Review Reports

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The purpose of this study is to develop a phantom simulating breast fatty tissue for microwave mammography studies. The authors tested several mixtures of low cost components and seem to have developed a final phantom that simulates well the conductivity and dielectric properties of breast fat.  As they point out the long term stability of the proposed phantom is unclear at this stage of development but beyond this issue, the presentation of the work is confusing and initial testing incomplete. Major issues:

Lines 28-31: "Conventional screening methods for breast cancer include X-ray mammography [2] and ultrasound [3]. ... technologists."   The way this first paragraph is written is misleading ... First, ultrasound is not a conventional or standard screening method.  Second, do you really imply that there is possible radiation exposure and pain from ultrasound? And the following sentence refers only to mammography and its reduced diagnostic accuracy in dense breasts. I recommend to leave ultrasound out of this paragraph or rewrite it.

Your argument in the introduction (line 33) is that conventional techniques fail in dense breasts. Yet, you aim at developing a fat equivalent phantom. How are these two reconciled? You may want to reconsider the introduction and justification of your work.

Lines 75-77: This sentence is confusing ... how are permittivity and conductivity calculated by substituting them (which ones?) into Eqs 1 and 2? Which model for breast's dielectric properties do these equations represent?

The presentation of the results in section 3 is very confusing and does not justify the claims of your work. The way results are presented, it seems that you had a better phantom from a previous study, now you developed a worse one and you compare improvements on the worse phantom (see Table 8). This does not make sense. You should compare the proposed phantom with 8.26 % and 16.9 % error rates to the previous phantom that showed 12.1% and 18.0% error rates.  Discussion of "ingredients" should also be done with respect to that phantom not the 110%, 160%.

The reproducibility of the results considering the materials of this phantom is crucial. And not in long term but short term. Have you tried repeating the measurements within 24 hours with the same phantom? Did you do just one measurement from 1-15 GHz to estimate the average error rate?

There are some minor grammatical and syntax errors as well as typos that need a more careful proofreading

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 2 Report

Comments and Suggestions for Authors

This manuscript investigates the development of a breast fat-equivalent phantom for microwave breast imaging by adjusting the composition of NaCl, cooking oil, TX-151, and detergent to improve dielectric matching over the 1–15 GHz frequency range. The topic is relevant to the practical development and evaluation of microwave imaging systems, and the manuscript addresses a meaningful engineering problem, namely the fabrication of a low-cost and reproducible phantom with electrical properties close to those of breast adipose tissue. The study also presents a clear objective and a relatively straightforward experimental route.
However, in its current form, the manuscript still reads more like an empirical formulation-adjustment study than a fully mature scientific paper. The main weaknesses concern limited novelty, insufficient experimental rigor, lack of statistical support, limited mechanistic interpretation, and several issues in writing and presentation. Therefore, I recommend major revision.
1. The novelty of the study should be clarified more explicitly.
At present, the manuscript appears to build incrementally on previous phantom formulations by adjusting the composition to reduce the average error relative to target dielectric properties. The reported improvements are useful, but the paper does not yet clearly articulate what the main scientific or methodological innovation is. The materials themselves are not new, the measurement method is standard, and the study is largely based on stepwise empirical adjustment of formulation parameters. The authors should clarify whether the novelty lies in achieving broadband matching over 1–15 GHz, identifying a reproducible formulation strategy, or revealing a previously underappreciated role of specific additives such as TX-151 or detergent in shaping dielectric response. Without a sharper statement of novelty, the contribution may appear limited.
2. The experimental design is too empirical and lacks statistical rigor.
The optimization process is essentially conducted in a one-factor-at-a-time manner: NaCl is adjusted first, followed by cooking oil, TX-151, and detergent. While this approach may be acceptable for preliminary exploration, it does not adequately account for interactions among factors, nor does it guarantee that the reported formulation is close to a true optimum. More importantly, the manuscript does not clearly report the number of replicate fabrications or repeated measurements, and no error bars, standard deviations, or statistical analyses are provided. This makes it difficult to judge the reproducibility and reliability of the reported results. The authors should at least report replicate numbers and variability, and ideally consider a more systematic optimization strategy such as design of experiments or response surface methodology.
3. The evaluation criteria are too limited.
The manuscript mainly uses the average error rate over 1–15 GHz relative to the target values as the criterion for judging performance. This is a useful summary index, but by itself it is insufficient. An average error can conceal substantial mismatches in specific frequency bands, which may be important depending on the intended operating range of the microwave imaging system. The authors should consider reporting additional metrics such as maximum error, band-specific error, or fitting quality across the spectrum. In particular, the final conductivity error of 16.9% still suggests noticeable deviation, so claims such as close agreement or practical suitability should be phrased more cautiously unless additional validation is provided.
4. The mechanistic interpretation is underdeveloped.
The manuscript provides a practical description of how NaCl, oil, TX-151, and detergent affect the dielectric properties, but the explanations remain largely phenomenological. NaCl is said to increase conductivity, oil to reduce relative permittivity, and detergent and TX-151 to influence dielectric behavior, yet the physical or physicochemical basis of these changes is not sufficiently discussed. This is especially important because the manuscript itself notes that additives previously thought to have little effect may actually influence the electrical properties through interactions with other substances. The discussion would be significantly strengthened by considering mechanisms such as emulsion structure, ion mobility, interfacial polarization, water-phase continuity, and viscosity-related effects. Even if additional experiments are not feasible, a deeper literature-based discussion is needed.
5. Practicality is overstated relative to the current evidence.
The manuscript suggests that the developed phantom may be useful for practical application and potentially for standard evaluation. However, the current study does not yet include key validation dimensions required to support such claims. For example, there is no assessment of batch-to-batch reproducibility, long-term stability, storage effects, dehydration, phase separation, temperature dependence, or mechanical durability. These factors are central to determining whether a phantom is truly practical for repeated experimental use. The authors themselves acknowledge the need for future evaluation of long-term stability and storage conditions, which indicates that the current conclusions should be more restrained. Statements about practical utility should therefore be softened unless additional stability and reproducibility data are added.
6. The target dielectric values require stronger justification.
The manuscript states that the target values were derived from prior literature, but the rationale for selecting those specific values should be explained more carefully. Biological tissues, including breast adipose tissue, show inter-subject variability and may depend on measurement conditions such as temperature and protocol. It would strengthen the study to clarify whether the target values represent breast adipose tissue specifically, whether they are point estimates or representative ranges, and how they compare with other literature sources. Comparing the measured results not only with a single target curve but also with an acceptable physiological range would make the conclusions more convincing.
7. The methodology section should provide more details to ensure reproducibility.
Although the manuscript describes the general fabrication procedure and lists the materials used, several important experimental details remain unclear. For example, the exact heating conditions, stirring conditions, cooling conditions, temperature during measurement, time interval between fabrication and measurement, and dielectric probe calibration procedure are not described in sufficient detail. Because these factors can materially influence dielectric measurements, especially when using the coaxial probe method, they should be reported more fully so that other researchers can reproduce the work.
Presentation and Writing Issues
8. The manuscript requires substantial language editing.
There are several noticeable grammatical and wording problems throughout the manuscript. For example, the keyword “coaxial prove method” should be corrected to “coaxial probe method,” and the phrase “One issues with the composition...” in the conclusion is grammatically incorrect. There are also places where wording is awkward or overly strong relative to the evidence. Professional English editing is recommended before publication.
9. Some claims are too strong and should be moderated.
Expressions such as “aligns with the target values” or implications of broad practical readiness are too strong in view of the remaining conductivity error and the lack of stability or reproducibility testing. More cautious wording such as “showed improved agreement with the target values” would be more appropriate.
10. Figures and tables could be improved.
The figures show the trends clearly, but they would be more informative if error bars or uncertainty indicators were included. The number of repeated measurements should also be stated either in the captions or in the main text. In addition, table titles and descriptions should be checked to ensure that they accurately reflect the data presented.
Overall, the manuscript addresses a relevant and practical problem in microwave breast imaging and presents encouraging formulation improvements for a breast fat-equivalent phantom. However, the current version still has important shortcomings in novelty framing, experimental rigor, statistical support, mechanistic explanation, and presentation quality. With substantial revision, the paper could become stronger and more convincing.

 

Comments on the Quality of English Language

The English could be improved to more clearly express the research.

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The authors have improved their manuscript and responded satisfactorily to my concerns.

It is recommended that Figures 2-5 and 7-9 are regenerated by modifying the y-axis scale. Almost all have multiple curves either very close to each other or overlapping making difficult to distinguish and compare to the target value. For example in Figure 8, 10 different measurements are presented that cannot be differentiated at all. Differences may be small but selecting a different y-axis scale can significantly help the reader. Why is permittivity plotted to 20 and conductivity to 5? There seem to be no data above 7 and 1 respectively. Hence, it is very likely that lower maxima will improve visualization in all these figures.

Should we assume that relative permittivity is presented as % in these figures?

Line 32 - "method involves" instead of "methods involve" and remove "possible" ... it is x-ray mammography!

Table 8 - keep only one "after" in column 1.

 

 

 

Comments on the Quality of English Language

Minor syntax and grammar issues.

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 2 Report

Comments and Suggestions for Authors

Accept in present form

Comments on the Quality of English Language

The English could be improved to more clearly express the research.

Author Response

Please see the attachment.

Author Response File: Author Response.docx