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Title: Direction-Modulated Brachytherapy for High-Dose-Rate Treatment of Cervical Cancer. I: Theoretical Design

Purpose: To demonstrate that utilization of the direction-modulated brachytherapy (DMBT) concept can significantly improve treatment plan quality in the setting of high-dose-rate (HDR) brachytherapy for cervical cancer. Methods and Materials: The new, MRI-compatible, tandem design has 6 peripheral holes of 1.3-mm diameter, grooved along a nonmagnetic tungsten-alloy rod (ρ = 18.0 g/cm{sup 3}), enclosed in Delrin tubing (polyoxymethylene, ρ = 1.41 g/cm{sup 3}), with a total thickness of 6.4 mm. The Monte Carlo N-Particle code was used to calculate the anisotropic {sup 192}Ir dose distributions. An in-house-developed inverse planning platform, geared with simulated annealing and constrained-gradient optimization algorithms, was used to replan 15 patient cases (total 75 plans) treated with a conventional tandem and ovoids (T and O) applicator. Prescription dose was 6 Gy. For replanning, we replaced the conventional tandem with that of the new DMBT tandem for optimization but left the ovoids in place and kept the dwell positions as originally planned. All DMBT plans were normalized to match the high-risk clinical target volume V100 coverage of the T and O plans. Results: In general there were marked improvements in plan quality for the DMBT plans. On average, D2cc for the bladder, rectum, and sigmoid were reduced by 0.59 ± 0.87 Gy (8.5% ± 28.7%), 0.48 ± 0.55 Gy (21.1% ± 27.2%), and 0.10 ± 0.38 Gy (40.6% ± 214.9%) amongmore » the 75 plans, with best single-plan reductions of 3.20 Gy (40.8%), 2.38 Gy (40.07%), and 1.26 Gy (27.5%), respectively. The high-risk clinical target volume D90 was similar, with 6.55 ± 0.96 Gy and 6.59 ± 1.06 Gy for T and O and DMBT, respectively. Conclusions: Application of the DMBT concept to cervical cancer allowed for improved organ at risk sparing while achieving similar target coverage on a sizeable patient population, as intended, by maximally utilizing the anatomic information contained in 3-dimensional imaging. A series of mechanical and clinical validations are to be followed.« less
Authors:
 [1] ;  [2] ;  [1] ;  [2] ; ; ; ;  [1] ;  [3] ;  [4] ;  [5] ;  [1] ;  [4]
  1. Department of Radiation Medicine and Applied Sciences, University of California San Diego, La Jolla, California (United States)
  2. (United States)
  3. Medical Physics Unit, McGill University, Montréal, Québec (Canada)
  4. (Canada)
  5. Department of Medical Physics, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario (Canada)
Publication Date:
OSTI Identifier:
22420354
Resource Type:
Journal Article
Resource Relation:
Journal Name: International Journal of Radiation Oncology, Biology and Physics; Journal Volume: 89; Journal Issue: 3; Other Information: Copyright (c) 2014 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; BIOMEDICAL RADIOGRAPHY; BLADDER; BRACHYTHERAPY; DOSE RATES; IRIDIUM 192; NEOPLASMS; NMR IMAGING; OPTIMIZATION; PATIENTS; PLANNING; RADIATION DOSE DISTRIBUTIONS; RADIATION DOSES; RECTUM; TUNGSTEN ALLOYS