Fast 3D dosimetric verifications based on an electronic portal imaging device using a GPU calculation engine.

Jinhan Zhu,Xiaowu Deng,Lixin Chen,Xiaowei Liu,Guangwen Luo,Along Chen

doi:10.1186/s13014-015-0387-7

Abstract

PurposeTo use a graphic processing unit (GPU) calculation engine to implement a fast 3D pre-treatment dosimetric verification procedure based on an electronic portal imaging device (EPID).MethodsThe GPU algorithm includes the deconvolution and convolution method for the fluence-map calculations, the collapsed-cone convolution/superposition (CCCS) algorithm for the 3D dose calculations and the 3D gamma evaluation calculations. The results of the GPU-based CCCS algorithm were compared to those of Monte Carlo simulations. The planned and EPID-based reconstructed dose distributions in overridden-to-water phantoms and the original patients were compared for 6 MV and 10 MV photon beams in intensity-modulated radiation therapy (IMRT) treatment plans based on dose differences and gamma analysis.ResultsThe total single-field dose computation time was less than 8 s, and the gamma evaluation for a 0.1-cm grid resolution was completed in approximately 1 s. The results of the GPU-based CCCS algorithm exhibited good agreement with those of the Monte Carlo simulations. The gamma analysis indicated good agreement between the planned and reconstructed dose distributions for the treatment plans. For the target volume, the differences in the mean dose were less than 1.8%, and the differences in the maximum dose were less than 2.5%. For the critical organs, minor differences were observed between the reconstructed and planned doses.ConclusionsThe GPU calculation engine was used to boost the speed of 3D dose and gamma evaluation calculations, thus offering the possibility of true real-time 3D dosimetric verification.

Highlights

As the frequency of dose prescriptions and the complexity of radiotherapy techniques increase, so too do the demands for accurate and efficient methods of verifying the doses delivered to patients
When our deconvolution model correction was applied to the raw electronic portal imaging device (EPID) data, the maximum difference between the EPID results and the ion-chamber measurements was less than 0.5% for both the 6 MV and 10-MV photon beams
The percent dose differences presented were normalized to the Monte Carlo simulated doses for a 2 cm depth in the case of the 6 MV beam and for a 5 cm depth in the case of the 10 MV beam; these depths correspond to positions in the muscle slab near the depth at which the maximum dose occurred

Summary

Introduction

As the frequency of dose prescriptions and the complexity of radiotherapy techniques increase, so too do the demands for accurate and efficient methods of verifying the doses delivered to patients. Dosimetric verification is a prerequisite to ensure correct treatment planning and delivery. An increasing number of reports have begun to focus on the 3D dosimetric verification of intensity-modulated radiation therapy (IMRT) treatment plans [1,2,3]. Most planar dosimetric verifications are based on uniform phantoms, but this method cannot be used to determine the algorithm error. Because of their sub-millimeter resolution, real-time response and lower workload, electronic portal imaging devices (EPIDs) are often utilized for pre-treatment and in vivo measurements [1,2,5,6,7].

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Conclusion