Computer tomographic investigation of subcutaneous adipose tissue as an indicator of body composition

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Abstract

Background

Modern computer tomography (CT) equipment can be used to acquire whole-body data from large animals such as pigs in minutes or less. In some circumstances, computer assisted analysis of the resulting image data can identify and measure anatomical features. The thickness of subcutaneous adipose tissue at a specific site measured by ultrasound, is used in the pig industry to assess adiposity and inform management decisions that have an impact on reproduction, food conversion performance and sow longevity. The measurement site, called "P2", is used throughout the industry. We propose that CT can be used to measure subcutaneous adipose tissue thickness and identify novel measurement sites that can be used as predictors of general adiposity.

Methods

Growing pigs ( N = 12), were each CT scanned on three occasions. From these data the total volume of adipose tissue was determined and expressed as a proportion of total volume (fat-index). A computer algorithm was used to determined 10,201 subcutaneous adipose thickness measurements in each pig for each scan. From these data, sites were selected where correlation with fat-index was optimal.

Results

Image analysis correctly identified the limits of the relevant tissues and automated measurements were successfully generated. Two sites on the animal were identified where there was optimal correlation with fat-index. The first of these was located 4 intercostal spaces cranial to the caudal extremity of the last rib, the other, a further 5 intercostal spaces cranially.

Conclusion

The approach to image analysis reported permits the creation of various maps showing adipose thickness or correlation of thickness with other variables by location on the surface of the pig. The method identified novel adipose thickness measurement positions that are superior (as predictors of adiposity) to the site which is in current use. A similar approach could be used in other situations to quantify potential links between subcutaneous adiposity and disease or production traits.

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Most cited references 25

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Technologies for the control of fat and lean deposition in livestock.

Martin N Sillence (2004)

When the ratio of lean to fat deposition is improved, so is feed conversion efficiency. Net benefits may include lower production costs, better product quality, less excretion of nitrogenous wastes into the environment, decreased grazing pressure on fragile landscapes, and reduced pressure on world feed supplies. However, finding a way to achieve these goals that is reliable, affordable, and acceptable to the majority of consumers has proved to be a major challenge. Since the European Union banned hormonal growth promoters (HGPs) 15 years ago, countries such as Australia and the United States have licensed new products for livestock production, including bovine growth hormone (GH), porcine and equine GH, and the beta-agonist ractopamine. There has also been considerable research into refining these products, as well as developing new technologies. Opportunities to improve beta-agonists include lessening their effects on meat toughness, reducing adverse effects on treated animals, and prolonging their duration of action. In the last regard, the combined use of a beta-agonist with GH, which upregulates beta-adrenoceptors, can produce an outstanding improvement in carcass composition and feed efficiency. Insulin-like growth factor-1 (IGF-1) mediates many of the actions of GH, but has proved to be of more use as a growth reporter/selection marker in pigs, than as a viable treatment. However, a niche for this product could exist in the manipulation of neonatal growth, causing a life-long change in lean:fat ratio. Another significant advance in endocrinology is the discovery of hormones secreted by muscle and fat cells, that regulate feed intake, energy metabolism, and body composition. Leptin, adiponectin and myostatin were discovered through the study of genetically obese, or double-muscled animals. Through genetic manipulation, there is potential to exploit these findings in a range of livestock species, although the production of transgenic animals is still hampered by the poor level of control over gene expression, and faces an uphill battle over consumer acceptance. There are several alternatives to HGPs and transgenics, that are more likely to gain world-wide acceptance. Genetic selection can be enhanced by using markers for polymorphic genes that control fat and lean, such as thyroglobulin, or the callipyge gene. Feed additives of natural origin, such as betaine, chromium and conjugated linoleic acid, can improve the fat:lean ratio under specific circumstances. Additionally, 'production vaccines' have been developed, which alter the neuro-endocrine system by causing an auto-immune response. Thus, antibodies have been used to neutralise growth-limiting factors, prolong the half-life of anabolic hormones, or activate hormone receptors directly. Unfortunately, none of these technologies is sufficiently well advanced yet to rival the use of exogenous HGPs in terms of efficacy and reliability. Therefore, further research is needed to find ways to control fat and lean deposition with due consideration of industry needs, animal welfare and consumer requirements.

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A multicompartment body composition technique based on computerized tomography.

M Alpsten, Peter Kvist, B Chowdhury … (1994)

The objective of this study was to develop a body composition method based on computerized tomography (CT) which would make it possible to divide the body into multiple compartments at the tissue and organ level. Eight healthy males (21-42 years old) with BMIs ranging from 18.6 to 25.3 kg/m2 were used for the methodological development. Areas of tissues, organs and air/gas were measured in 28 cross-sectional scans having defined and identical positions in all examined subjects. The area determinations were performed with the following attenuation intervals (given in Hounsfield units, HU): air, gas and lungs: -1001 to -191 HU; adipose tissue (AT): -190 to -30 HU; all other soft tissues and organs: -29 to +151 HU; skeleton: 152 to 2500 HU. Various tissue and organ areas in the -29 to +151 HU interval were obtained by means of cursor circumscriptions, while area determinations in other intervals were based on the number of pixels fulfilling given attenuation criteria. Volumes of tissues, organs and gas were obtained from corresponding areas and the distances between the scans. The body was divided into 12 main volumes of tissues, organs and gas that could be further subdivided by region. The main volumes observed (in litres; mean +/- s.d.) were: skeleton (subdivisible into dense skeleton, red and yellow bone marrow): 8.7 +/- 0.9; skeletal muscle: 31.9 +/- 5.1; visceral AT (subdivisible into intra- and retroperitoneal, cardiac, other thoracic AT): 3.0 +/- 1.7; intra- and retroperitoneal organs other than AT: 4.6 +/- 0.8; gastrointestinal gas: 0.25 +/- 0.09; heart: 0.61 +/- 0.12; lungs and bronchial air: 5.1 +/- 1.1; other thoracic organs: 0.32 +/- 0.08; mammary glands: 0.001 +/- 0.004; CNS (subdivisible into brain and contents of spinal channel): 1.6 +/- 0.15; air in sinuses and trachea: 0.19 +/- 0.05; subcutaneous AT: 11.6 +/- 2.8; skin: 2.4 +/- 0.39. Precision errors as determined from double analyses of different tissue volumes ranged from 0.01 to 0.3 litres. For validation purposes, CT-estimated organ weights were obtained by multiplying organ volumes by their assumed densities. The sums of all organ weights were then compared with the measured body weights. The error calculated from the individual differences between these weights was 0.6 kg (0.85%). The multicompartmentation technique described has a high validity and reproducibility and is applicable over a wide range of medical fields which require body composition measurements at the tissue and organ level.

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Subdivision of the subcutaneous adipose tissue compartment and lipid-lipoprotein levels in women.

Patrick Couture, André Tchernof, Daniel Deschênes … (2003)

The aim of this study was to compare the relative importance of computed tomography-measured abdominal fat compartment areas, including adipose tissue located posterior to the subcutaneous Fascia, in predicting plasma lipid-lipoprotein alterations. Areas of visceral as well as subcutaneous deep and superficial abdominal adipose tissue were measured by computed tomography in a sample of 66 healthy women, ages 37 to 60 years, for whom a detailed lipid-lipoprotein profile was available. Strong significant associations were observed between visceral adipose tissue area and most variables of the lipid-lipoprotein profile (r = -0.25, p or = p < or = 0.0001). Although previous studies have generated controversial data as to which abdominal adipose tissue compartment was more closely associated with insulin resistance, our results suggest that visceral adipose tissue area is a stronger correlate of other obesity-related outcomes such as lipid-lipoprotein alterations.

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Author and article information

Journal

Journal ID (nlm-ta): Acta Vet Scand

Title: Acta Veterinaria Scandinavica

Publisher: BioMed Central

ISSN (Print): 0044-605X

ISSN (Electronic): 1751-0147

Publication date Collection: 2009

Publication date (Electronic): 1 July 2009

Volume: 51

Issue: 1

Page: 28

Affiliations

[1 ]Department of Small Animal Clinical Sciences, Faculty of Life Sciences, University of Copenhagen, 32 Dyrlaegevej, DK-1870 Frederiksberg C, Denmark

[2 ]Danish Pig Production, 3 Axeltorv, DK-1609 Copenhagen, Denmark

Article

Publisher ID: 1751-0147-51-28

DOI: 10.1186/1751-0147-51-28

PMC ID: 2710334

PubMed ID: 19570228

SO-VID: 57da6953-cc48-406c-a305-f626f2ed7522

License:

This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Computer tomographic investigation of subcutaneous adipose tissue as an indicator of body composition

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Abstract

Background

Methods

Results

Conclusion

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Most cited references 25

Technologies for the control of fat and lean deposition in livestock.

A multicompartment body composition technique based on computerized tomography.

Subdivision of the subcutaneous adipose tissue compartment and lipid-lipoprotein levels in women.

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