Monitoring Osteoporosis With Into-Body Antennas: A Feasibility Study

This is the authors' abstract. We don't add key points for this paper.

Microwave sensing devices have the potential to be a non-ionizing, low-cost, and portable solution for monitoring osteoporosis. However, existing microwave sensors suffer from weak transmission into the tissues, small signal variation over different degrees of osteoporosis, and small bandwidth. In this work, we overcome challenges in the state-of-the-art by proposing a microwave-based sensing technique where two into-body antennas (specifically, high-contrast low-loss antennas, or HCLAs) are placed on either side of the wrist to monitor osteoporotic conditions. As a proof-of-concept, we first perform simulations and experiments over planar, layered structures, consisting of bone-only and 2/3 muscle-bone layers. To further assess performance in realistic scenarios, we perform full-wave simulations using a human arm voxel model. We use two bone volume fraction (BVF) models to quantify osteoporosis; where 10% and 40% BVF suggest osteoporotic and healthy bone, respectively. A unit cell analysis over the planar layered geometries indicates that HCLA transmission is very efficient, with only≈ 5dB lower transmission than the theoretically possible best values for frequencies$>2$GHz. The dynamic range (i.e., change in signal between healthy and osteoporotic bone) of the transmission coefficient magnitude and phase is≈ 2dB and and≈ 70 ^∘near 4 GHz, respectively. Voxel simulations show an irregular, yet considerable dynamic range of≈ 8dB and100 ^ ∘, respectively. Strong signal levels, large dynamic range over a wide bandwidth, and a small form factor suggest that HCLA measurements, when also combined in the future with appropriate calibration and post-processing, can be used as an efficient method to monitor osteoporosis.