Inverse planning simulated annealing for magnetic resonance imaging-based intracavitary high-dose-rate brachytherapy for cervical cancer

PURPOSE: To develop a technique using exclusively magnetic resonance imaging (MRI) to perform dwell position identification, targets and organs at risk delineation, and to apply inverse planning dose optimization to high-dose-rate brachytherapy for cervical cancer. METHODS AND MATERIALS: We included 15 consecutive women treated with high-dose-rate (HDR) brachytherapy for cervical cancer. All patients underwent MRI after placement of tandem and ring applicator containing a gadodiamide-filled dummy marker. This technique allowed direct visualization of the source pathway and precise definition of the intra-applicator source positions. For each patient, we delineated gross target volume (GTV), high-risk clinical target volume (HRCTV), and organs at risk on MRI, according to the European Gynecological GEC-ESTRO Working Group definitions. We performed inverse planning simulated annealing (IPSA) and analyzed the dose-volume histograms with the following endpoints: D9o, D,oo, and V1oo for GTV and HRCTV; D0.1 cc, D1 cc, D2 cc for bladder, rectum, and bowel; and dose at Point A. RESULTS: The intra-applicator source pathway was easily visualized on MRI using the gadodiamide-filled marker. IPSA provided excellent target coverage. The mean D90 and V100 for HR-CTV were 103 5% and 92 3%, respectively. IPSA provided excellent bladder sparing. Dl cc and D2 cc of bladder were 73 110% and 67 10%, respectively. CONCLUSIONS: We developed a novel technique that allows direct visualization of the intraapplicator source pathway on MRI. Using this technique, we successfully performed inverse planning directly from MRI. (c) 2008 American Brachytherapy Society. Published by Elsevier Inc. All rights reserved.