The development of novel parameter of the cerebral blood flow SPECT for differentiating Alzheimer disease and dementia with Lewy bodies

Objectives When we diagnose dementia using cerebral blood flow (CBF) SPECT, decrease of regional cerebral blood flow (rCBF) in posterior-cingulate gyrus, precuneus and parietal lobe is a characteristic finding in Alzheimer disease (AD). In addition to these areas, the blood flow decrease of the occipital lobe is a characteristic finding in dementia with Lewy bodies (DLB). However, a decrease in occipital lobe blood flow is sometimes found in AD. Also, differential diagnosis may be difficult when rCBF decrease diffusely. In contrast, the parameter using the reference of normal rCBF such as precentral gyrus will be stable. In the current study, we developed simple cerebral blood flow parameter for differentiating AD from DLB. Namely we calculated rCBF ratio of the superior occipital gyrus (SOG), the middle occipital gyrus (MOG), the inferior occipital gyrus (IOG) and the precentral gyrus (PCG) of ipsilateral side. Then, we evaluated the usefulness by comparing the differential diagnostic ability of the novel parameter to those of absolute rCBF values (ml/100g/min).

Methods We analyzed 28 patients (14 AD and 14 DLB ) data of Tc-99m SPECT retrospectively. Using soft-ware (Fine 3-dimensional stereotaxic ROI template, Fuji Film RI pharma, Japan), absolute values of rCBF were calculated in bilateral SOG, MOG, IOG and PCG. Then we calculated rCBF ratio of each occipital gyrus and the PCG on the ipsilateral hemisphere. We compared the mean value of each parameter and absolute rCBF values between the two groups statistically; the differential diagnostic ability using these parameters was compared by ROC analysis. In addition, we compared the diagnostic accuracy under the condition using optimal cut-off level obtained by ROC with McNemar test.

Results The blood flow ratio of each occipital gyrus and the PCG was significantly lower in DLB compared with those of AD (Figure). In the ROC analysis for distinguishing DLB from AD, the area under the curve (AUC) of the rCBF ratio of each occipital gyrus and PCG was significantly higher compared with those of absolute rCBF value of each occipital gyrus. Diagnostic accuracy of differentiating DLB from AD was significantly higher in the relative rCBF measurement than the absolute rCBF measurement (Table).

Conclusions In the differential diagnosis between DLB and AD, the rCBF ratio of each occipital gyrus and the precentral gyrus was a simple and clinically useful parameter. $$graphic_60C587B9-9219-42B3-B22D-B3D2FB7AE01A$$ $$graphic_FB3092BD-FBBA-4A0F-9984-C3E8FBBBFA3D$$