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Title: Dosimetric evaluation of daily rigid and nonrigid geometric correction strategies during on-line image-guided radiation therapy (IGRT) of prostate cancer

Abstract

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 to 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 clinicallymore » 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

Authors:
; ; ; ;  [1];  [2]
  1. Radiation Treatment Program, London Regional Cancer Program, London Health Sciences Centre, London, Ontario N6A 4L6 (Canada) and Department of Medical Biophysics, University of Western Ontario, London, Ontario N6A 5B8 (Canada)
  2. (Canada) and Department of Medical Biophysics, University of Western Ontario, London, Ontario N6A 5B8 (Canada) and Department of Oncology, University of Western Ontario, London, Ontario N6A 5B8 (Canada)
Publication Date:
OSTI Identifier:
20853926
Resource Type:
Journal Article
Resource Relation:
Journal Name: Medical Physics; Journal Volume: 34; Journal Issue: 1; Other Information: DOI: 10.1118/1.2405325; (c) 2007 American Association of Physicists in Medicine; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
62 RADIOLOGY AND NUCLEAR MEDICINE; BLADDER; CARCINOMAS; COMPUTERIZED TOMOGRAPHY; CORRECTIONS; DOSIMETRY; EVALUATION; FLUCTUATIONS; IMAGES; PATIENTS; PROSTATE; RADIATION DOSE DISTRIBUTIONS; RADIATION DOSES; RADIOTHERAPY; RECTUM; SIMULATION

Citation Formats

Song, William Y., Wong, Eugene, Bauman, Glenn S., Battista, Jerry J., Van Dyk, Jake, and Radiation Treatment Program, London Regional Cancer Program, London Health Sciences Centre, London, Ontario N6A 4L6. Dosimetric evaluation of daily rigid and nonrigid geometric correction strategies during on-line image-guided radiation therapy (IGRT) of prostate cancer. United States: N. p., 2007. Web. doi:10.1118/1.2405325.
Song, William Y., Wong, Eugene, Bauman, Glenn S., Battista, Jerry J., Van Dyk, Jake, & Radiation Treatment Program, London Regional Cancer Program, London Health Sciences Centre, London, Ontario N6A 4L6. Dosimetric evaluation of daily rigid and nonrigid geometric correction strategies during on-line image-guided radiation therapy (IGRT) of prostate cancer. United States. doi:10.1118/1.2405325.
Song, William Y., Wong, Eugene, Bauman, Glenn S., Battista, Jerry J., Van Dyk, Jake, and Radiation Treatment Program, London Regional Cancer Program, London Health Sciences Centre, London, Ontario N6A 4L6. Mon . "Dosimetric evaluation of daily rigid and nonrigid geometric correction strategies during on-line image-guided radiation therapy (IGRT) of prostate cancer". United States. doi:10.1118/1.2405325.
@article{osti_20853926,
title = {Dosimetric evaluation of daily rigid and nonrigid geometric correction strategies during on-line image-guided radiation therapy (IGRT) of prostate cancer},
author = {Song, William Y. and Wong, Eugene and Bauman, Glenn S. and Battista, Jerry J. and Van Dyk, Jake and Radiation Treatment Program, London Regional Cancer Program, London Health Sciences Centre, London, Ontario N6A 4L6},
abstractNote = {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 to 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.},
doi = {10.1118/1.2405325},
journal = {Medical Physics},
number = 1,
volume = 34,
place = {United States},
year = {Mon Jan 15 00:00:00 EST 2007},
month = {Mon Jan 15 00:00:00 EST 2007}
}