The research interests of Erik L. Ritman, M.D., Ph.D., include evaluating myocardial microcirculation with computerized tomography (CT).
CT analysis of myocardial microcirculatory function. The premise driving this proposal is that altered function of the myocardial microvasculature is a significant component of atherosclerosis, diabetes and hypertension. The functional status of the intramyocardial resistance and exchange vessels is quantitated by CT image analysis of intramyocardial blood flow, blood volume and endothelial permeability.
These CT-based parameters are quantitatively evaluated in experimental animals by comparison with in vivo techniques (intracoronary Doppler) and in vitro testing (perfused isolated microvessel) of the myocardial microcirculation.
First, Dr. Ritman and colleagues use acute microvascular embolization to evaluate the sensitivity and specificity with which different components of microcirculation can be characterized. Second, they evaluate the CT image analysis method's ability to detect, discriminate and quantitate disease states of the coronary microvasculature in diet-induced hypercholesterolemia and in chronic coronary artery stenosis induced by intracoronary stenting.
Dr. Ritman is collaborating with Lilach O. Lerman, M.D., Ph.D., and Zeljko Bajzer, Ph.D., on this research.
Multidisciplinary micro-CT 3-D imaging resource. The basis of this research is a recently implemented micro-CT scanner that scans volumes up to 2 centimeters3 consisting of 512 cubic voxels with side dimensions ranging from 5 to 20 micrometers. Of particular relevance to cardiovascular studies is the quantitation of basic structure-to-function relationships in pathophysiological processes, such as the impact of hypertrophy on the myocardial fiber architecture or the relationship of coronary artery branching geometry to shear stress at the endothelium.
Coronary artery wall calcification and vasa vasorum also are being studied. Other organ systems under study include microvasculature of colonic adenomas, biliary tree branching geometry and bone microarchitecture. Dr. Ritman and colleagues have also implemented a cryostatic micro-CT capability for scanning frozen specimens so that after the micro-CT scan, the specimens can be used for mRNA and other analyses that are destructive, but require fresh-frozen specimens.
Collaborators in this work include Birgit Kantor, M.D., Amir Lerman, M.D., Lilach O. Lerman, M.D., Ph.D., Michael J Yaszemski, M.D., Ph.D., and Nicholas F. LaRusso, M.D.
Coronary vasa vasorum — role of 3-D branching geometry. This project uses micro-CT images of the coronary artery vasa vasorum to compute the pressure drop along the vasa vasorum and compares this to the extravascular intramural pressure in the wall that is transmitted from the "parent" arterial lumen. With Dr. Amir Lerman and Dr. Lilach Lerman, Dr. Ritman also uses cryostatic micro-CT to measure the leakiness of the coronary and vasa vasorum endothelium — a factor in atherosclerosis, diabetes and hypertension.
Dr. Ritman is also using polycapillary X-ray optics to develop micro-SPECT and X-ray scatter imaging. These modalities will provide, respectively, a broader spectrum of functional (molecular) information and microstructural anisotropy at the 100 micrometer voxel resolution level.
Dr. Ritman's long-term research goal is to develop and evaluate novel technologies for more accurate diagnosis and treatment of cardiovascular diseases.