Imaging biomarker dedicated to diagnosis of Alzheimer disease

Abstract

With the approval of lecanemab, a disease–modifying drug for Alzheimer disease, in Japan in 2023, amyloid PET has also been clinically implemented. Does this mean that clinicians will be freed from spending time interpreting MRI and brain perfusion SPECT, by ordering only amyloid PET? Of course, this is not the case, and in reality, solid knowledge of various imaging biomarkers is more crucial than ever before. Behind the recent development of disease–modifying drugs for dementia is the fact that brain pathophysiology assessment technologies such as amyloid PET and tau PET have served as foundational technologies. These technologies have reduced misdiagnosis in patient inclusion in clinical trials, enabled monitoring of treatment efficacy, and allowed stratification of patients based on pathological severity. In clinical practice, one of the most important roles of imaging biomarkers for dementia is to avoid missing potentially treatable conditions, such as cerebrovascular disease, chronic subdural hematoma, brain tumors, and normal pressure hydrocephalus. A physician familiar with brain imaging will be able to characterize morphological changes and use a variety of nuclear medicine techniques to help differentiate brain pathologies. However, it should always be noted that there are various pitfalls in doing so. It is hoped that future interventions in patients in preclinical stages will delay or prevent the onset of dementia ; however, there are various issues to be resolved, including the development of affordable and less invasive screening methods. This paper focuses on brain imaging in relation to the recent progress of research on the pathophysiology of dementia and outlines the role of brain imaging in the development of disease–modifying drugs for dementia, including the results of clinical trials. In addition, the application of imaging biomarkers in clinical practice and the challenges and prospects in realizing precision medicine in the future will also be discussed.