Noninvasive in vivo millimeter-wave measurements of glucose: First results in human subjects

We present initial data on noninvasive millimeter-wave tracking of glucose levels in human subjects. Measurements were made using three separate test systems, all giving similar results: (1) a K-band (WR42) rectangular waveguide clamp coupled to a direct detector to measure transmission magnitude through the upper ear between 15 and 25 GHz; (2) a K-band waveguide clamp connected to a vector network analyzer to measure magnitude and phase of transmitted power through the ear lobe; and (3) a Ka-band rectangular waveguide clamp operating from 26-36 GHz also recording complex transmission coefficients through the ear lobe. A novel compact CMOS heterodyne transceiver operating at 19-21 GHz was also tested, but failed to show sufficient antenna-to-antenna power coupling to produce useful results. Data was collected during a standard oral glucose tolerance test (OGTT) in one healthy volunteer and correlated with blood glucose measurements using a commercial glucometer. Preliminary results show good correlation between blood glucose measurements (invasive) and both magnitude and phase of millimeter-wave transmission (non-invasive) through the skin, and are in accordance with our earlier animal experiments conducted on anesthetized rats.