Use of a colorimeter is a viable method to measure melanin and erythema content in the context of laser beam attenuation
2:03
Published: Journal of the Veterinary Medical Association, 2023
Keyword: Photobiomodulation, Laser, Laser Beam Attenuation, Class IV, Melanin, Colorimeter, Erythema Indices, Clipped, Unclipped, Hair, Tissue Thickness, Dog, Canine
Author(s): S. T. Rosenblum, D. A. McCarthy, D. L. Millis, and A. Odoi
Overview
The objective of this study was to evaluate class IV laser beam attenuation (LBA) by canine tissues using a colorimeter to evaluate melanin and erythema indices. It was hypothesized that greater melanin, erythema indices, and unclipped hair would increase LBA (decrease laser penetration) and these properties would vary among tissues.
Materials/Methods
Twenty client-owned dogs received laser applications at seven different sites each. A class IV laser was used. Colorimeter measurements and LBA in various tissues before and after clipping overlying hair were evaluated. Data was analyzed using generalized linear mixed models.
Results
Tissue thickness was directly associated with LBA (less light is left at depth in thicker tissues). Laser output power (W) was indirectly associated with LBA, with higher power having greater penetration. Higher surface treatment power (within safety limits) results in more light left at depth in deep tissue conditions.
Melanin index was significantly associated with LBA (the darker the skin of the patient, the more light was lost when penetrating through tissues). Sites with clipped hair had significantly greater laser penetration and lower mean LBA than LBA in non-clipped hair (~4% difference). Optimizing laser dose to accommodate a patient’s coat is needed. There was no association of LBA with erythema index.
Conclusions
This study evaluated LBA by different tissues in live dogs using a colorimeter to evaluate melanin and erythema indices. Clipping hair and/or using increased laser doses in thicker tissues and dogs with high melanin content will decrease laser beam attenuation. The colorimeter may be helpful in customizing patient treatment dosimetry. Future studies are necessary to determine therapeutic laser doses for adequate photobiomodulation effects.