FPGA-based Monte Carlo Computation of Light Absorption for Photodynamic Cancer Therapy

Photodynamic therapy (PDT) is a method of treating cancer that combines light and light-sensitive drugs to selectively destroy cancerous tumours without harming the healthy tissue. The success of PDT depends on the accurate computation of light dose distribution. Monte Carlo (MC) simulations can provide an accurate solution for light dose distribution, but have high computation time that prevents them from being used in treatment planning. To alleviate this problem, a hardware design of an MC simulation based on the gold standard software in biophotonics was implemented on a large modern FPGA. This implementation achieved a 28-fold speedup and 716-fold lower power-delay product compared to the gold standard software executed on a 3 GHz Intel Xeon 5160 processor. The accuracy of the hardware was compared to the gold standard using a realistic skin model. An experiment using 100 million photon packets yielded a light dose distribution that diverged by less than 0.1 mm. We also describe our development methodology, which employs an intermediate hardware description in SystemC prior to Verilog coding that led to significant design effort efficiency.