Quantification of functional deficit in Alzheimer's disease using a computer-assisted mapping program for99mTc-HMPAO SPECT

A computer-assisted mapping program was developed to determine changes of cerebral perfusion in normal and pathological aging using single photon emission computer tomography (SPECT) and^99mTc-hexamethylpropyleneamine oxime (HMPAO). The software program outlined the cortex on 14 adjacent brain slices, and superimposed a ring of 12 regions of interest on each slice. Regional/global and regional/cerebellar relative flow values were calculated in 27 patients with clinically diagnosed Alzheimer's disease (AD) (mean age 71 years, SD 7.6) and in 10 normal controls (mean age 73.7 years, SD 7.3). The Dementia Rating Scale (DRS) was used to assess mental status in all subjects. Multiple regression analysis demonstrated a significant correlation between relative flow values and the DRS score. Regional/cerebellar (R=0.88,p<0.0001) relative flow values were a better indicator of cortical impairment than regional/global relative flow values (R=0.68,p=0.003). Of the brain regions of interest, the left parietal flow values correlated best with the DRS score (r=0.83,p<0.0001), a cutoff value of 77 accurately classifing 80% of the normals and 100% of the patients diagnosed as having Alzheimer's disease. The data show that computer-assisted mapping of SPECT can provide semiquantitative flow values with high diagnostic accuracy.