Comparison of electrocardiogram synchronization and asynchronization in myocardial blood flow measurement with 15O-H2O PET

Purpose: Recently, many attempts to quantify myocardial blood flow from 15O-H2O myocardial dynamic PET have been reported. In this study, we developed a new method to estimate stable and accurate myocardial blood flow (MBF) in the ischemic myocardial lesion. It is hard to avoid the left ventricular (LV) wall motion artifacts in the conventional myocardial dynamic PET images. Therefore, in order to estimate accurate MBF, 15O-H2O Myocardial dynamic PET data and electro-cardiogram (ECG) are acquired at the same time, and we developed the software that extracts the end-diastolic myocardial data. Then, we analyzed the ECG-gated end-diastolic dynamic data and estimated rest and stress MBF, coronary flow reserve (CFR = stress MBF/ rest MBF) in the ischemic myocardial lesion. ECG gated myocardial dynamic PET would reduce heart beat motion artifact. Estimated CFR from the new method were compared with those from the conventional non-gated dynamic PET.

Methods: Twenty-seven patients with ischemic heart disease (67±11 years old, male 17, female 10) underwent dynamic 15O-H2O PET during rest and pharmacological (ATP) stress. We used Philips Gemini TF64. For each scan, 500MBq of 15O-H2O was infused slowly for 2min, dynamic data were scanned for 6min. Using list mode PET data and ECG signals, both non-gated dynamic data and ECG-gated end-diastolic data were reconstructed. Coronary arteriograms were also carried out for each patient, totally 50 ischemic segments with over 90% stenosis and 128 normal segments were evaluated in these patients. Single compartment model was used to estimate MBF and the perfusable tissue fraction (PTF). In addition, software for extracting end diastole images from ECG-gated PET data was developed using programming language C #, C++. Then we used visual studio 2017. Analyze and compare end-diastolic ECG-gated data and non-gated data.

Results: In the ischemic lesion, parameters (PTF, CFR and MBF) from ECG-gated dynamic PET and from non-gated PET were compared as follows. In the resting, PTF values from ECG-gated presented significantly lower (0.63 ± 0.09 (ml/ml)) than those from non-gated (0.72±0.09 (ml/ml)) (p<0.001). In the stress state, PTF values from ECG-gated yielded significantly lower (0.57 ± 0.10 (ml/ml)) than those from non-gated (0.65 ± 0.11 (ml/ml)) (p<0.001). CFR in the ischemic lesion, the former showed 1.23 ± 0.29, and the latter yielded 1.69 ± 0.71 (p <0.001). Beside in the normal site, the former presented 2.15 ± 0.76, the latter yielded 2.24 ± 0.79 (N.S), no significant difference was shown. MBF in the stress state, ECG-gated presented 1.00 ± 0.26 (ml/min/g), and non-gated yielded1.24 ± 0.44 (ml/min/g) (p <0.001), significant difference was shown.

Conclusions: In the ischemic lesion, ECG-gated PET estimated lower perfusable tissue fraction (PTF) than non-gated PET. This is shown that ECG-gated imaging decreased the LV wall motion artifact, and presented less blood fraction in the ischemic myocardial tissue ROI than the conventional imaging. More accurate estimation of PTF will lead to calculate more accurate MBF, and ECG-gated imaging dedicated lower MBF in the stress state than non-gated imaging. In the normal site, no significantly different CFR were estimated between ECG-gated and non-gated imaging. However, in the ischemic lesion, significantly lower CFR were yielded with ECG-gated than with non-gated imaging. These results show that ECG-gated dynamic PET improves detecting ischemic myocardial lesions.

• Download figure
• Open in new tab
• Download powerpoint