Quantitative Magnetic Resonance Fat Measurements in Humans Correlate With Established Methods but Are Biased

Abstract

Precision and accuracy of the quantitative magnetic resonance (QMR) system for measuring fat in phantoms and total body fat (TBF) in humans were investigated. Measurements were made using phantoms: oil, beef with water, beef with oil, and humans with oil and water. TBFQMR in humans was compared with TBF by a four-compartment model (TBF4C). The coefficient of variation (CV) for replicate TBFQMR was 0.437%. QMR fat was lower at 23 °C vs. 37 °C. The fat increase in QMR phantom studies was consistent with the oil increase. When oil was added with humans, the increase in TBFQMR was >250 g for the initial 250 g of oil. With additional oil increments, the increase in TBFQMR was consistent with the amount of oil added. When water was added with humans, the TBFQMR increased independent of the amount of water added. TBFQMR was significantly less (mean ± s.e.) than TBF4C (females: −0.68 ± 0.27 kg, males: −4.66 ± 0.62 kg; P = 0.0001), TBFBV (females: −1.90 ± 0.40 kg; males: −5.68 ± 0.75 kg; P = 0.0001), and TBFD2O for males, but greater for females (1.19 ± 0.43 kg vs. −3.69 ± 0.81 kg for males; P = 0.0003). TBFQMR was lower than TBFiDXA with the difference greater in males (P = 0.001) and decreased with age (P = 0.011). The strong linear relationships between TBFQMR and TBF4C, TBFBV, and TBFD2O with slopes consistent with unity suggest that modifications are required to improve the accuracy. Should the latter be accomplished, QMR holds promise as a highly precise, rapid, and safe, noninvasive method for estimating the amount of and changes in TBF in overweight and severely obese persons.

In VivoDetermination of Body Composition in Zebrafish (Danio rerio) by Quantitative Magnetic Resonance

“…8,[17][18][19][20] However, several studies also showed that QMR underestimated FM when using deuterium dilution and a fourcomponent model as the gold standard. [21][22][23][24][25][26] Values for both FM and FFM, while significantly different from CCA values, were still significantly correlated for each body compartment measure. For FFM, residual bias increased significantly with increasing CCA mass, while residual bias did not occur for FM.…”

Accuracy of quantitative magnetic resonance and eight-electrode bioelectrical impedance analysis in normal weight and obese women

“…The FM underestimation by QMR in obese women is in accordance with a previous report. 6 Combining normal weight and obese women into one group neutralized the differences in the present study, and resulted in very accurate average FM estimates by QMR, although the common BlandeAltman plot showed that FM errors were systematic. Hence, QMR could possibly be appropriate for large heterogeneous populations.…”

“…The nuclear magnetic resonance signals from fat, free water and muscle mass differ, 8 and multiple linear regression prediction formulas calibrated against canola oil, lean animal tissues and tap water are used to calculate fat, lean mass and free water. 6 Total body water is then derived from the difference between the total amount of protons and the fat found by regression analysis. 8 Consequently, TBW by QMR includes the sum of free water and water in lean mass.…”

“…7 The QMR technique is based on nuclear magnetic resonance. 8 Accuracy of cross-sectional FM measurements in humans by QMR has previously been scarcely evaluated, showing both underestimation of average FM 6,9 as well as overestimation. 5 The FM bias increased with increasing body weight (BW).…”

“…Quantitative magnetic resonance (QMR) provides excellent precision 5,6 and is a safe and noninvasive method for measuring body composition that is convenient for the subjects. 7 The QMR technique is based on nuclear magnetic resonance.…”