A multi-anode proportional counter for measuring [11C]carbon dioxide in exhaled air

The multi-anode gas proportional counter is sensitive enough for measuring the low concentrations of [11C]carbon dioxide in the air exhaled by the patient after intravenous injection of an 11C-labelled radiopharmaceutical. The results obtained in this study show that a multi-anode gas proportional counter could be reliably used for measuring the amount of [11C]carbon dioxide in exhaled air. Despite the low total amount of [11C]carbon dioxide exhaled by the patient, the additional measured contribution to the radioactivity balance might be of importance, especially in the modelling of the metabolism and the transport of the injected compound. The gas proportional counter developed in this work can also be used for the determination of the amount of 15O exhaled in connection with administration of [15O]O2 and [15O]CO2 to the patient, especially when the bolus inhalation technique is used. The detector turned out to be useful in connection with clinical investigations by means of positron emission tomography. (author)