Flexible Nine-Channel Photodetector Probe Facilitated Intraspinal Multisite Transcutaneous Photobiomodulation Therapy Dosimetry In Cadaver Dogs

This is a translational research study that describes the development and use of a flexible nine-channel photodetection probe for deployment within the spinal canal of a cadaver dog after hemilaminectomy to measure transcutaneously transmitted PBMT irradiance at nine sites over an eight cm spinal canal length.

Probe Design:

• The probe was built upon a 6.325-mm tubular stem, to the surface of which nine photodiodes were epoxied at approximately 1 cm apart. The photodiode has a form factor of 4.80 mm × 2.10 mm × 1.15 mm (length × width × height).
• Each photodiode was individually calibrated to deliver 1 V per 7.58 μW∕cm2 continuous irradiance at 850 nm.
• The outputs of eight photo diodes were logged concurrently using a data acquisition module interfacing eight channels of differential analog signals, while the output of the ninth photodiode was measured by a precision multimeter.
• This flexible probe rendered simultaneous intraspinal (nine-site) measurements of transcutaneous PBMT irradiations at 980 nm in a pilot cadaver dog model.

Results: At a surface continuous irradiance of 3.14 W∕cm² applied off-contact between L1 and L2, intraspinal irradiances picked up by nine photodiodes had a maximum of 327.48 μW∕cm² without the skin and 5.68 μW∕cm² with

Conclusions: This flexible nine-channel probe rendered the first set of simultaneous, nine-site intraspinal measurements of transcutaneously transmitted 980-nm PBMT light irradiation in a pilot cadaver dog. The amount of light reaching the spinal canal in the shallowest region (T13-L1 region) is comparable to that delivered transcranially in the human, which was shown to be effective in 2 out of 3 acute ischemic stroke trials in humans (Lampl et al 2007, Zivin et al 2009, Stemer et al 2010). Research is on-going with six more cadaver dogs to evaluate transcutaneous transmission of PBMT light at various surface applications and on subjects of various sizes that are expected to be more relevant to clinical protocols.

Published: J. Biomed. Opt. 23(1), 010503 (2018), doi: 10.1117/1.JBO.23.1.010503.

Keywords: photodetection; energy dose; laser therapy; penetration; photobiomodulation; hemilaminectomy; canine

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