Estimating the accumulative dose uncertainty for intracavitary and interstitial brachytherapy

Abstract

Background Image-guided adaptive brachytherapy shows the ability to deliver high doses to tumors while sparing normal tissues. However, interfraction dose delivery introduces uncertainties to high dose estimation, which relates to normal tissue toxicity. The purpose of this study was to investigate the high-dose regions of two applicator approaches in brachytherapy. Method For 32 cervical cancer patients, the CT images from each fraction were wrapped to a reference image, and the displacement vector field (DVF) was calculated with a hybrid intensity-based deformable registration algorithm. The fractional dose was then accumulated to calculate the position and the overlap of high dose (D2cc) during multiple fractions. Result The overall Dice similarity coefficient (DSC) of the deformation algorithm for the bladder and the rectum was (0.97 and 0.91). No significant difference was observed between the two applicators. However, the location of the intracavitary brachytherapy (ICBT) high-dose region was relatively concentrated. The overlap volume of bladder and rectum D2cc was 0.42 and 0.71, respectively, which was higher than that of interstitial brachytherapy (ISBT) (0.26 and 0.31). The cumulative dose was overestimated in ISBT cases when using the GEC-recommended method. The ratio of bladder and rectum D2cc to the GEC method was 0.99 and 1, respectively, which was higher than that of the ISBT method (0.96 and 0.94). Conclusion High-dose regions for brachytherapy based on different applicator types were different. The 3D-printed ICBT has better high-dose region consistency than freehand ISBT and hence is more predictable.

Fan beam CT-guided online adaptive external radiotherapy of uterine cervical cancer: a dosimetric evaluation

“…Due to the technical characteristics and factors such as less fractions of BT for UCC, online ART had been successfully applied in the BT stage of UCC. In the last two decades, the technique has gradually matured and become routine [ 54 – 56 ]. Currently, EBRT for UCC is usually performed using coplanar IMRT or VMAT with conventional splitting of dose and 23–28 fractions, which is characterized by multiple fractions and long duration.…”

Improving hybrid image and structure-based deformable image registration for large internal deformations

“…This was illustrated by Nix et al (2022) in a series of pelvic patients, where ANACONDA was only used when bladder volume changes were below 80%, pointing out its limitation in handling large deformations. Similarly, Wang et al (2021) acknowledged that ANACONDA struggles to achieve accurate registrations of the upper boundary of the bladder. ANACONDA has also been reported to perform poorly in brachytherapy scenarios characterized by complex deformations due to the applicator insertion (Rigaud et al 2019(Rigaud et al , 2020.…”