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

ABSTRACT

BACKGROUND: 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. METHODS AND RESULTS: 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. CONCLUSIONS: 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.