COMPARISON OF TECHNETIUM-99M-ECD TO XE-133 SPECT IN NORMAL CONTROLS AND IN PATIENTS WITH MILD-TO-MODERATE REGIONAL CEREBRAL BLOOD-FLOW ABNORMALITIES

Technetium-99m-1,1-ethyl cysteinate dimer (ECD) has been proposed as a ''chemical microsphere'' for SPECT measurement of regional cerebral b lood flow (rCBF). However, its distribution has not yet been compared in humans to an established rCBF measure. Therefore, we compared the u ptake and distribution of ECD with rCBF measured by Xe-133 SPECT in su bjects with mild to moderate flow abnormalities and in normal voluntee rs. Blood and urine chemistries and vital signs were unchanged from pr e-ECD values up to seven days postinjection. Profile plots demonstrate d pattern agreement between rCBF ratios (Xe-133) and ECD count density ratios. A significant correlation of rCBF ratios to ECD count density ratios was observed (r = 0.77), with a slope of 0.64 and intercept of 0.36. To explore whether or not the relationship between rCBF and ECD was dependent on absolute flow, ECD region of interest data were expr essed in units of ml/min/100 g by equating global CBF (Xe-133) and ECD global count density. A closer correlation (r = 0.88) was found for t hese data than for the count ratio data. The slope was closer to one ( m = 0.83) and the intercept was closer to zero (b = 8.2). Also, a sign ificant correlation was observed between ECD-derived rCBF and Xe-133 r CBF in the lesion area (r = 0.92) for patients with well-demarcated rC BF lesions. The slope (0.80) suggested a slight underestimation of les ion flow by ECD. Finally, ECD clearance from cortical gray matter ROIs derived from high-resolution scans from 1 to 4 hr postinjection was s low (2.4%/hr). In summary, ECD is a safe and effective marker of regio nal cerebral perfusion. The distribution of ECD is linearly related to rCBF measured by Xe-133 SPECT, although our data suggest a mild under estimation of flow at the high end of the normal range.