Functional Cerebral Blood Flow Images by Positron Emission Tomography

Abstract

In this study functional cerebral blood flow images (CBF) were generated using positron emission tomography (PET) for three different protocols. In the first protocol, C15O2 was inhaled by the patient for length of time 2.0 min (activity 6MBq/ml). In the second protocol, H215O was infused to the patient (2000 GBq/ml). In the third protocol a bolus of water was injected over a short time 5.0 sec (5000 GBq/ml). For each of these protocols, the optimum integral time for CBF images was evaluated. Thereafter, comparison between the three different protocols was made on the basis of relative error on CBF. Dynamic and integral analysis based on the Kety Model were applied to a dynamic sequences of positron emission tomographic scans collected during and following the administration of tracer. The dynamic analysis was used to correct continuously monitored arterial whole-blood activity for delay and dispersion relative to tissue scans. An integral analysis, including correction for this delay and dispersion was then used to calculate CBF on a pixel –by- pixel basis. Three computer programmers (TRACRS, MODELS and TURBCBF) were used to calculate CBF and generate functional CBF images. From these different dynamic studies, the calculations predict that, the statistical errors in CBF, delay and dispersion in the case of the third protocol were small compared with the first protocol. Also the effect of varying scanning time on relative error of CBF were investigated for the three different protocols.