A cone beam CT-guided online plan modification technique to correct interfractional anatomic changes for prostate cancer IMRT treatment

Abstract

The purpose of this work is to develop an online plan modification technique to compensate for the interfractional anatomic changes for prostate cancer intensity-modulated radiation therapy (IMRT) treatment based on daily cone beam CT (CBCT) images. In this proposed technique, pre-treatment CBCT images are acquired after the patient is set up on the treatment couch using an in-room laser with the guidance of the setup skin marks. Instead of moving the couch to rigidly align the target or re-planning using the CBCT images, we modify the original IMRT plan to account for the interfractional target motion and deformation based on the daily CBCT image feedback. The multileaf collimator (MLC) leaf positions for each subfield are automatically adjusted in the proposed algorithm based on the position and shape changes of target projection in the beam's eye view (BEV). Three typical prostate cases were adopted to evaluate the proposed technique, and the results were compared with those obtained with bony-structure-based rigid translation correction, prostate-based correction and CBCT-based re-planning strategies. The study revealed that the proposed modification technique is superior to the bony-structure-based and prostate-based correction techniques, especially when interfractional target deformation exists. Its dosimetric performance is closer to that of the re-planned strategy, but with much higher efficiency, indicating that the introduced online CBCT-guided plan modification technique may be an efficient and practical method to compensate for the interfractional target position and shape changes for prostate IMRT.

Adaptive radiotherapy strategies for pelvic tumors – a systematic review of clinical implementations

“…In addition to one in silico implementation of online compensation [58], these were the only studies where feedback from delivered dose triggered adaptations. Contributing to differences in applied strategies and workflows could be the additional manual contouring, which was a pre-requisite in over 70% of the simulated ART workflows [22,59,60,[62][63][64][65][66][68][69][70]72,74,78,79,[81][82][83]85,86,88,89,91,93,[95][96][97][98][100][101][102][103][104][105][106][107]. To reduce the need of manual contours, the segmentation could be propagated using deformable image registration.…”

“…Deformable image registration was more frequently applied in the in silico studies, mostly for online re-planning/re-optimization [59,61,67,71,86,87,94] and offline re-planning/re-optimization strategies [60,63,66,69,75,107] but also applied for online MLC/field adjustments [77,89]. To facilitate adaptations, especially for online execution, modifications of the planning system or automatic activation/selection of plans was applied in 50% of the in silico studies [58][59][60][61][67][68][69]71,72,[74][75][76][77][78][79][80][82][83][84][85][86][87][88][92][93][94]. In view of the increasing speed of optimization algorithms, limited in-room imaging quality together with manual (re-)contouring remains the biggest bottlenecks for clinical implementation of many of the ART strategies and certainly limiting online applications.…”

A deformable head and neck phantom with in‐vivo dosimetry for adaptive radiotherapy quality assurance

“…Several studies demonstrate the use of CBCT for dose reconstruction and ART replanning. 30,31 This phantom has been verified to be tissue equivalent for MV imaging modalities, so it is not limited by image modality and can truly be an end-to-end QA phantom for any new ART technologies before implementing in clinics. This ART QA phantom is modeled based on a HN CT slice; therefore, it is designed to be used in HN ART clinical workflow, and mainly to evaluate DIR algorithms that are suitable for HN treatment sites.…”

A GPU-based finite-size pencil beam algorithm with 3D-density correction for radiotherapy dose calculation

“…Online adaptive radiotherapy (ART) appears to be attractive, as it allows real-time adaptation of the treatment to daily anatomical variations (Wu et al , 2002; Wu et al , 2004; Court et al , 2005; Mohan et al , 2005; Court et al , 2006; Wu et al , 2008; Lu et al , 2008; Ahunbay et al , 2008; Fu et al , 2009; Godley et al , 2009; Men et al , 2009; Gu et al , 2009; Gu et al , 2010b; Men et al , 2010a; Men et al , 2010b; Ahunbay et al , 2010). However, it is challenging to implement online ART in clinical practice due to various technical barriers.…”