What is the prospect of transcutaneous transmission of 980nm photobiomodulation therapy light to the spinal canal?

The clinical prospect of treating spinal cord injury by photobiomodulation therapy (PBMT) is unclear as the spinal dosimetry of transcutaneous laser application is unknown, yet essential for clinical recommendations. Light irradiances at 9 sites over an 8cm length along the thoracic to lumbar segment of the spinal canal were measured in 6 cadaver dogs using a flexible intra-spinal probe, under a surface irradiance of 3.14W/cm2. The skin transmits 4-12% of 980nm PBMT light. On-contact technique is ~5 times more efficient than off-contact technique. Transcutaneous transmission of photobiomodulatory irradiance to the spinal canal will benefit from contact-probe technique and skin-clearing approaches.