Mechanical Assessment in Atherosclerosis Based on Photoacoustic Viscoelasticity Imaging

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

In this manuscript by Zhang et al., they conducted study using PAVEI for plaque detection. However, I found no novelties in this manuscript. A similar paper by Zhao et al., Optics Letters, 2016 has demonstrated using the same modality to detect lipid and similar change between lipid vs collagen. Therefore, this current manuscript has little novelty as there is no significant advancement in the study subject or methods. Surprisingly, the authors also did not even cite this very relevant relevant research, which is rather an ethical concern for me. Below are some more comments:

1) All phantom images are lacking. Figure 2 and Figure 3 should show the photograph of the phantoms. Otherwise it is very hard to appreciate what are the imaging subject.

2) Authors should provide statement for animal procedure approval, which involves the alteration of the diet for ApoE mice. Also, authors should include high fat diet catalog.

3) Authors used 15 mice, but why results from one animal is using. How are the results from other animals? Where is the statistical analysis?

4) I am not sure I understand Figure 5. Are the authors claiming that you started feeding high fat diet at 4 week of age, and before you feeding high fat diet, the animals already have plaque forming (Fig. 5A)?

5) If the system resolution is 65 µm, why the images in Figure 4 and Figure 5 looked like very low resolution?

 

4) Supplementary file equations are of low quality. Please be consistent on the font style and size. All figures need to have better resolution.

Comments on the Quality of English Language

Quite a few grammatical errors. Also, the authors lack a structure for clearly presenting the results. Suggest editing help from fluent English speakers.

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The paper entitled “Mechanical Assessment in Atherosclerosis Based on Photoacoustic Viscoelasticity Imaging” presents an interesting application of photoacoustics lock-in method to investigate the mechanical properties of atherosclerosis plaques. The structure of the article is quite clear, but the experimental data are not always clearly reported.

I can recommend this paper for publication after major revision:

- Please, may the authors add a comment/explanation of the different ratios measured with the rheometer in comparison with the ratios estimated by PAVEI? (14.5 % vs 29.4 %??, data from figure 3, page 4)

- May the authors provide the details about the authorization for the experiments with animal?

- Figure 5b: may the authors add a scale bar?

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

The paper suggested a novel photoacoustic viscoelasticity imaging technique to measure the viscosity-elasticity ratio of atherosclerotic plaques. Overall, the idea is interesting and the manuscript is well-presented and certainly merits publication. However, the authors still need to address below issues.

1.   The article proposes that changes in the ratio of lipids and collagen will affect the mechanical properties of plaques? The author should provide further detailed explanations.

2.    In Fig. 2(D), the data of PAVEI is slightly higher than that obtained by the rheometer, can the author explain the reason?

3.   In Fig. 4(B), what is the main component of the unstained part in the control artery？

4.   Macrophages play an important role in the development of fatty plaques.  Do macrophages also play a role in the formation of vulnerable plaques?

5.   Whether the viscoelasticity of different atherosclerotic plaques can determine the degree of vulnerability of atherosclerotic plaques, the authors should discuss the potential of this technique in the identification of vulnerable plaques.

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

1) I do not agree with the author's replies to the Figure 4 and Figure 5 regarding resolution. According to your scale bar, the vessel diameter is >1 mm surely. Author should justify better. Also, what is the step size during scanning?

2) For Fig. 5c, please also do statistical comparison, e.g. ANOVA or t-test.

3) Authors should show the PAVEI image of phantoms, to fully understand its capability for collagen + lipid imaging.

4) I do not agree doing on ApoE KO mouse vs. rabbit is a huge novelty. All are ex vivo studies, so far authors still did not show its capability for in vivo imaging.

5) So authors mentioned 3 mice as controls, where are the results from the controlled group?

6) The authors copy pasted a few paragraphs from their previous paper into the Discussion section. This was unethical. The authors should rewrite them.

Comments on the Quality of English Language

Authors SHOULD NOT copy paste from papers, even from your own previous ones. This is UNETHICAL. Please re-write.

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

This revised paper can be published as is. 

Author Response

Thank you very much for your comments on the manuscript.

Round 3

Reviewer 1 Report

Comments and Suggestions for Authors

Thanks for addressing the questions. For the statistical comparison, how did the authors do it? A method section of statistical comparison needs to be added. I am not sure what values were obtained to do the comparison, e.g., Fig. 5c. Did authors just simply average the values from Fig. 5a? Are there any masks applied? Are there thresholding applied before averaging? Overall, details for processing data for statistical comparison are missing.

Comments on the Quality of English Language

Please check thoroughly for spellings and grammatical errors. For example, line 183, should be "were also shown".

Author Response

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Author Response File: Author Response.pdf