ATOM INDONESIA
Author's Responses to Review D
Article : 1112
Article Title : Comparisons of water-equivalent diameter measured on images of abdominal routine computed tomography with and without contrast agent
Line # Referee’s Comments Author's Responses
Page 1 line 14
The introduction is well written. However, the goal of the manuscript is very superficial. The author has to explain what is the benefit of knowing that the impact of contrast agent is negligible, how to use the equation the author provided within the manuscript, etc. The author explained the effect of contrast agent to HU, but the author never shows what happened to HU after the contrast had been introduced. is there large pixel area will be affected or only small fraction area? the author has to synchronize the introduction, material and method, discussion and conclusion
Thank you very much for your valuable comments and suggestions.
We have added the problem gap in the Introduction section: “Based on our best knowledge, no previous study investigated the Dw and SSDE before and after contrast agent injection. As consequence, the Dw and SSDE before and after contrast agent injection are considered the same without justifying from the careful study. Therefore, this study aims to calculate the DW values based on axial CT images of a CT examinations with and without the use of contrast agent. In addition, we also evaluated the SSDE value before and after contrast agent injection. The results of this study will be useful to confidently consider the Dw and SSDE for examination with contrast agent administrations.” Please see the revised manuscript, page 2, lines 65-77.
The pixel values (HU) will increase is some tissues (it may be small or large part depending on agent contrast distribution) before and after contrast injection. We have added the information in the revised manuscript “Because the pixel values (HU) within image increase in some tissues before and after agent contrast injection, the DW and the SSDE may change as a result”.
Please see the revised manuscript page 2, lines 63-66. We have added Figure 4 to show how the image before and after contrast agent injection. Please see page 4, lines 203-208.
We have synchronized the introduction, material and method, discussion and conclusion. Please see the revised
manuscript.
Page 1.
Line 17
References? We have two references for this. Please see
the revised manuscript, page 1, line 20-21.
Page 1.
Line 32
Write in full name prior making it into an acronym SSDE
We have revised based on your comments.
Please see the revised manuscript, page 3, line 32-33.
Page 1.
Line 34-36
Does the X-ray attenuation refer to density?
Elaborate the sentence to explain what X-ray attenuation that the author refers to.
Yes, it does. We have changed the sentence to make it clearer. “In this case, the patient characteristics include X-ray attenuation and patient size. The X-ray attenuation is based many factors, such as type of material and its density and energy of X-ray beam. The X-ray attenuation is fundamental parameter effecting X-ray absorption and dose absorbed by patient”. Please see the revised manuscript, page 1, lines 41-47.
Page 2.
Line 61
The author needs to explain how to treat the dicom data from the scanner. Furthermore, no explanation regarding the CT procedures performed for infant and adult patient. The scanner has an AEC system called Caredose to manage tube loading to optimize dose delivery.
once the Caredose was used, the tube loading for each slide would be different due to different patient equivalent thickness.
Thank you for your constructive
comments. All the exposure parameters mentioned were obtained from each patient's DICOM header. The scanner was equipped with AEC or Caredose. In the revised manuscript, we used the more general terms of “tube current modulation (TCM)”. We have added an explanation:
“All the exposure parameters mentioned were obtained from each patient's DICOM header. In addition, both the abdominal CT examination protocol in children and adults applied the tube current modulation (TCM) technique.
The TCM was to manage tube loading to optimize dose delivery. Once the TCM was used, the tube loading for each slide would be different due to different patient equivalent thickness.” Please see the revised manuscript, page 2, lines 96- 106.
Page 2.
Line 72-77
Does the procedure use AEC system? if not, please mention that the procedure were perform without AEC. Since the author mention the weight range from 3.5-90 Kg, there is an indication that the patient is infant.
Conducting CT procedure for infant without using AEC is not allowed. please clarify and explain the CT procedure for infant and how the author extract the mAs value from the the dicom data
Yes, it does. Our CT scanner applies the tube current modulation (TCM)
technique for all patients during both abdominal CT with and without the contrast agent injection. As mentioned, we used terms of “TCM”, instead of
“AEC”. We also have clarified how the data were extracted from DICOM info and CT dose summary. We have added the information. Please see the revised manuscript, page 2, lines 96-106. We
have added a print screen of CT dose summary.
Page 2.
Line 88-89
References?
We have two references for this. Please see the revised manuscript, page 2, line 118.
Page 2.
Line 108
The image quality is very poor and hard to read.
We have enlarged the image. Please see the revised manuscript, page 3, line 150.
Page 2.
Line 136
General comment for results and discussion the discussion is too shallow and not explaining the impact of introducing contrast agent to CT image to the image, such as how much and how many percent of the affected pixel due to existence of contrast. The reader will have to guess how is the relation between the area of affected pixel to Dw. Furthermore, if the affected pixel is less than 1% of the total pixel, the impact to Dw will be negligible and what happened if the affected area is 10% of the patient image.
All the raw data were calculated and formulated in equation without fundamental explanation what is the benefit of the equations and why most of gradients nearly 1.00.
We have given the abdominal CT images with and without contrast agent and the difference of the HU between these two images. However, the increase HU is only in some areas depending on the slice location. We added: ”It shows that the axial CT images of the abdomen with the use of a contrast agent and a portal venous phase scan provides better visualization of the portal vein and solid organs, i.e. the liver, spleen, kidney, and pancreas than the axial CT images of the abdomen without the use of a contrast agent due to the HU values increase in these areas [27,28]. The mean HU value in some areas of the axial CT images of the abdomen was 22.6% greater than without the use of contrast agents.”
Please see the revised manuscript, page 5, lines 174-185.
We have added explanation the meaning of R2 value. “The correlation is strong (R2 = 0.974) which indicates that two Dws have strong correlations. Based on this finding, the DW,contrast can be accurately calculated from DW,non-contrast.” Please see the revised manuscript, page 4, lines 191-195.
Page 2.
Line1 39
How much is the HU increase due to the use of contrast.
In some organs, the mean HU increases up to 22.6%. Please see the revised
manuscript, page 4, lines 170-180.
Page 3.
Line 147-
148
Since the mean value between Dw and Dw contrast are pretty close, it is hard to see the difference within the box plot figure. In order to make the reader could see what is happening between both data, Put the value of the mean, upper and lower of the box plot.
Done. Please see the revised Figures 5-7.
Page 3.
Line 152
Is there any relation between the increase of CTDI with the tube loading?
Of course. The relationships between CTDI and tube loading in TCM technique have been reported in the previous study (Reference number 18). We have added
explanation in the revised manuscript, page 5, page 238-241.
Page 3.
Line 165
What is the benefit of knowing this relation in clinical application.
The relationship of two parameters can be used to estimate one parameter if another parameter is known. We found that the R2 of all relationship are almost 1. It means that the relationships are very strong. Fortunately, the Dw, CTDIvol, and SSDE before and after contrast agent injection are very similar with
differences lower than 2%, therefore we can obtain the Dw, CTDIvol and SSDE for contrast agent injection from the image without contrast agent, without applying these relationships. We have added this information in the revised manuscript. Page 4, lines 190-193.
Page 4.
Line 190-
191
Please explain at which value for Dw and SSDE to be consider giving significant effect?
The author has not mention at which level the value should be consider as significant or not significant.
The different is not significant. We have added the information in the revised manuscript page 4, lines 251-254.
Page 4.
Line 192
It is very obvious that the contrast will not giving any significant effect on dose. the conclusion is too shallow. The discussion also too shallow to provide better conclusion.
During routine CT examination,
implementing caredose feature on Siemens CT will provide better patient protection for unnecessary dose delivery. Introducing contrast agent during CT procedure will not increase generous current compare to non- contrast technique. Observation of the tube loading between contrast and non-contrast procedure is sufficient to understand that the dose increase will not noticible
The author has to explore more from the gathered data and elaborate everything within the
manuscript.
Thank you for your nice comments. We previously did know the impact of the contrast agent in the Dw, CTDIvol, and SSDE. We, very recently (In middle January 2021 and it is now still in Accepted Manuscript), found the
publication dealing this same issue in the Medical Physics and reported the
comparable results with ours (reference number 29). This indicates that the investigation of this issue of contrast agent is important. The results of this study will be useful to confidently consider the Dw and SSDE for examination with contrast agent administrations. All information is added in the revised manuscript.
Please return to Atom Indonesia Editorial Office via supplementary file in OJS aplication.
March 1, 2021
