Quantitative CT perfusion measurement: normal values and reproducibility in man
Purpose To establish normal values of cerebral blood flow (CBF), cerebral blood volume (CBV), and mean transit time (MTT) as measured by dynamic contrast enhanced computed tomography (CT Perfusion) and to determine their short-term variabilities in healthy volunteers. Method and Materials The studies involved ten healthy volunteers, 6 females and 4 males, between 39 and 49 years old. For each subject two single-slice contrast enhanced dynamic CT studies separated by an interval of 30 min were performed at the level of the basal ganglia. Arterial oxygen saturation (SaO2), end-tidal CO2 tension (ETCO2), and blood pressure(BP) were continuously monitored to ensure the same basal conditions were maintained throughout the studies and the waiting period between them. Each study began with intravenous injection of 40 ml of contrast at 4 ml/s and at 5 s into the injection, 60 1 s CT scans were acquired continuously. Functional images of absolute CBF, CBV, and MTT were calculated by deconvolution of an intracranial artery’s contrast enhancement curve with tissue curves. Normal CBF, CBV and MTT values of the entire slice as well as those of frontal and insular grey matter, basal ganglia, frontal white matter, and the cerebellum were analyzed. Short-term variability was calculated using a standardized set of 24 regions of interest (ROI). The size of each ROI was about 4% of the entire brain slice. Results There were no significant differences in SaO2, ETCO2 and BP between the two studies for each subject. CBF was the highest in insular grey matter (67.8 ml/100g/min), intermediate in frontal grey matter, basal ganglia, and cerebellum (42–48 ml/100g/min), and the lowest in frontal white matter (14.5 ml/100g/min). The values of CBV followed the same trend as CBF. Short-term variability was 13.3%, 12.4% and 8.8% for CBF, CBV and MTT respectively without significant differences among the parameters. Conclusion CT imaging of absolute CBF, CBV, and MTT in healthy volunteers provides results similar to those known from the literature. The short-term variabilities of these quantitative functional images are acceptable for clinical applications.