Estimation of Input Function for Rapid Dual Table ARG Method

Measurements of the oxygen consumption in brain have been studied by PET. Autoradiographic method(ARG) was suggested (Mintum et al.) to yield CMRO2. This method required separately obtained information about CBF, CBV, thus time of 30-60 min. is required for three separate scans. We developed a rapid dual table method, in which water and oxygen are continuously administrated with the 90-180 sec of water and 180 sec of oxygen scan. In order to derive the quantitative CMRO2 in PET scan, it is necessary to obtain the arterial blood time activity curve. In this study, a method to estimate the input functions corresponds to [¹⁵O]water injection and [¹⁵O]oxygen inhalation, in a continuously administration study, was developed. A method developed was model-based, employing a fitting method. In order to estimate the reliability of developed method, input functions of [¹⁵O]water injection and [¹⁵O]oxygen inhalation obtained separately in a clinical study was combined with time lag of 90 seconds and 180 seconds. The reproducibility was examined by comparing the blood input functions obtained from present method and from original input functions obtained in clinical study. After fitting the combined input function with model function, each input function of [¹⁵O]water injection and [¹⁵O]oxygen inhalation was derived. The whole shapes were in agreement with each other. This method could be used for estimation of each input function in continuously water and oxygen administrated study.