TINSLEY, FRANK C., GERSH Z. TAICHER, AND MARK L. HEIMAN. Evaluation of a quantitative magnetic resonance method for mouse whole body composition analysis. Obes Res. 2004;12:150 -160. Objective: To evaluate applicability, precision, and accuracy of a new quantitative magnetic resonance (QMR) analysis for whole body composition of conscious live mice. Research Methods and Procedures: Repeated measures of body composition were made by QMR, DXA, and classic chemical analysis of carcass using live and dead mice with different body compositions. Caloric lean and dense diets were used to produce changes in body composition. In addition, different strains of mice representing widely diverse populations were analyzed. Results: Precision was found to be better for QMR than for DXA. The coefficient of variation for fat ranged from 0.34% to 0.71% compared with 3.06% to 12.60% for DXA. Changes in body composition in response to dietary manipulation were easily detected using QMR. An increase in fat mass of 0.6 gram after 1 week (p Ͻ 0.01) was demonstrated in the absence of hyperphagia or a change in mean body weight. Discussion: QMR and DXA detected similar fat content, but the improved precision afforded by QMR compared with DXA and chemical analysis allowed detection of a significant difference in body fat after 7 days of consuming a diet rich in fat even though average body weight did not significantly change. QMR provides a very precise, accurate, fast, and easy-to-use method for determining fat and lean tissue of mice without the need for anesthesia. Its ability to detect differences with great precision should be of value when characterizing phenotype and studying regulation of body composition brought about by pharmacological and dietary interventions in energy homeostasis.

in bone tissue there is a strong correlation between hydrogen NMR signal and bone-mineral density as measured by X-ray. QMR provides a very precise, accurate, fast, and easy to use method for determining fat and lean mass of mice without the need for anesthesia. Its ability to detect differences and monitor changes in body composition in mice with great precision should be of great value in characterizing phenotypes and studying drugs affecting obesity.

Quantitative magnetic resonance (QMR) is a nuclear magnetic resonance-based method for measuring the fat, lean, and water content of the total body of the live animal. The purpose of this study was to evaluate the use of QMR for measuring the body composition of chickens while comparing QMR results to those obtained by dual x-ray absorptiometry (DXA) and chemical analysis (CA). A total of 191 birds were scanned live (nonanesthetized) by QMR, killed, and then scanned by DXA. The birds were Ross 708 broiler chickens and ranged in weight from 786 to 3,130 g. In addition, 48 of the carcasses were chemically analyzed for total body lipid, water, and ash content. Compared with CA, QMR underestimated the percentage of total body fat by 34% whereas DXA overestimated the percentage of fat by 50% (10.35 ± 3.35 by CA vs. 6.73 ± 3.90 by QMR and 15.55 ± 4.01 by DXA; P < 0.05). Both QMR and DXA measurements of percentage total body fat were highly correlated with the CA measurement (R(2) = 0.94 and 0.68, respectively). Both QMR and DXA estimates of total body water were close to the CA measurement (1,166 ± 277 g by CA vs. 1,214 ± 279 g by QMR and 1,217 ± 255 g by DXA; P > 0.05), with R(2) values of 0.90 and 0.91, respectively. Based on regression analysis, when prediction equations were applied to the entire group of birds, the QMR and DXA measurements of total body water and total body lean mass were in good agreement, with no significant difference (1,125 ± 244 g vs. 1,135 ± 246 g and 1,377 ± 311 g vs. 1,403 ± 309 g, respectively; P > 0.05) and highly correlated (R(2) = 0.97 for both). Likewise, the QMR measurement of total body fat agreed closely with that measured by DXA (164 ± 48 g and 167 ± 47 g, respectively) and was highly correlated (R(2) = 0.72). The results of this study demonstrate that with proper calibration, both QMR and DXA can provide accurate measurements of the body composition of chickens. The major advantage of the QMR method is that no anesthesia is required, thus facilitating the ease of measurement and repeated measurements.

During studies of the growth of neonatal piglets it is important to be able to accurately assess changes in body composition. The purpose of this study was to compare the in vivo measurements of body composition of small piglets using QMR and DXA and to validate those results by chemical analysis. A total of 25 pigs (1.7 ‐ 4.1 kg) were measured by QMR (EchoMRI) and by DXA (Lunar Prodigy). Both instruments were tested as supplied by the manufacturer, with QMR measuring total body fat, water, and lean and DXA measuring total body fat and lean. The chemical measure of total body fat was highly correlated with both the QMR (r = 0.96) and DXA (r = 0.98) fat measurements and the correlation (r) between QMR and DXA was 0.93. However, DXA overestimated the amount of fat by 31% (P<0.05), whereas QMR overestimated the amount of fat by only 3.4% (P>0.05). The chemical measure of total body water was highly correlated with both the QMR (r = 0.98) and DXA (r = 0.99) measurements of total body lean mass and the correlation between QMR and DXA was 0.99. The DXA measure of total body lean was 18% more (P<0.05) than that measured by QMR. The QMR measure of total body water was 8% less (P>0.05) than that measured by chemical analysis. These studies indicate that QMR represents a potentially accurate method for measuring the body composition of piglets offers the advantages of no exposure to X‐ray radiation and measurement without the pig being anesthetized.