Elsevier Editorial System(tm) for The Veterinary Journal Manuscript Draft
Manuscript Number: YTVJL-D-10-00623R2
Title: Application of high-frequency ultrasound for the detection of surgical anatomy in the rodent abdomen
Article Type: Original Article
Keywords: Rat abdomen, High-frequency ultrasound, Anatomy, Living image Corresponding Author: Professor Chuan-Mu Chen, Ph.D.
Corresponding Author's Institution: National Chung Hsing University First Author: Jiun-Yu Chen, Ph.D.
Order of Authors: Jiun-Yu Chen, Ph.D. ; Hsiao-Ling Chen, Ph.D.; Sheng-Hai Wu, Ph.D.; Tung-Chou Tsai, Ph.D.; Ming-Fong Lin, M.D.; Chih-Ching Yen, M.D., Ph.D.; Wu-Huei Hsu, M.D.; Wei Chen, M.D.; Chuan-Mu Chen, Ph.D.
Abstract: Rats are used extensively in abdominal disease research. To monitor disease progress in vivo, high-frequency ultrasound (HFU) can be a powerful tool for obtaining high-resolution images of biological tissues. However, there is a paucity of data regarding the correlation between rat anatomy and corresponding HFU images. Twenty-four adult male Sprague-Dawley (SD) rats underwent
abdominal scans using high-frequency ultrasound (40-MHz) surgical procedures to identify abdominal organs and major vessels as well as in situ scanning to confirm the imaging results. The results were compared with those of human abdominal organs in ultrasonographic scans. The rat liver, paired kidneys, stomach, intestines, and major blood vessels were identified by HFU. The ultrasonic morphologies of the liver and kidneys showed differences between rats and humans. Clinically relevant anatomical structures were identified using HFU imaging of the rat abdomen, and these structures were compared with the corresponding structures in humans. Increased knowledge with regard to identifying the anatomy of rat abdominal organs by ultrasound allows scientists to conduct more detailed intra-abdominal research in rodents.
Original article
1
Application of high-frequency ultrasound for the detection of surgical anatomy
2
in the rodent abdomen
3
4
J.Y. Chen a,†, H.L. Chen b,†,S.H. Wu a, T.C. Tsai a, M.F. Lin a,c, C.C. Yen a,d, 5
W.H. Hsu d,W. Chen a,e,*, C.M. Chen a,f,* 6
7
a
Department of Life Sciences, National Chung Hsing University, Taichung 402; 8
b
Department of Molecular Biotechnology, Da-Yeh University, Changhwa 515; 9
c
Taichung Hospital, Department of Health, Taichung 403; 10
d
Department of Internal Medicine, China Medical University Hospital, Taichung 404; 11
e
Department of Internal Medicine, Chia-Yi Christian Hospital, Chia-Yi 600; 12
f
School of Chinese Medicine, China Medical University, Taichung, 404; Taiwan 13
14 †
These authors contributed equally to this work 15
16
* Corresponding authors: Tel.: +886 4 2285 6309; fax: +886 4 2285 1797. 17
E-mail address: [email protected] (C.M. Chen) or 18
[email protected] (W. Chen) 19
Abstract
21
Rats are used extensively in abdominal disease research. To monitor disease 22
progress in vivo, high-frequency ultrasound (HFU) can be a powerful tool for 23
obtaining high-resolution images of biological tissues. However, there is a paucity of 24
data regarding the correlation between rat anatomy and corresponding HFU images. 25
Twenty-four adult male Sprague-Dawley (SD) rats underwent abdominal scans using 26
high-frequency ultrasound (40-MHz) surgical procedures to identify abdominal 27
organs and major vessels as well as in situ scanning to confirm the imaging results. 28
The results were compared with those of human abdominal organs in ultrasonographic 29
scans. The rat liver, paired kidneys, stomach, intestines, and major blood vessels were 30
identified by HFU. The ultrasonic morphologies of the liver and kidneys showed 31
differences between rats and humans. Clinically relevant anatomical structures were 32
identified using HFU imaging of the rat abdomen, and these structures were compared 33
with the corresponding structures in humans. Increased knowledge with regard to 34
identifying the anatomy of rat abdominal organs by ultrasound allows scientists to 35
conduct more detailed intra-abdominal research in rodents. 36
37
Keywords: Rat abdomen; High-frequency ultrasound; Anatomy; Living image 38
Introduction
40
Experimental models using small animals are receiving increasing recognition 41
as a powerful means of study in genomics research, disease research, pharmacological 42
research and molecular biology (Feldman and Brunner, 1994; Poltorak et al., 1998; 43
Van Rhijn et al., 2008). The ability to reproduce human disease using such models has 44
been proven, providing researchers with new diagnostic and therapeutic approaches. 45
Thus, the development of a non-invasive modality for small-animal imaging is 46
critically important because it may provide the possibility of longitudinal research on 47
the same animal, shortened observation times, and reduced requirements for animal 48
sacrifice (Grassi et al., 2009). Several non-invasive devices have been developed 49
recently for small-animal experiments, including ultrasound, magnetic resonance 50
(MR), computed tomography (CT), single photon emission computed tomography 51
(SPECT) and positron emission tomography (PET). Among these devices, ultrasound 52
has the advantages of low cost, rapid imaging speed, portability and high resolution 53
(Foster et al., 2002). 54
55
Ultrasound techniques have aided the diagnosis of human diseases for decades, 56
especially with regard to hepatology (Robinson, 2008; Wieckowska and Feldstein, 57
2008), gastroenterology (Nylund et al., 2009), pulmonology ( Yang, 2000; Tsai and 58
Yang, 2003), cardiology (Kpodonu et al., 2008), gynaecology (Benacerraf et al., 2005), 59
and nephrology (Mostbeck et al., 2001). However, the applications of ultrasound in 60
small-animal research have been limited by its resolution because conventional 61
ultrasonic imaging systems for humans typically use a frequency range of 2 - 15 MHz. 62
To improve spatial resolution, one strategy would be to increase the ultrasound 63
frequency. Due to technical advances, high-frequency ultrasound (HFU), which refers 64
to frequencies above 20 MHz, has become more readily available (Foster et al., 2000; 65
Knspik et al., 2000; Goertz et al., 2003). HFU provides non-invasive, real-time 66
images with a spatial resolution of less than 100 μm. 67
68
Significant research efforts have been directed toward liver and kidney diseases 69
and have used rats as animal models. Such diseases include hepatocellular carcinoma 70
(Lu et al., 2009), liver cirrhosis (de Lima et al., 2008), obstructive uropathy (Chuang 71
et al., 2000), and nephritis (Jaimes et al., 2009). In these models, ultrasound could be 72
a useful tool for evaluating disease progression and pharmacological effects (Fleck et 73
al., 2002; Lee et al., 2005). However, there is a paucity of data regarding the 74
correlation between rat abdominal anatomy and the corresponding images obtained 75
using high-frequency ultrasound. 76
The aim of this study was to describe and identify rat abdominal organs 78
(including the liver, kidneys, stomach, and spleen) using HFU. To obtain these images, 79
a commercially available ultrasonic imaging system (Visual Sonics Vevo 770) was 80
used. The results of rat imaging were then correlated with human anatomical 81
structures. 82
83
Materials and methods
84
Animals 85
Twenty-four male Sprague-Dawley (SD) rats weighing 250-300 g were used. 86
Animals were housed at a controlled temperature (23 oC) with a daily exposure to a 87
12-h: 12-h light-dark cycle (Yen et al., 2009). The animal use protocol in this study 88
has been reviewed and approved by the Institutional Animal Care and Use Committee 89
of the National Chung Hsing University (IACUC Approval number: 97-54). 90
91
Study protocol 92
To thoroughly understand rat abdominal organ anatomy, we reviewed relevant 93
published studies (Corman et al., 1985; Morehouse et al., 1995; Kogure et al., 1999; 94
Madrahimov et al., 2006; Martins and Neuhaus, 2007). After completing our review 95
of rat abdominal anatomy, we performed ultrasound scanning and recorded images. 96
Thereafter, the rats were sacrificed, and the transducer was placed in direct contact 97
with the organs to confirm the results of the images obtained using ultrasound. 98
99
HFU examination 100
During the surgical procedures, animals were lightly anesthetised with gas 101
consisting of 0.5-1 L/min of oxygen-enriched air mixed with 2.0-2.5% isoflurane 102
vapour. The animals were fasted for 3 h prior to high-frequency ultrasound (HFU)
103
scanning.The animals were placed in supine positions and were breathing
104
spontaneously. After being anesthetised, each rat abdomen was shaved and further 105
cleaned with a chemical hair remover to minimize ultrasound attenuation. Typical 106
diagnostic scanners emit ultrasound at frequencies ranging from 2-15 MHz. This 107
range of frequencies cannot provide sufficient resolution to the image axons. 108
Therefore, a commercially available HFU apparatus (Visual Sonics Vevo 770 with the
109
RMV 704) was used in this experiment. A transducer that was used for imaging rat
110
abdominal organs had a central frequency of 40 MHz and provided an axial resolution 111
of 40 μm with a 14.6-mm field of view. Ultrasound gel was placed on the skin as a 112
coupling fluid before using the transducer. 113
114
Areas of key importance to this study were those where the data provided by in 115
situ images corresponded with those obtained from the rat abdominal tissues. Thus, 116
for both control and experimental animals, abdominal tissues were imaged in situ 117
through the overlying musculature. This overlying musculature was then held apart 118
with surgical spreaders, and the animals were sacrificed. The exposed abdominal 119
tissues were then imaged by applying the ultrasound probe. 120
121
Surgical procedure and identification of rat anatomy 122
After the ultrasound examination, each rat underwent a surgical procedure for 123
anatomy identification. In anesthetized rats, midlaparotomies were followed by lateral 124
transverse incisions. Then, the liver ligaments were incised. The intestinal loops were 125
dissected to show the liver, kidneys and inferior vena cava (Fig. 1). Euthanasia was 126
performed after anatomic dissection. 127
128
Results
129
Anatomy and ultrasonographic presentations of rat kidneys 130
Anatomy: in rats, paired kidneys were located behind the intestinal loops, one on 131
each side of the spine. As shown in Fig. 1, the right kidney was situated just below the 132
inferior right lobe (IRL) of the liver, and the left kidney was situated below the left 133
lateral lobe (LLL) of the liver and posterior to the stomach. The asymmetry caused by 134
the liver within the abdominal cavity typically resulted in the left kidney being 135
slightly lower than the right. This arrangement was opposite that of human kidneys. 136
Each kidney weighed between 1.8 and 2.2 g and had a transverse diameter measuring 137
between 8 and 10 mm.
138
139
Ultrasound examination: in rats, the right kidney was a good landmark for the 140
initiation of ultrasonic scanning. The examination began just below the right lowest 141
rib in the transverse plane (Fig. 2a), and the transducer was moved slightly and slowly 142
around that region to locate the right kidney. On ultrasound, the kidney appeared as an 143
oval with a longitudinal diameter measuring between 11 and 14 mm and a transverse 144
diameter measuring between 7.5 and 8.0 mm. By tilting and moving the transducer 145
leftward slightly, it was possible to locate the portion of the liver that surrounded the 146
right kidney. This portion of the liver was the inferior right lobe (Fig. 2b and 2d). The 147
central potion (medulla) was relatively hyperechogenic due to the abundant interfaces 148
produced by the blood vessels and drainage system. In this portion, there were a few 149
relatively hypoechoic pyramids that were surrounded by the cortical layer (Fig. 2c and
150
2e). The kidney was scanned in at least two planes to adequately visualize all of the 151
parenchyma and supplying blood vessels. Two main vessels passed through this 152
region from the medulla to the hilum; one was the renal artery, and the other was the 153
renal vein. We were able to identify the renal artery using Doppler ultrasound, which 154
demonstrated a frequency shift during systole with a gradual decrease in flow 155
throughout diastole. On the other hand, the renal vein flow was constant throughout 156
the cardiac cycle. 157
158
Anatomy and ultrasonographic presentations of the rat liver 159
Anatomy: in rats, the liver was the largest internal organ, accounting for 160
approximately 5% of the total bodyweight (BW). It was a soft, pinkish-brown, 161
multilobed organ, located in the right and left upper quadrants of the abdominal cavity, 162
resting just below the diaphragm (Fig. 1). In rat liver weighting range from 9.6 to 13.5
163
g, the liver’s mean weight was 12.5 g. Gross anatomy divided the liver into four major
164
lobes, the median lobe, the right lobe, the left lobe and the caudate lobe. These 165
divisions were based on surface features. In Fig. 1, the caudate lobe (CL) was not 166
visible because it was situated behind the left lateral lobe (LLL). The median lobe 167
(ML) was located just below the diaphragm and was sub-divided by a main fissure 168
into a right medial lobe (RML) and a left medial lobe (LML). The right lobe was 169
located to the right of the vena cava and was almost completely covered by the medial 170
lobe. The rat liver was further divided by a horizontal fissure into two lobules: the 171
superior right lobe (SRL) and the inferior right lobe (IRL). 172
173
Ultrasound examination: after scanning for the right kidney, the transducer was 174
moved leftward slightly in a transverse plane near the midline. It was possible to see 175
the relative position between the inferior vena cava (IVC) and the hepatic vasculature 176
(Fig. 3). The extrahepatic portal vein was located posterior and lateral to the hepatic 177
artery (HA) and the common bile duct (CBD). Then, by moving the transducer 178
upward near the xiphoid, the right part of the liver was visible (Fig. 4a). The margin 179
of the right liver was smooth and wedge-shaped, and the corresponding region was 180
the RML (Fig. 4b and 4e). The liver parenchyma had a uniform, sponge-like texture of 181
low-level echogenicity. Passing through it were the blood vessels, which were seen as 182
branching tubular structures that could be traced toward the porta (portal veins; PV) or 183
the hepatic veins (IVC). Portal veins were usually surrounded by reflective tissue,
184
whereas hepatic veins usually appeared as simple hypoechoic tubular structures (Fig.
185
4c and 4f). By moving the transducer slightly toward the midline, one could observe
186
that the SRL lay posterior to the RML near a fissure (Fig. 4d and 4g). 187
188
By moving the transducer just across the midline (Fig. 5a), one could see that 189
the LML is near the left side of the RML. A vertical fissure, called the main fissure or 190
umbilical fissure, was located between the two lobes (Fig. 5b and 5d). At this location, 191
a compression manoeuvre was used to image the deeper part of the liver. Then, it was 192
possible to observe the pulsating aorta and portal triad in this section (Fig. 5c and 5e). 193
By moving the transducer to the left (Fig. 6a), a wedge-shaped border of the left liver 194
(LLL) could be seen (Fig. 6b and 6d). After tilting the transducer slightly and in a 195
hyperechoic curve line below the LLL, the stomach was visible (Fig. 6c and 6e). 196
197
Anatomy and ultrasonographic presentations of the rat spleen 198
Anatomy: the spleen lay in the left upper quadrant of the abdomen, immediately 199
beneath the left hemi-diaphragm (Fig. 1). It was an approximately triangular organ 200
and was fixed by ligaments in a position between the left diaphragm and the stomach. 201
202
Ultrasound examination: after scanning for the left portion of the liver, the 203
transducer was moved laterally and caudally to locate the spleen, which was observed 204
as a triangular organ with evenly distributed fine echoes (Fig. 7a). The best landmark 205
in this case was the left kidney, which lay caudal to the spleen and was readily 206
identified by its distinct sonographic pattern (Fig. 7b and 7c). 207
208
Discussion
209
Micro-ultrasound has proven to be a useful tool for monitoring and assessing 210
abdominal diseases in small animals (Chuang et al., 2000; de Lima et al., 2008; 211
Jaimes et al., 2009; Lu et al., 2009; Sullivan et al., 2009). Thus, detailed scanning 212
techniques and a thorough description and identification of anatomy by ultrasound are 213
crucial when designing and performing experiments with regard to the rat abdomen. 214
To our knowledge, this is the first study investigating the correlation between 215
ultrasonic imaging and rat abdominal anatomy using high-frequency ultrasound 216
(40-MHz). In this study, we report our experiences with scanning technique to clearly 217
identify abdominal organs by HFU. 218
219
Scanning abdominal organs in rats is much more difficult than scanning humans 220
because of the faster respiratory rates of rats (approximately 90 breaths / min). Thus, 221
the images on the screen swing constantly despite the rat being under anaesthesia. A 222
novice performing the ultrasound procedure must overcome this difficulty. Even using 223
a mini-transducer, scanning should be conducted very slowly and steadily; otherwise, 224
tiny organs could be missed. 225
226
The best landmark in rat abdominal ultrasound examinations was probably the 227
right kidney, which lay inferior to the right diaphragm and could be identified easily 228
by its distinct ultrasonographic patterns (Fig. 2a and 2b). Relative to their 229
identification in humans, it was much easier to identify both kidneys by ultrasound in 230
rats when they are placed in the supine position. Because human kidneys are located 231
in the retroperitoneal cavity, obtaining optimal views sometimes requires subjects to 232
lie in a decubitus or prone position. The kidney also differs significantly in their 233
ultrasonographic demonstrations between rats and humans. The rat kidney did not 234
show an obvious border between the medulla and the cortex, whereas the human 235
kidney was strongly echogenic in the central portion and had hypoechoic 236
surroundings (Fig. 8a, right panel). In addition, it was easy to scan the main blood 237
vessels passing through the rat kidney (Fig. 2c), but it was rare to see these features 238
during human ultrasounds. Thus, future studies may include measurements of the 239
intra-renal artery resistance index by Doppler to evaluate the severity of kidney 240
injuries. 241
242
Ultrasound has proven to be an effective tool for monitoring and assessing 243
hepatomas (Yang et al., 1993; Oh et al., 2002; Di Stefano et al., 2008) and liver 244
cirrhosis (Yan et al., 2007; de Lima et al., 2008; Dias et al., 2008) in small animal 245
experiments. However, it is difficult to scan the rat liver properly because it is easy to 246
flatten the liver by compression (Fig. 5b and 5c). Thus, we suggest first scanning the 247
liver lightly and gently and then applying pressure to the organ to examine deeper 248
areas. 249
250
The greatest difference between the hepatobiliary systems of rats and humans is 251
the fact that the rat has no gallbladder (Fig. 8a, left panel). In humans, Murphy’s point 252
in the right upper quadrant refers to the gallbladder, and this is a useful landmark for 253
guidance to specific target organs (Taylor et al., 1976). In addition, human liver lobes 254
have no clear fissure lines or divisions under ultrasonographic depictions, whereas rat 255
livers show multiple lobes with clear fissures between them (Fig. 4d and 5b). The 256
differences in ultrasound imaging between rats and humans are summarised in Table 257
1. 258
259
The ultrasonographic pattern of the rat spleen (Fig. 7b) was very similar to that 260
of the human spleen (Fig. 8b). Both are triangular in shape and exhibit evenly 261
distributed, fine echoes. The pancreas is not difficult to find during a human 262
ultrasound, but we could not identify the rat pancreas in our study. 263
264
HFU technique has inherent limitations. The images have a limited depth of 265
field because of the short wavelength and the low fixed F-number of conventional 266
transducers (Mamou et al., 2009). However, in our investigation, we could still scan 267
most abdominal organs thoroughly using various scanning techniques, such as tilting, 268
compression, and rotation of the transducer. 269
270
Conclusions
271
In conclusion, the rat is the most commonly used experimental model for 272
simulating abdominal diseases. The employment of high-frequency ultrasound 273
requires detailed knowledge of regional abdominal anatomy and optimal scanning 274
techniques. In this study, we identified the anatomy of the kidneys, liver, stomach, and 275
spleen in situ immediately. By the knowledge, we may observe the process of tissue
276
regeneration or severity of tissue injury of the abdominal organs more accurately in
277
the future. The data show that sonography, with a resolution of 40 μm, permits
278
observation of hepatic repair and kidney regeneration processes in rats. 279
280
Conflict of interest statement
281
None of the authors has any financial or personal relationships that could 282
inappropriately influence or bias the content of this paper. 283
284
Acknowledgments
285
This research was supported in part by grant NSC-98-2313-B-005-012 from the 286
National Science Council, grant COA-97-6.2.1-U1(9) from the Council of Agriculture, 287
and the Ministry of Education, Taiwan, Republic of China, under the ATU plan. 288
289
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Yang, P.C., 2000. Ultrasound-guided transthoracic biopsy of the chest. Radiologic 428
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590-598. 440
Table 1.
442
Sonographic comparison of rat and human abdominal organs
443
444
Rat Human
Kidneys
Right kidney is superior to left kidney Left kidney is superior to right kidney Easy to scan in supine position Relatively difficult to obtain ideal
view, sometimes need decubitus position from the flanks
Lack of obvious border between the
medulla and the cortex
Strongly echogenic (medulla) in central portion with hypoechoic surroundings (cortex)
Easy to view supplying blood vessels passing through the kidneys
Hard to view supplying blood vessels passing through the kidneys
Liver
Gallbladder absent Gallbladder present
Multilobed liver with clear fissures Liver lobes have no clear fissure lines or divisions
Right liver border is shaped like a C-curve
Right liver border is wedge-shaped
Easy to deform by compression Shape unchanged by compression 445
Figure legends
446
Fig. 1. Anatomy of rat abdominal organs after removal of stomach and intestines. 447
RML, right medial lobe; LML, left medial lobe; LLL, left lateral lobe; SRL, superior 448
right lobe; IRL, inferior right lobe; RK, right kidney; LK, left kidney; IVC, inferior 449
vena cava. 450
451
Fig. 2. Ultrasonographic demonstration of the right kidney in longitudinal section by 452
different angles of 40-MHz transducer sweeps through a sonic window. (a) Cartoon
453
diagram of stereo location of right kidney detected by different scanning angles
454
(shown as arrow b and arrow c) of transducer sweeps. (b) Right kidney (RK) sits
455
just below the inferior right lobe (IRL) of the liver. (c) The parenchyma comprises the
456
relatively hypoechoic medullary pyramids, which lie centrally. (d) A schematic
457
diagram of (b). IRL, inferior right lobe; RK, right kidney. (e) A schematic diagram of
458
(c). SL, skin layer; ML, muscle layer; RRA, right renal artery; RRV, right renal vein;
459
RC, renal capsule.
460
461
Fig. 3. Ultrasonographic demonstration (40-MHz) of the vessels below the liver in 462
transverse section. (a) Cartoon diagram of space distribution of celiac artery round as
463
shown with an arrow. (b) The ultrasound of hepatic portal area and celiac artery round.
(c) A schematic diagram of (b). CBD, common bile duct; HA, hepatic artery; PV,
465
portal vein; IRL, inferior right lobe of the liver; IVC, inferior vena cava.
466
467
Fig. 4. Ultrasonographic demonstration (40-MHz) of the right part of the liver in 468
transverse section. (a) Cartoon diagram of space distribution of liver and celiac artery
469
round. Images (b) and (c) were produced using different angles of transducer sweeps
470
through a sonic window. Image (d) was a slightly left-shifted scan. (e) A schematic
471
diagram of (b). RML, right medial lobe; M, margin of the right liver. (f) A schematic
472
diagram of (c). HV, hepatic vein; PV, portal vein. (g) A schematic diagram of (d).
473
RML, right medial lobe; F, fissure; SRL, superior right lobe.
474
475
Fig. 5. Ultrasonographic demonstration (40-MHz) of the middle part of the liver in 476
transverse section. (a) Cartoon diagram of space distribution of the middle liver. (b)
477
Superficial view. (c) Deep view of the same transverse section after transducer
478
compression. (d) A schematic diagram of (b). LML, left medial lobe; RML, right
479
medial lobe; F, fissure between LML and RML. (e) A schematic diagram of (c). LLL,
480
left lateral lobe; PT, portal triad; A, aorta.
481
482
Fig. 6. Ultrasonographic demonstration of the left part of the liver in transverse 483
section using different angles of 40-MHz transducer sweeps through a sonic window. 484
(a) Cartoon diagram of space distribution of the left liver and stomach. (b) Superior
485
view. (c) Inferior view. (d) A schematic diagram of (b). LLL, left lateral lobe; M,
486
margin of the LLL. (e) A schematic diagram of (c). LLL, left lateral lobe; S, stomach.
487
488
Fig. 7. Ultrasonographic demonstration (40-MHz) of the spleen in longitudinal section. 489
(a) Cartoon diagram of space distribution of spleen and celiac round. (b) Inferior part
490
of the left spleen. (c) A schematic diagram of (b). Sp, spleen.
491
492
Fig. 8. Ultrasonographic demonstration (5-MHz) of human liver, gallbladder, spleen, 493
and right kidney. L: liver; GB: gallbladder; K: kidney; Sp: spleen. 494
Figure 1
Figure 2
Figure 3
Figure 4
Figure 5
Figure 6
Figure 7
Figure 8
Modifications and revisions
Thank you very much forReviewers’valuableopinions.Thepaperwasrevised based upon your constructive suggestions. And the followings are the point-by-point response to your comments:
For reviewer #1:
Q1. What RMV scan head was used for the ultrasound analysis?
Answer: The mode of RMV scan head is “RMV-704”. The information has been added in the description in the Materials and methods section (Lines 107-108) as followed:“Therefore, a commercially available HFU apparatus (Visual Sonics Vevo 770 with the RMV 704) was used in this experiment”.
Q2. Were the animals fasted prior to scanning to limit intestinal motions during the imaging? Answer: Yes, the animals were fasted for 3 h prior to high-frequency ultrasound (HFU) scanning. This description has been added in the HFU examination paragraph of Materials and Methods section (Lines 101-102).
.
Q3. Why not use the aorta as a structural landmark?
Answer: In gray scale, it is not easy to differentiate the aorta from other vascular system, such as inferior vena cava, portal vein or hepatic artery because all of them appear as simple hypoechoic tubular structures under transverse view. In our experience, the right kidney is a good landmark for the initiation of ultrasonic scanning because of its particular structure (oval-shape with relatively hyperechogenic central portion) and easy approach.
Q4. Is the imaging done free hand or using the rail system?
Answer:The HFU imaging was done by free hand operation as the same situation of clinical ultrasound scanning. In this study, Two HFU operators were applied, one is a well-trained HFU expertise (Mr. Jiun-Yu Chen) and the other is a clinical medical doctor (Dr. Wei Chen). All of the HFU images were double check between these two operators.
Q5. Is the gating feature used?
Answer:No gating feature was used in this study.
Q6. For ALL images I would suggest including a panels for each figure with I of the panels
showing a clear outline of the structure of interest. Even for people accustomed to looking at ultrasound images it is difficult to "find" what the authors are trying to highlight.
Answer:According to reviewer’s suggestion, all the HFU images of figures 2-7 were added the panels showing a clear outline of the structures of interest. The abbreviation labels in the interpretive diagrams were also described in the figure legends.
Q7. Line 161, I believe there is a problem with the weight of the rats as stated. The liver's
weigh 12.5 g but the rats weigh 9.6-13.5 g.
Answer:The meaning is a range of liver weights between 9.6 and 13.5 g, but our description was unclear. The sentence has been revised as followed: “In rat liver weighting range from
9.6 to 13.5 g, the liver’s mean weight was 12.5 g”.
For reviewer #2:
Q1. Abstract - Change "in vitro scanning" to "in situ scanning".
Answer: According to reviewer’s suggestion, the term of "in vitro scanning" has been changed to "in situ scanning" (Line 27 in the Abstract section).
Q2. Typographical error on line 87: "12-sh"
Answer:The typographical error of "12-sh" has been corrected as "12-h".
Q3. Line 136 - change measurement units to mm to be consistent with the diameters given
below.
Answer:The measurement units have been changed as “….between 8 and 10 mm”.
Q4. Line 161 - the sentence regarding rat weights doesn't quite make sense. Please check
this.
Answer:The meaning is a range of liver weights between 9.6 and 13.5 g, but our description was unclear. The sentence has been revised as followed: “In rat liver weighting range from
9.6 to 13.5 g, the liver’s mean weight was 12.5 g”.
Q5. Line 271 - consider changing the word "development" to "employment" or similar. Answer:The word of "development" has been changed to "employment".
detect progress in liver regeneration. The authors should re-word this sentence accordingly.
Answer: The sentence has been revised as followed: “By the knowledge, we may observe the process of tissue regeneration or severity of tissue injury of the abdominal organs more
accurately in the future.”
Q7. Figure labeling: Would it be possible to avoid using the same numbers for different
anatomical features within the same figure? For example, in Figure 5, the number 2 indicates the right medial lobe in Fig. 5a but the portal triad in Fig 5b. This is a little confusing. Using the abbreviations (e.g. LML) rather than numbers on the figures might be easier to understand at a glance.
Answer:To avoid the confusing of the numbers labeling, all of the labels have been revised using the abbreviations as shown in Figures 1 to 8 and their figure legends.
Q8. Table 1: Consider changing "Unobvious" to "Lack of obvious"
Answer: According to reviewer’s suggestion, the word of "Unobvious" has been revised as "Lack of obvious".
Dr. Andrew Higgins Nov. 17, 2010 Editor-in-Chief
The Veterinary Journal
Dear Editor Higgins:
Thank you and the referees for your careful consideration of our manuscript entitled
“Application of high-frequency ultrasound for the detection of surgical anatomy in the rodent abdomen”coded YTVJL-D-10-00623R1. Following your helpful comments, we
have enumerated our responses to the reviewers’ comments and modified our manuscript accordingly.
Please find two attached files including a list of the modifications to the original manuscript and our replies to the comments, and a full-text of the revised manuscript. We are confident that this revised paper is now suitable for publication in the
Veterinary Journal.
We are looking forward to hearing from you and deeply appreciate your kindly help!
Yours sincerely,
Chuan-Mu Chen, Ph.D. Professor / Dean
Department of Life Sciences National Chung Hsing University 250 Kuo Kuang Road, Taichung 402, Taiwan
TEL: 886-4-2285-6309 FAX: 886-4-2287-4740
E-mail: [email protected]
