Measurement of regional pulmonary blood flow with PET

We have previously reported a method for measuring regional pulmonary blood flow (PBF) in experimental animals using 15O-water and PET. The method requires withdrawing blood from the pulmonary artery during the PET scan, so that the input function can be estimated for the one-compartment model used to analyze the data. The purpose of the present study was to modify and validate this technique for a more general use in humans.

PBF was measured after injections of 15O-water in 15 normal subjects and in five patients with reduced cardiac output. In ten of the normal subjects, PBF was also measured after the injection of 68Ga-albumin macroaggregates (MAA). In the five other normal subjects and in the cardiomyopathy patients, PBF was measured twice after two separate 15O-water administrations. The input function was estimated from a region of interest (ROI) over the right ventricle (RV), with corrections when necessary, for time delays between RV and lung tissue.

The mean value for PBF in the normal subjects was 121 +/- 32 ml/min/100 ml lung, and was 57 +/- 33 ml/min/100 ml lung in the patients with cardiomyopathy. The correlation between PBF measured with 15O-water and PBF measured with 68Ga-MAA was r = 0.96. There was no significant difference in the mean value for PBF or the ventral-dorsal distribution of PBF when sequential measurements were made in the same individual. PBF increased in general in the ventral-dorsal direction in these supine subjects, although PBF was more evenly distributed in the cardiomyopathy patients.

Measurement of regional PBF with 15O-water and PET appears to be a valid, noninvasive approach for evaluating the pulmonary perfusion pattern of humans.