Comparison of mean cerebral transit time and single-photon emission tomography for estimation of stroke outcome

Mean cerebral transit time (MCTT) scanning is a possible alternative to cerebral single-photon emission tomography (SPET) for early assessment of cerebral perfusion after acute ischaemic stroke. Although MCTT is rapid, inexpensive and does not require sophisticated equipment, the relationship between MCTT and functional outcome is unknown. This study aimed to compare the effectiveness of SPET and MCTT in the prediction of functional outcome. Sixty-three patients undergoing cerebral computed tomography (CT), technetium-99m MCTT, and technetium-99m-labelled hexamethylpropylene amine oxime SPET soon after acute ischaemic stroke had outcome assessed after 3 months. Cerebral CT, SPET and MCTT scans were interpreted without reference to the clinical data; a single independent observer assessed outcome using the Barthel Index. The 3-month Barthel score in survivors was significantly correlated with volume of lesion on SPET (Spearman's r=-0.425, P<0.005) and with the ratio of mean affected hemisphere transit times to mean unaffected hemisphere transit times (Spearmen's r=-0.356, P <0.01), but not with CT lesion volume (Spearman's r = -0.175, P >0.1). Stepwise logistic regression identified volume of lesion on SPET as the only significant predictor of good functional outcome (Barthel score>70). The overall predictive accuracy was 73%. It is concluded that MCTT, although significantly correlated with functional outcome, failed to predict good functional recovery in individual stroke survivors. Since SPET provides more detailed localisation of perfusion deficits, and since SPET lesion volume can be used to predict functional outcome, SPET remains preferable to MCTT when perfusion imaging is required.