An easy Z-score imaging system for discrimination between very early Alzheimer's disease and controls using brain perfusion SPECT in a multicentre study

Background and aim In Alzheimer's disease (AD), regional cerebral blood flow (rCBF) in the posterior cingulate gyrus and precuneus has been reported to decrease even at a very early stage. We performed a multicentre SPECT study to evaluate the discrimination ability of an easy Z-score imaging system (eZIS) by detecting an rCBF decrease in this area with a common normal database between very early AD patients at the stage of mild cognitive impairment and age-matched healthy volunteers. Methods Brain perfusion SPECT images of 40 Alzheimer's disease patients and 40 healthy volunteers were acquired from four gamma camera systems in different institutions. Systematic differences of SPECT images between different gamma cameras were corrected using conversion maps calculated from the SPECT images of the same brain phantom. Ten observers with various degrees of expertise graded eZIS results for receiver operating characteristic (ROC) curves. ROC curves for a positive Z-score in the volume of interest (VOI) of the posterior cingulate gyrus and precuneus were also analysed. Results An area under the ROC curve value (A(Z)) for ten observers showed the highest value of 0.866 on average with the smallest standard deviation of 0.027 in the condition of the lower threshold of a Z-score map of 2 without superimposition of VOI. Automated analysis of a Z-score in the VOI showed an A(Z) value of 0.895. Conclusion Since the degree of expertise of the observers with respect to reading eZIS did not influence the performance and an eZIS can use a common normal database by converting site-specific SPECT data to the core data, the eZIS was considered to be very useful for diagnosing early AD in routine studies in many institutions.