Spot Scanning Using Radioactive¹¹C Beams for Heavy-Ion Radiotherapy

Abstract

A scheme for spot scanning using 11 C 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 a 11 C 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 of 11 C 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 mm 3 was optimized and spot scanning using 11 C beams was carried out. The flatness was within ±2.3% with an error of 1% in the detector resolution.