Significance: Oxygenation is one of the skin tissue physiological properties to follow for patient care management. Furthermore, long-term monitoring of such parameters is needed at the patient bed as well as outside the hospital. Diffuse reflectance spectroscopy has been widely used for this purpose.
Aim: The aim of the study is to propose a low-cost system for the long-term measurement of skin physiological parameters in contact.
Approach: We have developed a low-cost, wearable, CMOS-based device. We propose an original method for processing diffuse reflectance data to calculate the tissue oxygen saturation (StO2).
Results: We tested the device for the assessment of tissue oxygenation during a first-in-human clinical trial that took place at the Grenoble University Hospital France.
Conclusions: The results of this clinical trial show a good accordance between our sensor and commercial devices used a reference.
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.
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.
Diffuse reflectance spectroscopy has been widely used in the field of biological tissue characterization with various modalities [1-5,6]. One of these modalities consists in measuring the spatially resolved diffuse reflectance (SRDR). In this technique, light is collected at multiple distances from the excitation point. The obtained reflectance decay curve is used to determine scattering and absorption properties of the tissue , which are directly related to tissue content and structure. Existing systems usually use fiber optics to collect light reflected from the tissue and transfer it to an optical sensor [1,6]. Such devices make it possible to perform SRDR measurements directly in contact with the tissue. However, they offer poor spatial sampling of the reflectance and low light collection efficiency. We propose to overcome these limitations by using a CMOS sensor placed in contact with the tissue to achieve light collection with high spatial sampling over several millimeters and with increased fill factor. Our objective in this paper is to demonstrate the potential of our instrument to determine the optical properties of tissues from SRDR measurements. We first describe the instrument and the employed methodology. Then, preliminary results obtained on optical phantoms are presented. Finally, the potential of our system for SRDR measurements is evaluated through comparison with a fiber-optic probe previously developed in our laboratory [6,8].