Dosimetric comparison of various optimization techniques for high dose rate brachytherapy of interstitial cervix implants

Abstract

HDR brachytherapy treatment planning often involves optimization methods to calculate the dwell times and dwell positions of the radioactive source along specified afterloading catheters. The purpose of this study is to compare the dose distribution obtained with geometric optimization (GO) and volume optimization (VO) combined with isodose reshaping. This is a retrospective study of 10 cervix HDR interstitial brachytherapy implants planned using geometric optimization and treated with a dose of 6 Gy per fraction. Four treatment optimization plans were compared: geometric optimization (GO), volume optimization (VO), geometric optimization followed by isodose reshape (GO_IsoR), and volume optimization followed by isodose reshape (VO_IsoR). Dose volume histogram (DVH) was analyzed and the four plans were evaluated based on the dosimetric parameters: target coverage (normalV100), conformal index (COIN), homogeneity index (HI), dose nonuniformity ratio (DNR) and natural dose ratio (NDR). Good target coverage by the prescription dose was achieved with GO_IsoR (mean normalV100 of 88.11%), with 150% and 200% of the target volume receiving 32.0% and 10.4% of prescription dose, respectively. Slightly lower target coverage was achieved with VO_IsoR plans (mean normalV100 of 86.11%) with a significant reduction in the tumor volume receiving high dose (mean normalV150 of 28.29% and mean normalV200 of 7.3%). Conformity and homogeneity were good with VO_IsoR (mean COIN=0.75 and mean HI=0.58) as compared to the other optimization techniques. VO_IsoR plans are superior in sparing the normal structures while also providing better conformity and homogeneity to the target. Clinically acceptable plans can be obtained by isodose reshaping provided the isodose lines are dragged carefully.PACS number: 87.53 Bn

Interstitial high-dose-rate brachytherapy using cobalt-60 source for cervical cancer: dosimetric and clinical outcomes from a single institute

“…Sharma et al used Paris technique for dose prescription and found that DHI, DNR, and COIN were 0.61, 0.31, and 0.79, respectively [22]. Swetha et al reported DHI, DNR, and COIN as 0.57, 0.43, and 0.73, respectively, in their study using inverse planning technique [23]. In the present study, the DHI, DNR, and COIN values were 0.57, 0.43, and 0.72, respectively, similar to Swetha et al…”

“…Swetha et al . reported DHI, DNR, and COIN as 0.57, 0.43, and 0.73, respectively, in their study using inverse planning technique [ 23 ]. In the present study, the DHI, DNR, and COIN values were 0.57, 0.43, and 0.72, respectively, similar to Swetha et al .…”

Dosimetric comparison of volume-based and inverse planning simulated annealing–based dose optimizations for high–dose rate brachytherapy

“…ODI 11 is the ratio of the target volume that receives a dose equal to or more than twice the reference dose. [11][12][13][14] is defined as the ratio of high-dose volume relative to the reference volume. DNR is used to evaluate the quality of the plan.…”

First clinical implementation of the Capri applicator

“…This model can be used for both tumors and normal tissues. Several quality factors were calculated in this study, as used by various reports in the literature (12,13) …”