Verification of a semi-automated MRI-guided technique for non-invasive determination of the arterial input function in 15O-labeled gaseous PET

A semi-automated MR-guided technique has been evaluated for non-invasive estimation of cerebral metabolic rate of oxygen (CMRO2) using the sequential administration of 15O oxygen (O2) and 15O carbon dioxide (CO2) during a single PET scan. Two mathematical models, which assess the arterial input function (AIF) from time-activity curves (TAC) in the internal carotid artery region, were tested, namely one with a simple correction for the recovery coefficient (RC) and another with corrections for RC and spillover from surrounding tissues. RC was determined from MRA and black-blood image. RC was also determined from C15O blood volume images as a reference. RC agreed between MR-based and C15O-PET based methods, suggesting validity of MR-based methods. Area-under-the-curve (AUC) of the early portion of estimated AIF agreed with that of measured AIF in both models. AUC of the delayed phase of estimated AIF was largely overestimated in the first model, but was sufficiently improved by the spillover correction implemented in the second model.