Feasibility of secondary 15O beam production for in-beam PET

Abstract

For the purpose of in situ visualization of an irradiation field in particle therapy, it is ideal to use radioactive beams for in-beam positron emission tomography (PET) imaging. In the Heavy Ion Medical Accelerator in Chiba (HIMAC), there is a beam course to produce 11C and 10C as secondary beams, but generation of 15O has never been investigated. This study was devoted to analysis of the feasibility of secondary 15O production for in-beam PET by 16O primary beam in different absorbing materials (targets) with various thicknesses in order to find out the optimum target material and its thickness. The study was performed using analytical method, LISE++ code, and the Monte Carlo method, PHITS code. The calculation results showed that the highest intensity of the secondary 15O beam observed for primary 16O beam decelerating in liquid hydrogen but practically almost impossible to apply. The final optimum target was considered to be polyethylene with thickness of 11 cm. The 15O beam was produced in the HIMAC secondary beam line using the optimum target and the in-beam PET imaging was presented for a PMMA phantom irradiated with the produced beam.