SU-E-J-263: Dosimetric Analysis On Breast Brachytherapy Based On Deformable Image Registration

Abstract

Purpose: To quantitatively compare and evaluate the dosimetry difference between breast brachytherapy protocols with different fractionation using deformable image registration. Methods: The accumulative dose distribution for multiple breast brachytherapy patients using four different applicators: Contura, Mammosite, Savi, and interstitial catheters, under two treatment protocols: 340cGy by 10 fractions in 5 days and 825cGy by 3 fractions in 2days has been reconstructed using a two stage deformable image registration approach. For all patients, daily CT was acquired with the same slice thickness (2.5mm). In the first stage, the daily CT images were rigidly registered to the initial planning CT using the registration module in Eclipse (Varian) to align the applicators. In the second stage, the tissues surrounding the applicator in the rigidly registered daily CT image were non‐rigidly registered to the initial CT using a combination of image force and the local constraint that enforce zero normal motion on the surface of the applicator, using a software developed in house. We calculated the dose distribution in the daily CTs and deformed them using the final registration to convert into the image domain of the initial planning CT. The accumulative dose distributions were evaluated by dosimetry parameters including D90, V150 and V200, as well as DVH. Results: Dose reconstruction results showed that the two day treatment has a significant dosimetry improvement over the five day protocols. An average daily drop of D90 at 1.3% of the prescription dose has been observed on multiple brachytherapy patients. There is no significant difference on V150 and V200 between those two protocols. Conclusion: Brachytherapy with higher fractional dose and less fractions has an improved performance on being conformal to the dose distribution in the initial plan. Elongated brachytherapy treatments need to consider the dose uncertainty caused by the temporal changes of the soft tissue.

Deformable image registration for defining the postimplant seroma in permanent breast seed implant brachytherapy

“…Recently, deformable registration has been introduced to brachytherapy to aid in dose accumulation in fractionated HDR treatment of gynecologic cancer (21e24) and also in prostate brachytherapy (25,26). In breast brachytherapy, Chen et al (27) have used DIR and dose accumulation to study the impact of HDR breast brachytherapy protocol on delivered dose using CT images obtained at each treatment fraction. Furthermore, Shaitelman et al (28) investigated the consistency of CTV between balloon and interstitial approaches to HDR breast brachytherapy by using deformable registration to map CTVs derived from image sets with balloons in place to balloon-free images.…”

Usability of Deformable Image Registration for Adaptive Radiotherapy in Head and Neck Cancer and an Automatic Prediction of Replanning

“…For instance, organ contours have been transferred from the planning CT images to the rescan images using DIR methods such as auto-segmentation [22]- [29]. However, the applicability of DIR in IMRT for HNSCC has been less known and poorly established.…”