(Radiology. 1999;211:283-286.)
© RSNA, 1999
Abdominal Fat: Standardized Technique for Measurement at CT1
Tohru Yoshizumi, RT,
Tadashi Nakamura, MD, PhD,
Mitsukazu Yamane, MD, PhD,
Abdul Hasan M. Waliul Islam, MD, PhD,
Masakazu Menju, MD, PhD,
Kouichi Yamasaki, MD, PhD,
Takeshi Arai, MD, PhD,
Kazuaki Kotani, MD, PhD,
Tohru Funahashi, MD, PhD,
Shizuya Yamashita, MD, PhD and
Yuji Matsuzawa, MD, PhD
1 From the Division of Radiology (T.Y., K.Y.) and the Department of Internal Medicine (M.M.), Minoh City Hospital, Osaka, Japan, and the Second Department of Internal Medicine, Osaka University Medical School, 2-2, Yamadaoka, Suita, Osaka 565-0871, Japan (T.N., M.Y., A.H.M.W.I., T.A., K.K., T.F., S.Y., Y.M.). Received September 29, 1997; revision requested December 15; revision received August 3, 1998; accepted October 26. Supported in part by grant 07671132 from the Ministry of Education, Science, and Culture of Japan and a grant from the Uehara Memorial Foundation, 1996. Address reprint requests to T.N.
 |
Abstract
|
|---|
The authors estimated abdominal fat distribution on the basis of measurements at computed tomography (CT). The attenuation range for fat tissue was defined as the interval within the mean plus or minus 2 SDs considered to be individual variation. Fat areas found with this method were closely correlated with those obtained by means of the computed planimetric method or with a fixed attenuation range from -190 to -30 HU as the standard of reference. Although the average CT numbers obtained with different scanners were distributed widely, the calculated fat areas were almost identical. This method might be a practical and standardized method at CT.
Index terms: Abdomen, anatomy, 70.92, 80.92 • Fat, CT • Computed tomography (CT), tissue characterization
|
Introduction
|
|---|
Abdominal obesity, as calculated with indexes such as the waist-to-hip circumference ratio, is related to metabolic disorders and hypertension and to an increased frequency of total mortality and cardiovascular disease (1–3). In recent years, intraabdominal visceral fat accumulation has been suggested as playing an important and etiologic role in these relationships (4–6). Computed tomography (CT) is an optimal technique for the accurate assessment of intraabdominal fat (7,8). We previously developed a method for measuring the fat volume in the human body by using this technique (7). Several studies revealed that visceral fat areas from a single scan obtained at the level of the umbilicus (approximately the level of L4 and L5) were highly correlated with the total visceral fat volume (7–9). Accordingly, a technique for the measurement of abdominal fat distribution based on findings at CT may be a practical and widely usable method for the evaluation of visceral fat accumulation, which is one of the most important cardiovascular risk factors. In the literature, however, several different attenuation ranges have been used to measure adipose tissue. Since the areas measured on the basis of different attenuation ranges may not be identical, we developed and evaluated a standardized method for measuring abdominal fat volume with CT.
|
Materials and Methods
|
|---|
Subjects
Our study population included 120 subjects (60 male and 60 female patients; age range, 15–70 years; mean age, 50 years ± 9) with a body mass index between 17.3 and 39.1 kg/m2 who were in- or outpatients at the Minoh City Hospital. In addition, six male volunteers, aged 32–40 years (mean age, 35 years ± 5) with a body mass index from 20.0 to 25.8 kg/m2 were also included for the evaluation of intra- and interobserver reproducibilities. An additional four male subjects, aged 25–48 years (mean age, 34 years ± 5) with a body mass index between 20.7 and 29.3 kg/m2, were included for the evaluation of interequipment reproducibility. This study was approved by the hospital's subcommittee on human studies, and all of the subjects gave their informed consent before participating in the investigation.
Method Protocol
CT (TCT-900S Helix; Toshiba, Tokyo, Japan) was performed with all subjects supine (120 kV, 200 mA, section thickness of 5 mm, scanning time of 2 seconds, field of view of 400 mm). Interequipment reproducibility was evaluated with five scanners: TCT-900S Helix, Toshiba; W-2000, Hitachi, Tokyo; Tomo Scan 300, Philips Medical Systems, Tokyo; Pro Seed, GE Yokogawa Medical Systems, Tokyo; and Somatom Plus, Siemens-Asahi Medical, Tokyo.
In the 120 subjects, subcutaneous and visceral fat areas were measured on one cross-sectional scan obtained at the umbilicus. Figure 1 shows a method for determining the adipose tissue area on a CT scan. A region of interest of the subcutaneous fat layer was defined by tracing its contour on each scan, and the attenuation range of CT numbers (in Hounsfield units) for fat tissue was calculated (Fig 1, part a). A histogram for fat tissue was computed on the basis of mean attenuation plus or minus 2 SD (Fig 1, part b). Intraperitoneal tissue was defined by tracing its contour on the scan (Fig 1, part c); within that region of interest, tissue with attenuation within the mean plus or minus 2 SD was considered to be the visceral fat area (Fig 1, part d). The pixels with attenuation values in the selected attenuation range were depicted as white. From those white regions, the total fat area was calculated by counting the number of pixels in each; the visceral fat area was subtracted, and the remainder was defined as the subcutaneous fat area.
View larger version (76K):
[in this window]
[in a new window]
|
Figure 1. Images demonstrate our method for determining abdominal fat distribution on a CT scan obtained at the umbilicus. a, The white line, made with a cursor, outlines the subcutaneous fat layer, in which attenuation is measured. b, Histogram of CT numbers (in Hounsfield units) in the region outlined in a (mean ± 2 SDs). c, The white line outlines the intraperitoneal tissue. WL = window level, WW = window width (in Hounsfield units). d, Within the region outlined in c, tissue with mean attenuation plus or minus 2 SDs was regarded as visceral fat tissue, which is white. The total fat area was calculated in the region outlining the circumference of the abdominal wall. The visceral fat area was subtracted, and the remainder was regarded as the subcutaneous fat area.
|
|
Results with this method were compared to those with a computerized planimetric method (KL 4300 Digitizer; Graphtec, Tokyo) and with a fixed attenuation range from -190 to -30 HU as the standard of reference, as defined by Sjöstrom et al (8) and Kvist et al (9).
Reliability of Method and Statistical Analysis
To determine the relationship between the total, visceral, and subcutaneous fat areas calculated with the different methods, analysis of variance was performed and intraclass and Spearman rank correlations were calculated. To determine intra- and interobserver reproducibilities, analysis of variance was performed for measurements in the six volunteers performed by different radiologic technicians. To evaluate interequipment reproducibility, the visceral fat area in the four volunteers was calculated with five different CT scanners.
|
Results
|
|---|
The distribution of average CT numbers for fat tissue in the 120 subjects is shown in Figure 2. Wide variation was seen among individual values. Accordingly, the fat area was determined on the basis of the area of variation. The Table shows the correlations between the areas determined with each method, which were extremely high.
View larger version (43K):
[in this window]
[in a new window]
|
Figure 2. Graph depicts distribution of the average CT numbers for the subcutaneous fat layer in 120 subjects.
|
|
Intraobserver variation was tested with measurements in one volunteer made by three observers. Each observer measured the total fat area five times. Errors were small (coefficient of variation, 1.7%, 1.5%, and 1.2%), with only slight variation (coefficient of variation range, 0.2%–0.8%). Interobserver variation was tested with measurements in six volunteers made by six observers. Each observer measured the visceral fat area in each volunteer one time. Errors were small (2.0%–4.9%), with only slight variation (mean coefficient of variation, 2.8% ± 1.2).
Interequipment variation was tested with measurements in four volunteers made with five CT scanners (Fig 3). The average CT numbers varied widely (Fig 3, top), but the visceral fat areas were almost identical (Fig 3, bottom).
View larger version (18K):
[in this window]
[in a new window]
|
Figure 3. Graphs depict findings obtained with five CT scanners in four volunteers. A = TCT-900S Helix, B = W-2000, C = Tomo Scan 300, D = Pro Seed, E = Somatom Plus.
|
|
|
Discussion
|
|---|
In the current study, we developed a practical, standardized technique for determining the abdominal fat area at CT. Several techniques have been developed to assess intraabdominal visceral fat. Although anthropometric measurements, such as waist-to-hip circumference ratio and sagittal abdominal diameter, are simple and useful indicators of visceral fat accumulation, these indexes are not always accurate (10–13). Ultrasonography (US) is also a technique that is suitable for evaluating intraabdominal fat; the time needed for a single measurement is very short, but reproducibility and accuracy are somewhat poor (14–16). The usefulness of US indexes for changes in fat mass during weight reduction has not been established. Although magnetic resonance (MR) imaging is also a technique that can be used to assess abdominal fat distribution (17,18), MR imaging equipment is expensive and less available than is CT equipment. Accordingly, CT may be a more commonly used and accurate technique for the measurement of visceral fat tissue. One of the limitations of this technique, however, is that it is not applicable in extremely obese subjects because of the weight limits for the table attached to the CT scanner.
The window width at CT defines the fat tissue area. In the literature, numerous window widths have been described to measure adipose tissue. We previously used a window width from -140 to -40 HU (7). Another group used various windows widths, such as -190 to -30 HU, -250 to -50 HU, -250 to -30 HU, -250 to -20 HU, -130 to -30 HU, and -150 to -50 HU (18). Rössner et al (19) performed CT measurements with a direct morphometric method in a cadaveric study; they reported close agreement among measurements with different window widths (-140 to -40 HU, -190 to -30 HU, and -250 to -50 HU) (19). However, the number of subjects in their study was small. In the present study, we observed wide variation among the average CT numbers for fat tissue in many subjects; this result suggests that area determined on the basis of a fixed attenuation range may be subject to error. To our knowledge, there has been no attempt to determine fat areas on the basis of a flexible attenuation range.
In the current study, we found that areas determined on the basis of an attenuation range of the mean plus or minus 2 SD are closely correlated with those calculated by means of the computed planimetric method or on the basis of a fixed attenuation range from -190 to -30 HU. We also found high inter- and intraobserver reproducibilities. It might be reasonable to establish an appropriate attenuation range for fat tissue each time measurements are made in an individual. We also found that average CT numbers for fat tissue varied considerably depending on the CT scanner; thus, fat areas determined on the basis of these measurements in the same subject might not be the same. With our method, however, we found that the fat areas measured in an individual were almost identical, regardless of the scanner used. Consequently, this method may be one of the most practical techniques for determining abdominal fat distribution at CT, with results that can be generalized among many medical institutions.
|
Footnotes
|
|---|
Author contributions: Guarantor of integrity of entire study, T.N.; study concepts, T.Y., T.N.; study design, T.Y.; definition of intellectual content, T.F.; literature research, T.N.; clinical studies, M.M., K.Y., M.Y., K.K., T.A.; data acquisition, A.H.M.W.I.; data analysis, T.Y.; statistical analysis, T.N.; manuscript preparation, T.N.; manuscript editing, S.Y.; manuscript review, Y.M.
|
References
|
|---|
-
Kissebah AH, Vydelingum N, Murray R, et al. Relation of body fat distribution to metabolic complications of obesity. J Clin Endocrinol Metab 1982; 54:254-260.[Abstract]
-
Peiris AN, Sothmann MS, Hoffmann RG, et al. Adiposity, fat distribution, and cardiovascular risk. Ann Intern Med 1989; 110:867-872.
-
Larsson B, Svardsudd K, Welin L, Wilhelmsen L, Bjorntorp P, Tibblin G. Abdominal adipose tissue distribution, obesity, and risk of cardiovascular disease and death: 13-year follow up of participants in the study of men born in 1913. Br Med J 1984; 288:1401-1404.
-
Fujioka S, Matsuzawa Y, Tokunaga K, Tarui S. Contribution of intra-abdominal fat accumulation to the impairment of glucose and lipid metabolism in human obesity. Metabolism 1987; 36:54-59.[Medline]
-
Kanai H, Matsuzawa Y, Kotani K, et al. Close correlation of intra-abdominal fat accumulation to hypertension in obese women. Hypertension 1990; 16:484-490.[Abstract/Free Full Text]
-
Nakamura T, Tokunaga K, Shimomura I, et al. Contribution of visceral fat accumulation to the development of coronary artery in non-obese men. Atherosclerosis 1994; 107:239-246.[Medline]
-
Tokunaga K, Matsuzawa Y, Ishikawa K, Tarui S. A novel technique for the determination of body fat by computed tomography. Int J Obes 1983; 7:437-445.[Medline]
-
Sjöstrom L, Kvist H, Cederbblad A, Tylen U. Determination of total adipose tissue and body fat in women by computed tomography, 40K, and tritium. Am J Physiol 1986; 250:E736-E745.[Abstract/Free Full Text]
-
Kvist H, Chowdhury B, Sjöstrom L, Tylen U, Cederblad A. Adipose tissue volume determination in males by computed tomography and 40K. Int J Obes 1988; 12:249-266.[Medline]
-
Ashwell M, Cole TJ, Dixon AK. Obesity: new insight into the anthropometric classification of fat distribution shown by computed tomography. Br Med J 1985; 290:1692-1694.
-
Seidell JC, Oosterlee A, Deurenberg P, Hautvast JGAJ, Ruiji JHJ. Abdominal fat depots measured with computed tomography: effects of degree of obesity, sex and age. Eur J Clin Nutr 1988; 42:805-815.[Medline]
-
Kvist H, Chowdhury B, Grangard U, Tylen U, Sjöstrom L. Total and visceral adipose-tissue volumes derived from measurements with computed tomography in adult men and women: predictive equations. Am J Clin Nutr 1988; 48:1351-1361.[Abstract/Free Full Text]
-
Svendsen OL, Hassager C, Bergmann I, Christiansen C. Measurement of abdominal and intra-abdominal fat in postmenopausal women by dual energy x-ray absorptiometry and anthropometry: comparison with computerized tomography. Int J Obes 1993; 17:45-51.
-
Armellini F, Zamboni M, Robbi R, et al. Total and intra-abdominal fat measurements by ultrasound and computerized tomography. Int J Obes 1993; 17:209-214.
-
Suzuki R, Watanabe S, Hirai Y, et al. Abdominal wall fat index, estimated by ultrasonography, for assessment of the ratio of visceral fat to subcutaneous fat in the abdomen. Am J Med 1993; 95:309-314.[Medline]
-
Bellisari A, Roche AF, Siervogel RM. Reliability of B-mode ultrasonic measurements of subcutaneous adipose tissue and intra-abdominal depth: comparisons with skinfold thickness. Int J Obes 1993; 17:475-480.
-
Seidell JC, Bakker CJG, van der Kooy K. Imaging techniques for measuring adipose-tissue distribution: a comparison between computed tomography and 1.5T magnetic resonance. Am J Clin Nutr 1990; 51:953-957.[Abstract/Free Full Text]
-
van der Kooy K, Seidell JC. Techniques for the measurement of visceral fat: a practical guide. Int J Obes 1993; 17:187-196.[Medline]
-
Rössner S, Bo WJ, Hiltbarandt E, et al. Adipose tissue determinations in cadavers: a comparison between cross-sectional planimetry and computed tomography. Int J Obes 1990; 14:893-902.[Medline]
This article has been cited by other articles:
|
|
|
|
 
F. Saremi, S. Channual, S. Krishnan, S. V. Gurudevan, J. Narula, and A. Abolhoda
Bachmann Bundle and Its Arterial Supply: Imaging with Multidetector CT--Implications for Interatrial Conduction Abnormalities and Arrhythmias
Radiology,
August 1, 2008;
248(2):
447 - 457.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
M. Kono, K. Tatsumi, T. Saibara, A. Nakamura, N. Tanabe, Y. Takiguchi, and T. Kuriyama
Obstructive Sleep Apnea Syndrome Is Associated With Some Components of Metabolic Syndrome
Chest,
May 1, 2007;
131(5):
1387 - 1392.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
E. Aghdassi, B. Arendt, I. E. Salit, and J. P. Allard
Estimation of Body Fat Mass Using Dual-Energy X-Ray Absorptiometry, Bioelectric Impedance Analysis, and Anthropometry in HIV-Positive Male Subjects Receiving Highly Active Antiretroviral Therapy
JPEN J Parenter Enteral Nutr,
March 1, 2007;
31(2):
135 - 141.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
D. Dey, T. Callister, P. Slomka, F. Aboul-Enein, H. Nishina, X. Kang, H. Gransar, N. D. Wong, R. Miranda-Peats, S. Hayes, et al.
Computer-Aided Detection and Evaluation of Lipid-Rich Plaque on Noncontrast Cardiac CT
Am. J. Roentgenol.,
June 1, 2006;
186(6_Supplement_2):
S407 - S413.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
T. Iwasaki, A. Nakajima, M. Yoneda, Y. Yamada, K. Mukasa, K. Fujita, N. Fujisawa, K. Wada, and Y. Terauchi
Serum Ferritin Is Associated With Visceral Fat Area and Subcutaneous Fat Area
Diabetes Care,
October 1, 2005;
28(10):
2486 - 2491.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
R. Shimura, K. Tatsumi, A. Nakamura, Y. Kasahara, N. Tanabe, Y. Takiguchi, and T. Kuriyama
Fat Accumulation, Leptin, and Hypercapnia in Obstructive Sleep Apnea-Hypopnea Syndrome
Chest,
February 1, 2005;
127(2):
543 - 549.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
M. Ryo, K. Maeda, T. Onda, M. Katashima, A. Okumiya, M. Nishida, T. Yamaguchi, T. Funahashi, Y. Matsuzawa, T. Nakamura, et al.
A New Simple Method for the Measurement of Visceral Fat Accumulation by Bioelectrical Impedance
Diabetes Care,
February 1, 2005;
28(2):
451 - 453.
[Full Text]
[PDF]
|
|
|
|
|
|
|
W. Shen, M. Punyanitya, Z. Wang, D. Gallagher, M.-P. St-Onge, J. Albu, S. B Heymsfield, and S. Heshka
Visceral adipose tissue: relations between single-slice areas and total volume
Am. J. Clinical Nutrition,
August 1, 2004;
80(2):
271 - 278.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
T. Okura, Y. Nakata, K. Yamabuki, and K. Tanaka
Regional Body Composition Changes Exhibit Opposing Effects on Coronary Heart Disease Risk Factors
Arterioscler. Thromb. Vasc. Biol.,
May 1, 2004;
24(5):
923 - 929.
[Abstract]
[Full Text]
|
|
|
|
|
|
|
H. Nagaretani, T. Nakamura, T. Funahashi, K. Kotani, M. Miyanaga, K. Tokunaga, M. Takahashi, H. Nishizawa, K. Kishida, H. Kuriyama, et al.
Visceral Fat Is a Major Contributor for Multiple Risk Factor Clustering in Japanese Men With Impaired Glucose Tolerance
Diabetes Care,
December 1, 2001;
24(12):
2127 - 2133.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
A. Taniguchi, Y. Nakai, M. Sakai, S. Yoshii, M. Hayashi, K. Nishitani, D. Hamanaka, S. Nakaishi, T. Kamamoto, I. Nagata, et al.
Relationship of Regional Adiposity to Insulin Resistance in Nonobese Japanese Type 2 Diabetic Patients
Diabetes Care,
May 1, 2001;
24(5):
966 - 968.
[Full Text]
|
|
|
TOP
Abstract
Introduction
