Accelerating radiation dose calculation: A multi-FPGA solution

Remarkable progress has been made in the past few decades in various aspects of radiation therapy (RT). However, some of these promising technologies, such as image-guided online replanning and arc therapy, rely heavily on the availability of fast dose calculation. In this article, based on a popular dose calculation algorithm, the Collapsed-Cone Convolution/Superposition (CCCS) algorithm, we present a multi-FPGA accelerator to speed up radiation dose calculation. Our performance-driven design strategy yields a fully pipelined architecture, which includes a resource-economic raytracing engine and high-performance energy deposition pipeline. An evaluation based on a set of clinical treatment planning cases confirms that our FPGA design almost fully utilizes the available external memory bandwidth and achieves close to the best possible performance for the CCCS algorithm while using less resource. Compared with an existing FPGA design which aimed to accelerate the identical algorithm, the proposed design achieved 1.9X speedup by providing better memory bandwidth utilization (81.7% v.s. 43% of the available external memory bandwidth), higher working frequency (90MHz v.s. 70MHz) and less logic resource usage (25K v.s. 55K logic cells). Furthermore, it obtains a speedup of 20X over a commercial multithreaded software on a quad-core system and 15X performance improvement over closely related results. In terms of accuracy, the measured less than 1% statistical fluctuation indicates that our solution is practical in real medical scenarios.