Transcutaneous Transmission of Light of Photobiomodulation Therapy Wavelengths at 808 nm, 915 nm, 975 nm, and 1064 nm to the Spinal Canal of Cadaver Dogs

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

It is a well-structured manuscript of good quality with important research. However, it can be improved for publication in the following aspect: I liked the way the data was presented in the discussion, but it is necessary to include more data from the literature to support your discussion. I found a lack of references in the discussion. Please include more references to discuss or support your results.

Author Response

Reviewer 1  (response to the comments of reviewer 1 is marked by cyn color and underline)

 

It is a well-structured manuscript of good quality with important research. However, it can be improved for publication in the following aspect: I liked the way the data was presented in the discussion, but it is necessary to include more data from the literature to support your discussion.

I found a lack of references in the discussion. Please include more references to discuss or support your results.

 

Responses:

Thank you. Eight references have been cited in the Discussions:

 

[23]        C. Ash, M. Dubec, K. Donne, and T. Bashford, “Effect of wavelength and beam width on penetration in light-tissue interaction using computational methods,” Lasers Med Sci, vol. 32, no. 8, pp. 1909–1918, Nov. 2017, doi: 10.1007/s10103-017-2317-4.

[24]         L. Finlayson et al., “Depth Penetration of Light into Skin as a Function of Wavelength from 200 to 1000 nm,” Photochem & Photobiology, vol. 98, no. 4, pp. 974–981, Jul. 2022, doi: 10.1111/php.13550.

[25]         W.-C. Lin, M. Motamedi, and A. J. Welch, “Dynamics of tissue optics during laser heating of turbid media,” Appl. Opt., vol. 35, no. 19, p. 3413, Jul. 1996, doi: 10.1364/AO.35.003413.

[26]         V. K. Nagarajan, J. M. Ward, and B. Yu, “Association of Liver Tissue Optical Properties and Thermal Damage,” Lasers Surg Med, vol. 52, no. 8, pp. 779–787, Oct. 2020, doi: 10.1002/lsm.23209.

[27]         R. A. Weersink, J. He, I. Veilleux, J. Trachtenberg, and B. C. Wilson, “Monitoring changes in tissue optical properties following interstitial photothermal therapy of ex vivo human prostate tissue,” presented at the SPIE BiOS, B. J. Tromberg, A. G. Yodh, and E. M. Sevick-Muraca, Eds., San Francisco, California, USA, Mar. 2013, p. 85781G. doi: 10.1117/12.2004578.

[28]         Z. Zhao and P. W. Fairchild, “Dependence of light transmission through human skin on incident beam diameter at different wavelengths,” presented at the BiOS ’98 International Biomedical Optics Symposium, S. L. Jacques, Ed., San Jose, CA, May 1998, p. 354. doi: 10.1117/12.308184.

[29]         T. Ando et al., “Comparison of Therapeutic Effects between Pulsed and Continuous Wave 810-nm Wavelength Laser Irradiation for Traumatic Brain Injury in Mice,” PLoS ONE, vol. 6, no. 10, p. e26212, Oct. 2011, doi: 10.1371/journal.pone.0026212.

[30]         J. T. Hashmi et al., “Effect of pulsing in low‐level light therapy,” Lasers Surg Med, vol. 42, no. 6, pp. 450–466, Aug. 2010, doi: 10.1002/lsm.20950.

 

 

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

This manuscript is a very interesting study with implications for improving PBMT for spinal cord injuries. The research design is well described, but the small sample size and variability among the cadaver dogs limit the generalizability of the findings. The presentation of methods and results is detailed, but the manuscript would benefit from clearer structure and some language editing. 

1. The introduction has a comprehensive background but could be made more concise. This would improve readability and focus the attention on the key points. 

2. The methods are described in great detail, which is excellent for reproducibility. However, editing for clarity, especially for readers who are not specialists in the field, would be helpful. 

3. The statistical analysis section needs more details. It is important to indicate whether the assumptions of one-way ANOVA were tested. Additionally, mention if any post-hoc tests were conducted to identify specific differences between wavelengths. 

4. The section for results should be only "results" because there is already a section for "discussion". 

5. In the discussion, it would be helpful to mention the limitations of the generalizability of the findings when acknowledging the small sample size. 

6. There is a typographical error on page 19, line 699. The wavelength should be corrected to "1064nm": "These findings suggest that 064nm may be a more effective wavelength for transcutaneous PBMT for spinal cord injury."

Overall, while the study presents valuable data, addressing these comments will enhance the clarity and impact of the manuscript.

Author Response

This manuscript is a very interesting study with implications for improving PBMT for spinal cord injuries. The research design is well described, but the small sample size and variability among the cadaver dogs limit the generalizability of the findings. The presentation of methods and results is detailed, but the manuscript would benefit from clearer structure and some language editing. 

1. The introduction has a comprehensive background but could be made more concise. This would improve readability and focus the attention on the key points. 

We found it difficult to shorten the introduction without impacting the integrity of the manuscript. Hopefully the addition of a couple of references that respond to the reviewer #3 will make the Introduction more coherent.  

 

2. The methods are described in great detail, which is excellent for reproducibility. However, editing for clarity, especially for readers who are not specialists in the field, would be helpful. 

We believe that it is necessary to keep the technical details at is, to give adequate reference should other groups find it compelling to replicate the study.  

 

3. The statistical analysis section needs more details. It is important to indicate whether the assumptions of one-way ANOVA were tested. Additionally, mention if any post-hoc tests were conducted to identify specific differences between wavelengths. 

For comparisons of more than two group means, the one-way ANOVA has been suggested as the appropriate method instead of the t test [21]. The choice of one-way ANOVA over t test for comparing more than two group means is justifiable as the ANOVA is based on the same assumption with the t test and the interest of ANOVA is on the locations of the distributions represented by means too as t test is [21]. Additionally, no post-hoc tests were conducted to identify specific differences between wavelengths.

 

4. The section for results should be only "results" because there is already a section for "discussion". 

Corrected, thank you!

 

5. In the discussion, it would be helpful to mention the limitations of the generalizability of the findings when acknowledging the small sample size. 

This study assessed the differences in transcutaneous transmission among the four wavelengths (808nm, 915nm, 985nm, and 1064nm) commonly used in PBMT. The assessments were based on measurements obtained from only three cadaver dogs, which varied considerably in weight and skin-spinal tissue thickness. These differences contributed to a large variability in the measurements of transcutaneous transmission, despite being conducted under the same controllable conditions. The small sample size and variability among the cadaver dogs thus limit the generalizability of the findings.

 

6. There is a typographical error on page 19, line 699. The wavelength should be corrected to "1064nm": "These findings suggest that 064nm may be a more effective wavelength for transcutaneous PBMT for spinal cord injury."

Corrected, thank you!

 

Overall, while the study presents valuable data, addressing these comments will enhance the clarity and impact of the manuscript.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

This is a very interesting paper that compares the target level irradiances of photobiomodulation therapy (PBMT) at four wavelengths (808 nm, 915 nm, 975 nm, and 1064 nm) from the thoracic to lumbar segments of the interior spinal canal in three cadaver dogs, using the same surface irradiance. I believe this study is very important for the development of future laser devices used for PBMT applications and for the choice of optimized parameters. I recommend publication after minor revisions. My suggestions are as follows:

Title:

Consider changing the title, as this study is more of a proof of concept than an application of photobiomodulation therapy itself. There are no photochemical effects occurring in cadavers; rather, the penetration of light is based on the optical properties of the irradiated tissues.

Abstract:

• Lines 17-19: The sentence is too long. I suggest breaking it into two sentences.

Introduction:

• Lines 36-37: Neuropathic pain can be a consequence of a neurological lesion, not the lesion itself. Additionally, there are several types of neuropathic pain that are not necessarily related to a lesion in the spinal cord, so its pathophysiology is quite diverse. I suggest the authors revise these concepts and improve the references.
• Line 54: Check the use of abbreviations throughout the manuscript. “Spinal cord injury (SCI)” was already used and will be written in full elsewhere.
• Line 65: There are other potential mechanisms by which PBMT can promote analgesia. I suggest including the following studies for a better understanding of additional mechanisms: DOI: 10.1038/s41598-022-19947-2; DOI: 10.1002/jbio.201900135.
• Line 76: Remove "therapeutic" from this context, as the therapeutic effect of PBMT is cumulative and results from photochemical and photophysical effects at the cellular level. "Therapeutic" should be used in a broader aspect, as a summation of several optimized biochemical reactions within the cells.
• Line 81: Exclude the first "and" and place a comma before the second "and".
• Line 93: Authors might use the abbreviation for near-infrared (NIR) after this point.

Materials and Methods:

• Line 158: Authors should revisit the guidelines to check how to mention Figures throughout the manuscript. Sometimes a dot is used, e.g., “Figure. 1”, sometimes not. There are several other typos. Please revise the text carefully.
• Line 160: Authors should choose whether to use a space between “PD” and “#5” and apply the same format for all other PDs, and between numbers and units of measurement.
• Line 239: Does the word "Silicon" need to be capitalized?
• Line 252: Replace "milliwatts" with "mW".
• Lines 256-258: This is a very long sentence with many instances of "wavelength". I suggest breaking it into two sentences.
• Lines 272-273: Replace "Watts" with "W".
• Line 300: Use “kg” instead of “Kg”.
• Line 371: Use “wavelengths”.

Results "and Discussions":

• If you have a separate section for Discussion, I suggest removing “Discussions” from here.
• Line 490: Authors need to pay attention to the subheadings format. They used it inconsistently.

Discussion:

• Line 584: Why are references bolded?
• Line 665: The term “spinal cord injuries” was abbreviated earlier.

Conclusion:

I suggest "Conclusions" instead of "Conclusion".

• Line 685: “Continuous wave” was abbreviated earlier.

Figures:

• Prepare figures using the same style regarding colors, font, style of axis titles, etc. Each figure in this paper currently has a different format. The manuscript needs to be consistent.

 

Author Response

Reviewer 3  (response to the comments of reviewer 3 is marked by green highlight)

 

This is a very interesting paper that compares the target level irradiances of photobiomodulation therapy (PBMT) at four wavelengths (808 nm, 915 nm, 975 nm, and 1064 nm) from the thoracic to lumbar segments of the interior spinal canal in three cadaver dogs, using the same surface irradiance. I believe this study is very important for the development of future laser devices used for PBMT applications and for the choice of optimized parameters. I recommend publication after minor revisions. My suggestions are as follows:

Title:

Consider changing the title, as this study is more of a proof of concept than an application of photobiomodulation therapy itself. There are no photochemical effects occurring in cadavers; rather, the penetration of light is based on the optical properties of the irradiated tissues.

Transcutaneous transmission of light of photobiomodulation therapy wavelengths at 808nm, 915nm, 975nm, and 1064nm to the spinal canal of cadaver dogs  

Abstract:

• Lines 17-19: The sentence is too long. I suggest breaking it into two sentences.

 

This study compared the transcutaneous target level irradiances from the thoracic to lumbar segments of the interior spinal canal in three cadaver dogs, measured for light at four wavelengths (808nm, 915nm, 975nm, and 1064nm) common to photobiomodulation therapy (PBMT). Intra-spinal irradiances at nine sites spanning approximately 8cm in length were measured by using a flexible intra-spinal probe under surface application of continuous wave (CW) light with powers ranging from 0.5W up to 2W.

 

Introduction:

• Lines 36-37: Neuropathic pain can be a consequence of a neurological lesion, not the lesion itself. Additionally, there are several types of neuropathic pain that are not necessarily related to a lesion in the spinal cord, so its pathophysiology is quite diverse. I suggest the authors revise these concepts and improve the references.

 

See the response to line 65 at below

 

• Line 54: Check the use of abbreviations throughout the manuscript. “Spinal cord injury (SCI)” was already used and will be written in full elsewhere.

 

Corrected, thank you

 

• Line 65: There are other potential mechanisms by which PBMT can promote analgesia. I suggest including the following studies for a better understanding of additional mechanisms: DOI: 10.1038/s41598-022-19947-2; DOI: 10.1002/jbio.201900135.

 

Several other studies have also suggested additional mechanisms that may govern PBMT’s promotion of analgesia [8] [9].

 

[8]           W. F. Vieira et al., “Anti-hyperalgesic effects of photobiomodulation therapy (904 nm) on streptozotocin-induced diabetic neuropathy imply MAPK pathway and calcium dynamics modulation,” Sci Rep, vol. 12, no. 1, p. 16730, Oct. 2022, doi: 10.1038/s41598-022-19947-2.

[9]           W. F. Vieira, S. F. De Magalhães, F. H. Farias, A. A. De Thomaz, and C. A. Parada, “Raman spectroscopy of dorsal root ganglia from streptozotocin‐induced diabetic neuropathic rats submitted to photobiomodulation therapy,” Journal of Biophotonics, vol. 12, no. 11, p. e201900135, Nov. 2019, doi: 10.1002/jbio.201900135.

 

• Line 76: Remove "therapeutic" from this context, as the therapeutic effect of PBMT is cumulative and results from photochemical and photophysical effects at the cellular level. "Therapeutic" should be used in a broader aspect, as a summation of several optimized biochemical reactions within the cells.

 

potentially therapeutic

 

• Line 81: Exclude the first "and" and place a comma before the second "and".

 

Corrected, thank you!

 

• Line 93: Authors might use the abbreviation for near-infrared (NIR) after this point.

 

Corrected, thank you!

 

Materials and Methods:

• Line 158: Authors should revisit the guidelines to check how to mention Figures throughout the manuscript. Sometimes a dot is used, e.g., “Figure. 1”, sometimes not. There are several other typos. Please revise the text carefully.
• Line 160: Authors should choose whether to use a space between “PD” and “#5” and apply the same format for all other PDs, and between numbers and units of measurement.
• Line 239: Does the word "Silicon" need to be capitalized?
• Line 252: Replace "milliwatts" with "mW".

 

All implemented, thank you!

• Lines 256-258: This is a very long sentence with many instances of "wavelength". I suggest breaking it into two sentences.

 

After completing the measurements at one wavelength, the light was switched to another wavelength by one of the two methods of the following. (1) If the wavelength to be switched to was available from the same dual-wavelength research-laser, the wavelength was changed directly on the control panel of the laser. (2) If the wavelength to be switched to was available from the other dual-wavelength research-laser, the fiber patch-cable coupling to the treatment head was manually switched to the other dual-wavelength research-laser, on which the wavelength of choice was set by the control panel.

 

• Lines 272-273: Replace "Watts" with "W".
• Line 300: Use “kg” instead of “Kg”.
• Line 371: Use “wavelengths”.

 

All implemented, thank you!

 

Results "and Discussions":

• If you have a separate section for Discussion, I suggest removing “Discussions” from here.
• Line 490: Authors need to pay attention to the subheadings format. They used it inconsistently.

All implemented, thank you!

Discussion:

• Line 584: Why are references bolded?
• Line 665: The term “spinal cord injuries” was abbreviated earlier.

 

Conclusion:

I suggest "Conclusions" instead of "Conclusion".

• Line 685: “Continuous wave” was abbreviated earlier.

 

All implemented, thank you!

 

Figures:

• Prepare figures using the same style regarding colors, font, style of axis titles, etc. Each figure in this paper currently has a different format. The manuscript needs to be consistent.

 

Figures 1-3, and 5-8 have been revised to try to make the font sizes and styles consistent, and the notations in alignment with the descriptions in the main text.  

 

Author Response File: Author Response.pdf