The split-dose technique for the study of psychological and pharmacological activation with the cerebral blood flow marker 99m-Tc-exametazime and single photon emission computed tomography (SPECT): reproducibility and rater reliability

Single photon emission cornputed tomography 99m-Tc-labelled Exametazime has been used in the study of regional cerebral blood flow (rCBF) in organic and functional brain diseases. In order to extend its use to the dynamic imaging of rCBF changes during psychological and pharmacological activation, a split-dose technique using repeat injection of Exametazime has been developed. In the present study 54 patients with various brain disorders and controls were examined twice in the same imaging session., on both occasions under baseline conditions. Regional isotope uptake was most effectively normalised using whole slice counts. Split-dose repetition errors across diagnostic categories ranged from 2% to 20% for different regions of interest. The error due to repeated image analysis was examined and compared with inter-rater error, and also with the effect of immediate and delayed re-scanning. The most important predictor of reproducibility was a large size of the region of interest, with slightly poorer results in organic disease than in controls. It is concluded that the proposed split-dose technique yields repeatable and reliable measures of regional isotope uptake which should allow for hte detetion of regional changes in blood flow observed during functional activation.