On-line re-optimization of prostate IMRT plans for adaptive radiation therapy

Abstract

For intermediate and high risk prostate cancer, both the prostate gland and seminal vesicles are included in the clinical target volume. Internal motion patterns of these two organs vary, presenting a challenge for adaptive treatment. Adaptive techniques such as isocenter repositioning and soft tissue alignment are effective when tumor volumes only exhibit translational shift, while direct re-optimization of the intensity-modulated radiation therapy (IMRT) plan maybe more desirable when extreme deformation or differential positioning changes of the organs occur. Currently, direct re-optimization of the IMRT plan using beamlet (or fluence map) has not been reported. In this study, we report a novel on-line re-optimization technique that can accomplish plan adjustment on-line. Deformable image registration is used to provide position variation information on each voxel along the three dimensions. The original planned dose distribution is used as the 'goal' dose distribution for adaptation and to ensure planning quality. Fluence maps are re-optimized via linear programming, and a plan solution can be achieved within 2 min. The feasibility of this technique is demonstrated with a clinical case with large deformation. Such on-line ART process can be highly valuable with hypo-fractionated prostate IMRT treatment.

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.…”

“…The most common approach for plan library creation in bladder cancer was to use 2-5 planning CTs with varying bladder fillings, which was employed at Helsinki University Central Hospital, Helsinki, Royal Marsden Hospital, Sutton and Catharina Hospital Eindhoven, Eindhoven [52,54,55,59]. The enrolled patients received a uniform bladder dose with either conventional or hypo-fractionated regimen, simultaneous integrated tumor dose or a hypo-fractionated partial bladder treatment.…”

Application programming in C# environment with recorded user software interactions and its application in autopilot of VMAT/IMRT treatment planning

“…This process is along the line of our earlier work in automated weighting factors and model parameters determination 6 , 16 , 17 . Instead of simply using prior knowledge extracted from previous clinical treatment plan(s) as a “class solution” or as upper/lower bounds to examine the results of the optimization calculation, 18 , 19 , 20 , 21 , 22 , 23 , 24 in our approach, the reference information is utilized throughout the plan selection process. During the process, the parameters used in the Eclipse optimizer are constantly updated through the comparison of current and prior knowledge characterized by reference plans.…”

Adaptive and robust radiation therapy optimization for lung cancer

“…Many studies have proposed using daily computed tomography (CT) images as a form of feedback. For example, Mohan et al [2005], Lu et al [2006], Wu et al [2006] and Wu et al [2008] all studied schemes where daily CT images are used to periodically assess the treatment plan for errors in dose delivery due to organ deformation and intrafraction motion, and to aid either the re-adjustment or complete re-optimization of the treatment for subsequent fractions. Other imaging methods have also been proposed for off-line ART.…”