Reconstruction of rapidly acquired Germanium-68 transmission scans for cardiac PET attenuation correction

Abstract

Transmission (TX) scan time by use of radionuclide sources for cardiac positron emission tomography prolong imaging and increase the likelihood of patient motion artifacts. A reconstruction algorithm combining ordered-subsets expectation maximization with a Bayesian prior was developed and applied to rapid Germanium-68 (Ge-68) TX scans. A cardiac phantom with Fluorine-18 (Fl-18) was used to determine a minimal count threshold for Ge-68 TX scanning. Images were acquired over a count range from 2.5 x 10(6) to 8 x 10(7) and for a high-count scan of 1.6 x 10(9) counts to study reconstruction parameters and to determine the minimum TX count threshold. The method was compared against clinical 4-minute TX scans in ten Rubidium-82 (Rb-82) rest/stress myocardial perfusion studies (body mass index, 30 +/- 4 kg/m(2)). The minimal count threshold was 20 x 10(6), and the mean scan time for the Rb-82 studies was 70.5 +/- 3.4 seconds. More than 90% of the segmental scores computed from images acquired via rapid TX scans differed by less than 5% from those obtained with 4-minute TX scans. The mean differences in perfusion scores between the rapid and 4-minute TX scans were 0.46% (95% confidence interval, -1.84% to 0.93%) at rest and 0.39% (95% confidence interval, -1.84% to 1.07%) at stress, demonstrating equivalency of the rapid and 4-minute scans. Ordered-subsets expectation maximization with a Bayesian prior accurately and efficiently reconstructs rapidly acquired Ge-68 TX scans for Rb-82 myocardial perfusion positron emission tomography studies.