ABML2011

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2011年11月3日-5日 東京（芝浦工業大学）

B モード超音波検査における腹部脂肪量の測定
An Novel Method for Abdominal Fatness Measurement with the Help of B-Mode Ultrasonography○周

遊 a，小泉 憲裕 a，窪田
門脇a

直人 b，浅野岳晴 b，湯橋孝 b，佐久間 一郎 a，廖

一仁 b，望月

剛 c，

洪恩 a

東京大学大学院工学系研究科, b 東京大学大学院医学系研究科, c アロカ株式会社
You Zhou a, No rihiro Koizu mi a , Naoto Kubota b , Takaharu Asano b , Kazuh ito Yuhashi b ,Takashi Mochizu ki c , Takashi Kado waki b , Ich iro Saku ma a and Hongen Liao aaGraduate Schoo l o f Eng ineering, The University o f To kyo, Japanb

Graduate School of Medicine, The Un iversity o f To kyo, Japanc
Alo ka Co . Ltd , To kyo, Japan

Abstract: Subcutaneous and visceral fat acculmulat ion in abdo men has close relationship with o f Metabolic Syndro me(MS) and other d iseases, and therefore serve as impo rtant indicato rs of them. Abdo minal co mputed to mog raphy (CT)enables precise quantificat ion of the Subcutaneous Fat Area (SFA) and Visceral Fat Area (VFA ) and has been considered as
the gold standard for body fatness assessment. In this paper, the d istribution of fatness accumu lat ion in abdo min ial area
were studied and some p rincip les have been discovered, and we develope a novel method to measure the SFA and VFA
quickly and stably with u ltrasound (US) and some d rawbacks o f existing methods have been overco me. Then, we
evaluated the novel method on 100 patients. Strong correlat ion relationship between our method and CT method has been
confirmed : Fo r SFA and VFA, the mean dev iation bet ween US-method and CT-method wasandrespectively.
Key words : Visceral Fat A rea, Subcutaneous Fat A rea, Ult rasound Diagnosis, Abdo minal CT Image.
1. Introdu ction
The term metabolic syndrome (M S), a combination of
medical disorders that increases the risk of chronic dis eas es
such as diabetes, hypertension, and cardiovascular disease, hasbeen adopted by International D iabetes Federation (IDF) in2006. M S is a major public health problem, the prevalence of
which has increased worldwide. Despite differences inhistology, physiology and gene expression profile among f at
depots, it is generally believed that excessive fat accumulationin abdominal has similar negative health connotations. For
example, both visceral fat and subcutaneous fat depots are
related to insulin res istance and dyslipidemia, albeit to different
degrees[5].
Abdominal obes ity, colloquially known as belly fat or
clinically as central obesity, is the accumulation of abdominal
fat resulting in an increas e in waist size. Abdominal obesity isthought to be a fundamental pathology for M S in particular andtherefore, the accurate measurement of abdominal obes ity
represents an important tool in assessing the ocurring anddeveloping of M S. There are two kinds of adipose tissue
accumulation in abdomial obes ity: subcutaneous fat and vis ceralfat. Subcutaneous fat is found just beneath the skin as opposed
to visceral fat which is found in the peritoneal cavity. Vis ceralfat, also known as organ fat, packes in between internal organs
and the torso, as opposed to subcutaneous fat which is foundunderneath the skin. Since subcutaneous fat and visceral fat
cannot be observed directly, the accurate assessment of themhas prooven to be challenging work.
Abdominal computed tomography (CT) has been considered
the most accurate and reproducible technique of body fat nessmeasurement, particularly abdominal adipose tissue. Abdominal
CT enables visualization and accurate quantification of both
subcutaneous fat area (SFA) and visceral fat area (VFA) andtherefore serves as the gold standard for abdominal obes ity
assessment [1]. However, abdominal CT has many drawbacks,
including exposure to radiat ion, lack of s implicity, high cost,
and time-consuming. Due to these limitations , a variety ofalternative methods are being used to assess visceral fat amountand distribution. Previous studies have shown that waist
circumference (WC), and WC-based indices can perform assome indicators of the level of visceral obesity [2]. These
measurements are recommended as a simpler and eas ier
screening method. However, due to the lack of the individual
visualization of internal adipose tissue, thes e methods have fatal
drawbacks such as inability to distinguish subcutaneous fat
from vis ceral fat, inability to take into account an individual’s
specific information, low level of reproducibility in the case of
marked obesity, and most important, poor accuracy .
In recent years, simple methods for assessing abdominal
fatness accumulation us ing ultrasonography (US) have beenstudied and w ere further confirmed by strong correlations w ith
CT-detected VFA [3][4][6][7]. U ltrasound has many advantages
such as non invasive to human bodies, low-cost, easy to be
operated, real time and enables the visualization of adipose
tissue. Therefore, U S-based methods show a balance on
simplicity and accuracy between abdominal CT and WC-based
indices. However, the performance of the existing U S-based
methods depend s eriously upon the quality of US image, which
differs largely due to the diagnosis s ituations such as doctors
experience and probe accuracy, and therefore the pract ical
applications of thes e methods cannot be too highly expectedunder universal environment.
In this study, to overcome some drawbacks of existing
methods, a novel method has been developed for abdominal
fatness studies to provided an estimation of the ab dominal SFA
and VFA with the help of ultrasound diagnosis.
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In the visual field of an abdominal U S, due to the Doppler
Effect, the flow of blood in the aorta is nearly the most distinct
marker for U S. Thus, the belt-shaped device is des igned to be
fixed in the exact position from where the aorta can be observed
most clearly. As a result, the diagnosis process will be finishedin seconds, which is convenient for patients as well. With anelastic material, this belt-shaped device would bend s moothly
and mold to patient's abdomen. It is easy to understand that: apatient with mild visceral obesity in normal range of waist
circumference would have a 'flatter' shape in abdomen, whichmeans that the belt-shaped device will be less bent when
diagnosing. On the other hand, a patient with more serious
abdomenial obesity would get a 'plumper' waist, and as a result
more bent the belt-shaped device becomes when diagnos ing.
Hence, the curvature of the belt is proportional to the curvatureof abdomen, which can s erve as a valuable characteristic ofindividual seriousness level of vis ceral obesity and give areasonable class ification of patients. In the next sections, withthe help of three probe-diagnosing positions rather than one, wewill give a method to des cribe the curvature of abdomen
quantitively.

2. Diagnosis Method for US Probe
For providing repeatability and simplicity of operations, weplan to develop a measuring method for ultrasound image whichis easy to follow. The measuring method must fulfill therequirements that: 1) Same positions and angles for ultrasoundprobe on different patients during diagnosis ; 2) Distinct markers
easy to be observable in U S image; 3) Quantitive measurementon patients’ curvature of abdomen. Unlike CT, the ultrasoundcan only provide a limit ed scope ins ide one patient's body. The
diagnosing angle and position of probe may differ from doctor
to doctor due to their own experiences. As a result, we must
provide doctors a standard which is easy to operate.
Due to the swiftly distance-attenuation of ultrasound, thediagnosis from s ide-positions and behind-positions can hardly
take aorta into view and as a result no other distinct marks canbe observed. This will make the diagnosis process quite
unreliable even impossible to be standardized. So, w e chose ourdiagnosis positions in front side of one patient's body. Threekinds of US measurements of fatness are taken. A), Total
distance: the distance between the ant erior w all of the aorta andskin; B), subcutaneous fat thickness: the distance between
anterior face of the rectus abdominis muscle and skin; C),visceral fat thickness: the distance between the internal face ofthe rectus abdominis muscle and the anterior wall of theaorta(Fig.1.). And these three kinds of distances are measured
from the three diagnos is positions in order.

Fig. 2. U ltrasound probe compatible device. The distance
between two adjacent probe positions is 50mm, and the angle
between two adjacent probes isin unbent situation.
(a)Diagnos is method for the belt-shaped device. (b) Clinicalexperiment for the belt-shaped device on a patient.
3. An Analysis on Regional Fatness Distribution
We want to discover some principles of the regional visceral fat
distribution. For this analysis, 146 patients’ abdominal CT
cross-section images at navel level have been collected asmaterials from the s ame urban hospital. Abdominal
cross-section by CT scanning was obtained in a single
tomographic slice at umbilical level as ultrasound probe did.
Abdominal cross-section by CT scanning was obtained in asingle tomographic slice at umbilical level as ultrasound probe
did. Portions with a CT number of −200 to −10 Hounsfield
Units (HU) were separated as adipose tissue and their areas
were automatically calculated .
We simulated the visual scope of US probe from three
postions on these CT images and computed the visceral fat areain view. The Pearson's product-moment correlation andunpaired t-test between total SFA and SFA observed from those
three positions was performanced. The results show ed that there
was strong correlation between the U S obs erved SFA from thesethree positions and the total SFA of an individual patient. The
coefficent was r = 0.647, 0.585, 0.635 for front-position,
left-position and right-position respectively, and for all threeof them, the level of significance was p -value < 2.2e-16 (Fig.

Fig. 1. U ltrasound diagnosis method. Totally nine distances will
be measured from three diagnos is positions.
In [6], Y. Zhou et al came up with the idea of a belt-shaped
ultrasound probe compatible device to provide a quick,easy-operated and accurate way to guide the ultrasonographic
procedures. The probe was fixed at the same positions andangles by the belt when diagnosing and the images were takenfrom a horizontal direction. however, through our clinicalexperiments, w e noticed that aorta, the most distinct mark inview mentioned in [6], w as only a small faint circle which caneasily be neglected sometimes. So we improved their idea anddeveloped another des ign of compatible device which makes the
US probe detect U S image from a vertical direction( Fig.2).
O3-1-23(a)(b)(c)). This result shows that subcutaneous fat accumulat es
quite stably in every local regions in abdomen. Thus, there issome reasonability to use the limited-scoped US image toestimate the total SFA. As far as we know, this is the firstattempt to analyze the regional distribution of subcutaneous fat
accumulation in abdomen. Although this analysis may not bevery exact for each individual patient, it provides us somedetailed information on the volume of fatness accumulation at
different regions in abdomen. And these information have been
proofed to be quite helpful in the estimate next.

abdomen and therefore serves as a quantitive description ofvisceral obesity.

Fig. 4. Practical diagnosis procedures for a patient. (a) US
Diagnos is. (b) Distance of visceral fat measured in US image.
The ultrasound probe w ere detecting from three positions by
the belt-shaped device. The information we can acquirecontains: , denotes the distance between the internal face ofthe rectus abdominis muscle and the centre of the aorta detectedfrom front, and is defined as semi-minor axis of ellipse; ,denotes the distance between front-end of ultrasound probe in
the central diagnosing position and the centre of the aorta
detected from front, , denotes the s ame distance detected fromone s ide;
, denotes the distance between two probes (50mm);, denotes the curve length between
andderived frombyas show ed in Fig. 5(a). Then, by ellipse
circumference and ellipse parametric equation (1), we cancalculate: , denotes the s emi-major axis; , denotes the angle
between two probes. An follow these steps, all of the areas offour quarter-ellipse can be computed as showed in Fig. 5(b).

(a)

(b)

(c)
Fig. 3.(a). (b). (c). Scattergram between total SFA and SFA
observed front, left-side, right-side probe position.
4. The Estimate of S ubcutaneous Fat Area
In this and next s ections, We tested our novel method ofassessing SFA and VFA on 100 patients from the samecommunity. All our ultrasonographic procedures w ere
performed by the same examiner us ing a portableultrasonography equipment (EUB-8500, HITACHI, Japan). The
center of the belt-shaped device fixed exactly 2 cm left toumbilicus for each patient. Each patient assumed a supine
position, and U S data were measured at the end of expiration by
a 6-M Hz 2D abdominal probe, while the probe was making
contact with patients’ skin as slight as possible (Fig.4).For eachpatients, the total diagnosis procedures lasted about 200 seconds.
This is quite an acceptable time during a medical examination.
In addition, M ore quick diagnosis speed is also expectable in
the future if doctors become more proficient in the operat ions of
this novel method.
For a current patient, we assess the SFA bas ed on an ellipse
approximation for the shape of abdominal cavity with aorta as
centre. The eccentricity of ellipse reflects the curvature ofO3-1-3Fig. 5. Ellipse approximation of abdominal cross-s ection. (a)Parameters of ellipse. From our measured information b,r,h, thearea of ellipse can be computed. (b) The areas of four
quarter-ellipse can be approached.
Since the lack of distribution information from back-s ide ofbody, we cannot give an integral estimate of subcutaneous fat
area. So, we define here that SFA=
. And
since abdominal CT holds the most accurate quantificat ion of
the fatness estimation, we treated it as the testing standard in
our experiment for SFA this s ection and for VFA next section.
The correlation between these two groups is also presented. The
coefficent was r = 0.715, and the mean deviation between SFA
measured by CT and our US method for each patient is.

the data of patients were collected from the s ame ethnic group.
For instance, the female body type in particular differs largely
between Westerners and Easterners. Thus, the generalization of
our results to other individuals of certain ethnic groups canhardly be approached directly and further discuss ions areneeding. On the other hand, once the database of specified ethic
group is established, our method can be s oon applied.
Till now, we have developed a U S-based method whose
accuracy is approaching the level of abdominal CT. However, it
is not an entirely impossible thing that the US-bas ed method
will become a more reliable indicator for M S than abdominal
CT in the future. Due to the non-invas iveness and simplity ofUS, diagnosis at different levels of the abdomen w ill beaccomplished without much difficulties. Cons equencely, 3D
individual visualization and estimation of visceral fat can berealized by US, while usually only one slice of abdominal
cross-section image can be acquired by CT in medical
examination due to the harmness of rediation. Secondly, due to
its real-time characteristics, U S allows us to detect visceral fat
over a period of time. One patient’s abdominal cross-sectional
area when expiring will differ largely from inspiring.
Abdominal CT cannot take this difference into cons ider andtherefore would be less convincing than US in this respect.
Further, by US, we may repres ent a us eful method formonitoring weight loss, variations and transfer of visceral fat,which can be expected to indicate the associated risks of M S
more accurately.
In conclusion, although its results are still rough and there aremany details need dis cussing, the results of present US-based
method is relatively correlated w ith results of CT method, andtherefore has been proofed to be a cons iderably stable andaccurate way for VFA and SFA estimation.

5. The Estimate of Visceral Fat Area
We have collect ed a database of 146 patients' abdominal CT
images, VFA and the nine distances in which has beenmeasured.
Firstly, we denote the distance C from Front position as Fc
and denote the distance C from Left position as Lc. Compare Fcof current patient with Fc of every CT images in database, andchoose those images whose Fc are nearest with current patient(12 pieces). In those 12 pieces of images, then chose six pieces
of images whose Fc/Lc are nearest with current patient’s Fc/Lc.
The reas on we us e Fc/L c is that Fc/Lc can demonstrate thecurvature of abdomen of one patient. Finally, define the VFA of
current patient as the average of VFA in these six pieces of CT
images.
By the diagnosis procedure mentioned in Section 2, we tested
our method on 100 patients from the same rural community andmeanwhile abdominal CT were taken. Then, we compared theresults of our U S method w ith the(abdominal CT. Figure.6
shows the comparisons of CT and our U S-bas ed method. The
correlation coefficent between thes e two groups was r = 0.715,
and the mean deviation between VFA measured by CT and our
US method for each patient is.

7. References
1. Enzi, G. and Gasparo, M . and Biondetti, PR and Fiore, D. andSemis a, M . and Zurlo, F.: Subcutaneous and vis ceral fat
distribution according to sex, age, and overweight, evaluatedby computed tomography, Am J C/in Nuir 1986;44:739-46.
2. Hsieh SD, Yoshinaga H, M uto T: Waist-to-height ratio, a
simple and practical index for ass essing central fat
distribution and metabolic risk in Japanese men and women.
Int J Obes Relat M etab Disord 2003; 27: 610–616.
3. Y Chiba, S Saitoh, et al. Relationship between Visceral F atand Cardiovas cular D isease Risk Factors: The Tanno andSobetsu Study. Hypertension Res earch (2007) 30, 229–236.
4. Fernando F. Ribeiro-Filho, et al. M ethods of Estimation of
Vis ceral Fat: Advantages of Ultrasonography. Obesity
Research Vol. 11 No. 12 December 2003
5. N Di Iorgi, S D M ittelman and V Gilsanz: Differential effectof marrow adiposity and vis ceral and subcut aneous fat on
cardiovascular risk in young, healthy adults, International
Journal of Obesity (2008) 32, 1854–1860
6. You Zhou, Norihiro Koizumi, Naoto Kubota, Takaharu
Asano, Takashi M ochizuki, Takashi Kadowaki, Ichiro
Sakuma, Hongen Liao: Fast and Accurate Ultrasonography
for Visceral F at M easurement, M ICCAI 2010, LNCS 6262,
pp.50-58.
7. Stien, A . and Irvine, R.J. and Langvatn, R. and Ropstad, E.:
Evaluation of ultrasound scanning as a method for measuringsubcutaneous fat in Svalbard reindeer, Rangifer, 23 (2):71-73, 2010.

Fig. 6. Camprison of our U S-bas ed method and CT method.
6. Discussions and Conclusion
This paper proposes an analysis on the regional fatness
distribution at navel level, and then based on this analysis, anovel U S-based method for estimation of SFA and VFA has
been developed. A fast and convenient diagnosis operation w as
introduced and a stable estimation method was proposed toestimate one patient’s VFA from US data automatically. As far
as we know, this is the first attempt to compute SFA by
ultrasound, and our results were shown to be relatively
correlated with CT measurements.
For VFA assessment, compared w ith existing s imple US
methods presented in [3][4][7], the accuracy of our method isextremely high, and it almost holds the same level of accuracy
with the method in [6]. In addition, another main advantage ofour method is its low level of dependency to the quality ofultrasound image. Compared w ith the complex VFA estimation
method presented in [6], the information detected from US by
our method is so stable that it is almost impossible to disturbed
by unexpectable turbulence of image quality. As a result, ourmethod can be easily used into mor e general clinicalenvironment with a low er requirement on US device.
However, one main limitation of this present study is that all
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