On-line measurement of exhaled [11C]CO2 during PET.

UNLABELLED

The purpose of this study was to develop and evaluate a system for the continuous on-line measurement of expired 11CO2 during 11C PET studies.

METHODS

A detector system was developed that allowed continuous sampling of expired air during PET. Healthy volunteers (n = 4) underwent PET with [11C]CO2 during which expired air, tomographic tissue activity, and blood data were collected. The measured expired-air 11CO2 radioactivity time courses were filtered, and an envelope was extracted and compared with the time course of 11CO2/H11CO3 in blood.

RESULTS

Good agreement was found between the shapes of the expired-air envelope and the time course in blood, enabling quantitative calibration against discrete blood samples.

CONCLUSION

A system for the continuous monitoring of expired radioactivity during PET has been developed and evaluated with [11C]CO2. This monitoring enables the quantitative continuous measurement of 11CO2/H11CO3- in blood.