Stefan Mo ¨hlenkamp, MD Thomas R. Behrenbeck, MD, PhD Amir Lerman, MD Lilach O. Lerman, MD, PhD V. Shane Pankratz, PhD Patrick F. Sheedy II, MD Amy L. Weaver, MS Erik L. Ritman, MD, PhD Index terms: Blood, volume Computed tomography (CT), electron beam, 51.12119 Coronary vessels, CT, 54.12119 Coronary vessels, flow dynamics, 54.12119 Myocardium, 511.12119 Published online: September 18, 2001 10.1148/radiol.2211001004 Radiology 2001; 221:229 –236 Abbreviations: ANOVA = analysis of variance APV = average peak velocity LAD = left anterior descending artery LV = left ventricular 1 From the Departments of Physiology and Biophysics (S.M., E.L.R.), the De- partment of Internal Medicine, Divisions of Cardiovascular Diseases (T.R.B., A.L.) and Hypertension (L.O.L.), the Section of Biostatistics (A.L.W., V.S.P.), and the Department of Diagnostic Radiology (P.F.S.), Mayo Clinic and Foundation, 200 First St SW, Alfred 2-409, Rochester, MN 55905. Received May 25, 2000; revision requested July 12; final revision received March 5, 2001; accepted March 23. Supported in part by Na- tional Institutes of Health research grant HL-43025. Address correspondence to E.L.R. (e-mail: elran@mayo.edu). © RSNA, 2001 Author contributions: Guarantor of integrity of entire study, E.L.R.; study concepts and design, all authors; literature research, S.M., T.R.B.; experimental studies, S.M., L.O.L., K.A.S., P.E.L.; data acquisition, S.M., T.R.B.; data analysis/interpreta- tion, all authors; statistical analysis, S.M., A.L.W., V.S.P.; manuscript prep- aration and definition of intellectual content, all authors; manuscript edit- ing, D.C.D., J.M.P.; manuscript revi- sion/review and final version approval, all authors. Coronary Microvascular Functional Reserve: Quantification of Long-term Changes with Electron-Beam CT—Preliminary Results in a Porcine Model 1 PURPOSE: To evaluate the ability of electron-beam computed tomography (CT) to help quantify long-term changes in coronary microvascular functional reserve in a porcine model. MATERIALS AND METHODS: Electron-beam CT– based intramyocardial blood volume and perfusion and Doppler ultrasonography (US)– based intracoronary blood flow were obtained in 13 pigs at baseline and again 3 months later. Mea- surements were obtained at rest and after the administration of adenosine. The short-term variation during 30 minutes of electron-beam CT measurements was assessed in nine additional pigs. RESULTS: Short-term variation of blood volume and perfusion averaged 8% and 9%, respectively, and was similar for both weight groups at rest and after adenosine administration. At rest, intracoronary blood flow, blood volume, and perfusion remained unchanged from baseline to follow-up. Long-term increases (percentage change with adenosine relative to that at rest) in blood volume and perfusion reserves were consistent with increasing intracoronary blood flow reserves. Despite these long-term changes in intracoronary blood flow, blood volume, and perfusion, the blood volume–to-perfusion relationship suggests a similar blood volume distri- bution among different microvascular functional components in normal porcine myocardium at both weight groups. CONCLUSION: Electron-beam CT may be of value for quantifying long-term changes in intramyocardial microvascular function. The coronary microcirculation, which plays an important role in the regulation of myo- cardial blood flow, undergoes functional and morphologic changes during various condi- tions. In the normal healthy heart, microvascular changes occur during growth and maturation (1). Various common important diseases such as diabetes mellitus, atheroscle- rosis, cardiomyopathies, and arterial hypertension also result in functional and morpho- logic microvascular alterations, which may precede clinical signs and symptoms (2). Furthermore, evolving therapeutic strategies target the coronary microcirculation to im- prove microvascularization to ischemic myocardium (3,4). Consequently, a minimally invasive technique that allows quantification of long-term changes in intramyocardial microvascular function, with sufficient sensitivity to help differentiate physiologic or pathologic changes from random variation of measurements, would be of value. We have previously demonstrated that minimally invasive computed tomography (CT) can be used to obtain quantitative indexes of intramyocardial microcirculatory function (5,6). In particular, by virtue of its ability to quantify regional intramyocardial micro- vascular blood volume and perfusion, electron-beam CT represents a promising tool for Experimental Studies 229