The University of Iowa Department of Radiology
Professor of Radiology, Physiology, and Biomedical Engineering
Chief, Division of Physiologic Imaging
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Research Interests
A broad-based backbone of my research program is the use of non-invasive, dynamic volumetric imaging for the evaluation of structure-to-function relationships (integrative physiology) with particular attention paid to the heart and lungs. Having been involved in the use and development of physiologic-based imaging protocols for the past 17 years, a strong interest of mine is to further our understanding of how far non-invasive imaging can be stretched to provide a means of gaining new insights into the functioning of the whole organism. Associated with these goals is the need to investigate new approaches to the interrogation of the image data sets. To this end, our group is actively involved not only in investigating cardiopulmonary physiology, but we also are actively developing new computer-based image display and analysis techniques for handling multidimensional image data sets, and we are developing new image gathering techniques, primarily using high-speed, volumetric x-ray, CT and magnetic resonance imaging. Physiologic-based research interests relate to the evaluation of the integrated mechanical functioning of the heart and lungs and the interactions between these two organ structures in determining global cardiac efficiency and the regional matching of pulmonary blood flow with regional differences in ventilation. Specifically:
Pulmonary Ventilation / Perfusion Relationships: The evaluation of the non-gravitational determinants of pulmonary ventilation and perfusion matching. Comparative imaging studies of dogs, horses, sloths, and humans, have demonstrated the important role of lobar fissures in minimizing the role of altered rib cage and diaphragm shape in modifying the regional ventilation/perfusion relationships and the important role of the shift in the intrathoracic position of the heart in determining the change in the distribution patterns of ventilation with change in body posture. In addition, we are interested in the role of the right ventricular pumping function in effecting the regional distribution of blood flow through the lungs.
Cardiac Mechanics: Evaluation of the mechanism for the integrated functioning of the heart whereby the total heart volume (contents of the pericardial sac) remains essentially constant throughout the cardiac cycle. We have hypothesized that the heart functions most efficiently by not having to move external structures (such as the lung) while it pumps blood. This is accomplished by the epicardial apex remaining fixed in space and the atrioventricular valve plane moving in a piston-like motion such that the atria fill as the ventricles empty. The relationship is disrupted by atrial fibrillation which stiffens the atrial walls and serves as an added after-load to the ventricles, preventing descent of the AV valve plane. Our current efforts are to expand this concept by developing the imaging tools nesessary to evaluate the mechanical efficiency of the congenital heart before and after surgical repairs.
Airway Reactivity via HRCCT: An additional area of research has been initiated to develop a means of utilizing volumetric High Resolution Cine CT scanning to evaluate intra-pulmonary airway reactivity with particular interest in the etiology and treatment of asthma. To date we have scanned a series of piglets to evaluate the airway response to Methacholine and we have established a dose response curve for airway responsiveness and have demonstrated that small airway response can be visualized by the imaging methods prior to the development of measureable changes in airway conductance.
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