Downloaded from http://bmjopen.bmj.com/ on June 18, 2017 - Published by group.bmj.com
PEER REVIEW HISTORY
BMJ Open publishes all reviews undertaken for accepted manuscripts. Reviewers are asked to
complete a checklist review form (http://bmjopen.bmj.com/site/about/resources/checklist.pdf) and
are provided with free text boxes to elaborate on their assessment. These free text comments are
reproduced below.
ARTICLE DETAILS
TITLE (PROVISIONAL)
AUTHORS
Measuring Shear-Wave Speed with Point Shear-Wave Elastography
and MR Elastography: a Phantom Study
Kishimoto, Riwa; Suga, Mikio; Koyama, Atsuhisa; Omatsu,
Tokuhiko; Tachibana, Yasuhiko; Ebner, Daniel; Obata, Takayuki
VERSION 1 - REVIEW
REVIEWER
REVIEW RETURNED
GENERAL COMMENTS
Giovanna Ferraioli
Fondazione IRCCS Policlinico San Matteo, University of Pavia,
Pavia, Italy
Giovanna Ferraioli has served as a speaker for Philips Medical
Systems, Hitachi Ltd, Toshiba Medical Systems.
23-Aug-2016
It is not correct to state that “there is a relative paucity of data
available regarding the validity and variability of SWE relative TE”. In
fact, plenty of studies have compared either pSWE or 2D-SWE with
TE. Please delete this sentence.
Palmeri et al. have studied the shear wave speed in viscoelatic
phantoms using several US equipment and the speed of the shear
wave was assessed at different depths. Their study should be cited
and commented [Palmeri M, et al. RSNA QIBA ultrasound shear
wave speed Phase II phantom study in viscoelastic media.
Proceedings of the 2015 IEEE Ultrasonics Symposium,
2015International 2013:397–400].
M&M
Page 10: the equation used to compare the values measured by US
and MR elastography in this study is missed.
Page 10, line 47: VTQ is not a system, it is a proprietary software.
It is stated that “SWS was measured by fixing the transducer
mechanically to the phantom with a pressure of 10 ± 0.5 kPa, a
value obtained by reference to the pressure of clinical examination”.
While this condition is true for the assessment of superficial organs,
such as thyroid and breast, it doesn’t apply to the liver, which is
studied through an intercostal space and a minimal pressure is
exerted on the skin and the intercostal muscles but on the liver.
Either the authors repeat the experiment also without any pressure
or they state in the discussion that these results are not applicable to
the study of the liver in vivo.
MR elastography stiffness values are reported as shear modulus,
while US elastography stiffness values are reported in Young
modulus. The Young modulus is three times the shear modulus.
Readers who are familiar with the stiffness values obtained with US
elastography may get confused. This issue should be clarified.
Moreover, the shear wave speed in the softest phantom was 1.41
m/s, and this speed in the liver tissue already indicates a significant
Downloaded from http://bmjopen.bmj.com/ on June 18, 2017 - Published by group.bmj.com
fibrosis. Using the same US equipment, in a meta-analysis that
included nine studies the optimal cutoff values were 1.34, 1.55, and
1.80 m/s, respectively, for staging clinically significant fibrosis,
severe fibrosis, and cirrhosis [Friedrich-Rust M, et al. Performance
of acoustic radiation force impulse imaging for the staging of liver
fibrosis: a pooled meta-analysis. J Viral Hepat 2012; 19:e212–e219].
Please clarify and discuss.
REVIEWER
REVIEW RETURNED
Po-Hsiang Tsui
Department of Medical Imaging and Radiological Sciences, Chang
Gung University, Taiwan
05-Oct-2016
GENERAL COMMENTS
This study compared shear wave speeds (SWS) of phantoms with
known shear modulus measured by ultrasound-based point shearwave elastography (pSWE) and magnetic resonance elastography
(MRE). The results showed that SWS obtained with both pSWE as
well as MRE had a strong correlation with those obtained by
rheometer. Note that the authors used commercial scanners for
validations. In general, before a formal proposal of a commercial
machine, the manufacturers perform testing and calibrations to
confirm that the output value is reliable. For this reason, the findings
in this work are expectable and not novel. Instead, the authors may
be interested in comparing performances of using pSWE and MRE
in characterizing clinical diseases. Such an experimental design may
be more meaningful.
REVIEWER
Katarzyna Dobruch-Sobczak
Cancer Center, Oncology Institute, Warsaw, Poland
08-Oct-2016
REVIEW RETURNED
GENERAL COMMENTS
RE: Shear-Wave Speed Measurement with Point Shear-Wave
Elastography and MR Elastography: a Phantom Study comparison
with rheometer `measurement.
Thank you for sending this interesting paper to BMJ Open.
REVIEWERS' COMMENTS:
An interesting paper about shear wave speed measurement with
pSWE and MR elastography, a phantom study
General comments
In general, this is a well-written paper that presents interesting data.
The advantage of this study is that authors compared SW speed
measurements in two different techniques. Do you think that these
results, which not provide viscoelastic properties like soft tissue,
could be the same in in vivo examination?
There are some drawbacks in this study.
I have the following concerns.
Specific comments
Introduction
The first paragraph should be supported by more references about
Downloaded from http://bmjopen.bmj.com/ on June 18, 2017 - Published by group.bmj.com
US elastography and MRE (page 6 line 14, 26, page 7 line 18)
Discussion:
1.P17 l53, instead the sentence: ” In another clinical study
comparing MR and 2D SWE, Yoon et al. suggested that two
methods may not be interchangeable, especially in stiffer livers”, is
to general.
It would be more convinient:
In another clinical study comparing MR and 2D SWE, Yoon et al.
sugessted that there was a moderate correlation in liver stiffness
measurements in both SWE and MR, but both examination
presented similar diagnostic performance for excluding hepatic
fibrosis”
2.Could you summarise the past work in a table to improve
readability?
3.Please add in conclusions how the results influenced on clinical
applications.
VERSION 1 – AUTHOR RESPONSE
Reviewer: 1
Reviewer Name: Giovanna Ferraioli
It is not correct to state that “there is a relative paucity of data available regarding the validity and
variability of SWE relative TE”. In fact, plenty of studies have compared either pSWE or 2D-SWE with
TE. Please delete this sentence.
Palmeri et al. have studied the shear wave speed in viscoelatic phantoms using several US
equipment and the speed of the shear wave was assessed at different depths. Their study should be
cited and commented [Palmeri M, et al. RSNA QIBA ultrasound shear wave speed Phase II phantom
study in viscoelastic media. Proceedings of the 2015 IEEE Ultrasonics Symposium, 2015International
2013:397–400].
We deleted that sentence and we have added the article of Dr. Palmeri et al. as Ref #13.
M&M
Page 10: the equation used to compare the values measured by US and MR elastography in this
study is missed.
Thank you for your suggestion. We have revised the equation visible.
Page 10, line 47: VTQ is not a system, it is a proprietary software.
We have changed it to “software”.
It is stated that “SWS was measured by fixing the transducer mechanically to the phantom with a
pressure of 10 ± 0.5 kPa, a value obtained by reference to the pressure of clinical examination”. While
this condition is true for the assessment of superficial organs, such as thyroid and breast, it doesn’t
apply to the liver, which is studied through an intercostal space and a minimal pressure is exerted on
the skin and the intercostal muscles but on the liver. Either the authors repeat the experiment also
without any pressure or they state in the discussion that these results are not applicable to the study
of the liver in vivo.
Downloaded from http://bmjopen.bmj.com/ on June 18, 2017 - Published by group.bmj.com
Thank you for your important comment. We have added some discussion about this in the sixth
paragraph in Discussion.
MR elastography stiffness values are reported as shear modulus, while US elastography stiffness
values are reported in Young modulus. The Young modulus is three times the shear modulus.
Readers who are familiar with the stiffness values obtained with US elastography may get confused.
This issue should be clarified.
We have added some explanation concerning shear modulus and Young modules in “Phantom” part
of Materials and Methods.
Moreover, the shear wave speed in the softest phantom was 1.41 m/s, and this speed in the liver
tissue already indicates a significant fibrosis. Using the same US equipment, in a meta-analysis that
included nine studies the optimal cutoff values were 1.34, 1.55, and 1.80 m/s, respectively, for staging
clinically significant fibrosis, severe fibrosis, and cirrhosis [Friedrich-Rust M, et al. Performance of
acoustic radiation force impulse imaging for the staging of liver fibrosis: a pooled meta-analysis. J
Viral Hepat 2012; 19:e212–e219]. Please clarify and discuss.
We have added some discussion about this and the article of Friedrich-Rust et al. in the same
paragraph discussing transducer pressure above. We think that MR and US elastography are going to
be used widely not only for liver but also in variety of organs and diseases.
Reviewer: 2
Reviewer Name: Po-Hsiang Tsui
This study compared shear wave speeds (SWS) of phantoms with known shear modulus measured
by ultrasound-based point shear-wave elastography (pSWE) and magnetic resonance elastography
(MRE). The results showed that SWS obtained with both pSWE as well as MRE had a strong
correlation with those obtained by rheometer. Note that the authors used commercial scanners for
validations. In general, before a formal proposal of a commercial machine, the manufacturers perform
testing and calibrations to confirm that the output value is reliable. For this reason, the findings in this
work are expectable and not novel. Instead, the authors may be interested in comparing
performances of using pSWE and MRE in characterizing clinical diseases. Such an experimental
design may be more meaningful.
Thank you for your comment. We have added mention of the present situation that manufacturers do
not release their measurement specification of devices in the Introduction.
Reviewer: 3
Reviewer Name: Katarzyna Dobruch-Sobczak
An interesting paper about shear wave speed measurement with pSWE and MR elastography, a
phantom study
General comments
In general, this is a well-written paper that presents interesting data.
The advantage of this study is that authors compared SW speed measurements in two different
techniques. Do you think that these results, which not provide viscoelastic properties like soft tissue,
could be the same in in vivo examination?
Downloaded from http://bmjopen.bmj.com/ on June 18, 2017 - Published by group.bmj.com
This is a difficult question. As we mentioned in discussion, the same tendencies were demonstrated in
some studies measuring liver stiffness. So we expect the same results will be obtained also in other
organs providing the appropriate examination, but we have not evaluated that yet. We need to verify
that in in-vivo examination. We have added these considerations in Discussion.
Specific comments
Introduction
The first paragraph should be supported by more references about US elastography and MRE (page
6 line 14, 26, page 7 line 18)
Thank you for your suggestion. We have added several more references.
Discussion:
1.P17 l53, instead the sentence: ” In another clinical study comparing MR and 2D SWE, Yoon et al.
suggested that two methods may not be interchangeable, especially in stiffer livers”, is to general.
It would be more convinient:
In another clinical study comparing MR and 2D SWE, Yoon et al. sugessted that there was a
moderate correlation in liver stiffness measurements in both SWE and MR, but both examination
presented similar diagnostic performance for excluding hepatic fibrosis”
Thank you for your kind comment. We have revised that according your suggestion.
2.Could you summarise the past work in a table to improve readability?
Thank you for your suggestion. We have added a supplementary table C, in which similar articles are
summarized.
3.Please add in conclusions how the results influenced on clinical applications.
We have added some conclusion about the influence in clinical practice. We also have added some
consideration in discussion concerning the influences on clinical applications.
VERSION 2 – REVIEW
REVIEWER
REVIEW RETURNED
GENERAL COMMENTS
Giovanna Ferraioli
Researcher, Fondazione IRCCS Policlinico San Matteo, University
of Pavia, Italy
Speaker for Philips Healthcare; Travel grant from Toshiba Medical
Systems, Hitachi Ltd, Esaote SpA
04-Nov-2016
The article is interesting and well written. There is only one minor
change that should be made in the discussion, on page 58, line 30:
Please delete the phrase “or for assessing the liver subcostally”
since the subcostal approach is not recommended for the
assessment of liver stiffness.
Downloaded from http://bmjopen.bmj.com/ on June 18, 2017 - Published by group.bmj.com
VERSION 2 – AUTHOR RESPONSE
Reviewer: 1
The article is interesting and well written. There is only one minor change that should be made in the
discussion, on page 58, line 30: Please delete the phrase “or for assessing the liver subcostally” since
the subcostal approach is not recommended for the assessment of liver stiffness.
We have deleted the phrase “or for assessing the liver subcostally”.
We have also exchanged Figure 2, because superscript of R2 had been missed.
Downloaded from http://bmjopen.bmj.com/ on June 18, 2017 - Published by group.bmj.com
Measuring shear-wave speed with point
shear-wave elastography and MR
elastography: a phantom study
Riwa Kishimoto, Mikio Suga, Atsuhisa Koyama, Tokuhiko Omatsu,
Yasuhiko Tachibana, Daniel K Ebner and Takayuki Obata
BMJ Open 2017 7:
doi: 10.1136/bmjopen-2016-013925
Updated information and services can be found at:
http://bmjopen.bmj.com/content/7/1/e013925
These include:
References
This article cites 25 articles, 2 of which you can access for free at:
http://bmjopen.bmj.com/content/7/1/e013925#BIBL
Open Access
This is an Open Access article distributed in accordance with the Creative
Commons Attribution Non Commercial (CC BY-NC 4.0) license, which
permits others to distribute, remix, adapt, build upon this work
non-commercially, and license their derivative works on different terms,
provided the original work is properly cited and the use is
non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/
Email alerting
service
Receive free email alerts when new articles cite this article. Sign up in the
box at the top right corner of the online article.
Topic
Collections
Articles on similar topics can be found in the following collections
Diagnostics (208)
Radiology and imaging (109)
Notes
To request permissions go to:
http://group.bmj.com/group/rights-licensing/permissions
To order reprints go to:
http://journals.bmj.com/cgi/reprintform
To subscribe to BMJ go to:
http://group.bmj.com/subscribe/