Appropriate parameters of the ordered-subset expectation maximization algorithm on measurement of myocardial blood flow and oxygen consumption with 11C-acetate PET.

Objective: The purpose of this study was to evaluate the appropriate parameters of a filter and of subsets (S) and iterations (I) of the ordered-subset expectation maximization (OSEM) algorithm in 11C-acetate PET.

Methods: A Hanning filter (HF) and a Gaussian filter (GF) were selected for filtered back-projection (FBP) and the OSEM algorithm, respectively. After evaluation of the optimal HF size, the GF size was optimized using healthy volunteers (HV). Myocardial blood flow (MBF) and oxygen consumption (k(mono)) values were calculated by combining 4S, 16S, or 28S with 2I, 4I, 6I, or 8I of the OSEM (MBF(OSEM) and k(monoOSEM), respectively) in eight HV and eight coronary artery disease (CAD) patients. These MBF(OSEM) and k(monoOSEM) values were compared with those obtained using FBP (MBF(FBP) and k(monoFBP), respectively).

Results: Optimal HF and GF (10.0GF) sizes for the FBP and OSEM algorithms, respectively, were 10.0 mm full-width resolution at half-maximum. MBF(OSEM) was changed by modifying the parameters of the OSEM algorithm. The best correlations were between MBF(FBP) and MBF(OSEM), with 28S6I and 10.0GF for HV patients and 28S8I for CAD patients. However, the MBF(OSEM) with 28S8I was significantly different from MBF(FBP) at the global myocardium in HV. The k(monoOSEM) with 28S6I was not significantly different from k(monoFBP) in HV or CAD patients.

Conclusion: Appropriate parameters are 28S6I with a 10.0GF on the MBF(OSEM) and k(monoOSEM) measurement using 11C-acetate. Diagnostic performance will improve using noiseless, artifact-reduction images, and accurate quantitative values that are provided by the OSEM algorithm with the appropriate parameters.