@article{oai:repo.qst.go.jp:00046461,
 author = {Ohya, Tomoyuki and Zhang, Ming-Rong and Fukumura, Toshimitsu and Fukushi, Kiyoshi and Kikuchi, Tatsuya and Irie, Toshiaki and 大矢 智幸 and 張 明栄 and 福村 利光 and 福士 清 and 菊池 達矢 and 入江 俊章},
 issue = {10},
 journal = {Nuclear Medicine Communications},
 month = {Sep},
 note = {Objective: The aim of this study was to develop a method to predict a tracer's alpha-value in the human brain on the basis of animal data. The alpha-value is the ratio of the conversion rate and the back-diffusion rate (k3/k2) and is one of the critical kinetic features of the detection sensitivity of target molecule activity, such as enzyme activity, in the measurement of PET and single-photon emission computed tomography using an irreversible-type radiotracer.
Method: The alpha-value in the rat brain was estimated by a simultaneous assay of the tracer uptake and the target biochemical activity using N-[14C]-methylpiperidin-4-yl acetate ([14C]MP4A) and N-[14C]-methylpiperidin-4-yl propionate ([14C]MP4P) as test tracers, both of which are metabolic trapping tracers for measurement of brain acetylcholinesterase. The alpha-value in humans was then extrapolated from the alpha-value in rats by considering the differences between the species. The predicted human alpha-values were compared with those obtained from the kinetic analyses of human PET studies using [11C]MP4A and [11C]MP4P.
Result: The alpha-values in the human brain cortex were predicted to be 0.51+/-0.1 for MP4A and 0.25+/-0.05 for MP4P. These results were close to values reported in other PET studies: 0.48+/-0.1 to 0.73+/-0.2 for MP4A and 0.15+/-0.04 to 0.18+/-0.04 for MP4P.
Conclusion: The alpha-value predicted by this method would be used for practical selection or development of irreversible-type radiotracers for human use.},
 pages = {1019--1023},
 title = {A method to predict the ratio of the tracer conversion rate to the tracer back-diffusion rate of an irreversible-type radiotracer in humans by preclinical evaluation},
 volume = {33},
 year = {2012}
}