Interference of dose application in scanned ion beam therapy and organ motion, also called interplay effect, may lead to dose deviations at target volumes. Current repainting methods are susceptible to artifacts due to a predominant scanning direction, ranging from fringed field edges to under and overdosed regions (hot and cold spots). To overcome the difficulties inherent in the repainting techniques of conventional proton therapy systems, new random repainting techniques are described herein for mitigating the under-dose and/or over-dose pattern inherent in existing repainting techniques using a random repainting approach that randomly selects spot locations within the target area.
