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Title: Interfractional Variations in the Setup of Pelvic Bony Anatomy and Soft Tissue, and Their Implications on the Delivery of Proton Therapy for Localized Prostate Cancer

Purpose: To quantify daily variations in the anatomy of patients undergoing radiation therapy for prostate carcinoma, to estimate their effect on dose distribution, and to evaluate the effectiveness of current standard planning and setup approaches employed in proton therapy. Methods: We used series of computed tomography data, which included the pretreatment scan, and between 21 and 43 in-room scans acquired on different treatment days, from 10 patients treated with intensity-modulated radiation therapy at Morristown Memorial Hospital. Variations in femur rotation angles, thickness of subcutaneous adipose tissue, and physical depth to the distal surface of the prostate for lateral beam arrangement were recorded. Proton dose distributions were planned with the standard approach. Daily variations in the location of the prescription isodose were evaluated. Results: In all 10 datasets, substantial variation was observed in the lateral tissue thickness (standard deviation of 1.7-3.6 mm for individual patients, variations of >5 mm from the planning computed tomography observed in all series), and femur rotation angle (standard deviation between 1.3{sup o} and 4.8{sup o}, with the maximum excursion exceeding 10{sup o} in 6 of 10 datasets). Shifts in the position of treated volume (98% isodose) were correlated with the variations in the lateral tissue thickness.more » Conclusions: Analysis suggests that, combined with image-guided setup verification, the range compensator expansion technique prevents loss of dose to target from femur rotation and soft-tissue deformation, in the majority of cases. Anatomic changes coupled with the uncertainties of particle penetration in tissue restrict possibilities for margin reduction in proton therapy of prostate cancer.« less
Authors:
 [1] ;  [2] ; ; ; ;  [1] ;  [3] ;  [4] ;  [3] ;  [1]
  1. Department of Radiation Oncology, Massachusetts General Hospital, Boston, MA (United States)
  2. Department of Radiation Oncology, Brigham and Women's Hospital, Boston, MA (United States)
  3. Department of Radiation Oncology, Morristown Memorial Hospital, Morristown, NJ (United States)
  4. Midwest Proton Radiotherapy Institute, Department of Radiation Oncology, Indiana University, Bloomington, IN (United States)
Publication Date:
OSTI Identifier:
21587588
Resource Type:
Journal Article
Resource Relation:
Journal Name: International Journal of Radiation Oncology, Biology and Physics; Journal Volume: 80; Journal Issue: 3; Other Information: DOI: 10.1016/j.ijrobp.2010.08.006; PII: S0360-3016(10)03052-X; Copyright (c) 2011 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; CARCINOMAS; CAT SCANNING; DAILY VARIATIONS; FEMUR; PROSTATE; PROTONS; RADIATION DOSE DISTRIBUTIONS; RADIATION DOSES; RADIOTHERAPY BARYONS; BODY; COMPUTERIZED TOMOGRAPHY; DIAGNOSTIC TECHNIQUES; DISEASES; DOSES; ELEMENTARY PARTICLES; FERMIONS; GLANDS; HADRONS; MALE GENITALS; MEDICINE; NEOPLASMS; NUCLEAR MEDICINE; NUCLEONS; ORGANS; RADIOLOGY; SKELETON; THERAPY; TOMOGRAPHY; VARIATIONS