Shielding Effects of Body-Shields for 3D PET

Abstract

We analyzed basic physics characteristics of body-shields which have been considered for screening out radioactivity outside the field of view (OFOV) in positron emission tomography (PET). Phantom experiments were performed with simple rectangular body-shields. A Monte Carlo simulation technique was used to analyze the experimental results and to simulate cases that were not examined experimentally. It was confirmed that the body-shields effectively reduced unwanted radiations from OFOV radioactivity for one of the latest commercial PET scanners, the ECAT EXACT HR⁺. The geometrical conditions were the most important factor in determining the shielding effect. The shield thickness should be large enough to keep the shield scatter component low. The body-shield should be carefully designed to minimize the gap between the body shield and radioactive distribution as much as possible to maximize the shielding effects, and to be applicable to clinical diagnoses.