Spot Scanning Using Radioactive11C Beams for Heavy-Ion Radiotherapy

Abstract

A scheme for spot scanning using¹¹C beams has been developed in order to form and verify a three-dimensionally conformal irradiation field for cancer radiotherapy. By selecting the momentum spread of a¹¹C beam, we could considerably decrease the distal falloff of the irradiation field, thus conserving the beam quality. To estimate and optimize the dose distribution in the irradiation field, it is essential to evaluate the precise dose distribution of spot beams. The coupling of the lateral dose and depth-dose distributions originating from a wide momentum spread should be taken into account to calculate the dose distribution of¹¹C beams. The reconstructed dose distribution of the irradiation field was in good agreement with the experimental results, i.e., within ±0.2%. An irradiation field of 35×35×43 mm³was optimized and spot scanning using¹¹C beams was carried out. The flatness was within ±2.3% with an error of 1% in the detector resolution.