[1] Stanford Univ, Dept Elect Engn, Ginzton Lab, Stanford, CA 94305 USA
[2] Stanford Univ, Sch Med, James H Clark Ctr Biomed Engn & Sci, Stanford, CA 94305 USA
[3] NECTEC, Pathum Thani, Thailand
[4] Chulalongkorn Univ, Fac Med, Bangkok 10330, Thailand
[5] Univ Michigan, Dept Med, Ann Arbor, MI 48109 USA