Linealization correction for acetazolamide (Diamox) ^99mTc-HMPAO SPECT image. A comparative study with PET

We attempted to make a linearization correction for the acetazolamide ^99mTc-HMPAO SPECT image. These results were compared to those by PET using the H₂¹⁵O-bolus injection method. The subjects consisted of eleven patients with cerebrovascular diseases. The SPECT images were obtained by the double injection method in the resting state and after an administration of acetazolamide (1 g). Linearization correction was performed according to the Lassen's method. In this study, three different methods were compared, namely fixed Fr and α (70 ml/min/100 ml and 1.08), individual determination of Fr and α based on PET data, and finally the normalization of the two scan for administered dose, fixed Fr and α (50 ml/min/100 ml and 1.5). The corrected count rate ratios of the ^99mTc-HMPAO SPECT images were correlated well with the values of regional cerebral blood flow measured by PET in all methods. Therefore, the first method was considered to be a simple and reliable one. In the last method, the relative change of cerebral blood flow after the administration of acetazolamide was calculated. The means of the percentage increase of cerebral blood flow were in good accord between ^99mTc-HMPAO SPECT and PET. However, they showed much discrepancy when individually compared.