Transient ischemic dilation ratio by [¹³N]NH₃ PET/CT in patients with variable extent of myocardial ischemia: relevance of software package and quantification method

Transient ischemic dilation has been conventionally calculated from the static images, and has been scarcely investigated by PET/CT. Therefore, we aim to evaluate the impact of the quantification method and software package on TID ratio by [¹³N]NH₃ PET/CT; moreover, perform a comprehensive evaluation of TID in normal-perfusion and myocardial ischemic patients. Retrospective analysis of 125 [¹³N]NH₃ PET/CT scans with Corridor 4DM and QPS/QGS software packages. TID ratio was calculated from static and gated left ventricular volumes. Comparisons were performed according to ischemic extent and software package. Correlations with LV function and perfusion variables were assessed. TID ratios were significantly higher in ischemic patients (p < 0.05), except for TID gated EDV from QPS/QGS. TID static and TID gated ESV from QPS/QGS were different between the very severe ischemic subgroup and the group without ischemia (p = 0.0003). TID gated ESV from Corridor 4DM was higher in moderate, severe, and very severe ischemic subgroups than the normal-perfusion group (p = 0.02). TID gated ESV presented strong inverse correlations with myocardial flow reserve (MFR) in the very severe ischemic subgroup with Corridor 4DM, and with ejection fraction (LVEF) reserve, independent of the software and percentage of ischemic extent. Upper limits for TID static, ESV, and EDV with QPS/QGS were 1.17, 1.57, and 1.3, respectively. TID static, ESV, and EDV upper limits with Corridor4DM were 1.25, 1.29, and 1.21, respectively. TID ratios from [¹³N]NH₃ PET/CT are higher in ischemic than in normal-perfusion patients and related to ischemic extent. TID ratios correlated strongly with LVEF reserve and MFR. The processing software and metric quantification method may influence the TID ratio.