Regional pulmonary perfusion estimated by high-speed volume scanning CT.

Three pigs with surgically created aortopulmonary shunts and two pigs who had sham operation were scanned in a fast computed tomography (CT) scanner, the dynamic spatial reconstructor (DSR). Each pig was scanned during injection of a bolus of roentgen contrast medium in the right atrium and during injection into the left ventricle. In addition to these DSR scans, radiolabeled, 15-micron-diameter microspheres were injected into the right atrium and into the left ventricle. The quantitative distribution of roentgen contrast agent was used to estimate regional pulmonary blood flow independently from the right and left circulations using analysis of the indicator dilution curves derived from the DSR images (Y). These values were compared to the regional values of pulmonary perfusion based on the microsphere distribution (X). The correspondence between the two methods (for all pigs together) was Y = 0.83X + 0.52 with r = 0.964. The less than unity slope is attributed to the partial collapse of the lung at the time of sectioning (for counting of tissue radioactivities). As regional air content of the lung also was measured from the DSR images, these data support the contention that regional ventilation and perfusion can be estimated from a fast CT scan of the thoracic contents during the passage of a bolus of contrast medium.