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.
Clinical cerebral oximeters based on near-infrared spectroscopy (NIRS) are a commonly used, non-invasive tool for intraoperative monitoring of hemoglobin saturation. Research to verify performance of cerebral oximeters in human subject trials has shown differences between commercially available devices. Test methods based on tissue-simulating phantoms have been proposed to augment clinical findings. While prior studies have focused on liquid phantoms, this work is aimed at developing methods based on solid polymer phantoms that are stable. Specifically, we have designed and fabricated a neonatal/pediatric head mimicking layered phantoms based on a 3D-printed cerebral matrix incorporating an array of vessel-simulating linear channels. Superficial layers incorporating homogeneous molded polydimethylsiloxane (PDMS) slabs were fabricated to represent CSF, scalp and skull regions. The cerebral matrix was filled with bovine blood desaturated with sodium dithionite to achieve oxygenation levels across the 40-90% range. Measurements were performed with a commercially available cerebral oximeter using two probes with different illumination-collection geometries, as designed for neonatal and pediatric patients. Reference measurements of samples were performed with a CO-oximeter before injection and after extraction. Results from applied cerebral oximeters indicate a strong sensitivity to the thickness of the superficial layer of the phantom. Better correlation with the reference CO-oximeter results were obtained in the superficial layer thickness of 0.8-2.5 mm range. Channel array phantoms with modular superficial layers represent a promising approach for performance testing of NIRS-based cerebral oximeters.