X-ray TV system for measuring microcirculation in small pulmonary vessels.

We developed a new system that consists of 1) a specially designed X-ray apparatus, 2) an X-ray-sensitive 1-in. Vidicon camera, and 3) a digital image-processing device. The picture element is approximately 20 micron in size, and the time required for one frame is 1/30 s. Using this system, we measured the internal diameter (ID), the cross-sectional area, flow velocity, volume flow, and transit time of small pulmonary vessels of approximately 100-500 micron at control and with serotonin in anesthetized cats. Flow velocity and volume flow from large [458 +/- 22 (SE) micron] to small (340 +/- 32 micron) arteries were 5.4 +/- 0.4 cm/s and 0.53 +/- 0.06 ml/min, respectively. Transit times of the contrast medium from large to small arteries (Ta) and to large veins (Tv) were 0.68 +/- 0.04 and 3.71 +/- 0.25 s, respectively. Serotonin injection (20-30 micrograms/kg iv) decreased ID, flow velocity, and volume flow of arteries by 8-48, 32, and 76%, respectively, whereas Ta and Tv increased by 91 and 69%, respectively. The system can provide useful information regarding the local circulation in the lung.