Study of Transit Time Measurement with a Lung Test Object

Abstract

We studied the radioactive indicator-dilution technique with a lung test object. A bolus of technetium-99m pertechnetate was injected repeatedly. The input time-activity curves were fitted by biexponential or gamma-variate functions; the output time-activity curves were described by gamma-variate functions. The mean transit time was calculated with the fitted modeling functions for input and output. Transit times were also obtained directly from the experimental data with the replacement of region of recirculation by extrapolation from the modeling function. The reproducibility of transit time measurement by the radioactive tracer technique was determined to be ±0.2 sec. We found no significant difference between the use of modeling function and the direct use of experimental data.