Imaging systems for Near-Infrared Spectroscopy
Several versions of the of Near-Infrared spectroscopy probes were developed for EPSRC (EP/K020315/1). Conventional NIRS probes use 2 to 3 wavelengths in their sources. Additional wavelengths increase the accuracy of resolving multiple chromophores in the blood, however adding further wavelengths increases the size of source hence reduces the spatial accuracy of the measurement. As a result, a miniaturised multi-wavelength LED source was developed consisting of eight discrete wavelengths from 650nm to 950nm. The die attachment, wire-bonding, and encapsulation processes were performed in-house. The miniaturised near infrared spectroscopy "tile" consist of 2 sources and 4 detectors in an 30x30 mm2 square shaped encapsulation. Each tile is part of an array of tiles which are easily connected to create an imaging array. The tile has a silicone encapsulation for clinical use and benefits from novel soft silicone rods for better optical coupling and clearing hair. The optical sensitivity of detector is approximately 370 fW which means measuring pico-amps of electrical current on the head.
(1/6) The multi-wavelength LED which was built in-house for the NIRS probe.
(2/6) The front and back view of the NIRS probe. The multiwavelength LED board (bottom left) and the photodiode detector board (bottom right).
(3/6) Exploded view of the NIRS tile. This consist of the electronic circuit board, sandwiched in a layer of protective acrylic and silicone. The soft silicone rods are the optical interface between the skin and the tile.
(4/6) A close-up view of the fully encapsulated NIRS tile. The external dimensions are approximately 35 x 35 mm.
(5/6) A front view of the encapsulated multi-wavelength NIRS tile. The LEDs and photodiode are visible through the silicone rods.
(6/6) Preliminary testing of the NIRS 4-tile system on a tissue equivalent phantom.
Image credit: © Danial Chitnis
Single channel NIRS Probe:
Danial Chitnis, Dimitrios Airantzis, David Highton, Rhys Williams, Phong Phan, Vasiliki Giagka, Samuel Powell, Robert J. Cooper, Ilias Tachtsidis, Martin Smith, Clare E. Elwell, Jeremy C. Hebden, and Nicholas Everdell, "Towards a wearable near infrared spectroscopic probe for monitoring concentrations of multiple chromophores in biological tissue in vivo", Review of Scientific Instruments, 2016
4-Tile NIRS Imaging System:
Danial Chitnis, Robert J. Cooper, Laura Dempsey, Samuel Powell, Simone Quaggia, David Highton, Clare Elwell, Jeremy C. Hebden, and Nicholas L. Everdell, "Functional imaging of the human brain using a modular, fibre-less, high-density diffuse optical tomography system," Biomed. Opt. Express 7, 4275-4288 (2016)
4-Tile Multi-wavelenght NIRS Imaging System:
D Highton, D Chitnis, S Brigadoi, P Phan, I Tachtsidis, R Cooper, N Everdell, J Hebden, M Smith, CE Elwell, "A Fibreless Multiwavelength NIRS System for Imaging Localised Changes in Cerebral Oxidised Cytochrome C Oxidase", Oxygen Transport to Tissue XL, Advances in Experimental Medicine and Biology, vol 1072, Springer, 2018