994-97 Quantitating Pulmonary Capillary Volume Using Digital Parametric Angiographic Analysis

Abstract

Assessment of the distal pulmonary vasculature in patients with pulmonary hypertension has been limited to qualitative description of pulmonary arteriograms. Digital parametric imaging, using contrast density and transit time, has been used to qualitative blood volume and flow in the coronary and renal vascular beds. This study was performed to determine whether digital parametric imaging can quantitate vascular volume in the distal pulmonary capillary bed with pulmonary flow intact. Two digital angiograms of the pulmonary vasculature were acquired in 11 patients with varying degrees of pulmonary hypertension. A balloon flotation catheter was advanced distally into the pulmonary artery. The first angiogram (static image) was performed with blood flow occluded by inflation of the catheter balloon. Non-ionic contrast was then hand injected to completely fill the vasculature beyond the balloon occlusion. The second angiogram (flow image) was performed with the balloon deflated and blood flow preserved. A hand injection of a rapid bolus of contrast, 1–2 cc, was given. Digital subtraction image data were obtained at 15 frames/sec at end expiration for both angiograms. Contrast density measurements of the distal pulmonary vasculature were determined from the static images in various 2 × 2 mm areas using digital parametric imaging. The maximum density in these same areas was similarly determined from the flow images. The correlation of the density measurements between the static and the flow images in 64 regions of interest was excellent (R = 0.92, regression slope = 0.98). This correlation was similar to that observed for repeated injections using the same technique (flow image) (R = 0.97, regression slope = 0.97). Digital parametric measurements of pulmonary capillary volume obtained with blood flow preserved are the same as those obtained with flow occluded and the entire bed replaced by contrast. This method allows quantitation of pulmonary vascular volume and flow using a simple, single contrast injection in the distal pulmonary artery.