Myocardial perfusion measurement by computed tomography.

摘要

Coronary artery disease (CAD) arising from coronary atherosclerosis can lead to myocardial ischemia and/or infarction (MI). Early revascularization of a stenosed or occluded coronary artery can improve the quality of life through reduction in angina, salvage the ischemic myocardium and thus reduce recurrent ischemia and heart failure (HF). Since revascularization has a definite risk to patients, the decision of percutaneous coronary interventions (PCI) should be based on the functional significance of a coronary stenosis and the viability status of the jeopardized myocardium, both of which can be assessed with the measurement of myocardial blood flow (MBF).;The goal of this research is to develop a technique for measuring MBF with computed tomography (CT), an imaging technique that has been used for coronary CT angiography (CTA) for detection of CAD. Our proposed technique, CT Perfusion, is based on cine (continuous) CT scanning of the heart following a bolus injection of iodinated contrast agent. Algorithms are developed to correct for cardiac motion and beam hardening of cine cardiac images to facilitate accurate measurement of arterial and myocardial contrast enhancement curves from which MBF was calculated.;A pilot study on twenty-six CAD patients was performed to determine the relationship between MBF measured by CT Perfusion and the degree of luminal narrowing in coronary arteries determined by conventional coronary angiography. Our results showed that segmental myocardial perfusion reserve (MPR) measured under pharmacological stress had an inverse relationship with the severity of coronary stenosis. This finding suggested that maximal MBF in the myocardium supplied by severely stenosed coronary arteries would be limited. Thus, CT Perfusion can be an effective tool to diagnose ischemia and assess CAD patients who are vulnerable to heart attack and may require immediate revascularization.;Finally, a porcine model of acute MI and reperfusion was created to investigate the relationship of MBF before and after ischemia/reperfusion and viability. Our results showed that MBF in the territory perfused by the transiently ligated left anterior descending (LAD) artery remained significantly lower than normal after successful reperfusion of the transiently occluded LAD. The region of 'no-reflow' (i.e. LAD territory) was a mixture of infarcted and viable tissue as confirmed by ITC (2,3,5-triphenyltetrazolium) staining. This work demonstrates that if a patient suffers a heart attack, CT can be used to assess the outcome of revascularization and recovery of the patient after an acute MI. MBF measured in pigs demonstrated a strong correlation (R=0.81) with that measured by the gold standard radiolabeled microspheres technique.;In summary, the work presented in this thesis showed that CT can assess the functional significance of coronary atherosclerosis and the recovery of perfusion following ischemia/reperfusion besides assessing vessel morphology. This dual morphological and functional imaging capability makes CT a comprehensive diagnostic modality for the evaluation of CAD.;Keywords. Computed tomography, CT Perfusion, myocardial perfusion, myocardial ischemia, myocardial infarction, coronary artery disease, myocardial perfusion reserve.