Noninvasive photobiomodulation therapy (PBMT) of spinal cord disease remains speculative due to the lack of evidence for whether photobiomodulatory irradiances can be transcutaneously delivered to the spinal cord under a clinically acceptable PBMT surface irradiation protocol. We developed 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. 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 photodiodes 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. 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 the skin.
Keywords: dosimetry; low-level light therapy; photobiomodulation therapy; spinal cord injury.
(2018) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE).