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Meyers SM, Winter JD, Obeidi Y, Chung P, Menard C, Warde P, Fong H, McPartlin A, Parameswaran S, Berlin A, Bayley A, Catton C, Craig T. A feasibility study of adaptive radiation therapy for postprostatectomy prostate cancer. Med Dosim 2023; 49:150-158. [PMID: 37985297 DOI: 10.1016/j.meddos.2023.10.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2023] [Revised: 10/13/2023] [Accepted: 10/21/2023] [Indexed: 11/22/2023]
Abstract
Postoperative prostate radiotherapy requires large planning target volume (PTV) margins to account for motion and deformation of the prostate bed. Adaptive radiation therapy (ART) can incorporate image-guidance data to personalize PTVs that maintain coverage while reducing toxicity. We present feasibility and dosimetry results of a prospective study of postprostatectomy ART. Twenty-one patients were treated with single-adaptation ART. Conventional treatments were delivered for fractions 1 to 6 and adapted plans for the remaining 27 fractions. Clinical target volumes (CTVs) and small bowel delineated on fraction 1 to 4 CBCT were used to generate adapted PTVs and planning organ-at-risk (OAR) volumes for adapted plans. PTV volume and OAR dose were compared between ART and conventional using Wilcoxon signed-rank tests. Weekly CBCT were used to assess the fraction of CTV covered by PTV, CTV D99, and small bowel D1cc. Clinical metrics were compared using a Student's t-test (p < 0.05 significant). Offline adaptive planning required 1.9 ± 0.4 days (mean ± SD). ART decreased mean adapted PTV volume 61 ± 37 cc and bladder wall D50 compared with conventional treatment (p < 0.01). The CTV was fully covered for 96% (97%) of fractions with ART (conventional). Reconstructing dose on weekly CBCT, a nonsignificant reduction in CTV D99 was observed with ART (94%) compared to conventional (96%). Reduced CTV D99 with ART was significantly correlated with large anterior-posterior rectal diameter on simulation CT. ART reduced the number of fractions exceeding our institution's small bowel D1c limit from 14% to 7%. This study has demonstrated the feasibility of offline ART for post-prostatectomy cancer. ART facilitates PTV volume reduction while maintaining reasonable CTV coverage and can reduce the dose to adjacent normal tissues.
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Affiliation(s)
- Sandra M Meyers
- Department of Radiation Medicine and Applied Sciences, Moores Cancer Center, University of California, San Diego, La Jolla, CA, USA
| | - Jeff D Winter
- Radiation Medicine Program, Princess Margaret Cancer Centre, Toronto, Ontario, Canada; Department of Radiation Oncology, University of Toronto, Toronto, Ontario, Canada
| | | | - Peter Chung
- Radiation Medicine Program, Princess Margaret Cancer Centre, Toronto, Ontario, Canada; Department of Radiation Oncology, University of Toronto, Toronto, Ontario, Canada
| | - Cynthia Menard
- Centre Hospitalier de l'Université de Montréal, Montréal, Québec, Canada
| | - Padraig Warde
- Radiation Medicine Program, Princess Margaret Cancer Centre, Toronto, Ontario, Canada; Department of Radiation Oncology, University of Toronto, Toronto, Ontario, Canada
| | - Heng Fong
- The Ministry of Health Malaysia, Daerah Timur Laut, Penang, Malaysia
| | - Andrew McPartlin
- Radiation Medicine Program, Princess Margaret Cancer Centre, Toronto, Ontario, Canada; Department of Radiation Oncology, University of Toronto, Toronto, Ontario, Canada
| | | | - Alejandro Berlin
- Radiation Medicine Program, Princess Margaret Cancer Centre, Toronto, Ontario, Canada; Department of Radiation Oncology, University of Toronto, Toronto, Ontario, Canada
| | - Andrew Bayley
- Department of Radiation Oncology, University of Toronto, Toronto, Ontario, Canada; Department of Radiation Oncology, Sunnybrook Odette Cancer Center, University of Toronto, Toronto, Ontario, Canada
| | - Charles Catton
- Radiation Medicine Program, Princess Margaret Cancer Centre, Toronto, Ontario, Canada; Department of Radiation Oncology, University of Toronto, Toronto, Ontario, Canada
| | - Tim Craig
- Radiation Medicine Program, Princess Margaret Cancer Centre, Toronto, Ontario, Canada; Department of Radiation Oncology, University of Toronto, Toronto, Ontario, Canada.
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Lee M, Simeonov A, Stanescu T, Dawson LA, Brock KK, Velec M. MRI evaluation of normal tissue deformation and breathing motion under an abdominal compression device. J Appl Clin Med Phys 2021; 22:90-97. [PMID: 33449447 PMCID: PMC7882116 DOI: 10.1002/acm2.13165] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2020] [Revised: 12/16/2020] [Accepted: 12/22/2020] [Indexed: 11/12/2022] Open
Abstract
Purpose Abdominal compression can minimize breathing motion in stereotactic radiotherapy, though it may impact the positioning of dose‐limiting normal tissues. This study quantified the reproducibility of abdominal normal tissues and respiratory motion with the use of an abdominal compression device using MR imaging. Methods Twenty healthy volunteers had repeat MR over 3 days under an abdominal compression plate device. Normal tissues were delineated on daily axial T2‐weighted MR and compared on days 2 and 3 relative to day 1, after adjusting for baseline shifts relative to bony anatomy. Inter‐fraction organ deformation was computed using deformable registration of axial T2 images. Deformation > 5 mm was assumed to be clinically relevant. Inter‐fraction respiratory amplitude changes and intra‐fraction baseline drifts during imaging were quantified on daily orthogonal cine‐MR (70 s each), and changes > 3 mm were assumed to be relevant. Results On axial MR, the mean inter‐fraction normal tissue deformation was > 5 mm for all organs (range 5.1–13.4 mm). Inter‐fraction compression device misplacements > 5 mm and changes in stomach volume > 50% occurred at a rate of 93% and 38%, respectively, in one or more directions and were associated with larger adjacent organ deformation, in particular for the duodenum. On cine‐MR, inter‐fraction amplitude changes > 3 mm on day 2 and 3 relative to day 1 occurred at a rate of < 12.5% (mean superior–inferior change was 1.6 mm). Intra‐fraction baseline drifts > 3 mm during any cine‐MR acquisition occurred at a rate of 23% (mean superior–inferior changes was 2.4 mm). Conclusions Respiratory motion under abdominal compression is reproducible in most subjects within 3 mm. However, inter‐fraction deformations greater than 5 mm in normal tissues were common and larger than inter‐ and intra‐fraction respiratory changes. Deformations were driven mostly by variable stomach contents and device positioning. The magnitude of this motion may impact normal tissue dosimetry during stereotactic radiotherapy.
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Affiliation(s)
- Maureen Lee
- Department of Radiation Oncology, Princess Margaret Cancer Centre, University Health Network, University of Toronto, 610 University Avenue, Toronto, ON, M5G 2M9, Canada
| | - Anna Simeonov
- Department of Radiation Oncology, Princess Margaret Cancer Centre, University Health Network, University of Toronto, 610 University Avenue, Toronto, ON, M5G 2M9, Canada
| | - Teo Stanescu
- Department of Radiation Oncology, Princess Margaret Cancer Centre, University Health Network, University of Toronto, 610 University Avenue, Toronto, ON, M5G 2M9, Canada.,TECHNA Institute, University Health Network, 100 College Street, Toronto, ON, M5G 1L5, Canada
| | - Laura A Dawson
- Department of Radiation Oncology, Princess Margaret Cancer Centre, University Health Network, University of Toronto, 610 University Avenue, Toronto, ON, M5G 2M9, Canada
| | - Kristy K Brock
- Department of Imaging Physics, The University of Texas MD Anderson Cancer Center, Houston, TX, 77030, USA
| | - Michael Velec
- Department of Radiation Oncology, Princess Margaret Cancer Centre, University Health Network, University of Toronto, 610 University Avenue, Toronto, ON, M5G 2M9, Canada.,TECHNA Institute, University Health Network, 100 College Street, Toronto, ON, M5G 1L5, Canada
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Shi X, Diwanji T, Mooney KE, Lin J, Feigenberg S, D'Souza WD, Mistry NN. Evaluation of template matching for tumor motion management with cine-MR images in lung cancer patients. Med Phys 2014; 41:052304. [PMID: 24784397 DOI: 10.1118/1.4870978] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
PURPOSE Accurate determination of tumor position is crucial for successful application of motion compensated radiotherapy in lung cancer patients. This study tested the performance of an automated template matching algorithm in tracking the tumor position on cine-MR images by examining the tracking error and further comparing the tracking error to the interoperator variability of three human reviewers. METHODS Cine-MR images of 12 lung cancer patients were analyzed. Tumor positions were determined both automatically with template matching and manually by a radiation oncologist and two additional reviewers trained by the radiation oncologist. Performance of the automated template matching was compared against the ground truth established by the radiation oncologist. Additionally, the tracking error of template matching, defined as the difference in the tumor positions determined with template matching and the ground truth, was investigated and compared to the interoperator variability for all patients in the anterior-posterior (AP) and superior-inferior (SI) directions, respectively. RESULTS The median tracking error for ten out of the 12 patients studied in both the AP and SI directions was less than 1 pixel (= 1.95 mm). Furthermore, the median tracking error for seven patients in the AP direction and nine patients in the SI direction was less than half a pixel (= 0.975 mm). The median tracking error was positively correlated with the tumor motion magnitude in both the AP (R = 0.55, p = 0.06) and SI (R = 0.67, p = 0.02) directions. Also, a strong correlation was observed between tracking error and interoperator variability (y = 0.26 + 1.25x, R = 0.84, p < 0.001) with the latter larger. CONCLUSIONS Results from this study indicate that the performance of template matching is comparable with or better than that of manual tumor localization. This study serves as preliminary investigations towards developing online motion tracking techniques for hybrid MRI-Linac systems. Accuracy of template matching makes it a suitable candidate to replace the labor intensive manual tumor localization for obtaining the ground truth when testing other motion management techniques.
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Affiliation(s)
- Xiutao Shi
- Department of Radiation Oncology, University of Maryland School of Medicine, Baltimore, Maryland 21201
| | - Tejan Diwanji
- Department of Radiation Oncology, University of Maryland School of Medicine, Baltimore, Maryland 21201
| | - Karen E Mooney
- Department of Radiation Oncology, University of Maryland School of Medicine, Baltimore, Maryland 21201
| | - Jolinta Lin
- Department of Radiation Oncology, University of Maryland School of Medicine, Baltimore, Maryland 21201
| | - Steven Feigenberg
- Department of Radiation Oncology, University of Maryland School of Medicine, Baltimore, Maryland 21201
| | - Warren D D'Souza
- Department of Radiation Oncology, University of Maryland School of Medicine, Baltimore, Maryland 21201
| | - Nilesh N Mistry
- Department of Radiation Oncology, University of Maryland School of Medicine, Baltimore, Maryland 21201
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Wysocka B, Moseley J, Brock K, Lockwood G, Wilson G, Simeonov A, Haider MA, Menard C, Bissonnette JP, Dawson LA, Ringash J. Assessment of nonrespiratory stomach motion in healthy volunteers in fasting and postprandial states. Pract Radiat Oncol 2013; 4:288-293. [PMID: 25194096 DOI: 10.1016/j.prro.2013.10.001] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2013] [Revised: 10/02/2013] [Accepted: 10/02/2013] [Indexed: 12/23/2022]
Abstract
PURPOSE To characterize nonrespiratory stomach motion in the fasting state and postprandial. METHODS AND MATERIALS Ten healthy volunteers underwent 2-dimensional Fiesta cine magnetic resonance imaging studies in 30-second voluntary breath hold, in axial, coronal, and 2 oblique planes while fasting, and 5, 15, 30, 45, and 60 minutes postmeal. Each stomach contour was delineated and sampled with 200 points. Matching points were found for all contours in the same 30-second acquisition. Using deformable parametric analysis (Matlab, version 7.1), mean magnitude, and standard deviation of displacement of each point were determined for each patient. Maximal, minimal, and median population values in 6 cardinal, and in any direction, were calculated. RESULTS The median of mean displacements for the baseline position of each point was small and rarely exceeded 1.1 mm; greatest value was 1.6 mm superior-inferior. Median displacement (pooled across time) in the right-left, superior-inferior, and anterior-posterior directions was 0.3 (range, -0.7 to 1.3), 0.8 (-0.4 to 2.4), and 0.3 (-1.1 to 1.6) mm, respectively. Fasting and postprandial standard deviation did not differ. CONCLUSIONS Nonrespiratory stomach displacement is small and stomach position is stable after a small, standard meal. Radiation therapy may be delivered at any time within the first hour after eating without significant compromise of planned planning target volumes.
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Affiliation(s)
- Barbara Wysocka
- Department of Radiation Oncology, Princess Margaret Cancer Centre, University of Toronto, Toronto, Ontario, Canada
| | - Joanne Moseley
- Department of Radiation Physics, Princess Margaret Cancer Centre, University of Toronto, Toronto, Ontario, Canada
| | - Kristy Brock
- Department of Radiation Physics, Princess Margaret Cancer Centre, University of Toronto, Toronto, Ontario, Canada
| | - Gina Lockwood
- Department of Biostatistics, University Health Network, Princess Margaret Cancer Centre, Toronto, Ontario, Canada
| | - Graham Wilson
- Department of Radiation Physics, Princess Margaret Cancer Centre, University of Toronto, Toronto, Ontario, Canada
| | - Anna Simeonov
- Department of Radiation Physics, Princess Margaret Cancer Centre, University of Toronto, Toronto, Ontario, Canada
| | - Masoom A Haider
- Department of Medical Imaging, Princess Margaret Cancer Centre, University of Toronto, Toronto, Ontario, Canada
| | - Cynthia Menard
- Department of Radiation Oncology, Princess Margaret Cancer Centre, University of Toronto, Toronto, Ontario, Canada
| | - Jean-Pierre Bissonnette
- Department of Radiation Physics, Princess Margaret Cancer Centre, University of Toronto, Toronto, Ontario, Canada
| | - Laura A Dawson
- Department of Radiation Oncology, Princess Margaret Cancer Centre, University of Toronto, Toronto, Ontario, Canada
| | - Jolie Ringash
- Department of Radiation Oncology, Princess Margaret Cancer Centre, University of Toronto, Toronto, Ontario, Canada.
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Tsang DS, Voncken FEM, Tse RV, Sykes J, Wong RKS, Dinniwell RE, Kim J, Ringash J, Brierley JD, Cummings BJ, Brade A, Dawson LA. A randomized controlled trial of lorazepam to reduce liver motion in patients receiving upper abdominal radiation therapy. Int J Radiat Oncol Biol Phys 2013; 87:881-7. [PMID: 24119833 DOI: 10.1016/j.ijrobp.2013.08.024] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2013] [Revised: 08/04/2013] [Accepted: 08/20/2013] [Indexed: 02/02/2023]
Abstract
PURPOSE Reduction of respiratory motion is desirable to reduce the volume of normal tissues irradiated, to improve concordance of planned and delivered doses, and to improve image guided radiation therapy (IGRT). We hypothesized that pretreatment lorazepam would lead to a measurable reduction of liver motion. METHODS AND MATERIALS Thirty-three patients receiving upper abdominal IGRT were recruited to a double-blinded randomized controlled crossover trial. Patients were randomized to 1 of 2 study arms: arm 1 received lorazepam 2 mg by mouth on day 1, followed by placebo 4 to 8 days later; arm 2 received placebo on day 1, followed by lorazepam 4 to 8 days later. After tablet ingestion and daily radiation therapy, amplitude of liver motion was measured on both study days. The primary outcomes were reduction in craniocaudal (CC) liver motion using 4-dimensional kV cone beam computed tomography (CBCT) and the proportion of patients with liver motion ≤5 mm. Secondary endpoints included motion measured with cine magnetic resonance imaging and kV fluoroscopy. RESULTS Mean relative and absolute reduction in CC amplitude with lorazepam was 21% and 2.5 mm respectively (95% confidence interval [CI] 1.1-3.9, P=.001), as assessed with CBCT. Reduction in CC amplitude to ≤5 mm residual liver motion was seen in 13% (95% CI 1%-25%) of patients receiving lorazepam (vs 10% receiving placebo, P=NS); 65% (95% CI 48%-81%) had reduction in residual CC liver motion to ≤10 mm (vs 52% with placebo, P=NS). Patients with large respiratory movement and patients who took lorazepam ≥60 minutes before imaging had greater reductions in liver CC motion. Mean reductions in liver CC amplitude on magnetic resonance imaging and fluoroscopy were nonsignificant. CONCLUSIONS Lorazepam reduces liver motion in the CC direction; however, average magnitude of reduction is small, and most patients have residual motion >5 mm.
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Affiliation(s)
- Derek S Tsang
- Princess Margaret Cancer Centre, University Health Network, Department of Radiation Oncology, University of Toronto, Toronto, Canada
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Lin JM, Chuang TC, Chung HW, Tsai SY. Quantitative comparison of post-processing methods for reduction of frequency modulation sidebands in non-water suppression 1H MRS. NMR IN BIOMEDICINE 2013; 26:400-409. [PMID: 23233288 DOI: 10.1002/nbm.2877] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/07/2012] [Revised: 08/29/2012] [Accepted: 08/31/2012] [Indexed: 06/01/2023]
Abstract
Non-water suppression MRS (NWS MRS) has several advantages. First, the unsuppressed water signal can be used as internal calibration for metabolite quantification and as a reliable frequency/phase reference for retrospective motion correction. Second, it avoids the potential artifacts caused by incomplete water suppression (WS) and extra radiofrequency deposition from WS pulses. However, the frequency modulation (FM) sidebands originating from a large water signal will distort the spectrum. Among the methods proposed to solve the problems caused by FM sidebands, post-acquisition processing methods are superior in flexibility for general use compared with experimental methods. In this study, we propose two algorithms based on advanced matrix decomposition to remove the FM sidebands. These methods, the simultaneous diagonalization (QZ) algorithm and its subsequent variant, the simultaneously generalized Schur decomposition (SGSD) algorithm, were numerically evaluated using computer simulations. In addition, we quantitatively compared the performance of these methods and the modulus method in an in vitro experiment and in vivo NWS MRS against conventional WS data. Our results show that the proposed SGSD algorithm can reduce the FM sidebands to achieve superior estimation of concentration on three major metabolites. This method can be applied directly to spectra pre-acquired under various experimental conditions without modifying the acquisition sequences.
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Affiliation(s)
- Jyh-Miin Lin
- Center for Advanced MR Development, Department of Radiology, Duke University Medical Center, Durham, NC, USA; Department of Electrical Engineering, National Sun Yat-sen University, Kaohsiung, Taiwan
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Foltz WD, Haider MA, Chung P, Bayley A, Catton C, Ramanan V, Jaffray D, Wright GA, Ménard C. Prostate T(1) quantification using a magnetization-prepared spiral technique. J Magn Reson Imaging 2011; 33:474-81. [PMID: 21274991 DOI: 10.1002/jmri.22450] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
PURPOSE To adapt a magnetization-prepared spiral imaging technique, termed T1prep, for time-efficient radiofrequency (RF)-insensitive prostate T(1) quantification at 1.5 T and evaluate signal-to-noise ratio (SNR) limits to voxel-based versus subregion analysis. MATERIALS AND METHODS A magnetization-prepared spiral imaging technique was adapted for robust T(1) contrast development, multislice imaging within 5 minutes, and data regression to a monoexponential decay. In vitro testing evaluated RF insensitivity of the multislice acquisition plus method accuracy. A pilot study was performed in 15 patients with low or intermediate risk localized prostate cancer. RESULTS The multislice design displayed excellent RF insensitivity (<1% error for RF mistunings to ± 20%) and accuracy (within 3% of gold standard for T(1) values between 140 and 2100 msec). A clinical pilot study reported significantly reduced T(1) from PZ to CG to tumor subregions (PZ: 1421 ± 168 msec, n = 11; CG: 1314 ± 49 msec, n = 13; 1246 ± 68 msec, n = 8). SNR measurements identified an inappropriateness of voxel-based analysis. CONCLUSION T1prep can quantify prostate T(1) as an adjunct measure for quantitative perfusion measurements and longitudinal treatment response monitoring. Intrapatient heterogeneities support T(1) assessment within individual patients. SNR calculations will support a transition to voxel-based analysis in future trials.
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Affiliation(s)
- Warren D Foltz
- Radiation Medicine Program, Princess Margaret Hospital, University of Toronto, Toronto, Ontario, Canada.
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Comparison of liver tumor motion with and without abdominal compression using cine-magnetic resonance imaging. Int J Radiat Oncol Biol Phys 2010; 79:602-8. [PMID: 20675063 DOI: 10.1016/j.ijrobp.2010.04.028] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2010] [Revised: 04/18/2010] [Accepted: 04/20/2010] [Indexed: 01/06/2023]
Abstract
PURPOSE Abdominal compression (AC) can be used to reduce respiratory liver motion in patients undergoing liver stereotactic body radiotherapy. The purpose of the present study was to measure the changes in three-dimensional liver tumor motion with and without compression using cine-magnetic resonance imaging. PATIENTS AND METHODS A total of 60 patients treated as a part of an institutional research ethics board-approved liver stereotactic body radiotherapy protocol underwent cine T2-weighted magnetic resonance imaging through the tumor centroid in the coronal and sagittal planes. A total of 240 cine-magnetic resonance imaging sequences acquired at one to three images each second for 30-60 s were evaluated using an in-house-developed template matching tool (based on the coefficient correlation) to measure the magnitude of the tumor motion. The average tumor edge displacements were used to determine the magnitude of changes in the caudal-cranial (CC) and anteroposterior (AP) directions, with and without AC. RESULTS The mean tumor motion without AC of 11.7 mm (range, 4.8-23.3) in the CC direction was reduced to 9.4 mm (range, 1.6-23.4) with AC. The tumor motion was reduced in both directions (CC and AP) in 52% of the patients and in a single direction (CC or AP) in 90% of the patients. The mean decrease in tumor motion with AC was 2.3 and 0.6 mm in the CC and AP direction, respectively. Increased motion occurred in one or more directions in 28% of patients. Clinically significant (>3 mm) decreases were observed in 40% and increases in <2% of patients in the CC direction. CONCLUSION AC can significantly reduce three-dimensional liver tumor motion in most patients, although the magnitude of the reduction was smaller than previously reported.
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A cinematic magnetic resonance imaging study of milk of magnesia laxative and an antiflatulent diet to reduce intrafraction prostate motion. Int J Radiat Oncol Biol Phys 2009; 77:1072-8. [PMID: 19783378 DOI: 10.1016/j.ijrobp.2009.06.005] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2008] [Revised: 04/29/2009] [Accepted: 06/04/2009] [Indexed: 11/23/2022]
Abstract
PURPOSE To determine the reduction of prostate motion during a typical radiotherapy (RT) fraction from a bowel regimen comprising an antiflatulent diet and daily milk of magnesia. METHODS AND MATERIALS Forty-two patients with T1c-T2c prostate cancer voided the bladder and rectum before three cinematic magnetic resonance imaging scans obtained every 9 s for 9 min in a vacuum immobilization device. The MRIs were at baseline without bowel regimen (MRI-BL), before CT planning with bowel regimen (MRI-CT), and before a randomly assigned RT fraction (1-42) with bowel regimen (MRI-RT). A single observer tracked displacement of the posterior midpoint (PM) of the prostate. The primary endpoints were comparisons of the proportion of time that the PM was displaced >3 mm (PTPM3) from its initial position, and the secondary endpoints were comparisons of the reduction of initial rectal area, with and without the bowel regimen. RESULTS The mean rectal area was: 13.5 cm(2) at MRI-BL, 12.7 cm(2) at MRI-CT, and 12.3 cm(2) at MRI-RT (MRI-BL vs. MRI-CT, p = 0.11; MRI-BL vs. MRI-CT, p = 0.07). Moving rectal gas alone (56%) and moving gas and stool (18%) caused 74% of intrafraction prostate motion. The PTPM3 was 11.3% at MRI-BL, 4.8% at MRI-CT, and 12.0% at MRI-RT (MRI-BL vs. MRI-CT, p = 0.12; MRI-BL vs. MRI-RT, p = 0.89). CONCLUSION For subjects voiding their rectum before imaging, an antiflatulent diet and milk of magnesia laxative did not significantly reduce initial rectal area or intrafraction prostate motion.
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