Abstract
ObjectivesTo determine precision of magnetic resonance imaging (MRI) based fat and muscle quantification in a group of postmenopausal women. Furthermore, to extend the method to individual muscles relevant to upper-body exercise.Materials and methodsThis was a sub-study to a randomized control trial investigating effects of resistance training to decrease hot flushes in postmenopausal women. Thirty-six women were included, mean age 56 ± 6 years. Each subject was scanned twice with a 3.0T MR-scanner using a whole-body Dixon protocol. Water and fat images were calculated using a 6-peak lipid model including R2*-correction. Body composition analyses were performed to measure visceral and subcutaneous fat volumes, lean volumes and muscle fat infiltration (MFI) of the muscle groups’ thigh muscles, lower leg muscles, and abdominal muscles, as well as the three individual muscles pectoralis, latissimus, and rhomboideus. Analysis was performed using a multi-atlas, calibrated water-fat separated quantification method. Liver-fat was measured as average proton density fat-fraction (PDFF) of three regions-of-interest. Precision was determined with Bland-Altman analysis, repeatability, and coefficient of variation.ResultsAll of the 36 included women were successfully scanned and analysed. The coefficient of variation was 1.1% to 1.5% for abdominal fat compartments (visceral and subcutaneous), 0.8% to 1.9% for volumes of muscle groups (thigh, lower leg, and abdomen), and 2.3% to 7.0% for individual muscle volumes (pectoralis, latissimus, and rhomboideus). Limits of agreement for MFI was within ± 2.06% for muscle groups and within ± 5.13% for individual muscles. The limits of agreement for liver PDFF was within ± 1.9%.ConclusionWhole-body Dixon MRI could characterize a range of different fat and muscle compartments with high precision, including individual muscles, in the study-group of postmenopausal women. The inclusion of individual muscles, calculated from the same scan, enables analysis for specific intervention programs and studies.
Highlights
Body composition measurements are increasingly important for diagnosis and monitoring of metabolic diseases [1,2], muscle diseases [3] and metabolic components of other diseases [4,5,6]
Body composition refers to the compartmental distribution of fat and muscle within the body including visceral adipose tissue volume (VAT), abdominal subcutaneous adipose tissue volume (ASAT), liver-fat fraction, muscle group volumes such as thigh muscles, individual muscle volumes, and muscle fat infiltration (MFI)
We found a coefficient of variation (CV) of 1.54% for VAT and 1.06% for ASAT, which was similar to previously published results by Borga et al [10] (VAT CV 1.6% and ASAT CV 1.1%) and results reported by Newman et al [21] (ASAT CV 2.98%), but lower than results reported by Middleton et al [22] who reported a VAT CV of 3.3% and ASAT CV of 2.2%
Summary
Body composition measurements are increasingly important for diagnosis and monitoring of metabolic diseases [1,2], muscle diseases [3] and metabolic components of other diseases [4,5,6]. Several methods have been put forward to determine fat and muscle distribution in the body, such as dual-energy x-ray absorptiometry (DXA) [7] and bioimpedance (BIA) [8]. These methods do not allow direct quantification of absolute compartmental tissue volumes in a consistent and accurate manner. Novel magnetic resonance imaging (MRI) techniques, on the other hand, allow rapid body composition measurements with high precision and accuracy, which makes it possible to utilize the techniques in research and clinical applications. Magnetic resonance imaging provides tomographic images with high soft tissue contrast, which enables quantification of fat and muscle compartmental volumes. Scanning the whole body with sufficient spatial resolution is achievable in 6–8 minutes on modern scanner systems, using specialized body composition protocols available today [10, 11]
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