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Liu Z, Moon HS, Li Z, Laforest R, Perlmutter JS, Norris SA, Jha AK. A tissue‐fraction estimation‐based segmentation method for quantitative dopamine transporter SPECT. Med Phys 2022; 49:5121-5137. [PMID: 35635327 PMCID: PMC9703616 DOI: 10.1002/mp.15778] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2022] [Revised: 04/25/2022] [Accepted: 05/16/2022] [Indexed: 11/09/2022] Open
Abstract
BACKGROUND Quantitative measures of dopamine transporter (DaT) uptake in caudate, putamen, and globus pallidus (GP) derived from dopamine transporter-single-photon emission computed tomography (DaT-SPECT) images have potential as biomarkers for measuring the severity of Parkinson's disease. Reliable quantification of this uptake requires accurate segmentation of the considered regions. However, segmentation of these regions from DaT-SPECT images is challenging, a major reason being partial-volume effects (PVEs) in SPECT. The PVEs arise from two sources, namely the limited system resolution and reconstruction of images over finite-sized voxel grids. The limited system resolution results in blurred boundaries of the different regions. The finite voxel size leads to TFEs, that is, voxels contain a mixture of regions. Thus, there is an important need for methods that can account for the PVEs, including the TFEs, and accurately segment the caudate, putamen, and GP, from DaT-SPECT images. PURPOSE Design and objectively evaluate a fully automated tissue-fraction estimation-based segmentation method that segments the caudate, putamen, and GP from DaT-SPECT images. METHODS The proposed method estimates the posterior mean of the fractional volumes occupied by the caudate, putamen, and GP within each voxel of a three-dimensional DaT-SPECT image. The estimate is obtained by minimizing a cost function based on the binary cross-entropy loss between the true and estimated fractional volumes over a population of SPECT images, where the distribution of true fractional volumes is obtained from existing populations of clinical magnetic resonance images. The method is implemented using a supervised deep-learning-based approach. RESULTS Evaluations using clinically guided highly realistic simulation studies show that the proposed method accurately segmented the caudate, putamen, and GP with high mean Dice similarity coefficients of ∼ 0.80 and significantly outperformed ( p < 0.01 $p < 0.01$ ) all other considered segmentation methods. Further, an objective evaluation of the proposed method on the task of quantifying regional uptake shows that the method yielded reliable quantification with low ensemble normalized root mean square error (NRMSE) < 20% for all the considered regions. In particular, the method yielded an even lower ensemble NRMSE of ∼ 10% for the caudate and putamen. CONCLUSIONS The proposed tissue-fraction estimation-based segmentation method for DaT-SPECT images demonstrated the ability to accurately segment the caudate, putamen, and GP, and reliably quantify the uptake within these regions. The results motivate further evaluation of the method with physical-phantom and patient studies.
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Affiliation(s)
- Ziping Liu
- Department of Biomedical Engineering Washington University St. Louis MO 63130 United States of America
| | - Hae Sol Moon
- Department of Biomedical Engineering Washington University St. Louis MO 63130 United States of America
| | - Zekun Li
- Department of Biomedical Engineering Washington University St. Louis MO 63130 United States of America
| | - Richard Laforest
- Mallinckrodt Institute of Radiology Washington University School of Medicine St. Louis MO 63110 United States of America
| | - Joel S. Perlmutter
- Mallinckrodt Institute of Radiology Washington University School of Medicine St. Louis MO 63110 United States of America
- Department of Neurology Washington University School of Medicine St. Louis MO 63110 United States of America
| | - Scott A. Norris
- Mallinckrodt Institute of Radiology Washington University School of Medicine St. Louis MO 63110 United States of America
- Department of Neurology Washington University School of Medicine St. Louis MO 63110 United States of America
| | - Abhinav K. Jha
- Department of Biomedical Engineering Washington University St. Louis MO 63130 United States of America
- Mallinckrodt Institute of Radiology Washington University School of Medicine St. Louis MO 63110 United States of America
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EANM dosimetry committee recommendations for dosimetry of 177Lu-labelled somatostatin-receptor- and PSMA-targeting ligands. Eur J Nucl Med Mol Imaging 2022; 49:1778-1809. [PMID: 35284969 PMCID: PMC9015994 DOI: 10.1007/s00259-022-05727-7] [Citation(s) in RCA: 68] [Impact Index Per Article: 34.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2021] [Accepted: 02/13/2022] [Indexed: 12/25/2022]
Abstract
The purpose of the EANM Dosimetry Committee is to provide recommendations and guidance to scientists and clinicians on patient-specific dosimetry. Radiopharmaceuticals labelled with lutetium-177 (177Lu) are increasingly used for therapeutic applications, in particular for the treatment of metastatic neuroendocrine tumours using ligands for somatostatin receptors and prostate adenocarcinoma with small-molecule PSMA-targeting ligands. This paper provides an overview of reported dosimetry data for these therapies and summarises current knowledge about radiation-induced side effects on normal tissues and dose-effect relationships for tumours. Dosimetry methods and data are summarised for kidneys, bone marrow, salivary glands, lacrimal glands, pituitary glands, tumours, and the skin in case of radiopharmaceutical extravasation. Where applicable, taking into account the present status of the field and recent evidence in the literature, guidance is provided. The purpose of these recommendations is to encourage the practice of patient-specific dosimetry in therapy with 177Lu-labelled compounds. The proposed methods should be within the scope of centres offering therapy with 177Lu-labelled ligands for somatostatin receptors or small-molecule PSMA.
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Kennedy J, Chicheportiche A, Keidar Z. Quantitative SPECT/CT for dosimetry of peptide receptor radionuclide therapy. Semin Nucl Med 2021; 52:229-242. [PMID: 34911637 DOI: 10.1053/j.semnuclmed.2021.11.004] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Neuroendocrine tumors (NETs) are uncommon malignancies of increasing incidence and prevalence. As these slow growing tumors usually overexpress somatostatin receptors (SSTRs), the use of 68Ga-DOTA-peptides (gallium-68 chelated with dodecane tetra-acetic acid to somatostatin), which bind to the SSTRs, allows for PET based imaging and selection of patients for peptide receptor radionuclide therapy (PRRT). PRRT with radiolabeled somatostatin analogues such as 177Lu-DOTATATE (lutetium-177-[DOTA,Tyr3]-octreotate), is mainly used for the treatment of metastatic or inoperable NETs. However, PRRT is generally administered at a fixed injected activity in order not to exceed dose limits in critical organs, which is suboptimal given the variability in radiopharmaceutical uptake among patients. Advances in SPECT (single photon emission computed tomography) imaging enable the absolute quantitative measure of the true radiopharmaceutical distribution providing for PRRT dosimetry in each patient. Personalized PRRT based on patient-specific dosimetry could improve therapeutic efficacy by optimizing effective tumor absorbed dose while limiting treatment related radiotoxicity.
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Affiliation(s)
- John Kennedy
- Department of Nuclear Medicine, Rambam Health Care Campus, Haifa, Israel; B. Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israel.
| | - Alexandre Chicheportiche
- Department of Nuclear Medicine and Biophysics, Hadassah Medical Organization and Faculty of Medicine, Hebrew University of Jerusalem, Israel
| | - Zohar Keidar
- Department of Nuclear Medicine, Rambam Health Care Campus, Haifa, Israel; B. Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israel
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Kennedy JA, Lugassi R, Gill R, Keidar Z. Digital Solid-State SPECT/CT Quantitation of Absolute 177Lu Radiotracer Concentration: In Vivo and In Vitro Validation. J Nucl Med 2020; 61:1381-1387. [PMID: 32111686 DOI: 10.2967/jnumed.119.239277] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2019] [Accepted: 01/10/2020] [Indexed: 12/16/2022] Open
Abstract
The accuracy of 177Lu radiotracer concentration measurements using quantitative clinical software was determined by comparing in vivo results for a digital solid-state cadmium-zinc-telluride SPECT/CT system with in vitro sampling. Methods: First, image acquisition parameters were assessed for an International Electrotechnical Commission body phantom emulating clinical count rates loaded with a lung insert and 6 hot spheres with a 12:1 target-to-background ratio of 177Lu solution. Then, the data of 28 whole-body SPECT/CT scans of 7 patients who underwent 177Lu prostate-specific membrane antigen radioligand therapy were retrospectively analyzed. Three users analyzed SPECT/CT images for in vivo urinary bladder radiotracer uptake using quantitative software. In vitro radiopharmaceutical concentrations were calculated using urine sampling obtained immediately after each scan, scaled to SUVs. Any in vivo or in vitro identity relations were determined by linear regression (ideally, slope = 1 and intercept = 0), within a 95% confidence interval. Results: Phantom results demonstrated lower quantitative error for acquisitions using the 113-keV 177Lu energy peak rather than including the 208-keV peak, given that only low-energy collimation was available in this camera configuration. In the clinical study, 24 in vivo-in vitro pairs were eligible for further analysis, with 4 having been rejected as outliers (via Cook distance calculations). All linear regressions (R 2 ≥ 0.82, P < 0.0001) provided identity in vivo-in vitro relations (95% confidence interval), with SUV averages from all users giving a slope of 0.96 ± 0.13, an intercept of -0.07 ± 0.46 g/mL, and an average residual difference of 19.5%. In acquisitions with the lower-energy 177Lu energy peak, solid-state SPECT/CT imaging provided an accuracy to within approximately 20% of in vivo urinary bladder radiotracer concentrations. Conclusion: This noninvasive in vivo quantitation method can potentially improve diagnosis, patient management, and treatment response assessment and provide data essential to 177Lu dosimetry.
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Affiliation(s)
- John A Kennedy
- Department of Nuclear Medicine, Rambam Health Care Campus, Haifa, Israel; and .,Ruth and Bruce Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israel
| | - Rachel Lugassi
- Department of Nuclear Medicine, Rambam Health Care Campus, Haifa, Israel; and
| | - Ronit Gill
- Department of Nuclear Medicine, Rambam Health Care Campus, Haifa, Israel; and
| | - Zohar Keidar
- Department of Nuclear Medicine, Rambam Health Care Campus, Haifa, Israel; and.,Ruth and Bruce Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israel
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Masoomi MA, Al-Shammeri I, Kalafallah K, Elrahman HM, Ragab O, Ahmed E, Al-Shammeri J, Arafat S. Wiener filter improves diagnostic accuracy of CAD SPECT images-comparison to angiography and CT angiography. Medicine (Baltimore) 2019; 98:e14207. [PMID: 30681596 PMCID: PMC6358408 DOI: 10.1097/md.0000000000014207] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
Many discrepancy in selection of proper filter and its parameters for individual cases exists. The authors investigate the impact of the most common filters on patient NM images with coronary artery disease (CAD), and compare the results with the computerized tomography (CT)-Angio and angiography for accuracy.The investigation initiated by performing various single photon emission computerized tomography (SPECT)/CT scan of the national electrical manufacturers association chest phantoms having hot and cold inserts. Data acquired on GE 670 PRO SPECT/CT; 360Ø, 64 frames, 60 seconds, low energy high resolution (LEHR) 128, low energy general purpose (LEGP) with CT attenuation (120 kV and 170 mA). The images reconstructed with filtered back projection and ITERATIVE ordered-subset expectation maximization utilizing filters; Hann, Butterworth, Metz, Hamming, and Wiener. The Image contrast was calculated to assess absolute nearness of the inserts. Based on the preliminary results, then scans of 92 patients with CAD; 64 males and 28 females, age 41 to 77 years old, who had been reported earlier reprocessed with the nominated filter and were reported by 2 NM expert. The results compared to the earlier reports and to the CT-Angio and angiography.The optimization suggested 3 filters; Wiener (Wi), Metz and Butterworth (But) provide the highest contrast (99- 66.4%) and (81- 32%) for the cold and hot inserts respectively, with the (Wi) filter to be the better option. The reprocessed patients scan with the (Wi) presented an elevated diagnostic accuracy, correlated well with the CT-Angio and angiography results (P < .001 and r = 0.79 for [Wi] and P = .004 and r = 0.39 for [But]). The percentage of the false negative for moderate to severe CAD cases reported using Wi filter reduced from 27% to 7% and similarly for mild CAD cases from 7% to 1%.It appears the Wiener filter could produce results with the highest contrast for phantom imaging of various cold and hot spheres and for the patient data which is more consistent with angiography results, with much-elevated accuracy in intermediate cases (r = 0.79 for Wiener and r = 0.39 for Butterworth vs angiography). However, the optimum parameters obtained for the filters have no relation with the resolution of the imaging system, but the details of the objects could be improved.
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Affiliation(s)
- Michael A. Masoomi
- Department of Nuclear Medicine and Molecular Imaging, Adan HospitalHadiya, KW
| | - Iman Al-Shammeri
- Department of Nuclear Medicine and Molecular Imaging, Adan HospitalHadiya, KW
| | - Khaled Kalafallah
- Department of Nuclear Medicine and Molecular Imaging, Adan HospitalHadiya, KW
- Department of Nuclear Medicine, Kuwait Cancer Control Centre, Sabah Medical District, Shuwaikh
| | - Hany M.A. Elrahman
- Department of Nuclear Medicine and Molecular Imaging, Adan HospitalHadiya, KW
| | - Osama Ragab
- Department of Nuclear Medicine and Molecular Imaging, Adan HospitalHadiya, KW
| | - Ebba Ahmed
- Department of Nuclear Medicine and Molecular Imaging, Adan HospitalHadiya, KW
| | - Jehan Al-Shammeri
- Department of Nuclear Medicine, Faculty of Medicine, Heath Science Centre, Kuwait University
| | - Sharif Arafat
- Department of Cardiology, Dabbous Cardiac Centre, Adan Hospital, Hadiya, Kuwait
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Bastiaannet R, Kappadath SC, Kunnen B, Braat AJAT, Lam MGEH, de Jong HWAM. The physics of radioembolization. EJNMMI Phys 2018; 5:22. [PMID: 30386924 PMCID: PMC6212377 DOI: 10.1186/s40658-018-0221-z] [Citation(s) in RCA: 57] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2017] [Accepted: 06/19/2018] [Indexed: 12/11/2022] Open
Abstract
Radioembolization is an established treatment for chemoresistant and unresectable liver cancers. Currently, treatment planning is often based on semi-empirical methods, which yield acceptable toxicity profiles and have enabled the large-scale application in a palliative setting. However, recently, five large randomized controlled trials using resin microspheres failed to demonstrate a significant improvement in either progression-free survival or overall survival in both hepatocellular carcinoma and metastatic colorectal cancer. One reason for this might be that the activity prescription methods used in these studies are suboptimal for many patients.In this review, the current dosimetric methods and their caveats are evaluated. Furthermore, the current state-of-the-art of image-guided dosimetry and advanced radiobiological modeling is reviewed from a physics' perspective. The current literature is explored for the observation of robust dose-response relationships followed by an overview of recent advancements in quantitative image reconstruction in relation to image-guided dosimetry.This review is concluded with a discussion on areas where further research is necessary in order to arrive at a personalized treatment method that provides optimal tumor control and is clinically feasible.
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Affiliation(s)
- Remco Bastiaannet
- Department of Radiology and Nuclear Medicine, University Medical Center Utrecht, Room E01.132, P.O. Box 85500, 3508 GA Utrecht, The Netherlands
| | - S. Cheenu Kappadath
- Department of Imaging Physics, The University of Texas MD Anderson Cancer Center, 1155 Pressler St, Unit 1352, Houston, TX 77030 USA
| | - Britt Kunnen
- Department of Radiology and Nuclear Medicine, University Medical Center Utrecht, Room E01.132, P.O. Box 85500, 3508 GA Utrecht, The Netherlands
| | - Arthur J. A. T. Braat
- Department of Radiology and Nuclear Medicine, University Medical Center Utrecht, Room E01.132, P.O. Box 85500, 3508 GA Utrecht, The Netherlands
| | - Marnix G. E. H. Lam
- Department of Radiology and Nuclear Medicine, University Medical Center Utrecht, Room E01.132, P.O. Box 85500, 3508 GA Utrecht, The Netherlands
| | - Hugo W. A. M. de Jong
- Department of Radiology and Nuclear Medicine, University Medical Center Utrecht, Room E01.132, P.O. Box 85500, 3508 GA Utrecht, The Netherlands
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Besson FL, Henry T, Meyer C, Chevance V, Roblot V, Blanchet E, Arnould V, Grimon G, Chekroun M, Mabille L, Parent F, Seferian A, Bulifon S, Montani D, Humbert M, Chaumet-Riffaud P, Lebon V, Durand E. Rapid Contour-based Segmentation for 18F-FDG PET Imaging of Lung Tumors by Using ITK-SNAP: Comparison to Expert-based Segmentation. Radiology 2018; 288:277-284. [DOI: 10.1148/radiol.2018171756] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
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8
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Park JG, Kim CH, Min CH, Jeong JH, Kim JB, Moon J, Jung SH. Experimental Test of Double-Layer Method for Industrial SPECT. NUCL TECHNOL 2017. [DOI: 10.13182/nt175-113] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Jang Guen Park
- Hanyang University, Department of Nuclear Engineering 17 Haengdang-dong, Seongdong-gu, Seoul 133-791, Korea
| | - Chan Hyeong Kim
- Hanyang University, Department of Nuclear Engineering 17 Haengdang-dong, Seongdong-gu, Seoul 133-791, Korea
| | - Chul Hee Min
- Hanyang University, Department of Nuclear Engineering 17 Haengdang-dong, Seongdong-gu, Seoul 133-791, Korea
| | - Jong Hwi Jeong
- Hanyang University, Department of Nuclear Engineering 17 Haengdang-dong, Seongdong-gu, Seoul 133-791, Korea
| | - Jong Bum Kim
- Korea Atomic Energy Research Institute, Dukjin-dong Yuseong-gu, Daejon 305-353, Korea
| | - Jinho Moon
- Korea Atomic Energy Research Institute, Dukjin-dong Yuseong-gu, Daejon 305-353, Korea
| | - Sung-Hee Jung
- Korea Atomic Energy Research Institute, Dukjin-dong Yuseong-gu, Daejon 305-353, Korea
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Gustafsson J, Sundlöv A, Sjögreen Gleisner K. SPECT image segmentation for estimation of tumour volume and activity concentration in 177Lu-DOTATATE radionuclide therapy. EJNMMI Res 2017; 7:18. [PMID: 28233160 PMCID: PMC5323339 DOI: 10.1186/s13550-017-0262-7] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2016] [Accepted: 01/31/2017] [Indexed: 11/23/2022] Open
Abstract
Background Dosimetry in radionuclide therapy has the potential to allow for a treatment tailored to the individual patient. One therapeutic radiopharmaceutical where patient-specific dosimetry is feasible is 177Lu-DOTATATE, used for the treatment of neuroendocrine tumours. The emission of gamma photons by 177Lu allows for imaging with SPECT (single photon emission computed tomography). One important step for dosimetry using this imaging technique is the SPECT image segmentation, which needs to be robust and accurate for the estimated quantities to be reliable. This work investigates different methods for automatic tumour delineation in 177Lu-DOTATATE SPECT images. Three segmentation methods are considered: a fixed 42% threshold (FT), the Otsu method (OM) and a method based on Fourier surfaces (FS). Effects of including resolution compensation in the iterative SPECT image reconstruction are also studied. Evaluation is performed based on Monte Carlo-simulated SPECT images from 24 h and 336 h post injection (p.i.), for determination of the volume, activity concentration and dice similarity coefficient. In addition, patient data are used to investigate the correspondence of tumour volumes when delineated in SPECT or morphological CT or MR images. Patient data are also used to examine the sensitivity to the operator-dependent initialization. Results For simulated images from 24 h p.i. reconstructed without resolution compensation, a volume and activity-concentration root-mean-square error below 15% is typically obtained for tumours above approximately 10 cm3 when using OM or FS, while FT performs considerably worse. When including resolution compensation, the tumour volume becomes underestimated and the activity concentration overestimated. The FS method appears to be robust to noise, as seen for the 336 h images. The differences between the tumour volumes estimated from the SPECT images and the volumes estimated from morphological images are generally larger than the discrepancies seen for the simulated data sets. Conclusions Segmentation results are encouraging for future dosimetry of tumours with volumes above approximately 10 cm3. Using resolution compensation in the reconstruction may have a negative effect on volume estimation.
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Affiliation(s)
- Johan Gustafsson
- Department of Medical Radiation Physics, Clinical Sciences Lund, Lund University, Lund, Sweden.
| | - Anna Sundlöv
- Department of Oncology and Pathology, Clinical Sciences Lund, Lund University, Lund, Sweden.,Department of Oncology, Skåne University Hospital, Lund, Sweden
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Ciernik IF, Brown DW, Schmid D, Hany T, Egli P, Davis JB. 3D-Segmentation of the 18F-choline PET Signal for Target Volume Definition in Radiation Therapy of the Prostate. Technol Cancer Res Treat 2016; 6:23-30. [PMID: 17241097 DOI: 10.1177/153303460700600104] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Volumetric assessment of PET signals becomes increasingly relevant for radiotherapy (RT) planning. Here, we investigate the utility of 18F-choline PET signals to serve as a structure for semi-automatic segmentation for forward treatment planning of prostate cancer. 18F-choline PET and CT scans of ten patients with histologically proven prostate cancer without extracapsular growth were acquired using a combined PET/CT scanner. Target volumes were manually delineated on CT images using standard software. Volumes were also obtained from 18F-choline PET images using an asymmetrical segmentation algorithm. PTVs were derived from CT 18F-choline PET based clinical target volumes (CTVs) by automatic expansion and comparative planning was performed. As a read-out for dose given to non-target structures, dose to the rectal wall was assessed. Planning target volumes (PTVs) derived from CT and 18F-choline PET yielded comparable results. Optimal matching of CT and 18F-choline PET derived volumes in the lateral and cranial-caudal directions was obtained using a background-subtracted signal thresholds of 23.0+/-2.6%. In antero-posterior direction, where adaptation compensating for rectal signal overflow was required, optimal matching was achieved with a threshold of 49.5+/-4.6%. 3D-conformal planning with CT or 18F-choline PET resulted in comparable doses to the rectal wall. Choline PET signals of the prostate provide adequate spatial information amendable to standardized asymmetrical region growing algorithms for PET-based target volume definition for external beam RT.
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Affiliation(s)
- I Frank Ciernik
- Center for Clinical Research, Zurich University Hospital, Zurich, Switzerland.
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SPECT Imaging of 2-D and 3-D Distributed Sources with Near-Field Coded Aperture Collimation: Computer Simulation and Real Data Validation. J Med Biol Eng 2016; 36:32-43. [PMID: 27069461 PMCID: PMC4791458 DOI: 10.1007/s40846-016-0111-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2015] [Accepted: 06/01/2015] [Indexed: 11/20/2022]
Abstract
The imaging of distributed sources with near-field coded aperture (CA) remains extremely challenging and is broadly considered unsuitable for single-photon emission computerized tomography (SPECT). This study proposes a novel CA SPECT reconstruction approach and evaluates the feasibilities of imaging and reconstructing distributed hot sources and cold lesions using near-field CA collimation and iterative image reconstruction. Computer simulations were designed to compare CA and pinhole collimations in two-dimensional radionuclide imaging. Digital phantoms were created and CA images of the phantoms were reconstructed using maximum likelihood expectation maximization (MLEM). Errors and the contrast-to-noise ratio (CNR) were calculated and image resolution was evaluated. An ex vivo rat heart with myocardial infarction was imaged using a micro-SPECT system equipped with a custom-made CA module and a commercial 5-pinhole collimator. Rat CA images were reconstructed via the three-dimensional (3-D) MLEM algorithm developed for CA SPECT with and without correction for a large projection angle, and 5-pinhole images were reconstructed using the commercial software provided by the SPECT system. Phantom images of CA were markedly improved in terms of image quality, quantitative root-mean-squared error, and CNR, as compared to pinhole images. CA and pinhole images yielded similar image resolution, while CA collimation resulted in fewer noise artifacts. CA and pinhole images of the rat heart were well reconstructed and the myocardial perfusion defects could be clearly discerned from 3-D CA and 5-pinhole SPECT images, whereas 5-pinhole SPECT images suffered from severe noise artifacts. Image contrast of CA SPECT was further improved after correction for the large projection angle used in the rat heart imaging. The computer simulations and small-animal imaging study presented herein indicate that the proposed 3-D CA SPECT imaging and reconstruction approaches worked reasonably well, demonstrating the feasibilities of achieving high sensitivity and high resolution SPECT using near-field CA collimation.
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Jeraj R, Bradshaw T, Simončič U. Molecular Imaging to Plan Radiotherapy and Evaluate Its Efficacy. J Nucl Med 2015; 56:1752-65. [PMID: 26383148 DOI: 10.2967/jnumed.114.141424] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2015] [Accepted: 09/08/2015] [Indexed: 12/25/2022] Open
Abstract
Molecular imaging plays a central role in the management of radiation oncology patients. Specific uses of imaging, particularly to plan radiotherapy and assess its efficacy, require an additional level of reproducibility and image quality beyond what is required for diagnostic imaging. Specific requirements include proper patient preparation, adequate technologist training, careful imaging protocol design, reliable scanner technology, reproducible software algorithms, and reliable data analysis methods. As uncertainty in target definition is arguably the greatest challenge facing radiation oncology, the greatest impact that molecular imaging can have may be in the reduction of interobserver variability in target volume delineation and in providing greater conformity between target volume boundaries and true tumor boundaries. Several automatic and semiautomatic contouring methods based on molecular imaging are available but still need sufficient validation to be widely adopted. Biologically conformal radiotherapy (dose painting) based on molecular imaging-assessed tumor heterogeneity is being investigated, but many challenges remain to fully exploring its potential. Molecular imaging also plays increasingly important roles in both early (during treatment) and late (after treatment) response assessment as both a predictive and a prognostic tool. Because of potentially confounding effects of radiation-induced inflammation, treatment response assessment requires careful interpretation. Although molecular imaging is already strongly embedded in radiotherapy, the path to widespread and all-inclusive use is still long. The lack of solid clinical evidence is the main impediment to broader use. Recommendations for practicing physicians are still rather scarce. (18)F-FDG PET/CT remains the main molecular imaging modality in radiation oncology applications. Although other molecular imaging options (e.g., proliferation imaging) are becoming more common, their widespread use is limited by lack of tracer availability and inadequate reimbursement models. With the increasing presence of molecular imaging in radiation oncology, special emphasis should be placed on adequate training of radiation oncology personnel to understand the potential, and particularly the limitations, of quantitative molecular imaging applications. Similarly, radiologists and nuclear medicine specialists should be sensitized to the special need of the radiation oncologist in terms of quantification and reproducibility. Furthermore, strong collaboration between radiation oncology, nuclear medicine/radiology, and medical physics teams is necessary, as optimal and safe use of molecular imaging can be ensured only within appropriate interdisciplinary teams.
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Affiliation(s)
- Robert Jeraj
- School of Medicine and Public Health, University of Wisconsin, Madison, Wisconsin; and Faculty of Mathematics and Physics, University of Ljubljana, Ljubljana, Slovenia
| | - Tyler Bradshaw
- School of Medicine and Public Health, University of Wisconsin, Madison, Wisconsin; and
| | - Urban Simončič
- Faculty of Mathematics and Physics, University of Ljubljana, Ljubljana, Slovenia
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Foster B, Bagci U, Mansoor A, Xu Z, Mollura DJ. A review on segmentation of positron emission tomography images. Comput Biol Med 2014; 50:76-96. [PMID: 24845019 DOI: 10.1016/j.compbiomed.2014.04.014] [Citation(s) in RCA: 219] [Impact Index Per Article: 21.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2013] [Revised: 03/19/2014] [Accepted: 04/16/2014] [Indexed: 11/20/2022]
Abstract
Positron Emission Tomography (PET), a non-invasive functional imaging method at the molecular level, images the distribution of biologically targeted radiotracers with high sensitivity. PET imaging provides detailed quantitative information about many diseases and is often used to evaluate inflammation, infection, and cancer by detecting emitted photons from a radiotracer localized to abnormal cells. In order to differentiate abnormal tissue from surrounding areas in PET images, image segmentation methods play a vital role; therefore, accurate image segmentation is often necessary for proper disease detection, diagnosis, treatment planning, and follow-ups. In this review paper, we present state-of-the-art PET image segmentation methods, as well as the recent advances in image segmentation techniques. In order to make this manuscript self-contained, we also briefly explain the fundamentals of PET imaging, the challenges of diagnostic PET image analysis, and the effects of these challenges on the segmentation results.
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Affiliation(s)
- Brent Foster
- Center for Infectious Disease Imaging, Department of Radiology and Imaging Sciences, National Institutes of Health (NIH), Bethesda, MD 20892, United States
| | - Ulas Bagci
- Center for Infectious Disease Imaging, Department of Radiology and Imaging Sciences, National Institutes of Health (NIH), Bethesda, MD 20892, United States.
| | - Awais Mansoor
- Center for Infectious Disease Imaging, Department of Radiology and Imaging Sciences, National Institutes of Health (NIH), Bethesda, MD 20892, United States
| | - Ziyue Xu
- Center for Infectious Disease Imaging, Department of Radiology and Imaging Sciences, National Institutes of Health (NIH), Bethesda, MD 20892, United States
| | - Daniel J Mollura
- Center for Infectious Disease Imaging, Department of Radiology and Imaging Sciences, National Institutes of Health (NIH), Bethesda, MD 20892, United States
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Li S, Sinusas AJ, Dobrucki LW, Liu YH. New approach to quantification of molecularly targeted radiotracer uptake from hybrid cardiac SPECT/CT: methodology and validation. J Nucl Med 2013; 54:2175-81. [PMID: 24221992 DOI: 10.2967/jnumed.113.123208] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
UNLABELLED Quantification of molecularly targeted radiotracer uptake in the myocardium from SPECT remains challenging in part due to potentially low levels of focal tracer uptake of presently available molecularly targeted agents and further degradation of cardiac SPECT by extracardiac radioactivity and partial-volume effect. The purpose of this study was to derive and validate a new SPECT quantification method for assessments of absolute radiotracer uptake in the myocardium. METHODS The method was integrated with a hybrid micro-SPECT/CT imaging protocol to calculate radiotracer uptake of a molecularly targeted agent in the ischemic myocardium. CT coregistered with SPECT was used to identify the position and orientation of the left ventricle. Corrections for extracardiac activity and partial-volume errors were performed via a heuristic method derived with a total count sampling scheme. Myocardial radiotracer uptake was quantified from SPECT using an external point source as a known reference. Methods were validated using an ischemic rat model injected with a (99m)Tc-labeled SPECT radiotracer targeted at αvβ3 integrin. SPECT-quantified myocardial radiotracer uptake was compared with postmortem myocardial tissue well-counted radioactivity. RESULTS Initial correlation between SPECT-quantified and well-counted radioactivity was fair (R(2) = 0.19, y = 0.50x + 0.05, P = 0.06) when no correction was applied to SPECT quantification. Correlation was significantly improved with tissue weight correction (R(2) = 0.84, y = 1.82x - 0.01, P < 0.001), and a trend toward the improvement of correlation was observed with extracardiac activity correction (R(2) = 0.85, y = 1.54x - 0.01, P < 0.001) and partial-volume correction (R(2) = 0.86, y = 1.68x - 0.01, P < 0.001). Reproducibility of the SPECT quantification was excellent, either with no correction (R(2) = 0.99, y = 1.00x + 0.00, P < 0.001) or with all corrections (R(2) = 1.00, y = 1.00x - 0.00, P < 0.001). CONCLUSION Corrections for the myocardial tissue weight, extracardiac activity, and partial-volume errors are crucial for precise assessments of myocardial radiotracer uptake using micro-SPECT/CT. The quantitative SPECT/CT approach developed provides a reasonable and reproducible in vivo estimation of absolute radiotracer uptake in a model of myocardial injury and should permit quantitative serial monitoring of subtle changes in the myocardial uptake of targeted radiotracers.
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Affiliation(s)
- Shimin Li
- Section of Cardiovascular Medicine, Department of Internal Medicine, Yale University School of Medicine, New Haven, Connecticut
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15
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Arenja N, Mueller C, Ehl NF, Brinkert M, Roost K, Reichlin T, Sou SM, Hochgruber T, Osswald S, Zellweger MJ. Prevalence, extent, and independent predictors of silent myocardial infarction. Am J Med 2013; 126:515-22. [PMID: 23597799 DOI: 10.1016/j.amjmed.2012.11.028] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/28/2012] [Revised: 11/12/2012] [Accepted: 11/16/2012] [Indexed: 12/13/2022]
Abstract
BACKGROUND The phenomenon of silent myocardial infarction is poorly understood. METHODS We aimed to evaluate the prevalence, extent, and independent predictors of silent myocardial infarction in 2 large independent cohorts of consecutive patients without a history of myocardial infarction referred for rest/stress myocardial perfusion single photon emission computed tomography. There were 1621 patients enrolled in the derivation cohort and 338 patients in the validation cohort. Silent myocardial infarction was diagnosed in patients with a myocardial scar ≥5% of the left ventricle. RESULTS In the derivation cohort, the prevalence of silent myocardial infarction was 23.3% (n = 377). The median infarct size was 10% (interquartile range [IQR] 5%-15%) of the left ventricle. The prevalence of silent myocardial infarction was 28.5% in diabetics and 21.5% in nondiabetics (P = .004). Diabetes mellitus was an independent predictor for the presence of silent myocardial infarction (odds ratio 1.5; 95% confidence interval, 1.1-1.9; P = .004). These findings were confirmed in the independent validation cohort. In the validation cohort, the prevalence of silent myocardial infarction was 26.3% (n = 89), while the prevalence was higher in diabetics (35.8%) than in nondiabetics (24%; P = .049). The median infarct size was 11.8% (IQR 5.9%-17.6%) of the left ventricle. Again, in logistic regression analysis, diabetes mellitus was a significant predictor of the presence of silent myocardial infarction. CONCLUSION Silent myocardial infarctions are more common than previously thought. One of 4 patients with suspected coronary artery disease had experienced a silent myocardial infarction; the extent in average is 10% of the left ventricle, and it is more common in diabetics.
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Affiliation(s)
- Nisha Arenja
- Department of Cardiology, University Hospital Basel, Switzerland
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Recommendations of the Spanish Societies of Radiation Oncology (SEOR), Nuclear Medicine & Molecular Imaging (SEMNiM), and Medical Physics (SEFM) on (18)F-FDG PET-CT for radiotherapy treatment planning. Rep Pract Oncol Radiother 2012; 17:298-318. [PMID: 24377032 DOI: 10.1016/j.rpor.2012.10.001] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2012] [Accepted: 10/11/2012] [Indexed: 12/16/2022] Open
Abstract
Positron emission tomography (PET) with (18)F-fluorodeoxyglucose (FDG) is a valuable tool for diagnosing and staging malignant lesions. The fusion of PET and computed tomography (CT) yields images that contain both metabolic and morphological information, which, taken together, have improved the diagnostic precision of PET in oncology. The main imaging modality for planning radiotherapy treatment is CT. However, PET-CT is an emerging modality for use in planning treatments because it allows for more accurate treatment volume definition. The use of PET-CT for treatment planning is highly complex, and protocols and standards for its use are still being developed. It seems probable that PET-CT will eventually replace current CT-based planning methods, but this will require a full understanding of the relevant technical aspects of PET-CT planning. The aim of the present document is to review these technical aspects and to provide recommendations for clinical use of this imaging modality in the radiotherapy planning process.
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Radiotherapy for head and neck tumours in 2012 and beyond: conformal, tailored, and adaptive? Lancet Oncol 2012; 13:e292-300. [PMID: 22748268 DOI: 10.1016/s1470-2045(12)70237-1] [Citation(s) in RCA: 85] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Intensity-modulated radiation therapy (IMRT) is a conformal irradiation technique that enables steep dose gradients. In head and neck tumours this approach spares parotid-gland function without compromise to treatment efficacy. Anatomical and molecular imaging modalities may be used to tailor treatment by enabling proper selection and delineation of target volumes and organs at risk, which in turn lead to dose prescriptions that take into account the underlying tumour biology (eg, human papillomavirus status). Therefore, adaptations can be made throughout the course of radiotherapy, as required. Planned dose increases to parts of the target volumes may also be used to match the radiosensitivity of tumours (so-called dose-painting), assessed by molecular imaging. For swift implementation of tailored and adaptive IMRT, tools and procedures, such as accurate image acquisition and reconstruction, automatic segmentation of target volumes and organs at risk, non-rigid image and dose registration, and dose summation methods, need to be developed and properly validated.
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Quantification and reduction of the collimator-detector response effect in SPECT by applying a system model during iterative image reconstruction: a simulation study. Nucl Med Commun 2012; 33:228-38. [PMID: 22134173 DOI: 10.1097/mnm.0b013e32834e755f] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
BACKGROUND Detector blurring and non-ideal collimation decrease the spatial resolution of the single-photon emission computed tomography (SPECT) images. Iterative reconstruction algorithms such as ordered subsets expectation maximization (OSEM) can incorporate degrading factors during reconstruction. We investigated the quantitative errors associated with poor SPECT resolution and evaluated the importance of two-dimensional (2D) and three-dimensional (3D) resolution recovery by modelling system response during iterative image reconstruction. METHODS Different phantoms consisted of the NURBS-based cardiac-torso (NCAT) liver phantom with small tumors, the Zubal brain phantom and the NCAT heart phantom were used in this study. Monte Carlo simulation was used to create SPECT projections. Gaussian functions were used to model collimator detector response (CDR). Modeled CDRs were applied during OSEM. Both noise-free and noisy projections were created. RESULTS Even with noise-free projections, conventional OSEM algorithm provided limited quantitative accuracy compared to both 2D and 3D resolution recovery. The 3D implementation of resolution recovery, however, yielded superior results compared to its 2D implementation. For the liver phantom, the ability to distinguish small tumors in both transverse and axial planes was improved. For the brain phantom, gray to white matter activity ratio was increased from 3.14 ± 0.04 in simple OSEM to 3.84 ± 0.06 in 3D OSEM. For the NCAT heart phantom, 3D resolution recovery, results in images with thinner wall and higher contrast for different noise levels. CONCLUSION There are considerable quantitative errors associated with CDR, especially when the size of the target is comparable with the spatial resolution of the system. Between different reconstruction algorithms, 3D OSEM that consider the 3D nature of CDR, improve both the visual quality and the quantitative accuracy of any SPECT studies.
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Thorwarth D, Beyer T, Boellaard R, de Ruysscher D, Grgic A, Lee JA, Pietrzyk U, Sattler B, Schaefer A, van Elmpt W, Vogel W, Oyen WJG, Nestle U. Integration of FDG-PET/CT into external beam radiation therapy planning: technical aspects and recommendations on methodological approaches. Nuklearmedizin 2012; 51:140-53. [PMID: 22473130 DOI: 10.3413/nukmed-0455-11-12] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2011] [Accepted: 03/19/2012] [Indexed: 12/20/2022]
Abstract
UNLABELLED This work addresses the clinical adoption of FDG-PET/CT for image-guided radiation therapy planning (RTP). As such, important technical and methodological aspects of PET/CT-based RTP are reviewed and practical recommendations are given for routine patient management and clinical studies. First, recent developments in PET/CT hardware that are relevant to RTP are reviewed in the context of quality control and system calibration procedures that are mandatory for a reproducible adoption of PET/CT in RTP. Second, recommendations are provided on image acquisition and reconstruction to support the standardization of imaging protocols. A major prerequisite for routine RTP is a complete and secure data transfer to the actual planning system. Third, state-of-the-art tools for image fusion and co-registration are discussed briefly in the context of PET/CT imaging pre- and post-RTP. This includes a brief review of state-of-the-art image contouring algorithms relevant to PET/CT-guided RTP. Finally, practical aspects of clinical workflow and patient management, such as patient setup and requirements for staff training are emphasized. PET/CT-guided RTP mandates attention to logistical aspects, patient set-up and acquisition parameters as well as an in-depth appreciation of quality control and protocol standardization. CONCLUSION Upon fulfilling the requirements to perform PET/CT for RTP, a new dimension of molecular imaging can be added to traditional morphological imaging. As a consequence, PET/CT imaging will support improved RTP and better patient care. This document serves as a guidance on practical and clinically validated instructions that are deemed useful to the staff involved in PET/CT-guided RTP.
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Affiliation(s)
- D Thorwarth
- University Hospital for Radiation Oncology, Section for Biomedical Physics, Eberhard-Karls University Tübingen, Germany.
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20
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Ljungberg M, Sjögreen-Gleisner K. The accuracy of absorbed dose estimates in tumours determined by quantitative SPECT: a Monte Carlo study. Acta Oncol 2011; 50:981-9. [PMID: 21767200 DOI: 10.3109/0284186x.2011.584559] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
BACKGROUND Dosimetry in radionuclide therapy estimates delivered absorbed doses to tumours and ensures that absorbed dose levels to normal organs are below tolerance levels. One procedure is to determine time-activity curves in volumes-of-interests from which the absorbed dose is estimated using SPECT with appropriate corrections for attenuation, scatter and collimator response. From corrected SPECT images the absorbed energy can be calculated by (a) assuming kinetic energy deposited in the same voxel where particles were emitted, (b) convolve with point-dose kernels or (c) use full Monte Carlo (MC) methods. A question arises which dosimetry method is optimal given the limitations in reconstruction- and quantification procedures. METHODS Dosimetry methods (a) and (c) were evaluated by comparing dose-rate volume histograms (DrVHs) from simulated SPECT of (111)In, (177)Lu, (131)I and bremsstrahlung from (90)Y to match true dose rate images. The study used a voxel-based phantom with different tumours in the liver. SPECT reconstruction was made using an iterative OSEM method and MC dosimetry was performed using a charged-particle EGS4 program that also was used to determined true absorbed dose rate distributions for the same phantom geometry but without camera limitations. RESULTS The DrVHs obtained from SPECT differed from true DrVH mainly due to limited spatial resolution. MC dosimetry had a marginal effect because the SPECT spatial resolution is in the same order as the energy distribution caused by the electron track ranges. For (131)I, full MC dosimetry made a difference due to the additional contribution from high-energy photons. SPECT-based DrVHs differ significantly from true DrVHs unless the tumours are considerable larger than the spatial resolution. CONCLUSION It is important to understand limitations in quantitative SPECT images and the reasons for apparent heterogeneities since these have an impact on dose-volume histograms. A MC-based dosimetry calculation from SPECT images is not always warranted.
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Affiliation(s)
- Michael Ljungberg
- Department of Medical Radiation Physics, Clinical Sciences, Lund, Lund University, Lund, Sweden.
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Kim N, Lee JG, Song Y, Kim HJ, S. Yeom J, Cho G. Evaluation of MRI resolution affecting trabecular bone parameters: Determination of acceptable resolution. Magn Reson Med 2011; 67:218-25. [DOI: 10.1002/mrm.22984] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2010] [Revised: 03/10/2011] [Accepted: 04/06/2011] [Indexed: 11/05/2022]
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Liu YH, Sahul Z, Weyman CA, Dione DP, Dobrucki WL, Mekkaoui C, Brennan MP, Ryder WJ, Sinusas AJ. Accuracy and reproducibility of absolute quantification of myocardial focal tracer uptake from molecularly targeted SPECT/CT: a canine validation. J Nucl Med 2011; 52:453-60. [PMID: 21321271 DOI: 10.2967/jnumed.110.082214] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
UNLABELLED Accurate and reproducible SPECT quantification of myocardial molecular processes remains a challenge because of the complication of heterogeneous background and extracardiac activity adjacent to the heart, which causes errors in the estimation of myocardial focal tracer uptake. Our aim in this study was to introduce a heuristic method for the correction of extracardiac activity into SPECT quantification and validate the modified quantification method for accuracy and reproducibility using a canine model. METHODS Dual-isotope-targeted (99m)Tc and (201)Tl perfusion SPECT images were acquired using a hybrid SPECT/CT camera in 6 dogs at 2 wk after myocardial infarction. Images were reconstructed with and without CT-based attenuation correction, and the reconstructed SPECT images were filtered and quantified simultaneously with incorporation of extracardiac radioactivity correction, gaussian fitting, and total-count sampling. Absolute myocardial focal tracer uptake was quantified from SPECT images using 3 different normal limits (maximum entropy [ME], mean-squared-error minimization [MSEM], and global minimum [GM]). SPECT-quantified percentage injected dose (%ID) was calculated and compared with the well-counted radioactivity measured from the postmortem myocardial tissue. SPECT quantitative processing was performed by 2 different individuals with extensive experience in cardiac image processing, to assess reproducibility of the quantitative analysis. RESULTS Correlations between SPECT-quantified and well-counted %IDs using 3 different normal limits were excellent (ME: r = 0.82, y = 0.932 x - 0.0102; MSEM: r = 0.73, y = 1.1413 x - 0.0052; and GM: r = 0.7, y = 1.2147 x - 0.0002). SPECT quantification using ME normal limits resulted in an underestimation of %ID, as compared with well-counted %ID. Myocardial focal tracer uptake quantified from SPECT images without CT-based attenuation correction was significantly lower than that with the attenuation correction. The %IDs quantified from attenuation-corrected SPECT images using MSEM and GM normal limits were not significantly different from well-counted %IDs. Reproducibility of the SPECT quantitative analysis was excellent (ME: r = 0.98, y = 0.9221 x + 0.0001; MSEM: r = 0.97, y = 0.9357 x + 0.0004; and GM: r = 0.96, y = 0.9026 x + 0.001). CONCLUSION Our SPECT/CT quantification algorithm for the assessment of regional radioactivity may allow for accurate and reproducible serial noninvasive evaluation of molecularly targeted tracers in the myocardium.
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Affiliation(s)
- Yi-Hwa Liu
- Department of Internal Medicine, Yale University School of Medicine, New Haven, CT, USA.
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Sattler B, Lee JA, Lonsdale M, Coche E. PET/CT (and CT) instrumentation, image reconstruction and data transfer for radiotherapy planning. Radiother Oncol 2010; 96:288-97. [PMID: 20709416 DOI: 10.1016/j.radonc.2010.07.009] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2010] [Revised: 07/08/2010] [Accepted: 07/08/2010] [Indexed: 10/19/2022]
Abstract
The positron emission tomography in combination with CT in hybrid, cross-modality imaging systems (PET/CT) gains more and more importance as a part of the treatment-planning procedure in radiotherapy. Positron emission tomography (PET), as a integral part of nuclear medicine imaging and non-invasive imaging technique, offers the visualization and quantification of pre-selected tracer metabolism. In combination with the structural information from CT, this molecular imaging technique has great potential to support and improve the outcome of the treatment-planning procedure prior to radiotherapy. By the choice of the PET-Tracer, a variety of different metabolic processes can be visualized. First and foremost, this is the glucose metabolism of a tissue as well as for instance hypoxia or cell proliferation. This paper comprises the system characteristics of hybrid PET/CT systems. Acquisition and processing protocols are described in general and modifications to cope with the special needs in radiooncology. This starts with the different position of the patient on a special table top, continues with the use of the same fixation material as used for positioning of the patient in radiooncology while simulation and irradiation and leads to special processing protocols that include the delineation of the volumes that are subject to treatment planning and irradiation (PTV, GTV, CTV, etc.). General CT acquisition and processing parameters as well as the use of contrast enhancement of the CT are described. The possible risks and pitfalls the investigator could face during the hybrid-imaging procedure are explained and listed. The interdisciplinary use of different imaging modalities implies a increase of the volume of data created. These data need to be stored and communicated fast, safe and correct. Therefore, the DICOM-Standard provides objects and classes for this purpose (DICOM RT). Furthermore, the standard DICOM objects and classes for nuclear medicine (NM, PT) and computed tomography (CT) are used to communicate the actual image data created by the modalities. Care must be taken for data security, especially when transferring data across the (network-) borders of different hospitals. Overall, the most important precondition for successful integration of functional imaging in RT treatment planning is the goal orientated as well as close and thorough communication between nuclear medicine and radiotherapy departments on all levels of interaction (personnel, imaging protocols, GTV delineation, and selection of the data transfer method).
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Affiliation(s)
- Bernhard Sattler
- Department of Nuclear Medicine, University Hospital Leipzig, Germany.
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Segmentation of positron emission tomography images: some recommendations for target delineation in radiation oncology. Radiother Oncol 2010; 96:302-7. [PMID: 20708286 DOI: 10.1016/j.radonc.2010.07.003] [Citation(s) in RCA: 113] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2010] [Revised: 07/07/2010] [Accepted: 07/07/2010] [Indexed: 10/19/2022]
Abstract
Positron emission tomography can be used in radiation oncology for the delineation of target volumes in the treatment planning stage. Numerous publications deal with this topic and the scientific community has investigated many methodologies, ranging from simple uptake thresholding to very elaborate probabilistic models. Nevertheless, no consensus seems to emerge. This paper reviews delineation techniques that are popular in the literature. Special attention is paid to threshold-based techniques and the caveats of this methodology are pointed out by formal analysis. Next, a simple model of positron emission tomography is suggested in order to shed some light on the difficulties of target delineation and how they might be eventually overcome. Validation aspects are considered as well. Finally, a few recommendations are gathered in the conclusion.
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Determination of calibration curves for 131I in thyroid tumour metabolic radiotherapy and other radionuclides used in SPECT imaging. J Radioanal Nucl Chem 2009. [DOI: 10.1007/s10967-009-0296-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Soneson H, Ubachs JF, Ugander M, Arheden H, Heiberg E. An Improved Method for Automatic Segmentation of the Left Ventricle in Myocardial Perfusion SPECT. J Nucl Med 2009; 50:205-13. [DOI: 10.2967/jnumed.108.057323] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
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Shcherbinin S, Celler A. An investigation of accuracy of iterative reconstructions in quantitative SPECT. ACTA ACUST UNITED AC 2008. [DOI: 10.1088/1742-6596/124/1/012044] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Shcherbinin S, Celler A, Belhocine T, Vanderwerf R, Driedger A. Accuracy of quantitative reconstructions in SPECT/CT imaging. Phys Med Biol 2008; 53:4595-604. [PMID: 18678930 DOI: 10.1088/0031-9155/53/17/009] [Citation(s) in RCA: 90] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The goal of this study was to determine the quantitative accuracy of our OSEM-APDI reconstruction method based on SPECT/CT imaging for Tc-99m, In-111, I-123, and I-131 isotopes. Phantom studies were performed on a SPECT/low-dose multislice CT system (Infinia-Hawkeye-4 slice, GE Healthcare) using clinical acquisition protocols. Two radioactive sources were centrally and peripherally placed inside an anthropometric Thorax phantom filled with non-radioactive water. Corrections for attenuation, scatter, collimator blurring and collimator septal penetration were applied and their contribution to the overall accuracy of the reconstruction was evaluated. Reconstruction with the most comprehensive set of corrections resulted in activity estimation with error levels of 3-5% for all the isotopes.
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Affiliation(s)
- S Shcherbinin
- Department of Radiology, University of British Columbia, 366-828 West 10th Avenue, Vancouver BC, V5Z 1L8, Canada.
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Han J, Köstler H, Bennewitz C, Kuwert T, Hornegger J. Computer-aided evaluation of anatomical accuracy of image fusion between X-ray CT and SPECT. Comput Med Imaging Graph 2008; 32:388-95. [DOI: 10.1016/j.compmedimag.2008.03.002] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2007] [Revised: 03/16/2008] [Accepted: 03/18/2008] [Indexed: 11/29/2022]
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Kim N, Seo JB, Song KS, Chae EJ, Kang SH. Semi-automatic measurement of the airway dimension by computed tomography using the full-width-half-maximum method: a study on the measurement accuracy according to the CT parameters and size of the airway. Korean J Radiol 2008; 9:226-35. [PMID: 18525225 PMCID: PMC2627250 DOI: 10.3348/kjr.2008.9.3.226] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2007] [Accepted: 11/16/2007] [Indexed: 11/15/2022] Open
Abstract
OBJECTIVE To assess the influence of variable factors such as the size of the airway and the CT imaging parameters such as the reconstruction kernel, field-of-view (FOV), and slice thickness on the automatic measurement of airway dimension. MATERIALS AND METHODS An airway phantom was fabricated that contained eleven poly-acryl tubes of various lumen diameters and wall thicknesses. The measured density of the poly-acryl wall was 150 HU, and the measured density of the airspace filled with polyurethane foam was -900 HU. CT images were obtained using a 16-MDCT (multidetector CT) scanner and were reconstructed with various reconstruction kernels, thicknesses and FOV. The luminal radius and wall thickness were measured using in-house software based on the full-width-half-maximum method. The measured values as determined by CT and the actual dimensions of the tubes were compared. RESULTS Measurements were most accurate on images reconstructed with use of a standard kernel (mean error: -0.03 +/- 0.21 mm for wall thickness and -0.12 +/- 0.11 mm for the luminal radius). There was no significant difference in accuracy among images with the use of variable slice thicknesses or a variable FOV. Below a 1-mm threshold, the measurement failed to represent the change of the real dimensions. CONCLUSION Measurement accuracy was strongly influenced by the specific reconstruction kernel utilized. For accurate measurement, standardization of the imaging protocol and selection of the appropriate anatomic level are essential.
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Affiliation(s)
- Namkug Kim
- Department of Radiology and Research Institute of Radiology, University of Ulsan College of Medicine, Asan Medical Center, Seoul 138-736, Korea
- Department of Industrial Engineering, Seoul National University, Seoul 138-736, Korea
| | - Joon Beom Seo
- Department of Radiology and Research Institute of Radiology, University of Ulsan College of Medicine, Asan Medical Center, Seoul 138-736, Korea
| | - Koun-Sik Song
- Department of Radiology and Research Institute of Radiology, University of Ulsan College of Medicine, Asan Medical Center, Seoul 138-736, Korea
| | - Eun Jin Chae
- Department of Radiology and Research Institute of Radiology, University of Ulsan College of Medicine, Asan Medical Center, Seoul 138-736, Korea
| | - Suk-Ho Kang
- Department of Industrial Engineering, Seoul National University, Seoul 138-736, Korea
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Affiliation(s)
- Yi-Hwa Liu
- Section of Cardiovascular Medicine, Department of Internal Medicine, Yale University School of Medicine, New Haven, Conn 06520, USA.
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van Dalen JA, Hoffmann AL, Dicken V, Vogel WV, Wiering B, Ruers TJ, Karssemeijer N, Oyen WJG. A novel iterative method for lesion delineation and volumetric quantification with FDG PET. Nucl Med Commun 2007; 28:485-93. [PMID: 17460540 DOI: 10.1097/mnm.0b013e328155d154] [Citation(s) in RCA: 95] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
OBJECTIVES The determination of lesion boundaries on FDG PET is difficult due to the point-spread blurring and unknown uptake of activity within a lesion. Standard threshold-based methods for volumetric quantification on PET usually neglect any size dependence and are biased by dependence on the signal-to-background ratio (SBR). A novel, model-based method is hypothesized to provide threshold levels independent f the SBR and to allow accurate measurement of volumes down to the resolution of the PET scanner. METHODS A background-subtracted relative-threshold level (RTL) method was derived, based on a convolution of the point-spread function and a sphere with diameter D. Validation of the RTL method was performed using PET imaging of a Jaszczak phantom with seven hollow spheres (D=10-60 mm). Activity concentrations for the background and spheres (signal) were varied to obtain SBRs of 1.5-10. An iterative procedure was introduced for volumetric quantification, as the optimal RTL depends on a priori knowledge of the volume. The feasibility of the RTL method was tested in two patients with liver metastases and compared to a standard method using a fixed percentage of the signal. RESULTS Phantom data validated that the theoretically optimal RTL depends on the sphere size, but not on the SBR. Typically, RTL=40% (D=15-60 mm), and RTL>50% for small spheres (D<12 mm). The RTL method is better applicable to patient data than the standard method. CONCLUSIONS Based on an iterative procedure, the RTL method has been shown to provide optimal threshold levels independent of the SBR and to be applicable in phantom and in patient studies. It is a promising tool for lesion delineation and volumetric quantification of PET lesions.
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Affiliation(s)
- Jorn A van Dalen
- Department of Nuclear Medicine, Radboud University Nijmegen Medical Centre, the Netherlands.
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Davis JB, Reiner B, Székely G, Ciernik IF. Reply to the Letter to the Editor by A.L. Hoffmann et al. Radiother Oncol 2007. [DOI: 10.1016/j.radonc.2007.02.012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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Hoffmann AL, van Dalen JA, Lee J, Grégoire V, Oyen WJG, Kaanders JHAM. Regarding Davis et al.: Assessment of (18)F PET signals for automatic target volume definition in radiotherapy treatment planning. Radiother Oncol 2007; 83:102-3; author reply 103. [PMID: 17218030 DOI: 10.1016/j.radonc.2006.11.020] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2006] [Accepted: 11/13/2006] [Indexed: 10/23/2022]
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Noz ME, Chung G, Lee BY, Maguire GQ, DeWyngaert JK, Doshi JV, Kramer EL, Murphy-Walcott AD, Zeleznik MP, Kwak NG. Enhancing the utility of prostascint SPECT scans for patient management. J Med Syst 2006; 30:123-32. [PMID: 16705997 DOI: 10.1007/s10916-005-7987-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
This project investigated reducing the artifact content of In-ill ProstaScint SPECT scans for use in treatment planning and management. Forty-one patients who had undergone CT or MRI scans and simultaneous Tc-99m RBC/In-111 ProstaScint SPECT scans were included. SPECT volume sets, reconstructed using Ordered Set-Expectation Maximum (OS-EM) were compared against those reconstructed with standard Filtered Back projection (FBP). Bladder activity in Tc-99m scans was suppressed within an ellipsoidal volume. Tc-99m voxel values were subtracted from the corresponding In-111 after scaling based on peak activity within the descending aorta. The SPECT volume data sets were merged with the CT or MRI scans before and after processing. Volume merging, based both on visual assessment and statistical evaluation, was not affected. Thus iterative reconstruction together with bladder suppression and blood pool subtraction may improve the interpretation and utility of ProstaScint SPECT scans for patient management.
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Affiliation(s)
- Marilyn E Noz
- Department of Radiology, NYU School of Medicine, New York, USA.
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Li S, Dobrucki LW, Sinusas AJ, Liu YH. A new method for SPECT quantification of targeted radiotracers uptake in the myocardium. ACTA ACUST UNITED AC 2006; 8:684-91. [PMID: 16686019 DOI: 10.1007/11566489_84] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
We developed a new method for absolute quantification of targeted radiotracers uptake in the myocardium using hybrid SPECT/CT and an external reference point source. A segmentation algorithm based on the level set was developed to determine the endocardial edges from CT, which were subsequently applied to the physically co-registered SPECT. A 3-D Gaussian fitting method was applied for quantification of the external point source. The total targeted radiotracer activity in the myocardium was normalized to that in the point source to calculate the absolute uptake of targeted radiotracer in the myocardium. Preliminary validation was performed in rats with ischemia-induced angiogenesis. The quantified in vivo radiotracer uptake was compared to the postmortem tissue radioactive well-counting of the myocardium. Our methods worked well for identification of the endocardial edges. Quantification of the focal uptake was consistent with the well-counting data. Our methods may have the potential of providing precise absolute quantification of targeted radiotracer uptake in the myocardium.
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MESH Headings
- Animals
- Drug Delivery Systems/methods
- Heart/diagnostic imaging
- Image Interpretation, Computer-Assisted/methods
- Myocardium/metabolism
- Neovascularization, Pathologic/diagnosis
- Neovascularization, Pathologic/etiology
- Neovascularization, Pathologic/metabolism
- Radioisotopes/pharmacokinetics
- Radiopharmaceuticals/pharmacokinetics
- Rats
- Reperfusion Injury/complications
- Reperfusion Injury/diagnosis
- Reperfusion Injury/metabolism
- Reproducibility of Results
- Sensitivity and Specificity
- Tomography, Emission-Computed, Single-Photon/methods
- Ventricular Dysfunction, Left/complications
- Ventricular Dysfunction, Left/diagnosis
- Ventricular Dysfunction, Left/etiology
- Ventricular Dysfunction, Left/metabolism
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Affiliation(s)
- Shimin Li
- Section of Cardiovascular Medicine, Department of Internal Medicine, Yale University School of Medicine, New Haven, CT, USA.
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Gantet P, Payoux P, Celler A, Majorel C, Gourion D, Noll D, Esquerré JP. Iterative three-dimensional expectation maximization restoration of single photon emission computed tomography images: Application in striatal imaging. Med Phys 2005; 33:52-60. [PMID: 16485409 DOI: 10.1118/1.2135908] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
Single photon emission computed tomography imaging suffers from poor spatial resolution and high statistical noise. Consequently, the contrast of small structures is reduced, the visual detection of defects is limited and precise quantification is difficult. To improve the contrast, it is possible to include the spatially variant point spread function of the detection system into the iterative reconstruction algorithm. This kind of method is well known to be effective, but time consuming. We have developed a faster method to account for the spatial resolution loss in three dimensions, based on a postreconstruction restoration method. The method uses two steps. First, a noncorrected iterative ordered subsets expectation maximization (OSEM) reconstruction is performed and, in the second step, a three-dimensional (3D) iterative maximum likelihood expectation maximization (ML-EM) a posteriori spatial restoration of the reconstructed volume is done. In this paper, we compare to the standard OSEM-3D method, in three studies (two in simulation and one from experimental data). In the two first studies, contrast, noise, and visual detection of defects are studied. In the third study, a quantitative analysis is performed from data obtained with an anthropomorphic striatal phantom filled with 123-I. From the simulations, we demonstrate that contrast as a function of noise and lesion detectability are very similar for both OSEM-3D and OSEM-R methods. In the experimental study, we obtained very similar values of activity-quantification ratios for different regions in the brain. The advantage of OSEM-R compared to OSEM-3D is a substantial gain of processing time. This gain depends on several factors. In a typical situation, for a 128 x 128 acquisition of 120 projections, OSEM-R is 13 or 25 times faster than OSEM-3D, depending on the calculation method used in the iterative restoration. In this paper, the OSEM-R method is tested with the approximation of depth independent resolution. For the striatum this approximation is appropriate, but for other clinical situations we will need to include a spatially varying response. Such a response is already included in OSEM-3D.
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Affiliation(s)
- Pierre Gantet
- Laboratoire de Biophysique EA3033, Université Paul Sabatier Toulouse, France
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38
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Hedström E, Palmer J, Ugander M, Arheden H. Myocardial SPECT perfusion defect size compared to infarct size by delayed gadolinium-enhanced magnetic resonance imaging in patients with acute or chronic infarction. Clin Physiol Funct Imaging 2004; 24:380-6. [PMID: 15522048 DOI: 10.1111/j.1475-097x.2004.00579.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
BACKGROUND Single photon emission computed tomography (SPECT) perfusion imaging has been considered a reference method for non-invasive estimation of infarct size in man. Recently, delayed gadolinium-enhanced magnetic resonance imaging (DE-MRI) has evolved as an accurate tool to quantify infarct size. Therefore, the present study was designed to compare perfusion defect size by SPECT to hyperenhanced volume by DE-MRI. METHODS DE-MRI was performed in 30 patients. Fourteen were patients with revascularized first-time acute infarctions, eight revascularized chronic infarctions, and eight clinically referred non-revascularized patients. SPECT was performed in the same patients and analysed by a commercial package. RESULTS The hypoperfused volume by SPECT was larger than the hyperenhanced volume by DE-MRI by 8 +/- 8 ml (6% +/- 5 percentage points), 10 +/- 18 ml (6% +/- 11 percentage points), and 26 +/- 30 ml (12% +/- 10 percentage points) in the acute, chronic and clinical populations, respectively. Left ventricle wall volume was smaller by SPECT in all settings. CONCLUSION The SPECT perfusion defect size was comparable with but generally slightly larger than the hyperenhanced volume by DE-MRI in both absolute and relative terms in patients with acute and chronic infarction. The results may be related to systematic differences between modalities but could also be influenced by biological phenomena such as wall thinning or hypoperfused but viable myocardium.
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Affiliation(s)
- Erik Hedström
- Department of Clinical Physiology, Lund University Hospital, SE-221 85 Lund, Sweden
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Saba OI, Hoffman EA, Reinhardt JM. Maximizing quantitative accuracy of lung airway lumen and wall measures obtained from X-ray CT imaging. J Appl Physiol (1985) 2003; 95:1063-75. [PMID: 12754180 DOI: 10.1152/japplphysiol.00962.2002] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
To objectively quantify airway geometry from three-dimensional computed tomographic (CT) images, an idealized (circular cross section) airway model is parameterized by airway luminal caliber, wall thickness, and tilt angle. Using a two-dimensional CT slice, an initial guess for the airway center, and the full-width-half-maximum principle, we form an estimate of inner and outer airway wall locations. We then fit ellipses to the inner and outer airway walls via a direct least squares fit and use the major and minor axes of the ellipses to estimate the tilt and in-plane rotation angles. Convolving the airway model, initialized with these estimates, with the three-dimensional scanner point-spread function forms the predicted image. The difference between predicted and actual images is minimized by refining the model parameter estimates via a multidimensional, unconstrained, nonlinear minimization routine. When optimization converges, airway model parameters estimate the airway inner and outer radii and tilt angle. Results using a Plexiglas phantom show that tilt angle is estimated to within +/-4 degrees and both inner and outer radii to within one-half pixel when a "standard" CT reconstruction kernel is used. By opening up the ability to measure airways that are not oriented perpendicular to the scanning plane, this method allows evaluation of a greater sampling of airways in a two-dimensional CT slice than previously possible. In addition, by combining the tilt-angle compensation with the deconvolution method, we provide significant improvement over the previous full-width-half-maximum method for assessing location of the luminal edge but not the outer edge of the airway wall.
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Affiliation(s)
- Osama I Saba
- Department of Biomedical Engineering, University of Iowa, Iowa City, IA 52242, USA
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40
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De Bondt P, Vandenberghe S, De Mey S, Segers P, De Winter O, De Sutter J, Van De Wiele C, Verdonck P, Dierckx R. Nucl Med Commun 2003; 24:771-777. [DOI: 10.1097/00006231-200307000-00006] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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41
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De Bondt P, Vandenberghe S, De Mey S, Segers P, De Winter O, De Sutter J, Van De Wiele C, Verdonck P, Dierckx RA. Validation of planar and tomographic radionuclide ventriculography by a dynamic ventricular phantom. Nucl Med Commun 2003; 24:771-7. [PMID: 12813195 DOI: 10.1097/01.mnm.0000080244.50447.ef] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Although there is increasing interest in the automatic processing of tomographic radionuclide ventriculography (TRV) studies, validation is mainly limited to a comparison of TRV results with data from planar radionuclide ventriculography (PRV) or gated perfusion single photon emission computed tomography (SPECT). The aim of this study was to use a dynamic physical cardiac phantom to validate the ejection fraction (EF) and volumes from PRV and TRV studies. A new dynamic left ventricular phantom was constructed and used to obtain 21 acquisitions in the planar and tomographic mode. The directly measured volumes and EFs of the phantom during the acquisitions were considered as the gold standard for comparison with TRV and PRV. EFs were calculated from PRV by background-corrected end-diastolic and end-systolic frames. Volumes and EFs were calculated from TRV by region growing with different lower thresholds to search for the optimal threshold. EF from PRV correlated significantly with the real EF (r=0.94, P=0.00). The optimal threshold value for volume calculation from TRV in 336 cases was 50% (r=0.98, P=0.00) yielding the best slope after linear regression. When considering these calculated end-diastolic and end-systolic volumes, EF correlated well (r=0.99, P=0.00) with the real EF, and this correlation was significantly (P=0.04) higher than that of the EF from PRV. Our experiments prove that EF measured by TRV yields more accurate results compared with PRV in dynamic cardiac phantom studies.
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Affiliation(s)
- P De Bondt
- Division of Nuclear Medicine, Ghent University Hospital, Ghent University, Ghent, Belgium.
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42
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Abstract
Radionuclides are used in nuclear medicine in a variety of diagnostic and therapeutic procedures. A knowledge of the radiation dose received by different organs in the body is essential to an evaluation of the risks and benefits of any procedure. In this paper, current methods for internal dosimetry are reviewed, as they are applied in nuclear medicine. Particularly, the Medical Internal Radiation Dose (MIRD) system for dosimetry is explained, and many of its published resources discussed. Available models representing individuals of different age and gender, including those representing the pregnant woman are described; current trends in establishing models for individual patients are also evaluated. The proper design of kinetic studies for establishing radiation doses for radiopharmaceuticals is discussed. An overview of how to use information obtained in a dosimetry study, including that of the effective dose equivalent (ICRP 30) and effective dose (ICRP 60), is given. Current trends and issues in internal dosimetry, including the calculation of patient-specific doses and in the use of small scale and microdosimetry techniques, are also reviewed.
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Affiliation(s)
- M G Stabin
- Radiation Internal Dose Information Center, Oak Ridge Associated Universities, TN 37831-0117, USA
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43
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Fleming JS, Alaamer AS. A rule based method for context sensitive threshold segmentation in SPECT using simulation. Phys Med Biol 1998; 43:2309-23. [PMID: 9725606 DOI: 10.1088/0031-9155/43/8/022] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Robust techniques for automatic or semi-automatic segmentation of objects in single photon emission computed tomography (SPECT) are still the subject of development. This paper describes a threshold based method which uses empirical rules derived from analysis of computer simulated images of a large number of objects. The use of simulation allowed the factors affecting the threshold which correctly segmented objects to be investigated systematically. Rules could then be derived from these data to define the threshold in any particular context. The technique operated iteratively and calculated local context sensitive thresholds along radial profiles from the centre of gravity of the object. It was evaluated in a further series of simulated objects and in human studies, and compared to the use of a global fixed threshold. The method was capable of improving accuracy of segmentation and volume assessment compared to the global threshold technique. The improvements were greater for small volumes, shapes with large surface area to volume ratio, variable surrounding activity and non-uniform distributions. The method was applied successfully to simulated objects and human studies and is considered to be a significant advance on global fixed threshold techniques.
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Affiliation(s)
- J S Fleming
- Department of Medical Physics, Southampton General Hospital, UK
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44
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Pretorius PH, King MA, Pan TS, de Vries DJ, Glick SJ, Byrne CL. Reducing the influence of the partial volume effect on SPECT activity quantitation with 3D modelling of spatial resolution in iterative reconstruction. Phys Med Biol 1998; 43:407-20. [PMID: 9509535 DOI: 10.1088/0031-9155/43/2/014] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Quantitative parameters such as the maximum and total counts in a volume are influenced by the partial volume effect. The magnitude of this effect varies with the non-stationary and anisotropic spatial resolution in SPECT slices. The objective of this investigation was to determine whether iterative reconstruction which includes modelling of the three-dimensional (3D) spatial resolution of SPECT imaging can reduce the impact of the partial volume effect on the quantitation of activity compared with filtered backprojection (FBP) techniques which include low-pass, and linear restoration filtering using the frequency distance relationship (FDR). The iterative reconstruction algorithms investigated were maximum-likelihood expectation-maximization (MLEM), MLEM with ordered subset acceleration (ML-OS), and MLEM with acceleration by the rescaled-block-iterative technique (ML-RBI). The SIMIND Monte Carlo code was used to simulate small hot spherical objects in an elliptical cylinder with and without uniform background activity as imaged by a low-energy ultra-high-resolution (LEUHR) collimator. Centre count ratios (CCRs) and total count ratios (TCRs) were determined as the observed counts over true counts. CCRs were unstable while TCRs had a bias of approximately 10% for all iterative techniques. The variance in the TCRs for ML-OS and ML-RBI was clearly elevated over that of MLEM, with ML-RBI having the smaller elevation. TCRs obtained with FDR-Wiener filtering had a larger bias (approximately 30%) than any of the iterative reconstruction methods but near stationarity is also reached. Butterworth filtered results varied by 9.7% from the centre to the edge. The addition of background has an influence on the convergence rate and noise properties of iterative techniques.
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Affiliation(s)
- P H Pretorius
- University of Massachusetts Medical Center, Worcester 01655, USA
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45
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Erdi YE, Mawlawi O, Larson SM, Imbriaco M, Yeung H, Finn R, Humm JL. Segmentation of lung lesion volume by adaptive positron emission tomography image thresholding. Cancer 1997. [DOI: 10.1002/(sici)1097-0142(19971215)80:12+<2505::aid-cncr24>3.0.co;2-f] [Citation(s) in RCA: 342] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Reinhardt JM, D'Souza ND, Hoffman EA. Accurate measurement of intrathoracic airways. IEEE TRANSACTIONS ON MEDICAL IMAGING 1997; 16:820-827. [PMID: 9533582 DOI: 10.1109/42.650878] [Citation(s) in RCA: 107] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Airway geometry measurements can provide information regarding pulmonary physiology and pathophysiology. There has been considerable interest in measuring intrathoracic airways in two-dimensional (2-D) slices from volumetric X-ray computed tomography (CT). Such measurements can be used to evaluate and track the progression of diseases affecting the airways. A popular airway measurement method uses the "half-max" criteria, in which the gray level at the airway wall is estimated to be halfway between the minimum and maximum gray levels along a ray crossing the edge. However, because the scanning process introduces blurring, the half-max approach may not be applicable across all airway sizes. We propose a new measurement method based on a model of the scanning process. In our approach, we examine the gray-level profile of a ray crossing the airway wall and use a maximum-likelihood method to estimate the airway inner and outer radius. Using CT scans of a physical phantom, we present results showing that the new approach is more accurate than the half-max method at estimating wall location for thin-walled airways.
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Affiliation(s)
- J M Reinhardt
- Department of Biomedical Engineering, University of Iowa, Iowa City 52242, USA.
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Qiu H, Hedlund LW, Gewalt SL, Benveniste H, Bare TM, Johnson GA. Progression of a focal ischemic lesion in rat brain during treatment with a novel glycine/NMDA antagonist: an in vivo three-dimensional diffusion-weighted MR microscopy study. J Magn Reson Imaging 1997; 7:739-44. [PMID: 9243396 DOI: 10.1002/jmri.1880070421] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Stroke was induced in two groups of anesthetized rats by occlusion of the middle cerebral artery (MCA) and ipsilateral common carotid artery. Group 1 (control) received vehicle and group 2 received the glycine N-methyl-D-aspartate (NMDA) antagonist ZD9379. Stroke volume was assessed by three-dimensional diffusion-weighted MR microscopy at 2.5 and 6 hours of MCA occlusion. At 2.5 hours, stroke volumes were identical in the two groups. At 6 hours, stroke volumes had increased by 15% in the control group; in contrast, the treated group showed a 40% reduced stroke volume. Conclusions from this in vivo study were as follows: (a) our technique allows more efficient and accurate measurement of stroke volume with an improvement in resolution over a previous method; (b) the ability to measure stroke volume at multiple time points shows volume change and assessment of time dependency of drug treatment; (c) at 6 hours, the glycine antagonist ZD9379 reduced stroke volume by 40%.
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Affiliation(s)
- H Qiu
- Center for In Vivo Microscopy, Duke University Medical Center, Durham, NC 27710, USA
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48
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Erwin WD, Groch MW, Macey DJ, DeNardo GL, DeNardo SJ, Shen S. A radioimmunoimaging and MIRD dosimetry treatment planning program for radioimmunotherapy. Nucl Med Biol 1996; 23:525-32. [PMID: 8832711 DOI: 10.1016/0969-8051(96)00036-4] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
A treatment planning program for radioimmunotherapy employing quantitative Anger camera imaging and the MIRD formalism has been designed and implemented on a clinical nuclear medicine computer. Radionuclide residence times are calculated from linear, mono- and bi-exponential, and cubic spline fits to regional activity versus time curves, and radiation-absorbed dose estimates for all target organs for 131I, 67Cu, and 58 other radionuclides can be calculated. This software has been successfully applied to radioimmunotherapy of B-cell malignancies and breast adenocarcinomas.
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Affiliation(s)
- W D Erwin
- Siemens Medical Systems, Hoffman Estates, IL 60195-7372, USA
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Sjörgreen K, Ljungberg M, Strand SE. Parameters influencing volume and activity quantitation in SPECT. Acta Oncol 1996; 35:323-30. [PMID: 8679264 DOI: 10.3109/02841869609101649] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Several factors influence the accuracy to which information on the in vivo activity concentration can be obtained from SPECT images. The accuracy in image contrast and the quantitation of volume and activity has here been examined for a SPECT system aimed for absorbed dose determinations in systemic radiation therapy. The influence of source dimensions, object contrast, noise level, energy window width and the reconstruction filter was examined. All the investigated parameters affected the recoveries. Volumes of above 20 cm3 could be quantified to within +/- 20%, for object contrasts of above 96%, and within +/- 40% for object contrasts above 81%, providing limited levels of noise. Both the image contrast and the volume quantification is expected to be improved in situations with low object contrasts, if accurate correction for scattered photons can be developed. Obtained limitations in the quantitation of activity with the present method should be reduced by development of a more accurate background subtraction technique.
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Affiliation(s)
- K Sjörgreen
- Department of Radiation Physics, Lund University Hospital, Lund, Sweden
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50
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Stapleton SJ, Caldwell CB, Ehrlich LE, Leonhardt CL, Black SE, Yaffe MJ. Effects of non-linear flow and spatial orientation on technetium-99m hexamethylpropylene amine oxime single-photon emission tomography. EUROPEAN JOURNAL OF NUCLEAR MEDICINE 1995; 22:1009-16. [PMID: 7588937 DOI: 10.1007/bf00808412] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The effects of two post-acquisition corrections on the visual and quantitative analysis of technetium-99m hexamethylpropylene amine oxime (HMPAO) single-photon emission tomography (SPET) were determined. The corrections were for: (1) the improper spatial orientation of the patient data sets, and (2) the non-linear uptake of HMPAO across the blood-brain barrier. Reorienting the SPET image data sets removed observers' uncertainty in assessment caused by suspected head tilt; however, it increased their uncertainty due to perceived subtle perfusion deficits. Applying the correction to compensate for the decrease in uptake of HMPAO in high-flow regions resulted in an increase in the number of positive assessments. In a study involving 30 patient studies, intra-observer reliability increased from 62% to 83% (average of two observers) after applying both of the corrections, while inter-observer reliability improved from 62% to 81%. Quantitative methods of analysing the images are also affected by the corrections. In an ROI-based classification scheme, the quantitative assessments of more than one-half of the images are affected by the two corrections. These results need to be considered when comparing both quantitative and visual results from different studies in which the corrections may or may not have been applied.
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Affiliation(s)
- S J Stapleton
- Department of Medical Biophysics, University of Toronto, Sunnybrook Health Science Centre, Canada
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