Comparison of pencil-beam and Monte Carlo calculated dose distributions for proton therapy of skull-base and para-spinal tumors

Abstract

Purpose: Pencil beam algorithms rely on kernels to model proton range in density-scaled water equivalent material. Monte Carlo dose calculation methods are more accurate by design. This study addresses the issue of clinical significance of potential differences between a commercial pencil-beam algorithm and Monte Carlo dose calculation. Skull-base or paraspinal tumors are challenging for dose calculations due to interfaces between high and low density areas in the irradiated volume. In addition, in particular for para-spinal cases, there are often metallic implants that not only distort the CT image but also affect the accuracy of dose calculations.