An evaluation of post-injection transmission measurement in PET

PET transmission scanning in the presence of emission activity has been investigated on two scanners with orbiting pin transmission sources. One phantom consisting of varying sized spherical inserts in a uniform background and another containing simulated lungs, spine, and cardiac insert and uniform background were imaged at various emission activity levels. Insert radioactivity concentration levels varied up to 3.5 μCi/mL. Transmission acquisitions were performed with the phantoms aligned with the emission scan position, and with the phantoms shifted to simulate patient motion between scans. Images were reconstructed with and without compensation for the emission contamination. Qualitative and quantitative evaluation of the resulting image sets was performed. The emission correction resulted in no visible artifacts and ~3% quantitative accuracy