A method is presented for rapid simultaneous quantification of the longitudinal T 1 relaxation, the transverse T 2 relaxation, the proton density (PD), and the amplitude of the local radio frequency B 1 field. All four parameters are measured in one single scan by means of a multislice, multiecho, and multidelay acquisition. It is based on a previously reported method, which was substantially improved for routine clinical usage. The improvements comprise of the use of a multislice spin-echo technique, a background phase correction, and a spin system simulation to compensate for the slice-selective RF pulse profile effects. The aim of the optimization was to achieve the optimal result for the quantification of magnetic resonance parameters within a clinically acceptable time. One benchmark was high-resolution coverage of the brain within 5 min. In this scan time the measured intersubject standard deviation (SD) in a group of volunteers was 2% to 8%, depending on the tissue (voxel size ‫؍‬ 0.8 ؋ 0.8 ؋ 5 mm). As an example, the method was applied to a patient with multiple sclerosis in whom the diseased tissue could clearly be distinguished from healthy reference values. Additionally it was shown that, using the approach of synthetic MRI, both accurate conventional contrast images as well as quantification maps can be generated based on the same scan. Tissues in the human body can be distinguished with magnetic resonance imaging (MRI) depending on their MR parameters, such as the longitudinal T 1 relaxation, the transverse T 2 relaxation, and the proton density (PD). In clinical routine, the MR scanner settings, such as echo time (T E ), repetition time (T R ), and flip angle (␣), are most often chosen to highlight, or saturate, the image intensity of tissues, resulting in T 1 -weighting or T 2 -weighting in a contrast image. These procedures are well-established and relatively quick. A major disadvantage of using such contrast images is that the absolute intensity has no direct meaning and diagnosis relies on comparison with surrounding tissues in the image. In many cases it is therefore necessary to perform several different contrast scans. A more direct approach is the absolute quantification of the tissue parameters T 1 , T 2 , and PD. In this case, pathology can be examined on a pixel basis to establish the absolute deviation compared to the normal values. Automatic segmentation of such tissue images would be straightforward and the progress of the disease could then be expressed in absolute numbers. An excellent overview of the use of absolute quantification on neurodegenerative diseases is provided in Ref. 1.Although the advantages of absolute quantification are obvious, its clinical use is still limited. At least two major hurdles need to be addressed to stimulate widespread clinical usage. For many methods, the excessive scan time associated with the measurement of the three parameters has so far prohibited its clinical application. However, in recent years there has been substantial progress (see, e.g., R...

Based on the seminal observation by Cannon and Nedergaard 1 that human PET scans sometimes depicted a symmetric cold induced uptake of FDG-glucose, three independent studies, published in April 2009, demonstrated metabolically highly active brown adipose tissue (BAT) in adult humans [2][3][4] . Subsequent investigations demonstrated an inverse association of obesity and type 2 diabetes mellitus and the presence of active BAT [5][6][7] . A unique characteristic of BAT is the expression of uncoupling protein 1 (UCP1, also known as thermogenin). Activation of this transmembrane protein by fatty acids in response to adrenergic signaling short-circuits the inner mitochondrial membrane's proton gradient thereby uncoupling oxidative phosphorylation from ATP synthesis. Hence, chemical energy stored in the gradient is dissipated as heat allowing for efficient direct thermogenesis without shivering 8 . This adaptive defense against cold has been examined extensively in rodents and many aspects of BAT development and function have been elucidated. In rodents it is evident 3 that not only the distinct thermogenic BAT organ located in the interscapular region (iBAT) consists of brown adipocytes, but that a second type of brown adipocytes, so-called beige or brite cells can appear in white adipose tissue (WAT) depots in response to cold or 3-adrenergic stimuli 9,10 . Recently, lineage tracing experiments revealed that the two cell types have a different developmental origin 11 . While classical brown adipocytes and skeletal muscle cells arise from precursors in the dermomyotome 12 , beige/brite cells seem to originate from endothelial and perivascular cells within WAT depots [13][14][15] . A recent study by Wu et al suggests that the previously described depots of human BAT are of the beige/brite type and raises the question whether humans altogether lack classical brown adipocytes 16 , this has also been the topic of a recent review 17 . Histomorphological studies performed in the 1970s indicated the existence of brown adipocytes within the interscapular region in human infants and that these disappeared with age 18 . Using a combination of high resolution imaging techniques and morphological and biochemical analyses, we tested the hypothesis that human infants, like small mammals, possess an anatomically distinguishable iBAT depot consisting of classical brown adipocytes, a cell type so far not proven to exist in humans.In an attempt to visualize potential iBAT in humans we performed post mortem MR imaging of eight human infants. Using the fat fraction method 19 we did not only identify BAT depots in the supraclavicular region, but importantly also a fat depot in the interscapular region presenting with an intermediate fat fraction as opposed to the high fat fraction of the surrounding subcutaneous WAT (Supplementary Fig. 1). Using a three dimensional reconstruction we were able to compute the volume of the tissue depot with an average (±SD) volume of 3.6±2.4 ml. Figure 1 displays a representative reconstruction of the iBAT...

This paper gives a brief overview of common non-invasive techniques for body composition analysis and a more in-depth review of a body composition assessment method based on fat-referenced quantitative MRI. Earlier published studies of this method are summarized, and a previously unpublished validation study, based on 4753 subjects from the UK Biobank imaging cohort, comparing the quantitative MRI method with dual-energy X-ray absorptiometry (DXA) is presented. For whole-body measurements of adipose tissue (AT) or fat and lean tissue (LT), DXA and quantitative MRIs show excellent agreement with linear correlation of 0.99 and 0.97, and coefficient of variation (CV) of 4.5 and 4.6 per cent for fat (computed from AT) and LT, respectively, but the agreement was found significantly lower for visceral adipose tissue, with a CV of >20 per cent. The additional ability of MRI to also measure muscle volumes, muscle AT infiltration and ectopic fat, in combination with rapid scanning protocols and efficient image analysis tools, makes quantitative MRI a powerful tool for advanced body composition assessment.

The method accurately quantified the whole-body skeletal muscle volume and the volume of separate muscle groups independent of field strength and image resolution.

ObjectiveThis study aimed to investigate the value of imaging‐based multivariable body composition profiling by describing its association with coronary heart disease (CHD), type 2 diabetes (T2D), and metabolic health on individual and population levels.MethodsThe first 6,021 participants scanned by UK Biobank were included. Body composition profiles (BCPs) were calculated, including abdominal subcutaneous adipose tissue, visceral adipose tissue (VAT), thigh muscle volume, liver fat, and muscle fat infiltration (MFI), determined using magnetic resonance imaging. Associations between BCP and metabolic status were investigated using matching procedures and multivariable statistical modeling.ResultsMatched control analysis showed that higher VAT and MFI were associated with CHD and T2D (P < 0.001). Higher liver fat was associated with T2D (P < 0.001) and lower liver fat with CHD (P < 0.05), matching on VAT. Multivariable modeling showed that lower VAT and MFI were associated with metabolic health (P < 0.001), and liver fat was nonsignificant. Associations remained significant adjusting for sex, age, BMI, alcohol, smoking, and physical activity.ConclusionsBody composition profiling enabled an intuitive visualization of body composition and showed the complexity of associations between fat distribution and metabolic status, stressing the importance of a multivariable approach. Different diseases were linked to different BCPs, which could not be described by a single fat compartment alone.

IntroductionQuantitative and accurate measurements of fat and muscle in the body are important for prevention and diagnosis of diseases related to obesity and muscle degeneration. Manually segmenting muscle and fat compartments in MR body-images is laborious and time-consuming, hindering implementation in large cohorts. In the present study, the feasibility and success-rate of a Dixon-based MR scan followed by an intensity-normalised, non-rigid, multi-atlas based segmentation was investigated in a cohort of 3,000 subjects.Materials and Methods3,000 participants in the in-depth phenotyping arm of the UK Biobank imaging study underwent a comprehensive MR examination. All subjects were scanned using a 1.5 T MR-scanner with the dual-echo Dixon Vibe protocol, covering neck to knees. Subjects were scanned with six slabs in supine position, without localizer. Automated body composition analysis was performed using the AMRA Profiler™ system, to segment and quantify visceral adipose tissue (VAT), abdominal subcutaneous adipose tissue (ASAT) and thigh muscles. Technical quality assurance was performed and a standard set of acceptance/rejection criteria was established. Descriptive statistics were calculated for all volume measurements and quality assurance metrics.ResultsOf the 3,000 subjects, 2,995 (99.83%) were analysable for body fat, 2,828 (94.27%) were analysable when body fat and one thigh was included, and 2,775 (92.50%) were fully analysable for body fat and both thigh muscles. Reasons for not being able to analyse datasets were mainly due to missing slabs in the acquisition, or patient positioned so that large parts of the volume was outside of the field-of-view.Discussion and ConclusionsIn conclusion, this study showed that the rapid UK Biobank MR-protocol was well tolerated by most subjects and sufficiently robust to achieve very high success-rate for body composition analysis. This research has been conducted using the UK Biobank Resource.

Which has been published in final form at https://dx.doi.org/10.1002/nbm.3432The WestminsterResearch online digital archive at the University of Westminster aims to make the research output of the University available to a wider audience. Copyright and Moral Rights remain with the authors and/or copyright owners.Whilst further distribution of specific materials from within this archive is forbidden, you may freely distribute the URL of WestminsterResearch: ((http://westminsterresearch.wmin.ac.uk/).In case of abuse or copyright appearing without permission e-mail repository@westminster.ac.uk Graphical abstractIn this study we tested the value of using the semi-automated fat-muscle-quantitation system analysis, the intra-observer coefficient of variation was 1.6 % for IAAT and 1.1 % for ASAT, the inter-observer coefficient of variation was 1.4 % for IAAT and 1.2 % for ASAT, the intra-observer correlation was 0.998 for IAAT and 0.999 for ASAT, and the inter-observer correlation was 0.999 for both IAAT and ASAT. These results indicate that precise and accurate measures of body fat content and distribution can be obtained in a fast and reliable form by the AMRA TM Profiler, opening up the possibility of large-scale human phenotypic studies.

Study Design Cross-sectional study. Background Findings of fat infiltration in cervical spine multifidus, as a sign of degenerative morphometric changes due to whiplash injury, need to be verified. Objectives To develop a method using water/fat magnetic resonance imaging (MRI) to investigate fat infiltration and cross-sectional area of multifidus muscle in individuals with whiplash-associated disorders (WADs) compared to healthy controls. Methods Fat infiltration and cross-sectional area in the multifidus muscles spanning the C4 to C7 segmental levels were investigated by manual segmentation using water/fat-separated MRI in 31 participants with WAD and 31 controls, matched for age and sex. Results Based on average values for data spanning C4 to C7, participants with severe disability related to WAD had 38% greater muscular fat infiltration compared to healthy controls (P = .03) and 45% greater fat infiltration compared to those with mild to moderate disability related to WAD (P = .02). There were no significant differences between those with mild to moderate disability and healthy controls. No significant differences between groups were found for multifidus cross-sectional area. Significant differences were observed for both cross-sectional area and fat infiltration between segmental levels. Conclusion Participants with severe disability after a whiplash injury had higher fat infiltration in the multifidus compared to controls and to those with mild/moderate disability secondary to WAD. Earlier reported findings using T1-weighted MRI were reproduced using refined imaging technology. The results of the study also indicate a risk when segmenting single cross-sectional slices, as both cross-sectional area and fat infiltration differ between cervical levels. J Orthop Sports Phys Ther 2016;46(10):886-893. Epub 2 Sep 2016. doi:10.2519/jospt.2016.6553.