Longitudinal analysis of brain structure using existence probability

INTRODUCTION: We propose a method to evaluate quantitatively the longitudinal structural changes in brain atrophy to provide early detection of Alzheimer's disease (AD) and mild cognitive impairment (MCI). METHODS: We used existence probabilities obtained by segmenting magnetic resonance (MR) images at two different time points into four regions: gray matter, white matter, cerebrospinal fluid, and background. This method was applied to T1‐weighted MR images of 110 participants with normal cognition (NL), 165 with MCI, and 82 with AD, obtained from the Japanese Alzheimer's Disease Neuroimaging Initiative database. RESULTS: We obtained the coefficients of probability change (CPC) for each dataset. We found high area under the receiver operating characteristic curve (ROC) values (up to 0.908 of the difference of ROCs) for some CPC regions that are considered indicators of atrophy. Additionally, we attempted to establish a machine‐learning algorithm to classify participants as NL or AD. The maximum accuracy was 92.1% for NL‐AD classification and 81.2% for NL‐MCI classification using CPC values between images acquired at first and sixth months, respectively. CONCLUSION: These results showed that the proposed method is effective for the early detection of AD and MCI.