Significance: Placenta is an essential organ for fetal development and successful reproduction. Placental insufficiency can lead to fetal hypoxia and, in extreme cases anoxia, leading to fetal death. Of the 145 million deliveries per year worldwide, ∼15 million neonates are small for gestational age and, therefore, at risk for antepartum and intrapartum hypoxia. Clinical methods to assess placental function largely rely on the assessment of fetal heart rate changes but do not assess placental oxygenation. Near-infrared spectroscopy (NIRS) allows non-invasive, real-time assessment of tissue oxygenation in intact organs, which can be used to assess placental oxygenation. However, tissue optical properties can affect the accuracy of methods to measure tissue oxygenation.
Aim: This study was performed to estimate the scattering coefficient of the human placenta. We have computed the scattering coefficients of the human placenta for the range of 659 to 840 nm using two methods of diffuse reflectance spectroscopy (DRS).
Approach: Measurements were performed using an in-house DRS device and a well-established frequency-domain diffuse optical spectroscopic system (DOSI). Measurements were performed in eight placentas obtained after cesarean deliveries. Placentas were perfused with normal saline to minimize the effects of absorption due to blood. Three sites per placenta were measured. Absorption and scattering coefficients were then calculated from the measured reflectance using the random walk theory for DRS and frequency-domain algorithm for DOSI.
Results: Average reduced scattering coefficient (μs ′ ) was 0.943 ± 0.015 mm − 1 at 760 nm and 0.831 ± 0.009 mm − 1 at 840 nm, and a power function μs ′ = 1.6619 (λ/500 nm) − 1.426 was derived for the human placental scattering coefficient.
Conclusion: We report for the first time the scattering coefficient of the human placenta. This information can be used to assess baseline scattering and improve measurements of placental oxygen saturation with NIRS.
We developed a wearable system for wireless monitoring of oxygenation of deep tissues such as liver and lung during exercise. It is also useful where subcutaneous fat thickness is high. Our system utilizes Continuous Wave Near Infrared Spectroscopy (CW NIRS) with source-detector distances from 10mm to 60mm. This allows us to observe tissues at various depths. To mitigate the interference of the overlaying tissue layers such as skin, fat and muscle, we developed a multi-layer Monte Carlo model for photon diffusion. Flexible structure of our device helps achieve better skin contact and expand its usability to most body parts.
Working memory (WM) is part of the short-term memory storage in human brain. N-back is a WM task to assess mental workload on the prefrontal cortex (PFC). In this work, we studied how mental workload changes in an N-back task over the length of the experiment. We focused on two task levels of two- and three-back. Examining both hemodynamics and behavioral data (correct answers), we found a significant difference between 2-back and 3-back tasks and a significant difference between the beginning and end of the 3-back task.
Point-of-care technologies have become increasingly important in diagnostic applications. Wireless capabilities provide easy storage and analysis of data. Thus, portable systems need to migrate to handheld versions. Previously we have been able to determine blood volume fraction and water content in human skin using near-infrared (NIR) imaging. We have also used this portable multispectral imager to successfully identify remission of disease after treatment in patients with Cushing disease. Here we present a handheld high resolution multispectral imager. This tool is designed to be light weight and easy to use to promote its use in any clinical setup. The device consists of a custom fabricated CMOS imaging camera with on-chip NIR filters, a 25mm lens and wireless communication electronics. Illumination is provided by a broad band incandescent lamp. The use of novel technology of on-chip filters avoids the need for large size filtering systems such as filter wheels, making it a handheld device. Eight NIR filters with wavelengths in the range 700 nm to 980 nm provide flexibility of detecting multiple chromophores in the skin such as oxy and deoxy hemoglobin, melanin etc. as well as water. Images are acquired simultaneously with exposure time of 300 ms to 500 ms. Each filtered image is about 340X340 pixel making it possible to use our curvature correction algorithm for accurate determination of parameters. Also, images at this resolution can provide reliable information about spatial variations. This tool can ultimately be used to the study other skin abnormalities such as Kaposi Sarcoma.
Conference Committee Involvement (3)
Biophotonics in Exercise Science, Sports Medicine, Health Monitoring Technologies, and Wearables VI
25 January 2025 | San Francisco, California, United States
Biophotonics in Exercise Science, Sports Medicine, Health Monitoring Technologies, and Wearables V
27 January 2024 | San Francisco, California, United States
Biophotonics in Exercise Science, Sports Medicine, Health Monitoring Technologies, and Wearables IV
28 January 2023 | San Francisco, California, United States
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