Frequency domain photon migration (FDPM) uses modulated laser light to measure the bulk optical properties of turbid
media and is increasingly being applied for noninvasive functional medical imaging. Though semiconductor edge emitting
laser diodes (EELs) have been traditionally used for this application, we show that VCSELs exhibit
performance characteristics suitable for FDPM measurements of tissue optical properties. Their output power and
modulation characteristics are more than sufficient for optical property recovery. In addition, their small size, high
efficiency, low cost, and simple packaging make them an attractive choice as components in clinical FDPM systems.
We demonstrate a unique, compact optical probe that was enabled by VCSEL technology.
This paper presents a safe, affordable, and noninvasive approach to estimate subcutaneous fat thickness by using a multi-distance
near infrared (MD-NIR) interactance-based wireless sensing platform. In order to perform the simultaneous
measurements at several distances, two light sources with different wavelengths are located at one end of a line followed
by seven photo diodes. Bluetooth Low Energy are adopted as their primary communication protocol as a wireless
communication. The measured data from the MD-NIR interactance sensors are wirelessly transmitted to a smartphone or
a tablet for analysis. The feasibility of the approach and wireless platform is demonstrated using the ex vivo pig fat layer
A board-level broadband frequency domain photon migration (mini-FDPM) instrument has been constructed to replace a conventional network-analyzer-based FDPM instrument. The mini-FDPM instrument with four wavelengths (681, 783, 823, and 850 nm), matches conventional FDPM instrument in performance (−88 dBm noise level, 100 dB dynamic range) and bandwidth (1 GHz), and recovers the same optical properties within about 6% in absorption and 4% in reduced scattering for liquid phantoms covering a wide range of relevant optical properties. Compared to the conventional FDPM instrument, the mini-FDPM instrument is more than 5× faster (~200 ms per 401 modulation frequencies) and several orders of magnitude less in size and cost. Standard fiber-optic-based probes can be used with the mini-FDPM instrument, which increases applications in a number of clinically relevant measurement scenarios. By drastically reducing size and cost, FDPM miniaturization lowers barriers to access and will help promote FDPM in clinical research problems. The mini-FDPM instrument forms the core of a modular broadband diffuse optical spectroscopy instrument that can be used for a variety of clinical problems in imaging and functional monitoring (i.e., breast/skin cancer, brain activation, and exercise physiology).