The Feasibility of Shadowed Image Restoration Using the Synthetic Aperture Focusing Technique

Round 1

Reviewer 1 Report (Previous Reviewer 1)

Dear authors,

First of all, the work has improved but I still detect flaws in the text. 

1. The abstract and conclusions do not quantitatively highlight the results. I think they need to be clearly highlighted.

2. The data provided prevents replication of the simulated model. I think that there is still a lack of good preparation in this section.

3. Likewise, the discussion should detail well the significant improvements. As other reviewers have commented, since there is already a lot of work on SAFT, the advantages over other methods should be clearly detailed. Also explain why, despite being of poorer quality than type B scanning, it has improvements.

Author Response

Please see the attachment

Author Response File: Author Response.pdf

Reviewer 2 Report (Previous Reviewer 2)

The authors modified their article. They proposed to reduce shadow in ultrasound image. The method is now applied in a phantom of water with wires experimentaly.

However I have my previous comments with no answers

Major Comments
==============
1) There is no section dedicated to the method. It is not clear what the image restoration: is it the application of SAFT? is it a supplement of SAFT? There is no ultrasound image before and after restoration to remove shadow. I suggest a block diagram to understand where the SAFT method is and where the novelty of the method is.

Main Comments
=============
2) There are no quantitative result in abstract

3) Section 2.3: To reconstruct image, Delays have to add before the sum. Moreover, the sum can be apodized to have the same F-number as a function of the depth, and so the same spatial resolution. What is the apodization used ?

4) There is no clear figure to compare the new method and the standard SAFT method.

Minor Comments
==============
Results: scales are in opposition with the usual scale where white is for higher values and black for smaller values.

Author Response

Please see the attachment

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report (Previous Reviewer 1)

Dear authors,
Your work has improved considerably. My congratulations. I think you now provide scientific quality and relevant data.
My opinion is that it can now be considered for publication.

Reviewer 2 Report (Previous Reviewer 2)

The authors improved their paper. It is clearer than the previous review, even if the novelty and it's consequences could be more highlighted.

This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.

Round 1

Reviewer 1 Report

Dear Authors:

First of all congratulate you for your work. It presents novelties to solve a known problem in the field of ultrasound. However, I think that the presentation of the article should be improved to make it easier to read. Some data are also missing. I leave you my considerations below:

1. In the abstract as well as in the conclusions, the most relevant results should be highlighted. Many results are given but I believe that those that the authors propose as novelty should be highlighted.

2. In the introduction, the limitations of ultrasound and the generation of artifacts are mentioned. Current techniques to improve SNR in US techniques (such as ultrasound lenses among others) should be added. At the end of the introduction, a clearer presentation of what is proposed in the paper should be included to link correctly with the rest of the paper.

3. In Figure 1, the font size should be increased, as it is too small to know for example which is Ht1, Ht2, etc.

4. In section 2.2, it would be good to have a reference to the transducer used to verify the frequency response curve and other parameters. Likewise with the Pulser used and the digital oscilloscope. A link to the manufacturer's website I think would detail better the experimental setup.

5. They talk about simulations, but do not detail the simulation method used (BEM, FEM, FDTD?) and the software used for the same (COMSOL, Matlab, Python, etc). This point should be significantly improved and details of the methodology used for the simulation should be given so that a third party can replicate it.

6. In Figure 2 the same problem as in Figure 1 occurs.

7. Figure 3 has the same problem as the previous ones.

8. Figure 5 and 6 are too small. I think that the font size of the axes and data should be adapted. 

9. In Section 4 (Discussion), it is said that the figure is more "clear". The data should be provided and contrasted. The reading is more complicated due to the fact that the table must be continuously checked. I propose that the data be presented and comparative values be given between them. 

10. In the Conclusions, the most relevant results should be highlighted. 

Reviewer 2 Report

The authors proposed a method using SAFT beamforming. It can help to reduce shadow in ultrasound image due to structures with a high impedance. The method is applied in an aluminium block experimentaly.

However I have some comments

Major Comments
==============
1) There is no section dedicated to the method. It is not clear what the image restoration: is it the application of SAFT? is it a supplement of SAFT? There is no ultrasound image before and after restoration to remove shadow.

2) The introduction and the discussion give a context of medical imaging. However the physical model and the experiment are applied in aluminium. What are the assumptions to link the physics in soft tissue (as in medical) and in solids (as in NDT) ? Is the method true for medical imaging ? Moreover, references are dedicated to NDT for solids, whereas the sentence is about medical diagnosis. Either the paper is for medical imaging and the data comes from soft tissue, or the paper is for NDT.

Main Comments
=============
3) There are no quantitative result in abstract

4) Section 2.3: To reconstruct image, Delays have to add before the sum. Moreover, the sum can be apodized to have the same F-number as a function of the depth, and so the same spatial resolution. What is the apodization used ?

5) The main reference of SAFT in missing (e.g. Karaman 2005, Jensen 2006). Moreover, as SAFT transmits a wave element by element, it is slow and the image can be blur, that is why it is not often used in medical imaging.

Minor Comments
==============
Results: scales are in opposition with the usual scale where white is for higher values and black for smaller values.

Reviewer 3 Report

 

The manuscript, entitled: “Advancing the Feasibility of Shadowed Image Restoration using the Synthetic Aperture Focusing Technique,” demonstrated that synthetic aperture focusing technique (SAFT) can restore shadowed images during ultrasound imaging.  My comments are as follows.

1.      The significance/innovation of the work is poor.  SAFT has been around for a long time and used extensively.  From scientific or engineering point of view, the current manuscript has very little value.  There is not much scientific, or engineering advances presented by this work.  A more detailed review on all the previous studies would help the authors to understand the current status of the relevant field.

 

2.      The B-mode images presented have very poor qualities in comparison with any image that can be obtained by a commercial ultrasound imaging machine.  The improvement should be shown against the current state-of-the-art to demonstrate “advancing”.

 

3.      On the technical side, more quantified results will be needed.  Improvements in position accuracy, SNR, or resolution need to be presented.