Lean R value for DXA two-component soft-tissue model: influence of age and tissue or organ type

Phenotyping of the Visceral Adipose Tissue Using Dual Energy X-Ray Absorptiometry (DXA) and Magnetic Resonance Imaging (MRI) in Pigs

The objective of this study was to phenotype visceral adipose tissue (VAT) in pigs. In this context, the ability to detect VAT by using the DXA CoreScan mode within the enCORE software, version 17 (GE Healthcare) was evaluated in comparison with MRI measurements (Siemens Magnetom C!) of the same body region. A number of 120 crossbred pigs of the F1 and F2 generation, with the parental breeds Large White, Landrace, Piétrain, and Duroc, were examined at an age of 150 days. A whole-body scan in two different modes ("thick", "standard") was carried out by a GE Lunar iDXA scanner. Very strong relationships (R² = 0.95, RMSE = 175cm³) were found for VAT between the two DXA modes. The comparison of VAT measured by MRI and DXA shows high linear relationships ("thick": R² = 0.76, RMSE = 399.25cm³/"standard": R² = 0.71, RMSE = 443.42cm³), but is biased, according to the Bland-Altman analysis. A variance analysis of VAT shows significant differences for both DXA modes and for MRI between male and female pigs, as well as between F1 and F2. In conclusion, DXA "CoreScan" has the ability to estimate VAT in pigs with a close relationship to MRI but needs bias correction.

Air displacement plethysmography: cradle to grave

Differences in body composition are associated with increased disease risk in various stages of life. Despite numerous available methods in assessing body composition (air displacement plethysmography, dual-energy X-ray absorptiometry, bioelectrical impedance, hydrometry, and magnetic resonance imaging), due to innate technical limitations, the ability for one singular method to track body composition over the life span (ie, infancy to adulthood) is challenging and imperfect. The primary goal of this review is to determine if there are body composition methods that can accurately track body composition from infancy into adulthood. After careful consideration and taking into account the best available scientific evidence, we feel air displacement plethysmography is the best instrument at this time for tracking body composition, starting in infancy and forward into adulthood, partly because it is the only "practical" clinical tool currently available for use during infancy.

Validation of longitudinal DXA changes in body composition from pre- to mid-adolescence using MRI as reference

Dual-energy X-ray absorptiometry (DXA) has been used extensively for bone mineral density and body composition assessments. Surprisingly, the role of DXA in monitoring changes in children's body composition, using direct imaging methods such as magnetic resonance imaging (MRI) as reference, is still yet to be validated. We aimed at validating the use of DXA in monitoring change in the thigh lean soft tissue mass (LSTM) and fat mass (FM) when compared with thigh skeletal muscle mass (SM) and FM, measured using MRI as the reference standard, from childhood to midadolescence. At baseline, 22 healthy children (16 boys and 6 girls) aged 8-11yr were included, and then recalled at pubertal stage Tanner2-Tanner4. LSTM-DXA and FM-DXA of the mid-third femur and SM-MRI and FM-MRI of the same region were measured on the same day. The same protocol was repeated 26-48mo later. At baseline, DXA overestimated LSTM-DXA on average by 222g (95% confidence interval [CI]: 33-410g) with a concordance C-LSTM=0.576. FM-MRI and FM-DXA were not significantly different (95% CI=213 to 199g, the C-FM=0.907). At follow-up, change in LSTM-DXA and FM-DXA were not significantly different to change in SM-MRI and FM-MRI, respectively (95% CI of the difference was -278 to 208g for LSTM, and -148 to 236g for FM). The coefficient of concordance between the 2 techniques was 0.88 for both LSTM and FM. This study validates the use of DXA in monitoring changes in LSTM and FM in children, confirming its significant potential in clinical and research roles in pediatric body composition.

Body fat measurement in adolescent athletes: multicompartment molecular model comparison

OBJECTIVE

To assess the accuracy of air displacement plethysmography (ADP) and dual energy X-ray absorptiometry (DXA) per cent body fat (%BF) estimations in comparison with a reference five-compartment (5C) model used as the reference method.

DESIGN

Cross-sectional study.

SETTING

Outpatient University Laboratory, Lisbon, Portugal.

METHODS

A total of 32 girls (age: 15.1+/-0.3 years) and 46 boys (age: 15.3+/-1.2 years) athletes were measured. Body volume was assessed by ADP; bone mineral content was assessed by DXA; and total-body water was assessed by deuterium dilution. Statistical analyses included examination of the coefficient of correlation (r), standard error of estimation (s.e.e.), slope, intercept, and pure error (p.e.) and the agreement between models.

RESULTS

For boys and girls, differences between the 5C model and ADP %BF were 0.2 and 1.7% (r = 0.86 and 0.98, s.e.e.= 2.50 and 1.55%, p.e.=2.77 and 2.23%), respectively. Differences between the 5C model and DXA %BF were -1.0 and -3.7% (r = 0.85 and 0.91, s.e.e.= 2.60 and 2.91%, p.e.= 2.90 and 4.66%), for boys and girls, respectively. For girls, regression between ADP and DXA against the reference method did not differ from the line of identity (P > 0.05) while for boys differences were found (P < 0.05). Dual energy X-ray absorptiometry overestimated %BF, particularly in girls. For both genders, large limits of agreement were found between the reference method and both techniques, with the exception of ADP in female athletes.

CONCLUSION

We conclude that the two techniques were not precise for individual %BF prediction, though ADP revealed better agreement for girls. However, considering all performance criteria for the mean group, our analysis highlights ADP as a valid and nonbiased tool for the evaluation of body composition in adolescent athletes.

Techniques used in measuring human body composition

Remarkable progress is evident in the field of body composition research. This review summarizes main body composition research concepts, examines new component measurement methodologies and identifies potential areas for future research. As the dual-energy X-ray absorptiometry is now gaining acceptance, both clinically and in the research laboratory, as a useful body composition method, particular emphasis is placed on this important approach.