Proton therapy dose calculations on GPU: Advances and challenges

Proton therapy can allow higher dose conformality compared to conventional radiation therapy. Radiation dose calculation has an integral role in the success of proton radiotherapy. An ideal dose calculation method should be both accurate and efficient. Over the years, a number of dose calculation methods have been developed. To overcome the high computational burden of these algorithms, or to further speed them up for advanced applications, e.g., inverse treatment planning, graphics processing units (GPUs) have recently been employed to accelerate the proton dose calculation process. In this paper, we will review a set of available GPU-based proton dose calculation algorithms including a pencil-beam method, a simplified Monte Carlo (MC) simulation method, a trackrepeating MC method, and a full MC simulation method. The advantages and limitations of these methods will be discussed. We will also propose a dose calculation method via solving the Boltzmann transport equations, which is expected to be of the same level of accuracy as a MC method but could be more efficient on GPU.