A MULTICOMPARTMENT BODY-COMPOSITION TECHNIQUE BASED ON COMPUTERIZED-TOMOGRAPHY

The objective of this study was to develop a body composition method b ased on computerized tomography (CT) which would make it possible to d ivide the body into multiple compartments at the tissue and organ leve l. Eight healthy males (21-42 years old) with BMIs ranging from 18.6 t o 25.3kg/m(2) were used for the methodological development. Areas of t issues, organs and air/gas were measured in 28 cross-sectional scans h aving defined and identical positions in all examined subjects. The ar ea determinations were performed with the following attenuation interv als (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 o rgans: -29 to +151 HU; skeleton: 152 to 2500 HU. Various tissue and or gan areas in the -29 to +151 HU interval were obtained by means of cur sor circumscriptions, while area determinations in other intervals wer e based on the number of pixels fulfilling given attenuation criteria. Volumes of tissues, organs and gas were obtained from corresponding a reas and the distances between the scans. The body was divided into 12 main volumes of tissues, organs and gas that could be further subdivi ded by region. The main volumes observed (in litres; mean +/- s.d.) we re: skeleton (subdivisible into dense skeleton, red and yellow bone ma rrow): 8.7 +/- 0.9; skeletal muscle: 31.9 +/- 5.1; visceral AT (subdiv isible 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 a nd bronchial air: 5.1 +/- 1.1; other thoracic organs: 0.32 +/- 0.08; m ammary glands: 0.001 +/- 0.004; CNS (subdivisible into brain and conte nts 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. Precisio n errors as determined from double analyses of different tissue volume s ranged from 0.01 to 0.3 litres. For validation purposes, CT-estimate d organ weights were obtained by multiplying organ volumes by their as sumed densities. The sums of all organ weights were then compared with the measured body weights. The error calculated from the individual d ifferences between these weights was 0.6 kg (0.85%). The multicompartm entation technique described has a high validity and reproducibility a nd is applicable over a wide range of medical fields which require bod y composition measurements at the tissue and organ level.