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Title: Is Dose Deformation–Invariance Hypothesis Verified in Prostate IGRT?

Abstract

Purpose: To assess dose uncertainties resulting from the dose deformation–invariance hypothesis in prostate cone beam computed tomography (CT)–based image guided radiation therapy (IGRT), namely to evaluate whether rigidly propagated planned dose distribution enables good estimation of fraction dose distributions. Methods and Materials: Twenty patients underwent a CT scan for planning intensity modulated radiation therapy–IGRT delivering 80 Gy to the prostate, followed by weekly CT scans. Two methods were used to obtain the dose distributions on the weekly CT scans: (1) recalculating the dose using the original treatment plan; and (2) rigidly propagating the planned dose distribution. The cumulative doses were then estimated in the organs at risk for each dose distribution by deformable image registration. The differences between recalculated and propagated doses were finally calculated for the fraction and the cumulative dose distributions, by use of per-voxel and dose-volume histogram (DVH) metrics. Results: For the fraction dose, the mean per-voxel absolute dose difference was <1 Gy for 98% and 95% of the fractions for the rectum and bladder, respectively. The maximum dose difference within 1 voxel reached, however, 7.4 Gy in the bladder and 8.0 Gy in the rectum. The mean dose differences were correlated with gas volume for the rectum and patient external contour variationsmore » for the bladder. The mean absolute differences for the considered volume receiving greater than or equal to dose x (V{sub x}) of the DVH were between 0.37% and 0.70% for the rectum and between 0.53% and 1.22% for the bladder. For the cumulative dose, the mean differences in the DVH were between 0.23% and 1.11% for the rectum and between 0.55% and 1.66% for the bladder. The largest dose difference was 6.86%, for bladder V{sub 80Gy}. The mean dose differences were <1.1 Gy for the rectum and <1 Gy for the bladder. Conclusions: The deformation–invariance hypothesis was corroborated for the organs at risk in prostate IGRT except in cases of a large disappearance or appearance of rectal gas for the rectum and large external contour variations for the bladder.« less

Authors:
 [1];  [2]; ; ;  [1];  [2];  [1];  [2];  [2]; ;  [1];  [2]; ;  [1];  [2];  [2]
  1. INSERM, U1099, 35000 Rennes (France)
  2. (France)
Publication Date:
OSTI Identifier:
22649873
Resource Type:
Journal Article
Resource Relation:
Journal Name: International Journal of Radiation Oncology, Biology and Physics; Journal Volume: 97; Journal Issue: 4; Other Information: Copyright (c) 2016 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
62 RADIOLOGY AND NUCLEAR MEDICINE; BLADDER; COMPUTERIZED TOMOGRAPHY; GY RANGE 01-10; GY RANGE 10-100; PROSTATE; RADIATION DOSE DISTRIBUTIONS; RADIATION HAZARDS; RADIOTHERAPY; RECTUM

Citation Formats

Simon, Antoine, E-mail: antoine.simon@univ-rennes1.fr, Laboratoire Traitement du Signal et de l'Image, Université de Rennes 1, 35000 Rennes, Le Maitre, Amandine, Nassef, Mohamed, Rigaud, Bastien, Laboratoire Traitement du Signal et de l'Image, Université de Rennes 1, 35000 Rennes, Castelli, Joël, Laboratoire Traitement du Signal et de l'Image, Université de Rennes 1, 35000 Rennes, Department of Radiotherapy, Centre Eugène Marquis, 35000 Rennes, Acosta, Oscar, Haigron, Pascal, Laboratoire Traitement du Signal et de l'Image, Université de Rennes 1, 35000 Rennes, Lafond, Caroline, Crevoisier, Renaud de, Laboratoire Traitement du Signal et de l'Image, Université de Rennes 1, 35000 Rennes, and Department of Radiotherapy, Centre Eugène Marquis, 35000 Rennes. Is Dose Deformation–Invariance Hypothesis Verified in Prostate IGRT?. United States: N. p., 2017. Web. doi:10.1016/J.IJROBP.2016.12.011.
Simon, Antoine, E-mail: antoine.simon@univ-rennes1.fr, Laboratoire Traitement du Signal et de l'Image, Université de Rennes 1, 35000 Rennes, Le Maitre, Amandine, Nassef, Mohamed, Rigaud, Bastien, Laboratoire Traitement du Signal et de l'Image, Université de Rennes 1, 35000 Rennes, Castelli, Joël, Laboratoire Traitement du Signal et de l'Image, Université de Rennes 1, 35000 Rennes, Department of Radiotherapy, Centre Eugène Marquis, 35000 Rennes, Acosta, Oscar, Haigron, Pascal, Laboratoire Traitement du Signal et de l'Image, Université de Rennes 1, 35000 Rennes, Lafond, Caroline, Crevoisier, Renaud de, Laboratoire Traitement du Signal et de l'Image, Université de Rennes 1, 35000 Rennes, & Department of Radiotherapy, Centre Eugène Marquis, 35000 Rennes. Is Dose Deformation–Invariance Hypothesis Verified in Prostate IGRT?. United States. doi:10.1016/J.IJROBP.2016.12.011.
Simon, Antoine, E-mail: antoine.simon@univ-rennes1.fr, Laboratoire Traitement du Signal et de l'Image, Université de Rennes 1, 35000 Rennes, Le Maitre, Amandine, Nassef, Mohamed, Rigaud, Bastien, Laboratoire Traitement du Signal et de l'Image, Université de Rennes 1, 35000 Rennes, Castelli, Joël, Laboratoire Traitement du Signal et de l'Image, Université de Rennes 1, 35000 Rennes, Department of Radiotherapy, Centre Eugène Marquis, 35000 Rennes, Acosta, Oscar, Haigron, Pascal, Laboratoire Traitement du Signal et de l'Image, Université de Rennes 1, 35000 Rennes, Lafond, Caroline, Crevoisier, Renaud de, Laboratoire Traitement du Signal et de l'Image, Université de Rennes 1, 35000 Rennes, and Department of Radiotherapy, Centre Eugène Marquis, 35000 Rennes. Wed . "Is Dose Deformation–Invariance Hypothesis Verified in Prostate IGRT?". United States. doi:10.1016/J.IJROBP.2016.12.011.
@article{osti_22649873,
title = {Is Dose Deformation–Invariance Hypothesis Verified in Prostate IGRT?},
author = {Simon, Antoine, E-mail: antoine.simon@univ-rennes1.fr and Laboratoire Traitement du Signal et de l'Image, Université de Rennes 1, 35000 Rennes and Le Maitre, Amandine and Nassef, Mohamed and Rigaud, Bastien and Laboratoire Traitement du Signal et de l'Image, Université de Rennes 1, 35000 Rennes and Castelli, Joël and Laboratoire Traitement du Signal et de l'Image, Université de Rennes 1, 35000 Rennes and Department of Radiotherapy, Centre Eugène Marquis, 35000 Rennes and Acosta, Oscar and Haigron, Pascal and Laboratoire Traitement du Signal et de l'Image, Université de Rennes 1, 35000 Rennes and Lafond, Caroline and Crevoisier, Renaud de and Laboratoire Traitement du Signal et de l'Image, Université de Rennes 1, 35000 Rennes and Department of Radiotherapy, Centre Eugène Marquis, 35000 Rennes},
abstractNote = {Purpose: To assess dose uncertainties resulting from the dose deformation–invariance hypothesis in prostate cone beam computed tomography (CT)–based image guided radiation therapy (IGRT), namely to evaluate whether rigidly propagated planned dose distribution enables good estimation of fraction dose distributions. Methods and Materials: Twenty patients underwent a CT scan for planning intensity modulated radiation therapy–IGRT delivering 80 Gy to the prostate, followed by weekly CT scans. Two methods were used to obtain the dose distributions on the weekly CT scans: (1) recalculating the dose using the original treatment plan; and (2) rigidly propagating the planned dose distribution. The cumulative doses were then estimated in the organs at risk for each dose distribution by deformable image registration. The differences between recalculated and propagated doses were finally calculated for the fraction and the cumulative dose distributions, by use of per-voxel and dose-volume histogram (DVH) metrics. Results: For the fraction dose, the mean per-voxel absolute dose difference was <1 Gy for 98% and 95% of the fractions for the rectum and bladder, respectively. The maximum dose difference within 1 voxel reached, however, 7.4 Gy in the bladder and 8.0 Gy in the rectum. The mean dose differences were correlated with gas volume for the rectum and patient external contour variations for the bladder. The mean absolute differences for the considered volume receiving greater than or equal to dose x (V{sub x}) of the DVH were between 0.37% and 0.70% for the rectum and between 0.53% and 1.22% for the bladder. For the cumulative dose, the mean differences in the DVH were between 0.23% and 1.11% for the rectum and between 0.55% and 1.66% for the bladder. The largest dose difference was 6.86%, for bladder V{sub 80Gy}. The mean dose differences were <1.1 Gy for the rectum and <1 Gy for the bladder. Conclusions: The deformation–invariance hypothesis was corroborated for the organs at risk in prostate IGRT except in cases of a large disappearance or appearance of rectal gas for the rectum and large external contour variations for the bladder.},
doi = {10.1016/J.IJROBP.2016.12.011},
journal = {International Journal of Radiation Oncology, Biology and Physics},
number = 4,
volume = 97,
place = {United States},
year = {Wed Mar 15 00:00:00 EDT 2017},
month = {Wed Mar 15 00:00:00 EDT 2017}
}
  • Purpose: Prostate deformation is assumed to be a secondary correction and is typically ignored in the planning target volume (PTV) margin calculations. This assumption needs to be tested, especially when planning margins are reduced with daily image-guidance. In this study, deformation characteristics of the prostate and seminal vesicles were determined, and the dosimetric impact on treatment plans with different PTV margins was investigated. Methods: Ten prostate cancer patients were retrospectively selected for the study, each with three fiducial markers implanted in the prostate. Two hundred CBCT images were registered to respective planning CT images using a B-spline-based deformable image registrationmore » (DIR) software. A manual bony anatomy-based match was first applied based on the alignment of the pelvic bones and fiducial landmarks. DIR was then performed. For each registration, deformation vector fields (DVFs) of the prostate and seminal vesicles (SVs) were quantified using deformation-volume histograms. In addition, prostate rotation was evaluated and compared with prostate deformation. For a patient demonstrating small and large prostate deformations, target coverage degradation was analyzed in each of three treatment plans with PTV margins of 10 mm (6 mm at the prostate/rectum interface), as well as 5, and 3 mm uniformly. Results: Deformation of the prostate was most significant in the anterior direction. Maximum prostate deformation of greater than 10, 5, and 3 mm occurred in 1%, 17%, and 76% of the cases, respectively. Based on DVF-histograms, DVF magnitudes greater than 5 and 3 mm occurred in 2% and 27% of the cases, respectively. Deformation of the SVs was most significant in the posterior direction, and it was greater than 5 and 3 mm in 7.5% and 44.9% of the cases, respectively. Prostate deformation was found to be poorly correlated with rotation. Fifty percent of the cases showed rotation with negligible deformation and 7% of the cases showed significant deformation with minimal rotation (<3°). Average differences in the D{sub 95} dose to the prostate + SVs between the planning CT and CBCT images was 0.4% ± 0.5%, 3.0% ± 2.8%, and 6.6% ± 6.1%, respectively, for the plans with 10/6, 5, and 3 mm margins. For the case with both a large degree of prostate deformation (≈10% of the prostate volume) and rotation (≈8°), D{sub 95} was reduced by 0.5% ± 0.1%, 6.8% ± 0.6%, and 20.9% ± 1.6% for 10/6, 5, and 3 mm margin plans, respectively. For the case with large prostate deformation but negligible rotation (<1°), D{sub 95} was reduced by 0.4 ± 0.3, 3.9 ± 1.0, and 11.5 ± 2.5 for 10/6, 5, and 3 mm margin plans, respectively. Conclusions: Prostate deformation over a course of fractionated prostate radiotherapy may not be insignificant and may need to be accounted for in the planning margin design. A consequence of these results is that use of highly reduced planning margins must be viewed with caution.« less
  • Purpose: To compare toxicity profiles and biochemical tumor control outcomes between patients treated with high-dose image-guided radiotherapy (IGRT) and high-dose intensity-modulated radiotherapy (IMRT) for clinically localized prostate cancer. Materials and Methods: Between 2008 and 2009, 186 patients with prostate cancer were treated with IGRT to a dose of 86.4 Gy with daily correction of the target position based on kilovoltage imaging of implanted prostatic fiducial markers. This group of patients was retrospectively compared with a similar cohort of 190 patients who were treated between 2006 and 2007 with IMRT to the same prescription dose without, however, implanted fiducial markers inmore » place (non-IGRT). The median follow-up time was 2.8 years (range, 2-6 years). Results: A significant reduction in late urinary toxicity was observed for IGRT patients compared with the non-IGRT patients. The 3-year likelihood of grade 2 and higher urinary toxicity for the IGRT and non-IGRT cohorts were 10.4% and 20.0%, respectively (p = 0.02). Multivariate analysis identifying predictors for grade 2 or higher late urinary toxicity demonstrated that, in addition to the baseline Internatinoal Prostate Symptom Score, IGRT was associated with significantly less late urinary toxicity compared with non-IGRT. The incidence of grade 2 and higher rectal toxicity was low for both treatment groups (1.0% and 1.6%, respectively; p = 0.81). No differences in prostate-specific antigen relapse-free survival outcomes were observed for low- and intermediate-risk patients when treated with IGRT and non-IGRT. For high-risk patients, a significant improvement was observed at 3 years for patients treated with IGRT compared with non-IGRT. Conclusions: IGRT is associated with an improvement in biochemical tumor control among high-risk patients and a lower rate of late urinary toxicity compared with high-dose IMRT. These data suggest that, for definitive radiotherapy, the placement of fiducial markers and daily tracking of target positioning may represent the preferred mode of external-beam radiotherapy delivery for the treatment of prostate cancer.« less
  • We wanted to investigate whether using an endorectal balloon (ERB) in lieu of image guidance is reasonable. We compared daily prostate motion in 2 cohorts of patients with fiducial markers implanted in the prostate, one group with the ERB and the other without. Twenty-nine patients were treated using intensity-modulated radiation therapy: 14 with an ERB, and 15 without. All had fiducial markers placed in the prostate. We reviewed the daily displacements necessary to place the isocenter on the prostate as determined by portal imaging. In addition, we used the data to determine whether there is a change in prostate motionmore » over the treatment course. The average prostate displacement for patients treated without an ERB was slightly greater than the average displacement for patients treated with the ERB. However, the difference observed with the ERB was not statistically significant (p > 0.05). The margins necessary to encompass the prostate 95% of the time for the patients treated without an ERB in the lateral, cranio/caudal, and anterior/posterior dimensions would be 4.8, 12.1, and 15.2 mm, respectively. When using the ERB, the margins necessary would be 4.1, 10.4, and 11 mm, respectively. Prostate motion in the anterior-posterior direction actually increased over the course of treatment in patients without an ERB. This increase was prevented by use of the ERB. Day-to-day variability of the position of the prostate is reduced in all dimensions with the water-filled ERB, but not significantly statistically. Use of the water-filled ERB did not obviate performing some form of image guidance daily.« less
  • Purpose: To quantify the mitigation of geometric uncertainties achieved with the application of various patient setup techniques during the delivery of hypofractionated prostate cancer treatments, using tumor control probability (TCP) and normal tissue complication probability. Methods and Materials: Five prostate cancer patients with {approx}16 treatment CT studies, taken during the course of their radiation therapy (77 total), were analyzed. All patients were planned twice with an 18 MV six-field conformal technique, with 10- and 5-mm margin sizes, with various hypofractionation schedules (5 to 35 fractions). Subsequently, four clinically relevant patient setup techniques (laser guided and image guided) were simulated tomore » deliver such schedules. Results: As hypothesized, the impact of geometric uncertainties on clinical outcomes increased with more hypofractionated schedules. However, the absolute gain in TCP due to hypofractionation (up to 21.8% increase) was significantly higher compared with the losses due to geometric uncertainties (up to 8.6% decrease). Conclusions: The results of this study suggest that, although the impact of geometric uncertainties on the treatment outcomes increases as the number of fractions decrease, the reduction in TCP due to the uncertainties does not significantly offset the expected theoretical gain in TCP by hypofractionation.« less
  • The purpose of this study is to evaluate a geometric image guidance strategy that simultaneously correct for various inter-fractional rigid and nonrigid geometric uncertainties in an on-line environment, using field shape corrections (called the 'MU-MLC' technique). The effectiveness of this strategy was compared with two other simpler on-line image guidance strategies that are more commonly used in the clinic. To this end, five prostate cancer patients, with at least 15 treatment CT studies each, were analyzed. The prescription dose was set to the maximum dose that did not violate the rectum and bladder dose-volume constraints, and hence, was unique tomore » each patient. Deformable image registration and dose-tracking was performed on each CT image to obtain the cumulative treatment dose distributions. From this, maximum, minimum, and mean dose, as well as generalized equivalent uniform dose (gEUD) were calculated for each image guidance strategy. As expected, some dosimetric differences in the clinical target volume (CTV) were observed between the three image guidance strategies investigated. For example, up to {+-}2% discrepancy in prostate minimum dose were observed among the techniques. Of them, only the 'MU-MLC' technique did not reduce the prostate minimum dose for all patients (i.e., {>=}100%). However, the differences were clinically not significant to indicate the preference of one strategy over another, when using a uniform 5 mm margin size. For the organ-at-risks (OARs), the large rectum sparing effect ({<=}5.7 Gy, gEUD) and bladder overdosing effect ({<=}16 Gy, gEUD) were observed. This was likely due to the use of bladder contrast during CT simulation studies which was not done during the treatment CT studies. Therefore, ultimately, strategies to maintain relatively constant rectum and bladder volumes, throughout the treatment course, are required to minimize this effect. In conclusion, the results here suggest that simple translational corrections based on three-dimensional (3D) images is adequate to maintain target coverage, for margin sizes at least as large as 5 mm. In addition, due to large fluctuations in OAR volumes, innovative image guidance strategies are needed to minimize dose and maintain consistent sparing during the whole course of radiation therapy.« less