CT-Based Collision Prediction Software for External-Beam Radiation Therapy.

Yu-Jen Wang,Feipei Lai,Jia-Sheng Yao,Jason Chia-Hsien Cheng

doi:10.3389/fonc.2021.617007

Abstract

PurposeBeam angle optimization is a critical issue for modern radiotherapy (RT) and is a challenging task, especially for large body sizes and noncoplanar designs. Noncoplanar RT techniques may have dosimetric advantages but increase the risk of mechanical collision. We propose a software solution to accurately predict colliding/noncolliding configurations for coplanar and noncoplanar beams.Materials and MethodsIndividualized software models for two different linear accelerators were built to simulate noncolliding gantry orientations for phantom/patient subjects. The sizes and shapes of the accelerators were delineated based on their manuals and on-site measurements. The external surfaces of the subjects were automatically contoured based on computed tomography (CT) simulations. An Alderson Radiation Therapy phantom was used to predict the accuracy of spatial collision prediction by the software. A gantry collision problem encountered by one patient during initial setup was also used to test the validity of the software. Results: In the comparison between the software estimates and on-site measurements, the noncoplanar collision angles were all predicted within a 5-degree difference in gantry position. The confusion matrix was calculated for each of the two empty accelerator models, and the accuracies were 98.7% and 97.3%. The true positive rates were 97.7% and 96.9%, while the true negative rates were 99.8% and 97.9%, respectively. For the phantom study, the collision angles were predicted within a 5-degree difference. The software successfully predicted the collision problem encountered by the breast cancer patient in the initial setup position and generated shifted coordinates that were validated to correspond to a noncolliding geometry.ConclusionThe developed software effectively and accurately predicted collisions for accelerator-only, phantom, and patient setups. This software may help prevent collisions and expand the range of spatially applicable beam angles.

Highlights

Collision prevention for patient safety is a key issue in radiation therapy (RT) [1]
The spatial optimization of beam angles remains essential and critical for RT; challenges of increased uncertainty can arise with large-size patients or noncoplanar beams, leading to potential gantry collisions
The ability to select noncoplanar beam angles that will not result in gantry collisions mainly depends on individual skill and experience

Summary

Introduction

Collision prevention for patient safety is a key issue in radiation therapy (RT) [1]. The spatial optimization of beam angles remains essential and critical for RT; challenges of increased uncertainty can arise with large-size patients or noncoplanar beams, leading to potential gantry collisions. A few preliminary methods have been proposed to prevent collisions [2, 4,5,6,7,8,9,10], such as a chart of couch-gantry combinations [7], prediction software for collision avoidance [8, 10], and the use of supplemental cameras [5, 11] or a 3-dimensional scanner [4]. Our goal is to establish a software platform that can integrate patient- and acceleratorspecific information into the estimation of the noncolliding space for coplanar/noncoplanar beam selection before the planning process in order to improve patient safety and prevent hardware damage

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Conclusion