Cardiovascular and pulmonary dynamics by quantitative imaging.

Abstract

The use of quantitative imaging techniques to study the heart, lungs and circulation is complicated by the fact that these vital functions are inseparably linked with nearly continuously varying cyclic motions in 3-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 the 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 3 organ systems in intact man and animals, would be greatly facilitated if their motions throughout individual cycles could be directly visualized and quickly measured with minimum or perferably no effect on these motions. Dynamic quantitative imaging of moving organs is discussed with special emphasis on images produced by X-rays. Many of the considerations also pertain to .gamma.-, positron, ultrasound or other types of radiation. Photon statistics seriously limit the use of emitted radiation for rapidly sequential imaging. Various new computerized techniques for 3-dimensional reconstruction from 2-dimensional projections are dealt with in detail. Future possibilities of cross-sectional reconstruction techniques are discussed; these envisage not only 3-dimensional structural geometry reconstructions but also biochemical cross-sectional reconstructions which would prove very useful in diagnostic procedures.