ここまでわかるアルツハイマー病の画像診断

In this article, we describe the various diagnostic imaging examinations currently used for evaluating dementia, with a focus on Alzheimer’s disease. There are many diseases that cause dementia, and Alzheimer’s disease is a typical disease, accounting for about ６７．６％ of dementia cases in patients ≥６５ years old. Naturally, it is not possible to diagnose dementia based on an imaging examination alone, but the importance of such examinations as powerful auxiliary tools has been widely recognized. Computed tomography and magnetic resonance imaging can confirm the presence of intracranial diseases, such as brain tumors, chronic subdural hematoma, normal-pressure hydrocephalus and other treatable diseases, as well as cerebral atrophy. Brain perfusion scintigraphy using compounds labeled with a radioisotope, such as １２３I, can visualize the blood flow distribution in the brain. After the non-linear transformation to Talairach’s standard brain coordinates, comparing it with a normal database, it is possible to objectively and accurately depict the site of blood flow reduction. Cardiac scintigraphy using １２３I-MIBG and dopamine transporter scintigraphy using １２３I-ioflupane can also visualize neurotransmitter functions and contribute to the diagnosis of dementia. Amyloid positron emission tomography, which can noninvasively detect the earliest event of Alzheimer’s disease（amyloid β deposition）is also becoming a common imaging examination. With these imaging examinations, the accuracy of diagnosing dementia is improving. Thus, the early diagnosis and differentiation of Alzheimer’s disease are gradually becoming possible thanks to advances in diagnostic imaging. There is currently no fundamental treatment for Alzheimer’s disease, but treatments are available that improve the symptoms or slow progression, so the early diagnosis and treatment/intervention remains important.