Reduced-time myocardial perfusion study processed with "Myovation Evolution" - assessment of diagnostic efficacy.

Background: While assessing images using standard segmental method, we felt that some defects were either underscored or missed. So this work is intended to compare results of low count myocardial perfusion studies (MPS) processed with "Myovation Evolution", applying complete evaluation of all available slices, with full count studies and assess impact of reduction of counts on diagnostic efficacy of the study.

Material And Methods: A retrospective study was conducted in a group of 95 patients (56 males, age 62 ± 9 years, BMI 28 ± 4) with known or suspected CAD, without clinical history or any signs of a previous myocardial infarction. All patients underwent coronary angiography (CA) within 3 months of MPS. CA was used as a reference method for diagnostic performance of MPS. Patients underwent a stress/rest 2-day MPS. Both studies were performed twice, with normal (25 s) and shortened (13 s) time/projection. Studies were processed using Myovation protocol (OSEM, 2 iterations, 10 subsets) for full time (FT) studies and a Myovation Evolution protocol for half time (HT) studies (OSEM, 12 iterations, 10 subsets, Resolution Recovery). Reconstructed images, with and without attenuation correction (AC), were evaluated by 2 experienced nuclear medicine specialists (a consensus) visually, taking into account all available slices, in a 5-grade scale (normal, probably normal, equivocal, probably abnormal and abnormal). Study results were additionally dichotomized as normal or abnormal. Perfusion defects were assigned to coronary arteries.

Results: An exact agreement between FT and HT study assessment, without AC, amounted to 66%, with AC it grew to 79%, p = 0.05. In studies without AC 10 perfusion defects were found only in HT studies in RCA area in male patients. A higher percentage of studies with perfusion defects in RCA area visible only in HT studies was found among discordant (7/25, 28%) than concordant results (3/70, 4%), p = 0.003. AC reduced this difference. HT study provided lower accuracy in detection of CAD than FT study (58% vs. 68%, p = 0.034). AC reduced this difference considerably. Dichotomized assessment agreed in 81% of studies without AC and in 87% with AC.

Conclusions: Myovation Evolution protocol requires application of AC otherwise perfusion defects in RCA area in male patients are falsely detected. Shortened studies reconstructed with "Myovation Evolution" package without AC reveal a tendency toward reduction of accuracy of the study in detection of CAD. AC makes up for this reduction.