Quantification of regional cerebral blood flow using H215O and PET. Improvement of accuracy in the measurement of arterial input function using β-ray probe system

Quantification of regional cerebral blood flow (rCBF) is important to assess pathological conditions in cerebral perfusion abnormalities. Positron emission tomography (PET) using H215O is a well-established technique for the purpose. To quantify rCBF, accurate measurement of radioactive concentration is necessary for brain using PET, but also for arterial blood (input function). Since intravenous bolus injection of H215O causes rapid change in the input function, a frequent arterial blood sampling should be applied. But manual sampling is difficult to achieve sufficient frequency and has risk to the radiation exposure. Therefore continuous monitoring systems have been developed. In order to obtain accurate rCBF, the monitoring system must be cross-calibrated for radioactive concentration with PET and should minimize the distortion of the input function. In the later part, we introduced the application of fiber-type β-ray microprobe system for the quantification of rCBF. We developed the cross-calibration procedure for β-ray concentration. The system was considered compact enough so that negligible distortion on the measured input function and we successfully quantified rCBF in monkeys. Nowadays, challenges have been made for the measurement of arterial input function in rodents. The collaboration of various technologies is necessary to break though the difficulties in small animal PET studies. (author)