head leakage only. Crossline scans at isocenter and offset positions were performed in full scatter condition. EBT3 radiochromic films were placed at 100 mm depth of solid water phantom to measure the OFD of clinical IMRT plans. All water tank data were normalized to Dmax of a 10 × 10 cm2field and the film results were presented as a fraction of the target mean dose.The OFD in the inline direction varied from 3.5% (15 × 15 cm2, 100 mm depth, 50 mm distance) to 0.014% (5 × 5 cm2, dmax, 400 mm distance). For all static fields, the collimator scatter was higher than the phantom scatter and head leakage at a distance of 100-400 mm. Head leakage remained the smallest among the three components, except at long distances (>375 mm) with small field size. Compared to the inline scans, the crossline scans at the isocenter showed higher doses at distances longer than 80 mm. All crossline profiles at longitudinal offset positions showed a cone shape with laterally shifted maxima. The OFD of IMRT deliveries varied with different target size. For prostate stereotactic body radiation therapy (SBRT) treatment, the OFD decreased from 2% to 0.03% at a distance of 50-500 mm. The OFDs have been measured for a 1.5 T MR-Linac. The presented dosimetric data are valuable for radiation safety assessments on patients treated with the MR-Linac, such as evaluating carcinogenic risk and radiation exposure to cardiac implantable electronic devices.
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Affiliation(s)
- Bin Yang
- Medical Physics Department, Hong Kong Sanatorium & Hospital, 2 Village Road, Happy Valley, Hong Kong, People's Republic of China
| | - Ka Keung Tang
- Medical Physics Department, Hong Kong Sanatorium & Hospital, 2 Village Road, Happy Valley, Hong Kong, People's Republic of China
| | - Chen-Yu Huang
- Medical Physics Department, Hong Kong Sanatorium & Hospital, 2 Village Road, Happy Valley, Hong Kong, People's Republic of China
| | - Hui Geng
- Medical Physics Department, Hong Kong Sanatorium & Hospital, 2 Village Road, Happy Valley, Hong Kong, People's Republic of China
| | - Wai Wang Lam
- Medical Physics Department, Hong Kong Sanatorium & Hospital, 2 Village Road, Happy Valley, Hong Kong, People's Republic of China
| | - Yeung Sum Wong
- Medical Physics Department, Hong Kong Sanatorium & Hospital, 2 Village Road, Happy Valley, Hong Kong, People's Republic of China
| | - Mei Yan Tse
- Medical Physics Department, Hong Kong Sanatorium & Hospital, 2 Village Road, Happy Valley, Hong Kong, People's Republic of China
| | - Ka Ki Lau
- Medical Physics Department, Hong Kong Sanatorium & Hospital, 2 Village Road, Happy Valley, Hong Kong, People's Republic of China
| | - Kin Yin Cheung
- Medical Physics Department, Hong Kong Sanatorium & Hospital, 2 Village Road, Happy Valley, Hong Kong, People's Republic of China
| | - Siu Ki Yu
- Medical Physics Department, Hong Kong Sanatorium & Hospital, 2 Village Road, Happy Valley, Hong Kong, People's Republic of China
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17
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Yang B, Yuan J, Cheung KY, Huang CY, Poon DMC, Yu SK. Magnetic Resonance-Guided Radiation Therapy of Patients With Cardiovascular Implantable Electronic Device on a 1.5 T Magnetic Resonance-Linac. Pract Radiat Oncol 2021; 12:e56-e61. [PMID: 34520872 DOI: 10.1016/j.prro.2021.08.011] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2021] [Revised: 08/28/2021] [Accepted: 08/31/2021] [Indexed: 11/17/2022]
Abstract
Magnetic resonance-guided radiation therapy is reported for treating patients with an insertable cardiac monitor and implantable cardiac pacemakers. All treatments were delivered using a 1.5 T MR-Linac. Among the 4 patients, 2 were treated with stereotactic body radiation therapy at a dose of 40 Gy in 5 fractions. A clinical safety protocol was developed to address the decision-making and patient selection, as well as the clarified responsibilities of different parties for management of patients with cardiovascular implantable electronic devices. Dose estimation based on out-of-field dose data are necessary for cardiovascular implantable electronic devices located outside the treatment fields.
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Affiliation(s)
- Bin Yang
- Medical Physics and Research Department, Happy Valley, Hong Kong, China.
| | - Jing Yuan
- Medical Physics and Research Department, Happy Valley, Hong Kong, China
| | - Kin Yin Cheung
- Medical Physics and Research Department, Happy Valley, Hong Kong, China
| | - Chen-Yu Huang
- Medical Physics and Research Department, Happy Valley, Hong Kong, China
| | - Darren M C Poon
- Comprehensive Oncology Centre, Hong Kong Sanatorium & Hospital, Happy Valley, Hong Kong, China
| | - Siu Ki Yu
- Medical Physics and Research Department, Happy Valley, Hong Kong, China
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18
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Yang B, Tang KK, Geng H, Lam WW, Wong YS, Huang CY, Chiu TL, Kong CW, Cheung CW, Cheung KY, Yu SK. Comparison of modeling accuracy between Radixact ®and CyberKnife ®Synchrony ®respiratory tracking system. Biomed Phys Eng Express 2021; 7. [PMID: 34416743 DOI: 10.1088/2057-1976/ac1fa5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2021] [Accepted: 08/20/2021] [Indexed: 11/12/2022]
Abstract
Synchrony Respiratory Tracking system adapted from CyberKnife has been introduced in Radixact to compensate the tumor motion caused by respiration. This study aims to compare the modeling accuracy of the Synchrony system between Radixact and CyberKnife. Two Synchrony plans based on fiducial phantoms were created for CyberKnife and Radixact, respectively. Different respiratory motion traces were used to drive a motion platform to move along the superoinferior and left-right direction. The cycle time and the amplitude of target/surrogate motion of one selected motion trace were scaled to investigate the dependence of modeling accuracy on the motion characteristic. The predicted target position, the correlation error, potential difference (Radixact only) and standard error (CyberKnife only) were extracted from raw data or log files of the two systems. The modeling accuracy was evaluated by calculating the root-mean-square (RMS) error between the predicted target positions and the input motion trace. A threshold T95 within which 95% of the potential difference or the standard error lay was defined and evaluated. Except for the motion trace with a small amplitude and a good (linear) correlation between target and surrogate motion, Radixact showed smaller RMS errors than CyberKnife. The RMS error of both systems increased with the motion amplitude and showed a decreasing trend with the increasing cycle time. No correlation was found between the RMS error and the amplitude of surrogate motion. T95 could be a good estimator of modeling accuracy for CyberKnife rather than Radixact. The correlation error defined in Radixact were largely affected by the number of fiducial markers and the setup error. In general, the modeling accuracy of the Radixact Synchrony system is better than that of the CyberKnife Synchrony system under unfavorable conditions.
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Affiliation(s)
- B Yang
- Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, 2 Village Road, Happy Valley, Hong Kong
| | - K K Tang
- Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, 2 Village Road, Happy Valley, Hong Kong
| | - H Geng
- Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, 2 Village Road, Happy Valley, Hong Kong
| | - W W Lam
- Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, 2 Village Road, Happy Valley, Hong Kong
| | - Y S Wong
- Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, 2 Village Road, Happy Valley, Hong Kong
| | - C Y Huang
- Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, 2 Village Road, Happy Valley, Hong Kong
| | - T L Chiu
- Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, 2 Village Road, Happy Valley, Hong Kong
| | - C W Kong
- Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, 2 Village Road, Happy Valley, Hong Kong
| | - C W Cheung
- Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, 2 Village Road, Happy Valley, Hong Kong
| | - K Y Cheung
- Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, 2 Village Road, Happy Valley, Hong Kong
| | - S K Yu
- Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, 2 Village Road, Happy Valley, Hong Kong
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19
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Yuan J, Law SCK, Wong KK, Lo GG, Kam MKM, Kwan WH, Xue C, Wong OL, Yu SK, Cheung KY. 3D T1-weighted turbo spin echo contrast-enhanced MRI at 1.5 T for frameless brain metastases radiotherapy. J Cancer Res Clin Oncol 2021; 148:1749-1759. [PMID: 34363123 DOI: 10.1007/s00432-021-03755-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2021] [Accepted: 07/31/2021] [Indexed: 11/27/2022]
Abstract
PURPOSE Performance of 3D-T1W-TSE has been proven superior to 3D-MP-GRE at 3 T on brain metastases (BM) contrast-enhanced (CE) MRI. However, its performance at 1.5 T is largely unknown and sparsely reported. This study aims to assess image quality, lesion detectability and conspicuity of 1.5 T 3D-T1W-TSE on planning MRI of frameless BM radiotherapy. METHODS 94 BM patients to be treated by frameless brain radiotherapy were scanned using 3D-T1W-TSE with immobilization on multi-vendor 1.5 T MRI-simulators. BMs were jointly diagnosed by 4 reviewers. Enhanced lesion conspicuity was quantitatively assessed by calculating contrast ratio (CR) and contrast-to-noise ratio (CNR). Signal-to-noise ratio (SNR) reduction of white matter due to the use of flexible coil was assessed. Lesion detectability and conspicuity were compared between 1.5 T planning MRI and 3 T diagnostic MRI by an oncologist and a radiologist in 10 patients. RESULTS 497 BMs were jointly diagnosed. The CR and CNR were 75.2 ± 39.9% and 14.2 ± 8.1, respectively. SNR reduced considerably from 31.7 ± 8.3 to 21.9 ± 5.4 with the longer distance to coils. 3 T diagnostic MRI and 1.5 T planning MRI yielded exactly the same detection of 84 BMs. Qualitatively, lesion conspicuity at 1.5 T was not inferior to that at 3 T. Quantitatively, lower brain SNR and lesion CNR were found at 1.5 T, while lesion CR at 1.5 T was highly comparable to that at 3 T. CONCLUSION 1.5 T 3D-T1W-TSE planning MRI of frameless BM radiotherapy was comprehensively assessed. Highly comparable BM detectability and conspicuity were achieved by 1.5 T planning MRI compared to 3 T diagnostic MRI. 1.5 T 3D-T1W-TSE should be valuable for frameless brain radiotherapy planning.
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Affiliation(s)
- Jing Yuan
- Medical Physics and Research Department, Hong Kong Sanatorium and Hospital, 8/F, Li Shu Fan Block, 2 Village Road, Happy Valley, Hong Kong SAR, China.
| | - Stephen C K Law
- Comprehensive Oncology Centre, Hong Kong Sanatorium and Hospital, Happy Valley, Hong Kong SAR, China
| | - Ka Kin Wong
- Department of Diagnostic and Interventional Radiology, Hong Kong Sanatorium and Hospital, Happy Valley, Hong Kong SAR, China
| | - Gladys G Lo
- Department of Diagnostic and Interventional Radiology, Hong Kong Sanatorium and Hospital, Happy Valley, Hong Kong SAR, China
| | - Michael K M Kam
- Comprehensive Oncology Centre, Hong Kong Sanatorium and Hospital, Happy Valley, Hong Kong SAR, China
| | - Wing Hong Kwan
- Comprehensive Oncology Centre, Hong Kong Sanatorium and Hospital, Happy Valley, Hong Kong SAR, China
| | - Cindy Xue
- Medical Physics and Research Department, Hong Kong Sanatorium and Hospital, 8/F, Li Shu Fan Block, 2 Village Road, Happy Valley, Hong Kong SAR, China
| | - Oi Lei Wong
- Medical Physics and Research Department, Hong Kong Sanatorium and Hospital, 8/F, Li Shu Fan Block, 2 Village Road, Happy Valley, Hong Kong SAR, China
| | - Siu Ki Yu
- Medical Physics and Research Department, Hong Kong Sanatorium and Hospital, 8/F, Li Shu Fan Block, 2 Village Road, Happy Valley, Hong Kong SAR, China
| | - Kin Yin Cheung
- Medical Physics and Research Department, Hong Kong Sanatorium and Hospital, 8/F, Li Shu Fan Block, 2 Village Road, Happy Valley, Hong Kong SAR, China
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Yuan J, Xue C, Lo G, Wong OL, Zhou Y, Yu SK, Cheung KY. Quantitative assessment of acquisition imaging parameters on MRI radiomics features: a prospective anthropomorphic phantom study using a 3D-T2W-TSE sequence for MR-guided-radiotherapy. Quant Imaging Med Surg 2021; 11:1870-1887. [PMID: 33936971 DOI: 10.21037/qims-20-865] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Background MRI pulse sequences and imaging parameters substantially influence the variation of MRI radiomics features, thus impose a critical challenge on MRI radiomics reproducibility and reliability. This study aims to prospectively investigate the impact of various imaging parameters on MRI radiomics features in a 3D T2-weighted (T2W) turbo-spin-echo (TSE) pulse sequence for MR-guided-radiotherapy (MRgRT). Methods An anthropomorphic phantom was scanned using a 3D-T2W-TSE MRgRT sequence at 1.5T under a variety of acquisition imaging parameter changes. T1 and T2 relaxation times of the phantom were also measured. 93 first-order and texture radiomics features in the original and 14 transformed images, yielding 1,395 features in total, were extracted from 10 volumes-of-interest (VOIs). The percentage deviation (d%) of radiomics feature values from the baseline values and intra-class correlation coefficient (ICC) with the baseline were calculated. Robust radiomics features were identified based on the excellent agreement of radiomics feature values with the baseline, i.e., the averaged d% <5% and ICC >0.90 in all VOIs for all imaging parameter variations. Results The radiomics feature values changed considerably but to different degrees with different imaging parameter adjustments, in the ten VOIs. The deviation d% ranged from 0.02% to 321.3%, with a mean of 12.5% averaged for all original features in all ten VOIs. First-order and GLCM features were generally more robust to imaging parameters than other features in the original images. There were also significantly different radiomics feature values (ANOVA, P<0.001) between the original and the transformed images, exhibiting quite different robustness to imaging parameters. 330 out of 1395 features (23.7%) robust to imaging parameters were identified. GLCM and GLSZM features had the most (42.5%, 153/360) and least (3.8%, 9/240) robust features in the original and transformed images, respectively. Conclusions This study helps better understand the quantitative dependence of radiomics feature values on imaging parameters in a 3D-T2W-TSE sequence for MRgRT. Imaging parameter heterogeneity should be considered as a significant source of radiomics variability and uncertainty, which must be well harmonized for reliable clinical use. The identified robust features to imaging parameters are helpful for the pre-selection of radiomics features for reliable radiomics modeling.
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Affiliation(s)
- Jing Yuan
- Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, Happy Valley, Hong Kong, Hong Kong SAR, China
| | - Cindy Xue
- Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, Happy Valley, Hong Kong, Hong Kong SAR, China
| | - Gladys Lo
- Department of Diagnostic & Interventional Radiology, Hong Kong Sanatorium & Hospital, Happy Valley, Hong Kong, Hong Kong SAR, China
| | - Oi Lei Wong
- Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, Happy Valley, Hong Kong, Hong Kong SAR, China
| | - Yihang Zhou
- Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, Happy Valley, Hong Kong, Hong Kong SAR, China
| | - Siu Ki Yu
- Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, Happy Valley, Hong Kong, Hong Kong SAR, China
| | - Kin Yin Cheung
- Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, Happy Valley, Hong Kong, Hong Kong SAR, China
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Yang B, Wong YS, Lam WW, Geng H, Huang CY, Tang KK, Law WK, Ho CC, Nam PH, Cheung KY, Yu SK. Initial clinical experience of patient-specific QA of treatment delivery in online adaptive radiotherapy using a 1.5 T MR-Linac. Biomed Phys Eng Express 2021; 7. [PMID: 33882471 DOI: 10.1088/2057-1976/abfa80] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2020] [Accepted: 04/21/2021] [Indexed: 11/11/2022]
Abstract
Purpose. This study aims to evaluate the performance of a commercial 1.5 T MR-Linac by analyzing its patient-specific quality assurance (QA) data collected during one full year of clinical operation.Methods and Materials. The patient-specific QA system consisted of offline delivery QA (DQA) and online calculation-based QA. Offline DQA was based on ArcCHECK-MR combined with an ionization chamber. Online QA was performed using RadCalc that calculated and compared the point dose calculation with the treatment planning system (TPS). A total of 24 patients with 189 treatment fractions were enrolled in this study. Gamma analysis was performed and the threshold that encompassed 95% of QA results (T95) was reported. The plan complexity metric was calculated for each plan and compared with the dose measurements to determine whether any correlation existed.Results. All point dose measurements were within 5% deviation. The mean gamma passing rates of the group data were found to be 96.8 ± 4.0% and 99.6 ± 0.7% with criteria of 2%/2mm and 3%/3mm, respectively. T95 of 87.4% and 98.2% was reported for the overall group with the two passing criteria, respectively. No statistically significant difference was found between adaptive treatments with adapt-to-position (ATP) and adapt-to-shape (ATS), whilst the category of pelvis data showed a better passing rate than other sites. Online QA gave a mean deviation of 0.2 ± 2.2%. The plan complexity metric was positively correlated with the mean dose difference whilst the complexity of the ATS cohort had larger variations than the ATP cohort.Conclusions. A patient-specific QA system based on ArcCHECK-MR, solid phantom and ionization chamber has been well established and implemented for validation of treatment delivery of a 1.5 T MR-Linac. Our QA data obtained over one year confirms that good agreement between TPS calculation and treatment delivery was achieved.
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Affiliation(s)
- B Yang
- Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, 2 Village Road, Happy Valley, Hong Kong
| | - Y S Wong
- Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, 2 Village Road, Happy Valley, Hong Kong
| | - W W Lam
- Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, 2 Village Road, Happy Valley, Hong Kong
| | - H Geng
- Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, 2 Village Road, Happy Valley, Hong Kong
| | - C Y Huang
- Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, 2 Village Road, Happy Valley, Hong Kong
| | - K K Tang
- Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, 2 Village Road, Happy Valley, Hong Kong
| | - W K Law
- Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, 2 Village Road, Happy Valley, Hong Kong
| | - C C Ho
- Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, 2 Village Road, Happy Valley, Hong Kong
| | - P H Nam
- Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, 2 Village Road, Happy Valley, Hong Kong
| | - K Y Cheung
- Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, 2 Village Road, Happy Valley, Hong Kong
| | - S K Yu
- Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, 2 Village Road, Happy Valley, Hong Kong
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Huang CY, Yang B, Lam WW, Tang KK, Li TC, Law WK, Cheung KY, Yu SK. Effects on skin dose from unwanted air gaps under bolus in an MR-guided linear accelerator (MR-linac) system. Phys Med Biol 2021; 66:065021. [PMID: 33607641 DOI: 10.1088/1361-6560/abe837] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Bolus is commonly used in MV photon radiotherapy to increase superficial dose and improve dose uniformity for treating shallow lesions. However, irregular patient body contours can cause unwanted air gaps between a bolus and patient skin. The resulting dosimetric errors could be exacerbated in MR-Linac treatments, as secondary electrons generated by photons are affected by the magnetic field. This study aimed to quantify the dosimetric effect of unwanted gaps between bolus and skin surface in an MR-Linac. A parallel-plate ionization chamber and EBT3 films were utilized to evaluate the surface dose under bolus with various gantry angles, field sizes, and different air gaps. The results of surface dose measurements were then compared to Monaco 5.40 Treatment Planning System (TPS) calculations. The suitability of using a parallel-plate chamber in MR-Linac measurement was validated by benchmarking the percentage depth dose and output factors with the microDiamond detector and air-filled ionization chamber measurements in water. A non-symmetric response of the parallel-plate chamber to oblique beams in the magnetic field was characterized. Unwanted air gaps significantly reduced the skin dose. For a frontal beam, skin dose was halved when there was a 5 mm gap, a much larger difference than in a conventional linac. Skin dose manifested a non-symmetric pattern in terms of gantry angle and gap size. The TPS overestimated skin dose in general, but shared the same trend with measurement when there was no air gap, or the gap size was larger than 5 mm. However, the calculated and measured results had a large discrepancy when the bolus-skin gap was below 5 mm. When treating superficial lesions, unwanted air gaps under the bolus will compromise the dosimetric goals. Our results highlight the importance of avoiding air gaps between bolus and skin when treating superficial lesions using an MR-Linac system.
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Cheung KY. Apparatus that separated radiotherapy from radiology. Hong Kong Med J 2021; 27:76-79. [PMID: 33568565 DOI: 10.12809/hkmj-hkmms202102] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
Affiliation(s)
- K Y Cheung
- Education and Research Committee, Hong Kong Museum of Medical Sciences Society
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Wong OL, Yuan JI, Zhou Y, Yu SK, Cheung KY. Longitudinal acquisition repeatability of MRI radiomics features: An ACR MRI phantom study on two MRI scanners using a 3D T1W TSE sequence. Med Phys 2021; 48:1239-1249. [PMID: 33370474 DOI: 10.1002/mp.14686] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2020] [Revised: 12/14/2020] [Accepted: 12/18/2020] [Indexed: 12/19/2022] Open
Abstract
PURPOSE The purpose of this study was to quantitatively assess the longitudinal acquisition repeatability of MRI radiomics features in a three-dimensional (3D) T1-weighted (T1W) TSE sequence via a well-controlled prospective phantom study. METHODS Thirty consecutive daily datasets of an ACR-MRI phantom were acquired on two 1.5T MRI simulators using a 3D T1W TSE sequence. Images were blindly segmented by two observers. Post-acquisition processing was minimized but an intensity discretization (fixed bin size of 25). One hundred and one radiomics features (shape n = 12; first order n = 16; texture n = 73) were extracted. Longitudinal repeatability of each feature was evaluated by Pearson correlation and coefficient of variance (CV68% ). Interobserver feature value agreement was also quantified using intraclass correlation coefficient (ICC) and Bland-Altman analysis. A most repeatable radiomics feature set on both scanners was determined by feature coefficient of variance (CV68% <5%), ICC (>0.75), and the ratio of the interobserver difference to the interobserver mean δ<5%. RESULTS No trend of radiomics feature value changed with time. Longitudinal feature repeatability CV68% ranged 0.01-38.60% (mean/median: 12.5%/9.9%), and 0.01-40.47%, (8.49%/7.34%) on the scanners A and B. Shape features exhibited significantly better repeatability than first-order and texture features (all P < 0.01). Significant longitudinal repeatability difference was observed in texture features (P < 0.001) between the two scanners, but not in shape and first-order features (P > 0.30). First-order and texture features had smaller interobserver-dependent variation than acquisition-dependent variation. They also showed good interobserver agreement on both scanners (A:ICC = 0.80 ± 0.23; B:ICC = 0.80 ± 0.22), independent of acquisition repeatability. The repeatable radiomics features in common on both scanners, including 12 shape features, 0 first-order features, and 3 texture features, were determined as the most repeatable MRI radiomics feature set. CONCLUSIONS Radiomics features exhibited heterogeneous longitudinal repeatability, while the shape features were the most repeatable, in this phantom study with a 3D T1W TSE acquisition. The most repeatable radiomics feature set derived in this study should be helpful for the selection of reliable radiomics features in the future clinical use.
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Affiliation(s)
- Oi Lei Wong
- Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, Happy Valley, Hong Kong SAR, China
| | - JIng Yuan
- Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, Happy Valley, Hong Kong SAR, China
| | - Yihang Zhou
- Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, Happy Valley, Hong Kong SAR, China
| | - Siu Ki Yu
- Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, Happy Valley, Hong Kong SAR, China
| | - Kin Yin Cheung
- Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, Happy Valley, Hong Kong SAR, China
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Xue C, Zhou Y, Lo GG, Wong OL, Yu SK, Cheung KY, Yuan J. Reliability of radiomics features due to image reconstruction using a standardized T 2 -weighted pulse sequence for MR-guided radiotherapy: An anthropomorphic phantom study. Magn Reson Med 2021; 85:3434-3446. [PMID: 33404129 DOI: 10.1002/mrm.28650] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2020] [Revised: 11/24/2020] [Accepted: 11/25/2020] [Indexed: 11/11/2022]
Abstract
PURPOSE To prospectively investigate the impact of image reconstruction on MRI radiomics features. METHODS An anthropomorphic phantom was scanned at 1.5 T using a standardized sequence for MR-guided radiotherapy under SENSE and compressed-SENSE reconstruction settings. A total of 93 first-order and texture radiomics features in 10 volumes of interest were assessed based on (1) accuracy measured by the percentage deviation from the reference, (2) robustness on reconstruction in all volumes of interest measured by the intraclass correlation coefficient, and (3) repeatability measured by the coefficient of variance over the repetitive acquisitions. Finally, reliable and unreliable radiomics features were comprehensively determined based on their accuracy, robustness, and repeatability. RESULTS Better accuracy and robustness of the radiomics features were achieved under SENSE than compressed-SENSE reconstruction. The feature accuracy under SENSE reconstruction was more affected by acceleration factor than direction, whereas under compressed-SENSE reconstruction, accuracy was substantially impacted by the increasing denoising levels. Feature repeatability was dependent more on feature types than on reconstruction. A total of 45 reliable features and 13 unreliable features were finally determined for SENSE, compared with 22 reliable and 26 unreliable features for compressed SENSE. First-order and gray-level co-occurrence matrix features were generally more reliable than other features. CONCLUSION Radiomics features could be substantially affected by MRI reconstruction, so precautions need to be taken regarding their reliability for clinical use. This study helps the guidance of the preselection of reliable radiomics features and the preclusion of unreliable features in MR-guided radiotherapy.
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Affiliation(s)
- Cindy Xue
- Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, Hong Kong, Hong Kong SAR, China
| | - Yihang Zhou
- Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, Hong Kong, Hong Kong SAR, China
| | - Gladys Goh Lo
- Department of Diagnostic & Interventional Radiology, Hong Kong Sanatorium & Hospital, Hong Kong, Hong Kong SAR, China
| | - Oi Lei Wong
- Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, Hong Kong, Hong Kong SAR, China
| | - Siu Ki Yu
- Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, Hong Kong, Hong Kong SAR, China
| | - Kin Yin Cheung
- Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, Hong Kong, Hong Kong SAR, China
| | - Jing Yuan
- Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, Hong Kong, Hong Kong SAR, China
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Zhou Y, Wong OL, Cheung KY, Yu SK, Yuan J. A pilot study of highly accelerated 3D MRI in the head and neck position verification for MR-guided radiotherapy. Quant Imaging Med Surg 2019; 9:1255-1269. [PMID: 31448211 DOI: 10.21037/qims.2019.06.18] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Background To evaluate the performance of a highly accelerated 3D MRI on inter-fractional positional measurement for MR-guided radiotherapy (MRgRT) in the head and neck (HN). Methods Fourteen healthy volunteers received 159 scans on a 1.5 T MR-sim to simulate MRgRT fractions. MRI acquisition included a high-resolution (HQI-MRI, voxel-size =1.05×1.05×1.05 mm3, duration =5 min) and a highly-accelerated low-resolution (true-LQI-MRI, acceleration-factor =9, voxel-size =1.4×1.4×1.4 mm3, duration =86 s) T1w spin-echo sequence (TR/TE =420/7.2 ms). The first session HQI-MRI was used as the reference to mimic planning MRI. Other HQI-MRI was also retrospectively down-sampled in K-space and GRAPPA reconstructed to generate pseudo-LQI-MRI. Inter-sessional positional shift calculated from HQI-MRI, true-LQI-MRI and pseudo-LQI-MRI rigidly registering to the reference were analyzed and compared in the overall HN and the sub-regions of brain, nasopharynx, oropharynx and hypopharynx. Results The calculated SD of systematic errors (Σ) from HQI-MRI/pseudo-LQI-MRI/true-LQI-MRI images for overall HN were 1.11/1.14/1.08, 0.28/0.26/0.29, 0.43/0.44/0.60, and 0.77/0.79/0.74 mm for translation in LR, AP, SI and 3D, respectively; The corresponding RMS of random errors (σ) were 0.97/0.98/0.96, 0.28/0.27/0.26, 0.77/0.77/0.72, and 0.85/0.87/0.85 mm. For all sub-regions, brain showed the smallest Σ and σ in 3D. Other sub-regions showed direction-dependent error patterns, but the positioning results were consistent, independent of the datasets used for registration. Conclusions A highly-accelerated 3D-MRI could be used for MR-guided HN radiotherapy without compromising position verification accuracy.
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Affiliation(s)
- Yihang Zhou
- Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, Hong Kong, China
| | - Oi Lei Wong
- Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, Hong Kong, China
| | - Kin Yin Cheung
- Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, Hong Kong, China
| | - Siu Ki Yu
- Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, Hong Kong, China
| | - Jing Yuan
- Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, Hong Kong, China
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27
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Eriksson E, Lysell J, Larsson H, Cheung KY, Filippini D, Mak WC. Geometric Flow Control Lateral Flow Immunoassay Devices (GFC-LFIDs): A New Dimension to Enhance Analytical Performance. Research (Wash D C) 2019; 2019:8079561. [PMID: 31549085 PMCID: PMC6750055 DOI: 10.34133/2019/8079561] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/18/2018] [Accepted: 05/13/2019] [Indexed: 01/14/2023]
Abstract
The nitrocellulose (NC) membrane based lateral flow immunoassay device (LFID) is one of the most important and widely used biosensor platforms for point-of-care (PoC) diagnostics. However, the analytical performance of LFID has limitations and its optimization is restricted to the bioassay chemistry, the membrane porosity, and the choice of biolabel system. These bottom neck technical issues resulted from the fact that the conventional LFID design principle has not evolved for many years, which limited the LFID for advanced biosensor applications. Here we introduce a new dimension for LFID design and optimization based on geometric flow control (GFC) of NC membranes, leading to highly sensitive GFC-LFID. This novel approach enables comprehensive flow control via different membrane geometric features such as the width (w) and the length (l) of a constriction, as well as its input angle (θ1) and output angle (θ2). The GFC-LFID (w=0.5 mm, l=7 mm, θ1= 60°, θ2= 45°) attained a 10-fold increase in sensitivity for detection of interleukin-6 (IL-6), compared with conventional LFID, whereas reducing by 10-fold the antibody consumption. The GFC-LFID detects IL-6 over a linear range of 0.1–10 ng/mL with a limit of detection (LoD) of 29 pg/mL, which even outperforms some commercial IL-6 LFIDs. Such significant improvement is attained by pure geometric control of the NC membrane, without additives, that only relaying on a simple high throughput laser ablation procedure suitable for integration on regular large-scale manufacturing of GFC-LFIDs. Our new development on GFC-LFID with the combination of facile scalable fabrication process, tailored flow control, improved analytical performance, and reduced antibodies consumption is likely to have a significant impact on new design concept for the LFID industry.
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Affiliation(s)
- E Eriksson
- Biosensors and Bioelectronics Centre, IFM-Linköping University, 58183 Linköping, Sweden
| | - J Lysell
- Biosensors and Bioelectronics Centre, IFM-Linköping University, 58183 Linköping, Sweden
| | - H Larsson
- Biosensors and Bioelectronics Centre, IFM-Linköping University, 58183 Linköping, Sweden
| | - K Y Cheung
- IKE-Linköping University, 58185 Linköping, Sweden
| | - D Filippini
- Optical Devices Laboratory, IFM-Linköping University, 58183 Linköping, Sweden
| | - W C Mak
- Biosensors and Bioelectronics Centre, IFM-Linköping University, 58183 Linköping, Sweden
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Yang B, Wong WKR, Lam WW, Geng H, Kong CW, Cheung KY, Yu SK. A novel method for monitoring the constancy of beam path accuracy in CyberKnife. J Appl Clin Med Phys 2019; 20:109-119. [PMID: 31004395 PMCID: PMC6523015 DOI: 10.1002/acm2.12585] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2018] [Revised: 03/18/2019] [Accepted: 03/23/2019] [Indexed: 11/24/2022] Open
Abstract
The aim of current work was to present a novel evaluation procedure implemented for checking the constancy of beam path accuracy of a CyberKnife system based on ArcCHECK. A tailor‐made Styrofoam with four implanted fiducial markers was adopted to enable the fiducial tracking during beam deliveries. A simple two‐field plan and an isocentric plan were created for determining the density override of ArcCHECK in MultiPlan and the constancy of beam path accuracy respectively. Correlation curves for all diodes involved in the study were obtained by analyzing the dose distributions calculated by MultiPlan after introducing position shifts in anteroposterior, superoinferior, and left–right directions. The ability of detecting systematic position error was also evaluated by changing the position of alignment center intentionally. The one standard deviation (SD) result for reproducibility test showed the RMS of 0.054 mm and the maximum of 0.263 mm, which was comparable to the machine self‐test result. The mean of absolute value of position errors in the constancy test was measured to 0.091 mm with a SD of 0.035 mm, while the root‐mean‐square was 0.127 mm with a SD of 0.034 mm. All introduced systematic position errors range from 0.3 to 2 mm were detected successfully. Efficient method for evaluating the constancy of beam path accuracy of CyberKnife has been developed and proven to be sensitive enough for detecting a systematic drift of robotic manipulator. Once the workflow is streamlined, our proposed method will be an effective and easy quality assurance procedure for medical physicists.
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Affiliation(s)
- Bin Yang
- Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, Hong Kong, Hong Kong
| | - Wing Kei Rebecca Wong
- Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, Hong Kong, Hong Kong
| | - Wai Wang Lam
- Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, Hong Kong, Hong Kong
| | - Hui Geng
- Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, Hong Kong, Hong Kong
| | - Chi Wah Kong
- Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, Hong Kong, Hong Kong
| | - Kin Yin Cheung
- Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, Hong Kong, Hong Kong
| | - Siu Ki Yu
- Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, Hong Kong, Hong Kong
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Yang B, Chiu TL, Law WK, Geng H, Lam WW, Leung TM, Yiu LH, Cheung KY, Yu SK. Performance evaluation of the CyberKnife system in real-time target tracking during beam delivery using a moving phantom coupled with two-dimensional detector array. Radiol Phys Technol 2019; 12:86-95. [PMID: 30604357 DOI: 10.1007/s12194-018-00495-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2018] [Revised: 12/16/2018] [Accepted: 12/19/2018] [Indexed: 10/27/2022]
Abstract
The aim of the current study was to evaluate the tracking error of the Synchrony Respiratory Tracking system by conducting beam-by-beam analyses to determine the variation in the tracking beams measured during target motion. A moving phantom of in-house design coupled with a two-dimensional (2D) detector array was used to simulate respiratory motion in the superoinferior (SI) and anteroposterior (AP) direction. A styrofoam block with four implanted fiducial markers was placed on top of the detector to enable the fiducial-based respiratory tracking. Measurements were performed with the phantom under either stationary mode or sinusoidal motion of 6-s cycle and 15/20-mm amplitude at SI and AP direction. The measurement data were saved as movie files that were used to calculate the center shift of the beam with 100-ms sampling time. The tracking accuracy of the system was defined as the targeting error, which could be tracked with probability of > 95% (Ep95). The mean ± standard deviation of Ep95 was 0.28 ± 0.08 mm under stationary condition; 0.66 ± 0.23 mm (range: 0.28-1.22 mm) under sinusoidal respiratory motion. The maximum drift of the beam center for all beam paths was 2.7 mm. The tracking accuracy of CyberKnife Synchrony system was successfully evaluated using a moving phantom and 2D detector array; the maximum tracking error was < 1.5 mm for sinusoidal motion of amplitude ≤ 20 mm.
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Affiliation(s)
- Bin Yang
- Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, 2 Village Road, Happy Valley, Hong Kong, China.
| | - Tin Lok Chiu
- Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, 2 Village Road, Happy Valley, Hong Kong, China
| | - Wai Kong Law
- Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, 2 Village Road, Happy Valley, Hong Kong, China
| | - Hui Geng
- Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, 2 Village Road, Happy Valley, Hong Kong, China
| | - Wai Wang Lam
- Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, 2 Village Road, Happy Valley, Hong Kong, China
| | - Tat Ming Leung
- Biomedical Engineering Department, Hong Kong Sanatorium & Hospital, 2 Village Road, Happy Valley, Hong Kong, China
| | - Lok Hang Yiu
- Biomedical Engineering Department, Hong Kong Sanatorium & Hospital, 2 Village Road, Happy Valley, Hong Kong, China
| | - Kin Yin Cheung
- Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, 2 Village Road, Happy Valley, Hong Kong, China
| | - Siu Ki Yu
- Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, 2 Village Road, Happy Valley, Hong Kong, China
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Zhou Y, Yuan J, Wong OL, Fung WWK, Cheng KF, Cheung KY, Yu SK. Assessment of positional reproducibility in the head and neck on a 1.5-T MR simulator for an offline MR-guided radiotherapy solution. Quant Imaging Med Surg 2018; 8:925-935. [PMID: 30505721 DOI: 10.21037/qims.2018.10.03] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Background Recently, a shuttle-based offline magnetic resonance-guided radiotherapy (MRgRT) approach was proposed. This study aims to evaluate the positional reproducibility in the immobilized head and neck using a 1.5-T MR-simulator (MR-sim) on healthy volunteers. Methods A total of 159 scans of 14 healthy volunteers were conducted on a 1.5-T MR-sim with thermoplastic mask immobilization. MR images with isotropic 1.053 mm3 voxel size were rigidly registered to the first scan based on fiducial, anatomical and gross positions. Mean and standard deviation of positional displacements in translation and rotation were assessed. Systematic error and random errors of positioning in the head and neck on the MR-sim were determined in the translation of, and in the rotation of roll, pitch and yaw. Results The systematic error (Σ) of translation in left-right (LR), anterior-posterior (AP) and superior-inferior (SI) direction was 0.57, 0.22 and 0.26 mm for fiducial displacement, 0.28, 0.10 and 0.52 mm for anatomical displacement, and 0.53, 0.22 and 0.49 mm for gross displacement, respectively. The random error (σ) in corresponding translation direction was 2.07, 0.54 and 1.32 mm for fiducial displacement, 1.34, 0.73 and 2.04 mm for anatomical displacement, and 2.24, 0.86 and 2.61 mm for gross displacement. The systematic error and random error of rotation were generally smaller than 1°. Conclusions Our results suggested that high gross positional reproducibility (<1 mm translational and <1° rotational systematic error) could be achieved on an MR-sim for the proposed offline MRgRT.
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Affiliation(s)
- Yihang Zhou
- Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, Hong Kong, China
| | - Jing Yuan
- Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, Hong Kong, China
| | - Oi Lei Wong
- Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, Hong Kong, China
| | - Winky Wing Ki Fung
- Department of Radiotherapy, Hong Kong Sanatorium & Hospital, Hong Kong, China
| | - Ka Fai Cheng
- Department of Radiotherapy, Hong Kong Sanatorium & Hospital, Hong Kong, China
| | - Kin Yin Cheung
- Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, Hong Kong, China
| | - Siu Ki Yu
- Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, Hong Kong, China
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Mak WC, Magne B, Cheung KY, Atanasova D, Griffith M. Thermo-rheological responsive microcapsules for time-dependent controlled release of human mesenchymal stromal cells. Biomater Sci 2018; 5:2241-2250. [PMID: 28972602 DOI: 10.1039/c7bm00663b] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Human mesenchymal stromal cells (hMSCs) are adult-source cells that have been extensively evaluated for cell-based therapies. hMSCs delivered by intravascular injection have been reported to accumulate at the sites of injury to promote tissue repair and can also be employed as vectors for the delivery of therapeutic genes. However, the full potential of hMSCs remains limited as the cells are lost after injection due to anoikis and the adverse pathologic environment. Encapsulation of cells has been proposed as a means of increasing cell viability. However, controlling the release of therapeutic cells over time to target tissue still remains a challenge today. Here, we report the design and development of thermo-rheological responsive hydrogels that allow for precise, time dependent controlled-release of hMSCs. The encapsulated hMSCs retained good viability from 76% to 87% dependent upon the hydrogel compositions. We demonstrated the design of different blended hydrogel composites with modulated strength (S parameter) and looseness of hydrogel networks (N parameter) to control the release of hMSCs from thermo-responsive hydrogel capsules. We further showed the feasibility for controlled-release of encapsulated hMSCs within 3D matrix scaffolds. We reported for the first time by a systematic analysis that there is a direct correlation between the thermo-rheological properties associated with the degradation of the hydrogel composite and the cell release kinetics. This work therefore provides new insights into the further development of smart carrier systems for stem cell therapy.
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Affiliation(s)
- W C Mak
- Department of Clinical and Experimental Medicine, Linköping University, SE58185, Linköping, Sweden.
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Yang B, Geng H, Ding Y, Kong CW, Cheung CW, Chiu TL, Lam WW, Cheung KY, Yu SK. Development of a novel methodology for QA of respiratory-gated and VMAT beam delivery using Octavius 4D phantom. Med Dosim 2018; 44:83-90. [PMID: 29602598 DOI: 10.1016/j.meddos.2018.02.008] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2017] [Revised: 12/28/2017] [Accepted: 02/15/2018] [Indexed: 11/26/2022]
Abstract
The objective of this study was to develop and evaluate a series of quality assurance (QA) techniques based on Octavius 4D phantom for testing of respiratory-gated treatment delivery, integrity of dose rate vs gantry speed in volumetric-modulated arc therapy (VMAT) commissioning, and multileaf collimator (MLC) positioning accuracy of a linear accelerator. An Octavius 4D phantom capable of rotating with the gantry and recording the detector signal with a sampling rate of 10 Hz was isocentrally set up and an inclinometer was also installed to measure the gantry angle simultaneously. A simple arc test was created and delivered with gating function activated to measure the timing accuracy of the gating window. A tailor-made dose rate vs gantry speed plan was also designed to test the accuracy of measured dose rate, gantry speed, and actual control points. All experiments were conducted while machine log files were collected for comparison. The variations of beam flatness, symmetry, and field size were analyzed as a function of gantry angle to evaluate the influence from the modulation of dose rate and gantry speed. MLC position accuracy was evaluated based on specific garden fence plans. The time of gating window was measured to be less than 10-millisecond deviation from the log data. Gantry backlash was observed and quantified to be 1.72° with an extra stabilization time of 1.16 seconds for a gating arc with gantry speed of 6°/s. In the dose rate vs gantry speed test, the mean deviation between measured gantry angle and log data was less than 0.2° after a time delay of 0.25 second was corrected. The measured dose rate agreed with the log data very well with a mean deviation of 0.05%, and even the transit of modulation was tracked successfully. There was a statistically significant difference on the variation of beam parameters between a VMAT plan and a simple arc plan. The induced MLC position errors were detected with an accuracy of 0.05 mm. The leaf position reproducibility was found to be better than 0.02 mm, whereas the routine MLC position accuracy was better than 0.1 mm. A time-resolved method using Octavius 4D phantom has been developed and proven to be convenient for respiratory gating QA, dose rate vs gantry speed test, and MLC QA. Gating time, dose rate, and gantry speed-induced leave position error could be directly measured with high accuracy after comparison with the machine log data. This study also highlights the capability of the phantom in quantifying the variation of flatness, symmetry, and field size during gantry rotation.
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Affiliation(s)
- Bin Yang
- Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, 2 Village Road, Happy Valley, Hong Kong.
| | - Hui Geng
- Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, 2 Village Road, Happy Valley, Hong Kong
| | - Ying Ding
- Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, 2 Village Road, Happy Valley, Hong Kong
| | - Chi Wah Kong
- Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, 2 Village Road, Happy Valley, Hong Kong
| | - Chi Wai Cheung
- Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, 2 Village Road, Happy Valley, Hong Kong
| | - Tin Lok Chiu
- Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, 2 Village Road, Happy Valley, Hong Kong
| | - Wai Wang Lam
- Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, 2 Village Road, Happy Valley, Hong Kong
| | - Kin Yin Cheung
- Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, 2 Village Road, Happy Valley, Hong Kong
| | - Siu Ki Yu
- Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, 2 Village Road, Happy Valley, Hong Kong
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Abstract
OBJECTIVES Using both clinical parameters and subjective measures of oral health, this study aimed to identify useful oral health indicators for the risk of malnutrition in elders. DESIGN Cross-sectional study. SETTING Five community centers run by non-government organizations (NGOs). PARTICIPANTS 195 community dwelling elders (65 or above). MEASUREMENTS An interviewer-administered questionnaire was completed to collect information on elders' socio-demographic background and oral health perception and practice. Their number of teeth, number of occluding tooth pairs, dental caries, and periodontal condition were examined. General Oral Health Assessment Index (GOHAI), an instrument for assessing oral health related quality of life (OHQoL), was used as a subjective measure of oral health. The elders' nutritional status was evaluated by using the Mini-Nutritional Assessment (MNA). RESULTS The mean (SD) DFT was 3.3 (3.1). Over 60% of elders had periodontal pockets; 33% had fewer than 20 teeth and 6% were edentulous. The mean (SD) of occluding tooth pairs was 7.1 (4.8). The mean (SD) total GOHAI score was 56.4 (8.0); 60% reported negative impact of oral health on their quality of life. The mean (SD) MNA score was 25.0 (2.9); 30% had malnutrition or were at risk. After controlling for socio-demographic factors, none of the clinical indicators (dental caries, periodontal status, number of teeth, and number of occluding tooth pairs) were associated with risk of malnutrition (all p>0.05). Poorer OHQoL indicated a higher chance for malnutrition in both adjusted models (OR of 0.914; 95% CI of 0.850-0.982; p=0.014 and OR of 0.915; 95% CI of 0.852-0.984; p=0.017). Tooth loss and untreated decayed teeth (DT) were significant/marginally significant determinants of poor OHQoL. CONCLUSION Elders' tooth loss and unmet treatment need for dental caries were associated with compromised quality of life, which indicated increased likelihood for malnutrition.
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Affiliation(s)
- L L Wu
- Dr. Xiaoli Gao, Dental Public health, Faculty of Dentistry, The University of Hong Kong, 3rd Floor, Prince Philip Dental Hospital, 34 Hospital Road, Sai Ying Pun, Hong Kong, ;
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Chung KL, Cheung KY, Kam CW. Differential Diagnosis of Acute Calf Pain and Swelling with Emergency Ultrasound. HONG KONG J EMERG ME 2017. [DOI: 10.1177/102490790501200106] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Acute calf pain and swelling are common causes of emergency department attendance. Differential diagnoses may mimic each other causing confusion and uncertainty in management. With emergency ultrasound, most of the differential diagnoses for acute calf pain and swelling can be identified with confidence. We present two cases of calf pain and swelling utilising ultrasound to clarify the diagnosis.
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Wong OL, Yuan J, Yu SK, Cheung KY. Image quality assessment of a 1.5T dedicated magnetic resonance-simulator for radiotherapy with a flexible radio frequency coil setting using the standard American College of Radiology magnetic resonance imaging phantom test. Quant Imaging Med Surg 2017; 7:205-214. [PMID: 28516046 DOI: 10.21037/qims.2017.02.08] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
BACKGROUND A flexible RF coil setting has to be used on an MR-simulator (MR-sim) in the head and neck simulation scan for radiotherapy (RT) purpose, while the image quality might be compromised due to the sub-optimized flexible coil compared to the normal diagnostic radiological (DR) head coil. In this study, we assessed the image quality of an MR-sim by conducting the standard American College of Radiology (ACR) MRI phantom test on a 1.5T MR-sim under RT-setting and comparing it to DR-setting. METHODS A large ACR MRI phantom was carefully positioned, aligned and scanned 9 times for each under RT- and DR-setting on a 1.5T MR-sim, following the ACR scanning instruction. Images were analyzed following the ACR guidance. Measurement results under two coil settings were quantitatively compared. Inter-observer disagreements under RT-setting between two physicists were compared using Bland-Altman (BA) analysis and intra-class correlation coefficient (ICC). RESULTS The MR-sim with RT-setting obtained sufficiently good image quality to pass all ACR recommended criteria. No significant difference was found in phantom length accuracy, high-contrast spatial resolution, slice thickness accuracy, slice position accuracy, and percent-signal ghosting. RT-setting significantly under-performed in low-contrast object detectability, while better performed in image intensity uniformity. BA analysis showed that 95% limit of agreement and biases of phantom test measurement under RT-setting between two observers were very small. Excellent inter-observer agreement (ICC >0.75) was achieved in all measurements except for slice thickness accuracy (ICC =0.42, moderate agreement) under RT-setting. CONCLUSIONS Very good and highly reproducible image quality could be achieved on a 1.5T MR-sim with a flexible coil setting as revealed by the standard ACR MRI phantom test. The flexible RT-setting compromised in image signal-to-noise ratio (SNR) compared to the normal DR-setting, and resulted in reduced low-contrast object detectability.
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Affiliation(s)
- Oi Lei Wong
- Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, Happy Valley, Hong Kong, Hong Kong SAR, China
| | - Jing Yuan
- Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, Happy Valley, Hong Kong, Hong Kong SAR, China
| | - Siu Ki Yu
- Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, Happy Valley, Hong Kong, Hong Kong SAR, China
| | - Kin Yin Cheung
- Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, Happy Valley, Hong Kong, Hong Kong SAR, China
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Cheung KY. Systems medicine for the delivery of better healthcare Services- International Union for Physical and Engineering Sciences (IUPESM) perspective. Health Technol 2017. [DOI: 10.1007/s12553-016-0164-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Yang B, Wong WKR, Geng H, Lam WW, Ho YW, Kwok WM, Cheung KY, Yu SK. Filmless methods for quality assurance of Tomotherapy using ArcCHECK. Med Phys 2017; 44:7-16. [PMID: 28044341 DOI: 10.1002/mp.12009] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2016] [Revised: 10/15/2016] [Accepted: 11/08/2016] [Indexed: 11/07/2022] Open
Abstract
PURPOSE Tomotherapy delivers an intensity-modulated radiation therapy (IMRT) treatment by the synchronization of gantry rotation, multileaf collimator (MLC), and couch movement. This dynamic nature makes the quality assurance (QA) important and challenging. The purpose of this study is to develop some methodologies using an ArcCHECK for accurate QA measurements of the gantry angle and speed, MLC synchronization and leaf open time, couch translation per gantry rotation, couch speed and uniformity, and constancy of longitudinal beam profile for a Tomotherapy unit. METHODS Four test plans recommended by AAPM Task Group 148 (TG148) and the manufacturer were chosen for this study. Helical and static star shot tests are used for checking the leaves opened at the expected gantry angles. Another helical test is to verify the couch traveled the expected distance per gantry rotation. The final test is for checking the couch speed constancy with a static gantry. ArcCHECK can record the detector signal every 50 ms as a movie file, and has a virtual inclinometer for gantry angle measurement. These features made the measurement of gantry angle and speed, MLC synchronization and leaf open time, and longitudinal beam profile possible. A shaping parameter was defined for facilitating the location of the beam center during the plan delivery, which was thereafter used to calculate the couch translation per gantry rotation and couch speed. The full width at half maximum (FWHM) was calculated for each measured longitudinal beam profile and then used to evaluate the couch speed uniformity. Furthermore, a mean longitudinal profile was obtained for constancy check of field width. The machine trajectory log data were also collected for comparison. Inhouse programs were developed in MATLAB to process both the ArcCHECK and machine log data. RESULTS The deviation of our measurement results from the log data for gantry angle was calculated to be less than 0.4°. The percentage differences between measured and planned leaf open time were found to be within 0.5% in all the tests. Our results showed mean values of MLC synchronization of 0.982, 0.983, and 0.995 at static gantry angle 0°, 45°, and 135°, respectively. The mean value of measured couch translation and couch speed by ArcCHECK had less than 0.1% deviation from the planned values. The variation in the value of FWHM suggested the couch speed uniformity was better than 1%. The mean of measured longitudinal profiles was suitable for constancy check of field width. CONCLUSION Precise and efficient methods for measuring the gantry angle and speed, leaf open time, couch translation per gantry rotation, couch speed and uniformity, and constancy of longitudinal beam profile of Tomotherapy using ArcCHECK have been developed and proven to be accurate compared with machine log data. Estimation of the Tomotherapy binary MLC leaf open time is proven to be precise enough to verify the leaf open time as small as 277.8 ms. Our method also makes the observation and quantification of the synchronization of leaves possible.
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Affiliation(s)
- B Yang
- Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, 2 Village Road, Happy Valley, Hong Kong
| | - W K R Wong
- Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, 2 Village Road, Happy Valley, Hong Kong
| | - H Geng
- Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, 2 Village Road, Happy Valley, Hong Kong
| | - W W Lam
- Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, 2 Village Road, Happy Valley, Hong Kong
| | - Y W Ho
- Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, 2 Village Road, Happy Valley, Hong Kong
| | - W M Kwok
- Biomedical Engineering Department, Hong Kong Sanatorium & Hospital, 2 Village Road, Happy Valley, Hong Kong
| | - K Y Cheung
- Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, 2 Village Road, Happy Valley, Hong Kong
| | - S K Yu
- Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, 2 Village Road, Happy Valley, Hong Kong
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Yang B, Geng H, Kong CW, Lam WW, Cheung KY, Yu SK. Dose rate versus gantry speed test in RapidArc commissioning: a feasibility study using ArcCHECK. Biomed Phys Eng Express 2016. [DOI: 10.1088/2057-1976/aa5196] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Hui AT, Lam YO, Chan CK, Cheung KY, Fung BH, Ng PW. A case of refractory seizure with cognitive impairment due to anti-GABA encephalitis. Hong Kong Med J 2016; 22:509-11. [PMID: 27738301 DOI: 10.12809/hkmj154604] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
Affiliation(s)
- A Th Hui
- Department of Medicine and Geriatrics, United Christian Hospital, Kwun Tong, Hong Kong
| | - Y O Lam
- Department of Medicine and Geriatrics, United Christian Hospital, Kwun Tong, Hong Kong
| | - C K Chan
- Department of Medicine and Geriatrics, United Christian Hospital, Kwun Tong, Hong Kong
| | - K Y Cheung
- Department of Medicine and Geriatrics, United Christian Hospital, Kwun Tong, Hong Kong
| | - B H Fung
- Department of Medicine and Geriatrics, United Christian Hospital, Kwun Tong, Hong Kong
| | - P W Ng
- Department of Medicine and Geriatrics, United Christian Hospital, Kwun Tong, Hong Kong
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Choi HHF, Leung TM, Chiu TL, Yang B, Wu PM, Cheung KY, Yu SK. SU-E-T-534: Level of Residual Radioactivity of Activated Parts of a Decommissioned Cyclotron. Med Phys 2015. [DOI: 10.1118/1.4924896] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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Choi HHF, Ho JPY, Yang B, Cheung KY, Yu SK. Technical note: Correlation between TQA data trends and TomoHD functional status. J Appl Clin Med Phys 2014; 15:4548. [PMID: 24710441 PMCID: PMC5875464 DOI: 10.1120/jacmp.v15i2.4548] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2013] [Revised: 11/04/2013] [Accepted: 10/07/2013] [Indexed: 11/29/2022] Open
Abstract
TomoTherapy Quality Assurance (TQA) is a software package developed to monitor certain aspects of machine performance. In this study, the TQA quantities or data trends most effective in monitoring energy drifts and magnetron stability were determined respectively. This retrospective study used data collected from three TomoHD units. The TQA modules investigated were Step‐Wedge Helical, Step‐Wedge Static, and Basic Dosimetry. First, the TQA quantities correlated with energy changes (|r|>0.85, where r is the Pearson's correlation coefficient) were found. The corresponding sensitivities to percentage depth dose (PDD) ratio changes were then calculated and compared. Second, the pulse‐by‐pulse dose stability was compared before and after each magnetron replacement using a nonparametric comparison test (Welch's t‐test), and the raw dose profiles were surveyed. In this study, exit detector flatness obtained in Basic Dosimetry was shown to be the most sensitive (r=0.945) to energy changes, followed by the energy differences in Step‐Wedge Static (r=0.942) and Step‐Wedge Helical (r=0.898). The three quantities could detect a PDD ratio change of 5.1×10−4,5.4×10−4, and 7.1×10−4, respectively. Pulse‐by‐Pulse Dose1 from Basic Dosimetry over a one‐week period before and after a magnetron replacement showed a significant difference (p<0.05) in only three of the nine instances. On the other hand, a raw output profile free from discontinuities, frequent dropped pulses and abnormal spikes was found to indicate that the magnetron would continue to function normally for a week 89% of the time. PACS numbers: 87.56.bd, 87.56.Fc, 84.40.Fe
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Cheung KY, Damilakis J. Message from the IOMP President, Dr. Kin Yin Cheung and the Chairman of the IOMP Education and Training Committee, Prof. John Damilakis on November 7, 2013: "International Day of Medical Physics". J Biomed Phys Eng 2013; 3:113-4. [PMID: 25505756 PMCID: PMC4204507] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2013] [Accepted: 11/24/2013] [Indexed: 11/25/2022]
Affiliation(s)
| | - J Damilakis
- The chairman of the IOMP Education and Training Committee
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Cheung KY. Status of Medical Physics in Asia Pacific Region. Med Phys 2013. [DOI: 10.1118/1.4815413] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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Meghzifene A, do Carmo Lopes M, Cheung KY, Constantinou C, Andreo P, Brandan ME, Castellanos ME, Ige TA, Frey GH. IAEA contribution to international harmonization of guidelines for clinical medical radiation physicists. Med Phys 2013. [DOI: 10.1118/1.4815410] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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Meghzifene A, Vano E, Le Heron J, Cheung KY. Roles and responsibilities of medical physicists in radiation protection. Eur J Radiol 2010; 76:24-7. [PMID: 20851545 DOI: 10.1016/j.ejrad.2010.06.035] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2010] [Accepted: 06/15/2010] [Indexed: 10/19/2022]
Affiliation(s)
- Ahmed Meghzifene
- International Atomic Energy Agency, Division of Human Health, Vienna, Austria.
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Cheung KY, Dunn ELW. A medium-term follow-up study of a cohort of Chinese patients after first hospitalisation in a gazetted hospital for mania. East Asian Arch Psychiatry 2010; 20:15-22. [PMID: 22351806] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
OBJECTIVES To study the characteristics of a cohort of first-episode manic patients treated in a regional psychiatric unit in Hong Kong, to explore the predictors of re-admission, and to investigate their functional outcomes 4 years after first hospitalisation. METHODS This was a medium-term follow-up study, using retrospective review of hospital records and clinical interviews at follow-up. Forty-four Chinese patients diagnosed as having their first-episode mania were discharged from a gazetted psychiatric ward in Hong Kong between January 1999 and June 2002. Their clinical characteristics on admission and prescribed medications on discharge were investigated. Their re-admission status was charted. The patients were contacted for follow-up assessment of their functional outcome at 4 years after their first hospitalisation. RESULTS In our cohort of 44 patients, their first-episode mania mostly presented in young adulthood, as significantly disturbed behaviour deemed to require compulsory admission. Nineteen (43%) of the patients were re-admitted at least once within 4 years of being discharged, 6 of whom were re-admitted more than once. Compulsory admission at the first-episode mania predicted future re-admission. Alcohol and substance abuse were associated with earlier re-admission after the first-episode mania. None of the patients died. For those who were reassessed (28 patients), most lived with family members. In all, 21 patients were able to sustain open employment at 4 years after discharge. About half (n = 14) of the traceable patients were able to continue in full-time employment at 4 years, while 7 were doing part-time work. The median Global Assessment of Functioning score of the traceable group was 88. CONCLUSION The results of this local study on patients with their first-episode of hospitalisation for mania were comparable to findings reported in western studies.
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Affiliation(s)
- K Y Cheung
- Department of Psychiatry, Pamela Youde Nethersole Eastern Hospital, 3 Lok Man Road, Chai Wan, Hong Kong.
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Chan APH, Sieh KM, Leung SM, Cheung KY, Fung KY. Extracorporeal Foley catheter spring device mimicking an intervertebral foreign body in transforaminal lumbar interbody fusion surgery. Hong Kong Med J 2009; 15:397-398. [PMID: 19801702] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/28/2023] Open
Affiliation(s)
- Alexander P H Chan
- Department of Orthopaedics and Traumatology, Alice Ho Miu Ling Nethersole Hospital, Tai Po, Hong Kong
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Kron T, Cheung KY, Dai J, Ravindran P, Soejoko D, Inamura K, Song JY, Bold L, Srivastava R, Rodriguez L, Wong TJ, Kumara A, Lee CC, Krisanachinda A, Nguyen XC, Ng KH. Medical physics aspects of cancer care in the Asia Pacific region. Biomed Imaging Interv J 2008; 4:e33. [PMID: 21611001 PMCID: PMC3097731 DOI: 10.2349/biij.4.3.e33] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2008] [Accepted: 06/17/2008] [Indexed: 11/17/2022] Open
Abstract
Medical physics plays an essential role in modern medicine. This is particularly evident in cancer care where medical physicists are involved in radiotherapy treatment planning and quality assurance as well as in imaging and radiation protection. Due to the large variety of tasks and interests, medical physics is often subdivided into specialties such as radiology, nuclear medicine and radiation oncology medical physics. However, even within their specialty, the role of radiation oncology medical physicists (ROMPs) is diverse and varies between different societies. Therefore, a questionnaire was sent to leading medical physicists in most countries/areas in the Asia/Pacific region to determine the education, role and status of medical physicists.Answers were received from 17 countries/areas representing nearly 2800 radiation oncology medical physicists. There was general agreement that medical physicists should have both academic (typically at MSc level) and clinical (typically at least 2 years) training. ROMPs spent most of their time working in radiotherapy treatment planning (average 17 hours per week); however radiation protection and engineering tasks were also common. Typically, only physicists in large centres are involved in research and teaching. Most respondents thought that the workload of physicists was high, with more than 500 patients per year per physicist, less than one ROMP per two oncologists being the norm, and on average, one megavoltage treatment unit per medical physicist.There was also a clear indication of increased complexity of technology in the region with many countries/areas reporting to have installed helical tomotherapy, IMRT (Intensity Modulated Radiation Therapy), IGRT (Image Guided Radiation Therapy), Gamma-knife and Cyber-knife units. This and the continued workload from brachytherapy will require growing expertise and numbers in the medical physics workforce. Addressing these needs will be an important challenge for the future.
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Affiliation(s)
- T Kron
- Physical Sciences, Peter MacCallum Cancer Centre, and RMIT University, Melbourne, Australia
| | - KY Cheung
- Department of Clinical Oncology, Prince of Wales Hospital, Hong Kong, China
| | - J Dai
- Cancer Institute (Hospital), Chinese Academy of Medical Sciences, China
| | - P Ravindran
- Department of Radiation Oncology, Christian Medical College, Vellore, India
| | - D Soejoko
- Physics Department, University of Indonesia, Jakarta, Indonesia
| | - K Inamura
- Dept of Radiology & Medical Engineering, Kansai University of International Studies, Hyogo, Japan
| | - JY Song
- Department of Radiation Oncology, Chonnam National University Hospital, Republic of Korea
| | - L Bold
- Radiotherapy Department, National Cancer Center, Ulaanbaatar, Mongolia
| | - R Srivastava
- B.P.Koirala Memorial Cancer Hospital, Bharatpur, Chitwan, Nepal
| | - L Rodriguez
- Department of Radiation Oncology, Jose R. Reyes Memorial Medical Center, Manila, Philippines
| | - TJ Wong
- Department of Therapeutic Radiology, National Cancer Centre, Singapore
| | - A Kumara
- Division of Medical Physics, National Cancer Institute, Sri Lanka
| | - CC Lee
- Department of Medical Imaging and Radiological Sciences, Chang Gung University, Taiwan
| | - A Krisanachinda
- Department of Radiology, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand
| | - XC Nguyen
- K Hospital, National Cancer Institute, Hanoi, Vietnam
| | - KH Ng
- Department of Biomedical Imaging, University of Malaya, and Medical Physics Unit, University of Malaya Medical Centre, Kuala Lumpur, Malaysia
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Wong SKH, Chiu PWY, Leung SF, Cheung KY, Chan ACW, Au-Yeung ACM, Griffith JF, Chung SSC, Ng EKW. Concurrent chemoradiotherapy or endoscopic stenting for advanced squamous cell carcinoma of esophagus: a case-control study. Ann Surg Oncol 2007; 15:576-82. [PMID: 18057993 DOI: 10.1245/s10434-007-9679-y] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2007] [Revised: 09/12/2007] [Accepted: 09/12/2007] [Indexed: 12/17/2022]
Abstract
BACKGROUND We evaluated the role of chemoradiotherapy (CRT) for patients with inoperable squamous esophageal cancer. METHODS Patients with locally advanced or metastatic squamous esophageal carcinoma who received CRT were recruited. The CRT consists of continuous infusion of 5-fluorouracil at 200 mg/m(2)/day, and cisplatin at 60 mg/m(2) on days 1 and 22, with concurrent radiotherapy for a total of 50 to 60 Gy in 25 to 30 fractions over 6 weeks. Efficacy was assessed by endoscopy and computed tomographic scan before and 8 weeks after completion of the treatment program. Median survival and the need for palliative esophageal stenting were compared with another group of patients who received endoscopic stenting. RESULTS From 1996 to 2003, a total of 36 consecutive patients (33 male, mean +/- SD age 63.2 +/- 9.5 years) with T4 disease (81%) with or without cervical nodal metastasis (50%) received CRT, while 36 patients treated with endoscopic stenting alone were recruited as controls. Both groups were comparable in demographics, pretreatment dysphagia score, comorbidities, and tumor characteristics. CRT was completed in 32 patients (89%). There was no treatment-related mortality. Tumor volume was greatly reduced after CRT in 19 patients. Four patients (11%) received salvage esophagectomy 9 to 42 months after CRT. Compared with the stenting group, CRT statistically significantly improved 5-year survival (15% vs. 0%, P = .01), median survival (10.8 months vs. 4.0 months, P < .005), and need for stenting (22% vs. 100%, P = .005). CONCLUSIONS Palliative CRT can effectively improve the symptoms of dysphagia in patients with inoperable squamous esophageal carcinoma. It results in better survival compared with endoscopic stenting in these patients.
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Affiliation(s)
- Simon K H Wong
- Department of Surgery, Prince of Wales Hospital, The Chinese University of Hong Kong, Hong Kong, China
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50
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Chau MC, Leung SF, Kam KM, Cheung KY, Kwan WH, Yu KH, Chiu KW, Chan TC. Feasibility of using interpolated contours of targets and organs at risk in intensity-modulated radiation therapy treatment planning for advanced-stage nasopharyngeal carcinoma. ACTA ACUST UNITED AC 2007; 51:480-4. [PMID: 17803802 DOI: 10.1111/j.1440-1673.2007.01874.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
To assess the dosimetric effect of using interpolated contours in planning intensity-modulated radiation therapy (IMRT) for advanced T-stage nasopharyngeal carcinoma. The present study focused on T3-T4 tumours where the proximity of targets to neurological organs poses a stringent test on the feasibility of such an approach. Contours of targets and organs were delineated on CT images of 2.5-mm interval and a reference IMRT plan was generated. An investigative (INV) IMRT plan was then generated with the same planning protocol, but based on interpolated contours that replaced deleted contours on alternate slices. The reference and INV plans were compared. Regarding target coverage, all targets in the INV plans met the acceptance criteria except for the PTV in one case. Regarding organs, the mean dose to 1% volume of the brainstem and spinal cord in the INV plans were kept below their dose limits. No significant differences in the mean doses to others organs were found. Satisfactory target coverage and protection of critical organs to a degree similar to full-scale contouring could be achieved with use of interpolated contours. The saving in manpower time for contouring is expected to significantly improve the throughput of the IMRT planning process.
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Affiliation(s)
- M C Chau
- Department of Clinical Oncology, Prince of Wales Hospital, Shatin, Hong Kong SAR.
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