Semi-quantitative evaluation of myocardial perfusion and left ventricular function: comparison between the standard Anger and novel CZT camera

Introduction: Single-photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI) is a well-established technique for the diagnosis and risk stratification of patients with suspected or known coronary artery disease (CAD). Conventional Anger camera systems for SPECT imaging use sodium iodide crystals and parallel-hole collimators. The novel gamma cameras with semiconductor Cadmium-Zinc-Telluride (CZT) detectors directly convert radiation into electric signals, allowing an improvement in terms of image accuracy and acquisition time. Aim: We conducted a retrospective study to compare the ability of CZT camera (D-SPECT) with that of conventional SPECT in detecting myocardial perfusion and functional abnormalities in patients referred for clinical evaluation of suspected or known CAD at our institution using semi-quantitative analysis of myocardial perfusion and function. Methods: We analyzed 517 consecutive patients with suspected or known CAD underwent gated stress MPI for the assessment of myocardial ischemia at our institution. Linear regression was used to evaluate the correlations between SSS, SRS, EDV, ESV, LVEF and TPD, by D-SPECT versus conventional SPECT and differences between the two methods were assessed by Bland-Altman analysis. In patients with angiographic available data, sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and diagnostic accuracy for the detection of CAD (≥50% luminal narrowing) were calculated for conventional SPECT and D-SPECT. A p-value of less than 0.05 was considered as statistically significant. Results: In the overall study population, an excellent correlation between SSS, SRS and TPD, measured by conventional SPECT and by D-SPECT was observed (r=0.808, 0.915, 0.892, p< 0.001, respectively). In Bland-Altman analysis, the mean differences in SSS, SRS and TPD (conventional SPECT minus D-SPECT) were 1.3%, 0.55% and 0.54%, respectively. In 478 patients (92%) who successfully completed LV functional analysis with electrocardiogram-gated SPECT, linear regression analysis showed an excellent correlation between EDV, ESV and LVEF (r=0.911, 0.926, 0.820, p<0.001). In Bland-Altman analysis, the mean differences in EDV, ESV and LVEF (conventional SPECT minus D-SPECT) were -13%, -8% and 3.4%, respectively. In 86 patients with coronary angiography data available, conventional SPECT yields sensitivity and specificity of 95% and 75% respectively, while for D-SPECT sensitivity and specificity of 86% and 85% were recorded. No statistical differences in sensitivity and specificity have been observed between the two methods (p=0.12 and p=0.36, respectively). The diagnostic accuracy for conventional SPECT and D-SPECT was not different (88% and 84%, respectively, p=0.5). The PPV and NPV for conventional and D-SPECT were 88% and 84%, p=0.48 and 87% and 85%, p=0.8, respectively. Conclusions: The novel CZT camera provides excellent image quality, which is equivalent to standard myocardial SPECT, despite a short scan time of less than half the standard time. Quantitative measures of myocardial perfusion and function, obtained using normal limits specific for the new technology, correlated extremely well with respective conventional SPECT measures. These findings support the use of this technology in nuclear laboratories using various radiopharmaceutical and stress protocols, evaluating patient populations with suspected or known CAD.