Comparison of Methods of Attenuation and Scatter Correction in Brain Perfusion SPECT

Objective: The radioactivity count distribution in the brain must be determined accurately to accurately measure cere-bral blood flow (CBF). Scatter and attenuation are factors that compromise the accuracy of determining radioactivity counts in the brain. Methods: We compared regional CBF in patients by an autoradiographic method using N-isopropyl-p-[123I] iodoam-phetamine when, first, attenuation correction alone was per-formed uniformly on SPECT images by using empiric -val-ues (Chang method); second, scatter correction was performed and the -values of a homogeneous-attenuation body of water were used for attenuation correction (triple-energy window [TEW] Chang method); and third, scatter correction was performed and the -values calculated by CT were used for attenuation correction (TEW CT method). We also compared regional CBF measured by these methods with the values obtained by the xenon CT/ CBF method, which uses CT and stable xenon. Results: Scatter correction reduced overestimation of re-gional CBF in low-flow regions. The TEW CT method yielded better regional and overall correlations with the xe-non CT/CBF method than did either of the other methods. Conclusion: The TEW CT method of correction gave the most accurate measurements of regional CBF. Key Words: brain perfusion SPECT; autoradiography method; stable XeCT regional CBF measurement; scatte