Reduction method for intrinsic random coincidence events from (176)Lu in low activity PET imaging.
For clinical studies, the effects of the intrinsic radioactivity of lutetium-based scintillators such as LSO used in PET imaging can be ignored within a narrow energy window. However, the intrinsic radioactivity becomes problematic when used in low-count-rate situations such as gene expression imaging or in-beam PET imaging. Time-of-flight (TOF) measurement capability promises not only to improve PET image quality, but also to reduce intrinsic random coincidences. On the other hand, we have developed a new reduction method for intrinsic random coincidence events based on multiple-coincidence information. Without the energy window, an intrinsic random coincidence is detected simultaneously with an intrinsic true coincidence as a multiple coincidence. The multiple-coincidence events can serve as a guide to identification of the intrinsic coincidences. After rejection of multiple-coincidence events detected with a wide energy window, data obtained included a few intrinsic random and many intrinsic true coincidence events. We analyzed the effect of intrinsic radioactivity and used Monte Carlo simulation to test both the TOF-based method and the developed multiple-coincidence-based (MC-based) method for a whole-body LSO-PET scanner. Using the TOF- and MC-based reduction methods separately, we could reduce the intrinsic random coincidence rates by 77 and 30 %, respectively. Also, the intrinsic random coincidence rate could be reduced by 84 % when the TOF+MC reduction methods were applied. The developed MC-based method showed reduced number of the intrinsic random coincidence events, but the reduction performance was limited compared to that of the TOF-based reduction method.
Molecular Imaging Center, National Institute of Radiological Sciences, 4-9-1 Inage-ku, Chiba, 263-8555, Japan, rush@nirs.go.jp.
Eiji
E
Yoshida
Hideaki
H
Tashima
Fumihiko
F
Nishikido
Hideo
H
Murayama
Taiga
T
Yamaya
D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008187:Lutetium; D009010:Monte Carlo Method; D049268:Positron-Emission Tomography; D011868:Radioisotopes
D011868:Radioisotopes; D008187:Lutetium