Calculation of pulmonary transit time and pulmonary blood volume by digital intravenous angiography: Assessment during interventions

The present series of studies are an adaptation of the precordial radionuclide counting techniques, but because of the superior spatial resolution of digital fluoroscopic images, precise regions-of-interest can be placed over the pulmonary artery and left atrium and time x-ray transmission curves simply obtained. This offers a potential advantage over the poorer resolution of radionuclide studies, where only approximate regions can be verified in the central circulation. The use of contrast material as an indicator has been previously proposed and the necessary systems detailed. The present studies were designed to determine if a measurement of x-ray transmission vs time during passage of a contrast bolus through the central circulation could be utilized to estimate the circulation time in the pulmonary bed. In three studies the authors examined: (1) the use of peak transit time as an alternative to mean transit time; (2) the accuracy of digital (peak) transit times when compared with standard green dye estimates of mean transit time; and (3) the use of digital transit time to characterize left ventricular function and its response during acute hemodynamic manipulations