[1] Tohoku Univ, Grad Sch Med, Dept Behav Neurol & Cognit Neurosci, Sendai, Miyagi 980, Japan
[2] Tohoku Univ, Grad Sch Med, Dept Neurol, Sendai, Miyagi 980, Japan
[3] Tohoku Univ, Grad Sch Med, Dept Diagnost Radiol, Sendai, Miyagi 980, Japan
[4] Tohoku Univ, Inst Dev Aging & Canc, Dept Nucl Med & Radiol, Sendai, Miyagi 980, Japan