Quantitative Analysis of Peripheral Benzodiazepine Receptor in the Human Brain Using PET with 11C-AC-5216
Michie Miyoshi 1,
Hiroshi Ito 2*,
Ryosuke Arakawa 2,
Hidehiko Takahashi 2,
Harumasa Takano 2,
Makoto Higuchi 2,
Masaki Okumura 2,
Tatsui Otsuka 2,
Fumitoshi Kodaka 2,
Mizuho Sekine 2,
Takeshi Sasaki 2,
Saori Fujie 2,
Chie Seki 2,
Jun Maeda 2,
Ryuji Nakao 3,
Ming-Rong Zhang 3,
Toshimitsu Fukumura 3,
Masayasu Matsumoto 4,
and
Tetsuya Suhara 2
1 Molecular Neuroimaging Group, Molecular Imaging Center, National Institute of Radiological Sciences, Chiba, Japan; Department of Clinical Neuroscience and Therapeutics, Hiroshima University Graduate School of Biomedical Sciences, Hiroshima, Japan
2 Molecular Neuroimaging Group, Molecular Imaging Center, National Institute of Radiological Sciences, Chiba, Japan
3 Molecular Probe Group, Molecular Imaging Center, National Institute of Radiological Sciences, Chiba, Japan
4 Department of Clinical Neuroscience and Therapeutics, Hiroshima University Graduate School of Biomedical Sciences, Hiroshima, Japan
* To whom correspondence should be addressed. E-mail: hito{at}nirs.go.jp.
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Abstract |
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Peripheral benzodiazepine receptor (PBR) is upregulated in activated glial cells and is therefore a useful biomarker for inflammation in the brain and neurodegenerative disorders. We developed a new PET radioligand, 11C-AC-N-benzyl-N-ethyl-2-(7-methyl-8-oxo-2-pheyl-7,8-dihydro-9H-purin-9-yl)acetamide (11C-AC-5216), that allows the imaging and quantification of PBRs in monkey and mouse brains. The aim of this study was to evaluate a quantification method of 11C-AC-5216 binding in the human brain. Methods: A 90-min dynamic PET scan was obtained for each of 12 healthy men after an intravenous injection of 11C-AC-5216. Regions of interest were drawn on several brain regions. Binding potential, compared with nondisplaceable uptake (BPND), was calculated by a nonlinear least-squares fitting (NLS) method with the 2-tissue-compartment model, and total volume of distribution (VT) was estimated by NLS and graphical analysis methods. Results: BPND was highest in the thalamus (4.6 ± 1.0) and lowest in the striatum (3.5 ± 0.7). VT obtained by NLS or graphical analysis showed regional distribution similar to BPND. However, there was no correlation between BPND and VT because of the interindividual variation of K1/k2. BPND obtained with data from a scan time of 60 min was in good agreement with that from a scan time of 90 min (r = 0.87). Conclusion: Regional distribution of 11C-AC-5216 was in good agreement with previous PET studies of PBRs in the human brain. BPND is more appropriate for estimating 11C-AC-5216 binding than is VT because of the interindividual variation of K1/k2. 11C-AC-5216 is a promising PET ligand for quantifying PBR in the human brain.
Key Words:
11C-AC-5216, peripheral benzodiazepine receptor, microglia, human brain, positron emission tomography
