We have developed a low-cost, wearable, CMOS-based device for the long-term measurement of skin physiological parameters in contact with tissue from spatially resolved diffuse reflectance measurements. The device has been tested for the assessment of the tissue oxygenation in vivo.
We developed an algorithm to estimate the optical properties of a bilayer material using diffuse reflectance analysis. This algorithm has been tested to the detection of liveness in a biometric device adapted to perform Structured Light Imaging. The liveness detection is based on the optical properties comparison between spoofs and living objects.
Diffuse optical tomography (DOT) estimates the optical properties inside a turbid medium by injecting light from the surface and measuring the reflected photons. In time-resolved technology, since to perform DOT reconstruction at time domain is too computationally expensive, datatypes are used instead. Temporal windows are the most used datatypes but until now just w(t) = tne−pt forms could be computed fast. In this work, we propose a new method to compute efficiently a larger set of window datatypes. The results show that with these new windows (1) the localization of inclusions deeper than 2.5 cm is improved and (2) the absorption quantification is ameliorated at all inclusion depths.
Spatially resolved diffuse reflectance spectroscopy (srDRS) is a well-established technique for noninvasive, in vivo characterization of tissue optical properties toward diagnostic applications. srDRS has a potential for depth-resolved analysis of tissue, which is desired in various clinical situations. However, current fiber-based and photodiode-based systems have difficulties achieving this goal due to challenges in sampling the reflectance with a high enough resolution. We introduce a compact, low-cost architecture for srDRS based on the use of a multipixel imaging sensor and light-emitting diodes to achieve lensless diffuse reflectance imaging in contact with the tissue with high spatial resolution. For proof-of-concept, a prototype device, involving a commercially available complementary metal–oxide semiconductor coupled with a fiber-optic plate, was fabricated. Diffuse reflectance profiles were acquired at 645 nm at source-to-detector separations ranging from 480 μm to 4 mm with a resolution of 16.7 μm. Absorption coefficients (μa) and reduced scattering coefficients (μs′) of homogeneous tissue-mimicking phantoms were measured with 4.2 ± 3.5 % and 7.0 ± 4.6 % error, respectively. The results obtained confirm the potential of our approach for quantitative characterization of tissue optical properties in contact imaging modality. This study is a first step toward the development of low-cost, wearable devices for skin condition diagnosis in vivo.