REGIONAL PERFUSION PARAMETERS FROM PULMONARY MICROFOCAL ANGIOGRAMS

An indicator-dilution model was developed to describe transport of vas cular contrast medium through an organ during acquisition of vascular dynamic contrast images. The model provides the theoretical basis for methods of determining regional blood flow blood volume, and mean tran sit time from time-absorbance curves acquired from the images of tissu e regions of interest (ROI) distal from the inlet site. The robustness of these methods was evaluated using a computer-simulated vessel netw ork, which simulated the passage of a bolus of contrast medium through arterioles, networks of capillaries, and venules. The network was use d to evaluate the reliability of ROI parameter estimation methods when the underlying model assumptions are violated. The shape of the ROI i nlet concentration curve and moderate amounts of random noise did not affect the ability of the method to recover accurate parameter estimat es. The estimates of ROI flow and transit time were degraded in the pr esence of significant dispersion of the inlet concentration curve as i t traveled through arteries upstream from the microvascular ROI or whe n the flow was redistributed within the ROI. The estimates of ROI volu me were relatively robust. The method was applied to image data of the dog pulmonary vasculature obtained using microfocal X-ray angiography to show that the results obtained from the simulations are consistent with actual data.