Multi-Electrode Architecture Modeling and Optimization for Homogeneous Electroporation of Large Volumes of Tissue
Round 1
Reviewer 1 Report
see the attached file
Comments for author File: 
Comments.docx
Author Response
The authors would like to thank the Reviewer for the review and the useful comments.
General comments
Comment 1- The idea is particularly interesting even if the use of patches is clinically difficult to defend for deep tumors as indicated by the authors. In addition, Figure 10 shows that the flexibility gained over the orientation of E field results in a loss of uniformity in the spatial distribution of the field; it requires a sequence of several controlled patches setting (CS) to restore a little uniformity.
To see the benefit on the orientation of the E-field, it is necessary to analyze the phenomenon at the cell scale. Under a "vertical" field, pores appear mainly at the poles; by orienting the field differently, one could induce a better distribution of the pores over the entire surface of the cell membrane. This would have consequences on the construction of the sequence of pulses: one pulse for a given CS, then another for a new CS, etc. ... Maybe the number of pulses required to electroporate a tissue would then be reduced.
The authors could modify the text in this direction.
Response 1- The authors would like to thank the reviewer for acknowledging the interesting areas of this proposal. It is important to note that the proposed configuration allows not only alternative special orientations, but also applying the same uniform field as with conventional parallel plates for uniformity. From this perspective, this approach combines state-of-the-art parallel plate performance with the benefits of improved spatial distribution.
The authors would like also to thank the reviewer for his analysis. These useful comments on the cell effects of this approach have been included in this revised version of the paper (lines 136-146).
“When a uniform electric field is applied in a single direction to a biological tissue, a transmembrane potential is induced in the membranes of its cells. The intensity of this potential at each point of the membrane depends on the applied normal electric field. The main advantage of the proposed electrode over traditional flat plates is that the area of the cell membrane where the transmembrane potential is concentrated can be changed. This is a great advantage, due to the geometry and imperfections of cell membrane, its dielectric strength is not constant over its entire surface and has areas that are more susceptible to electroporation. The proposed electrode allows to apply several electric field vectors by means of different CSs that can concentrate the electric field in different areas of the membrane, therefore it is possible to find an electric field vector or a combination that allows to electroporate the cells of the tissue in a more homogeneous and easy way.”
Specific comments
Comment 3- The sentence line 25 is wrong.
Response 3- This sentence has been fixed (line 26).
“Electroporation is a technique based on applying an electrical field to increase the permeability of the cell membrane to achieve the desired biological effects.”
Comment 4- The sentence line 152 is wrong.
Response 4- This sentence has been fixed (line 157).
“This is necessary as the use of MPPE is based on improving the treatment homogeneity applying wide variety of electric field vectors, and not a single vector.”
Comment 5- Explanations lines 206-215 are not understandable.
Response 5- This part of the text has been improved to make it more understandable (lines 218-236). In summary, this details the procedure followed to evaluate the different field direction applied with the proposed electrode structure.
“Therefore, the first step is to calculate the angles α1, β1, and Ω1 (Figure 7 (a-c)) which are all the possible relationships between the three electric field vectors applied on P1 of the example. These three vectors are considered independent if θmax > Ω1 > θmin, θmax > β1> θmin and θmax > α1 > θmin, that is, if all angle relationship are enough and therefore the three vectors are well distributed. Moreover, if θmax > β1 > θmin, θmax > Ω1 > θmin, and α1 < θmin or α1 > θmax it is considered that the red and yellow vector are applied in too close orientations, since the angle between them is considered not enough, therefore they will produce very similar effect and only one can be considered an independent vector. Moreover, if θmax > Ω1 > θmin, α1 < θmin or α1 > θmax, and β1 < θmin or β1> θmax the angular relationship of the yellow vector with the red and blue vectors is insufficient but between the red and blue vectors the angular relationship is enough to consider that they can produce different effects at the point P1 and therefore only the yellow vector is not considered independent. Finally, if, α1 < θmin or α1 > θmax, β1 < θmin or β1> θmax and, α1 < θmin or Ω1 > θmax it is considered that the three vectors produce the same effect and therefore in the point P1 only has been applied one independent electric field vector. This process is carried out in the i points of the model and next it is estimated the percentage that has been treated with 1, 2 or 3 independent electric field vectors. This methodology has been implemented in both models to evaluate the effectiveness of the different designs by applying n different CSs.”
Comment 6- Figure 8 is blurry. A detailed description of the image is required.
Response 6- This image has been improved and a more detailed description of the setup has been added in lines 247-259.
“The setup used during the experiment is composed of three parts:
- High voltage generator. This test-bench subset consists of high voltage monitoring/acquiring: an 8-bit LeCroy oscilloscope Wavesurfer 3024, three differential high-voltage probes LeCroy HVD3206, and one Pearson current monitor model 110.
- Electroporation ad hoc multioutput generator, which has been designed to be able to power eighteen outputs and to provide online impedance measurements [28]. The proposed generator is based on a multiple-output structure featuring IGBT (1700-V 100-A 3-phase IGBT power module FS100R17N3E4) an MOSFET (NVMTS0D4N04CTXG) devices [33]. This implementation allows high-performance omnidirectional electroporation treatments.
- Experimentation area, where the potato specimens are carved and placed.
”
Comment 7- The threshold (E = 300 V/m) line 265 is low compared to common values.
Response 7- This threshold has been selected for representation purposes (300 V/cm or higher), and because it correlates with experimental measurements and it is also used in previous papers. It is, however, a value non critical for the novelty of the paper and that can be adapted. The authors a have added more information in lines 287-288.
“at 300 V/cm or more, being this value the electroporation threshold for the tissue used [28]”
Comment 8- In Figure 10, it could be interesting to show the direction of the E field in the simulations. The distribution of the resulting E field could also be displayed in the vertical direction (Ez) and horizontal directions (Ex and Ez).
Response 8- The authors are grateful for the reviewer's comment. Please, be aware that the Figure 10 (a) already shows the main direction of the eight different CSs applied. Besides, the direction of the electric field of each of these configurations is represented in Figure 5. Following the reviewer’s advice, and to provide additional information, a new representation of the maximum electric field in vertical view has been included in Figure 10 and new text has been added to clarify the representation.
“In Figure 10 (a), the CSs that had been applied and their main electric field directions are represented for each combination of active electrode cells. In each experiment, 10 pulses of 100 µs, 800 V, and separated by 100 ms have been applied; and this process has been repeated in the 8 configurations represented in the Figure 10 (a). Electroporation was applied to 8 mm thick samples of young Monalisa potatoes. In Figures 10 (b-e), the images of the treated potatoes are shown, and the simulated contour of the area treated at 300 V/cm or more is superimposed on the image. In addition, these figures show a vertical and horizontal slice of the simulated models, where are represented the maximum electric field at each point of the tissue produced by the 8 simulated electric field distributions.”
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Language needs to be thoroughly revised. Some examples:
- Geometrie (spelling)
- It can be seen in Figure 9 (a) the ... (sentence word order)
- It is achieved a discrete... (just... wrong)
Author Response
The authors would like to thank the Reviewer for the review and the useful comments.
Comment 1- Language needs to be thoroughly revised. Some examples: Geometrie (spelling), It can be seen in Figure 9 (a) the ... (sentence word order), It is achieved a discrete... (just... wrong).
Response 1- This revised version of the paper has been carefully reviewed to avoid typos. Thank you for your review.
Author Response File: Author Response.pdf
Reviewer 3 Report
Please find the reviewer's comment as an attachment.
Comments for author File: Comments.pdf
Author Response
The authors would like to thank the Reviewer for the review and the useful comments.
Comment 1- Please emphasize the possibilities of practical/theoretical application of the solution developed in the paper.
Response 1- The authors are grateful for the reviewer's comment and have added new lines to the text to emphasize the applications of the proposed electrode (lines 360-370).
“The proposed multi-electrode is an alternative to the current parallel plates, but it al-lows to apply the electric field in a more flexible way to improve the homogenization of the treatments. It is therefore useful to treat large tumors located in areas accessible with-out surgery, or even to treat internal organs with high blood perfusion where needles cannot be used. This type of electrode could be useful in the treatment of liver tumors where metastases are common and it is necessary to treat large volumes of tissue, and electroporation has great advantages since it is not affected by the vascularization of the liver, and also the liver has been documented to be able to regenerate from the effects of electroporation. And finally, although parallel plates are often difficult to apply because they are usually applied by tweezers, the proposed electrodes can be built with flexible PCBs and could be applied in more easy way without tweezers.”
Comment 2- Section Introduction ‐ please add a more footnotes to References. Some sentences are not endorsed by References. Please, extend the References.
Response 2- The authors would like to thank the reviewer for these recommendations, and the bibliography has been extended in the introduction (lines: 35-74).
Comment 3- Please, provide an information referring the uncertainties of the modeling developed in the paper.
Response 3- More information has been added regarding the uncertainties of the modeling (lines: 185-192).
“In this model it has been considered that the external surface is electrically isolated except for the surfaces where the electric potential is applied, which are the active electrode cells. It has been assumed isotropic and homogeneous electrical properties in all the volumes. The tissue has been modeled without taking into account the structure and geometry of the cells, assuming a homogeneous block with equivalent electrical properties; and the effects of temperature on conductivity have been considered negligible because, despite the high instantaneous power applied, the pulses applied in the experiment had 100 µs of duration.”
Comment 4- All Figures and Tables ‐ the definition of units of physical quantities, should be written in square brackets, not round brackets.
Comment 5- All Figures, Tables and body of the text ‐ notation of physical quantities should be written in italics.
Response 4, 5- The authors would like to thank the reviewer for these recommendations. After carefully reviewing these proposals, and checking MDPI guidelines (https://www.mdpi.com/authors/layout#_bookmark33) as well as some relevant papers (https://www.mdpi.com/journal/energies/most_cited), it seems that the journal style uses often round brackets and non-italics font for units. For this reason, the authors have kept round brackets in this version of the paper. Thank you again for your feedback.
Comment 6- Symbols: =, <,>, etc. ‐ should be separated from the numerical values one space, e.g. Lines: 208, 212, 213.
Response 6- These typos have been fixed.
Comment 7- Symbol pi ‐ please do not write in italics, e.g. line 277.
Response 7- This typo has been fixed.
Comment 8- Please replace KHz by kHz, e.g. description below Figure 6.
Response 8- This typo has been fixed.
Comment 9- Please correct the paper for typos, e.g. lines: 55,226,281,293,316.
Response 9- Thank you for your detailed review. These typos have been fixed.
Author Response File: Author Response.pdf
Round 2
Reviewer 3 Report
All comments of the reviewer have been included in the revised version of the paper. Therefore, I recommend its publications in the present form.
Author Response
The authors would like to thank the Reviewer for the review and recommendation.
