IMAGING OF CEREBRAL BLOOD-FLOW WITH TECHNETIUM-99M-HMPAO AND TECHNETIUM-99M-ECD - A COMPARISON

Because Tc-99m-HMPAO and Tc-99m-ECD are both used for SPECT imaging of cerebral blood flow, the question arises whether there are any differ ences in their respective regional cerebral distribution, For that pur pose, visual and semiquantitative comparisons between Tc-99m-HMPAO and Tc-99m-ECD studies were performed. Methods: Seventeen patients (4 wom en; 13 men; age 45-89 yr; mean age 71 yr) with various neurological di seases, except acute/subacute stroke, were investigated twice with (TC )-T-99m-HMPAO and Tc-99M-ECD using a triple-headed rotating SPECT came ra. After image reorientation, the two studies were evaluated visually . Seventy regions of interest (ROls) were drawn manually and the same set of ROls was applied in both studies. Regional indices (RI) normali zed to individual brain values were calculated and first compared betw een two random patient groups. Second, for all patients, RI for 70 and later for 27 regions (gained after summing values of corresponding re gions in different brain slices) were compared by using a paired Stude nt's t-test applying Bonferroni's correction. Results: Visual evaluati on demonstrated relatively high Tc-99m-ECD uptake in occipital and com paratively low uptake in mediotemporal regions. Calculation of RI reve aled significantly higher values in the right cerebellum, brainstem, m ediotemporal regions, right basal ganglia and the thalamus in the Tc-9 9m-HMPAO SPECT Studies and higher values in the occipital, supratempor al/inferior parietal and parietal cortex in the Tc-99m-ECD SPECT studi es, respectively. Conclusion: Significant differences in regional trac er distribution between (TC)-T-99m-HMPAO and Tc-99m-ECD could be detec ted, probably caused by different tracer kinetics, The results indicat e that direct comparisons of studies performed with (TC)-T-99m-HMPAO a nd Tc-99m-ECD are not possible and the use of either tracer can be fav orable in different clinical questions.