Quantitative Alzheimer’s imaging possible with novel biomarker
Typical Alzheimer’s neuroimaging looks at amyloid deposition and neurofibrillary tangles, but a new quantitative method uses arterial input to bring signs of functional disease into sharper relief, according to a study published April 16 in the Journal of Nuclear Medicine.
The radionuclide agent is called choline-11 labeled 5-(6-{[tert-butyl(dimethyl)silyl]oxy}-1,3-benzothiazol-2-yl)pyridin-2-amine (C-11 AZD2184). It is catching attention due to its quick uptake and washout in the brain in Alzheimer’s studies.
A team of researchers including Hiroshi Ito, MD, PhD, from the Molecular Imaging Center and National Institute of Radiological Sciences in Chiba, Japan, observed C-11 AZD2184 in quantitative PET studies and used a compartment model analysis with a metabolite-corrected arterial input function. The researchers also assessed how accurate relatively simplified quantitative techniques that focus on a region of the brain really are.
A total of eight Alzheimer’s patients and six healthy controls were imaged with PET for 90 minutes. Arterial blood sampling and high-performance liquid chromatography analysis were used to create the input function. As a result, the total distribution volume ratios to the reference region in the cerebral cortex were substantially increased in patients with Alzheimer’s using the standard two-tissue compartment model.
Due to anomalous white-matter uptake, researchers also suspected binding to myelin in Alzheimer’s patients. However useful, the researchers concluded that arterial input function was not entirely necessary for an accurate view of agent binding.
“Although the white matter binding of C-11 AZD2184 may have some effect on cortical measurement, it can be concluded that the kinetic behavior of C-11 AZD2184 is suitable for quantitative analysis,” concluded Ito et al. “The standardized uptake value ratio can be used as a validated measure of 11C-AZD2184 binding in clinical examinations without arterial input function.”