Towards a wearable near infrared spectroscopic probe for monitoring concentrations of multiple chromophores in biological tissue in vivo

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; Nicholas Everdell

doi:10.1063/1.4954722

Towards a wearable near infrared spectroscopic probe for monitoring concentrations of multiple chromophores in biological tissue in vivo

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, Nicholas Everdell

Research output: Contribution to journal › Article › Scientific › peer-review

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Abstract

The first wearable multi-wavelength technology for functional near-infrared spectroscopy has been developed, based on a custom-built 8-wavelength light emitting diode (LED) source. A lightweight fibreless probe is designed to monitor changes in the concentrations of multiple absorbers (chromophores) in biological tissue, the most dominant of which at near-infrared wavelengths are oxyhemoglobin and deoxyhemoglobin. The use of multiple wavelengths enables signals due to the less dominant chromophores to be more easily distinguished from those due to hemoglobin and thus provides more complete and accurate information about tissue oxygenation, hemodynamics, and metabolism. The spectroscopic probe employs four photodiode detectors coupled to a four-channel charge-to-digital converter which includes a charge integration amplifier and an analogue-to-digital converter (ADC). Use of two parallel charge integrators per detector enables one to accumulate charge while the other is being read out by the ADC, thus facilitating continuous operation without dead time. The detector system has a dynamic range of about 80 dB. The customized source consists of eight LED dies attached to a 2 mm × 2 mm substrate and encapsulated in UV-cured epoxy resin. Switching between dies is performed every 20 ms, synchronized to the detector integration period to within 100 ns. The spectroscopic probe has been designed to be fully compatible with simultaneous electroencephalography measurements. Results are presented from measurements on a phantom and a functional brain activation study on an adult volunteer, and the performance of the spectroscopic probe is shown to be very similar to that of a benchtop broadband spectroscopy system. The multi-wavelength capabilities and portability of this spectroscopic probe will create significant opportunities for in vivo studies in a range of clinical and life science applications.

Original language	English
Article number	065112
Journal	Review of Scientific Instruments
Volume	87
Issue number	6
DOIs	https://doi.org/10.1063/1.4954722
Publication status	Published - 1 Jun 2016
Externally published	Yes

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Chitnis, D., Airantzis, D., Highton, D., Williams, R., Phan, P., Giagka, V., Powell, S., Cooper, R. J., Tachtsidis, I., Smith, M., Elwell, C. E., Hebden, J. C., & Everdell, N. (2016). Towards a wearable near infrared spectroscopic probe for monitoring concentrations of multiple chromophores in biological tissue in vivo. Review of Scientific Instruments, 87(6), Article 065112. https://doi.org/10.1063/1.4954722

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title = "Towards a wearable near infrared spectroscopic probe for monitoring concentrations of multiple chromophores in biological tissue in vivo",

abstract = "The first wearable multi-wavelength technology for functional near-infrared spectroscopy has been developed, based on a custom-built 8-wavelength light emitting diode (LED) source. A lightweight fibreless probe is designed to monitor changes in the concentrations of multiple absorbers (chromophores) in biological tissue, the most dominant of which at near-infrared wavelengths are oxyhemoglobin and deoxyhemoglobin. The use of multiple wavelengths enables signals due to the less dominant chromophores to be more easily distinguished from those due to hemoglobin and thus provides more complete and accurate information about tissue oxygenation, hemodynamics, and metabolism. The spectroscopic probe employs four photodiode detectors coupled to a four-channel charge-to-digital converter which includes a charge integration amplifier and an analogue-to-digital converter (ADC). Use of two parallel charge integrators per detector enables one to accumulate charge while the other is being read out by the ADC, thus facilitating continuous operation without dead time. The detector system has a dynamic range of about 80 dB. The customized source consists of eight LED dies attached to a 2 mm × 2 mm substrate and encapsulated in UV-cured epoxy resin. Switching between dies is performed every 20 ms, synchronized to the detector integration period to within 100 ns. The spectroscopic probe has been designed to be fully compatible with simultaneous electroencephalography measurements. Results are presented from measurements on a phantom and a functional brain activation study on an adult volunteer, and the performance of the spectroscopic probe is shown to be very similar to that of a benchtop broadband spectroscopy system. The multi-wavelength capabilities and portability of this spectroscopic probe will create significant opportunities for in vivo studies in a range of clinical and life science applications.",

author = "Danial Chitnis and Dimitrios Airantzis and David Highton and Rhys Williams and Phong Phan and Vasiliki Giagka and Samuel Powell and Cooper, {Robert J.} and Ilias Tachtsidis and Martin Smith and Elwell, {Clare E.} and Hebden, {Jeremy C.} and Nicholas Everdell",

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doi = "10.1063/1.4954722",

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Chitnis, D, Airantzis, D, Highton, D, Williams, R, Phan, P, Giagka, V, Powell, S, Cooper, RJ, Tachtsidis, I, Smith, M, Elwell, CE, Hebden, JC & Everdell, N 2016, 'Towards a wearable near infrared spectroscopic probe for monitoring concentrations of multiple chromophores in biological tissue in vivo', Review of Scientific Instruments, vol. 87, no. 6, 065112. https://doi.org/10.1063/1.4954722

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AU - Chitnis, Danial

AU - Airantzis, Dimitrios

AU - Highton, David

AU - Williams, Rhys

AU - Phan, Phong

AU - Giagka, Vasiliki

AU - Powell, Samuel

AU - Cooper, Robert J.

AU - Tachtsidis, Ilias

AU - Smith, Martin

AU - Elwell, Clare E.

AU - Hebden, Jeremy C.

AU - Everdell, Nicholas

PY - 2016/6/1

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AB - The first wearable multi-wavelength technology for functional near-infrared spectroscopy has been developed, based on a custom-built 8-wavelength light emitting diode (LED) source. A lightweight fibreless probe is designed to monitor changes in the concentrations of multiple absorbers (chromophores) in biological tissue, the most dominant of which at near-infrared wavelengths are oxyhemoglobin and deoxyhemoglobin. The use of multiple wavelengths enables signals due to the less dominant chromophores to be more easily distinguished from those due to hemoglobin and thus provides more complete and accurate information about tissue oxygenation, hemodynamics, and metabolism. The spectroscopic probe employs four photodiode detectors coupled to a four-channel charge-to-digital converter which includes a charge integration amplifier and an analogue-to-digital converter (ADC). Use of two parallel charge integrators per detector enables one to accumulate charge while the other is being read out by the ADC, thus facilitating continuous operation without dead time. The detector system has a dynamic range of about 80 dB. The customized source consists of eight LED dies attached to a 2 mm × 2 mm substrate and encapsulated in UV-cured epoxy resin. Switching between dies is performed every 20 ms, synchronized to the detector integration period to within 100 ns. The spectroscopic probe has been designed to be fully compatible with simultaneous electroencephalography measurements. Results are presented from measurements on a phantom and a functional brain activation study on an adult volunteer, and the performance of the spectroscopic probe is shown to be very similar to that of a benchtop broadband spectroscopy system. The multi-wavelength capabilities and portability of this spectroscopic probe will create significant opportunities for in vivo studies in a range of clinical and life science applications.

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Towards a wearable near infrared spectroscopic probe for monitoring concentrations of multiple chromophores in biological tissue in vivo

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