Regional distribution of an amyloid radiotracer in healthy aged human brain measured by PET with [18F]flutemetamol: a relation with myelin distribution
摘要
To measure amyloid-β deposits by positron emission tomography (PET), several radiotracers have been employed in the examination of the pathophysiology of Alzheimer’s disease. Although the nature of amyloid radiotracer binding to white matter is not fully understood, they may bind to myelin, which is organized in a beta-sheet structure similar to that of amyloid-β deposits. In the present study, a normal database of myelin distribution measured by PET with the amyloid radiotracer [18F]flutemetamol was constructed in healthy subjects.
MethodsThe data of [18F]flutemetamol PET and T1-weighted images (T1WI) of magnetic resonance imaging (MRI) for 45 healthy subjects were used. After anatomic standardization of all PET and MRI images, the standardized uptake value ratio (SUVR) images of PET, and white matter fraction (WM) images from MRI were obtained.
ResultsA database of normal PET images with [18F]flutemetamol was constructed. The SUVR in the white matter were not uniform across the brain. However, the SUVR per WM were mostly uniform in the cerebral white matter, due to a correction of effects of the limited spatial resolution of the PET scanner. The regional distributions of SUVR and SUVR per WM were similar to those previously reported for myelin using the myelin water imaging technique with MRI. Significant increases in the SUVR or the SUVR per WM with age were observed in almost all white matter regions. The myelin content measured by MRI with the myelin water imaging technique has also been reported to increase with age. Increases in the SUVR or the SUVR per WM with age may reflect ongoing myelin formation continuing during normal aging.
ConclusionsThe present study supports the binding of [18F]flutemetamol to myelin. Thus, a database reflecting normal myelin distribution as measured by PET might be successfully constructed.