ACETAZOLAMIDE CHALLENGE AND TECHNETIUM-99M-ECD VERSUS IODINE-123-IMP SPECT IN CHRONIC OCCLUSIVE CEREBROVASCULAR-DISEASE

We compared the acetazolamide challenge test using Tc-99m-ECD SPECT an d I-123-IMP SPECT images in patients with chronic occlusive cerebrovas cular disease. We also evaluated the usefulness of linearization corre ction for acetazolamide challenge test of Tc-99m-ECD SPECT. Methods: T wenty patients with unilateral chronic occlusive cerebrovascular disea se (10 patients had middle cerebral arterial lesion and 10 had interna l carotid lesion) were included in the study. Split-dose (a dose fract ioning was 1:2), and sequential SPECT technique was used for Tc-99m-EC D SPECT studies while only acetazolamide challenge test studies for I- 123-IMP SPECT were performed. Permeability surface area product model (PS model) and back-diffusion model (Lassen's correction) were used fo r linearization correction of acetazolamide challenge with (99mTc)-ECD SPECT. Results: Six of 16 patients with reduced vasodilatory capacity in I-123-IMP SPECT were underestimated by Tc-99m-ECD SPECT acetazolam ide challenge test. Relative ECD uptake normalized by cerebellar uptak e compared with IMP uptake showed a nonlinear relationship, indicating relatively less uptake in high flow range, The underestimations of li mited vasodilatory capacity observed in Tc-99m-ECD SPECT without linea rization correction was modified by linearization algorithm. However, the effect of correction based on PS model was superior than that of L assen's correction. The corrected Tc-99m-ECD uptake ratio, based on PS model, and IMP uptake ratio demonstrated a better linear relationship than that of Lassen's correction, Conclusion: Technetium-99m ECD SPEC T corrected based on the PS model is a better method of linearization for evaluating cerebrovascular reserve using acetazolamide challenge.