Cardiovascular and pulmonary dynamics by quantitative imaging.

THE USE of quantitative imaging techniques to study the heart, lungs, and circulation is complicated by the fact that their vital functions are dependent upon and inseparably linked with nearly continuously varying cyclic motions in three dimensions.Even a transient interruption of these motions, such as breath-holding for more than a few seconds, results in rapid alterations in physiological processes which in case of the heart and circulation may result in irreversible changes if cessation of their motion persists for more than a few seconds.The accuracy and range of studies on cardiovascular and pulmonary function, particularly for early detection of abnormalities in these three organ systems in intact man and animals, would be greatly facilitated if their motions throughout individual cycles (i.e., their changes in shape and dimensions and values derived therefrom) could be directly visualized and quickly measured with minimum or preferably no effect on these motions.Achievement of this objective requires development of techniques for quantitative, noninvasive or minimally invasive dynamic and stop-action imaging of these organ systems.However, because of the normal nearly continuous interand intracyclic variations and their functional dependency on essentially continuous motion, maximal utility of such imaging techniques requires "capture" of the images in rapid continuous sequences rather than by the recording of noncontinuous sequential images obtained, for example, by electrocardiographic gating techniques or by suspending the motion, e.g., breath-holding, to permit capture of the necessary information at a particular phase of single cycle or successive cycles.This is true particularly in relation to quantitative imaging of the physiologically and diagnostically important intracyclic phasic changes in overall and regional three-dimensional cardiac geometry during individual "normal" or perturbed (spontaneous or induced) cardiac