Magnetic resonance imaging in human body composition research. From quantitative to qualitative tissue measurement

Edema Index Predicts Mortality in Patients with Chronic Heart Failure: A Prospective, Observational Study

Introduction

Chronic fluid accumulation or congestion is considered an important pathophysiologic mechanism in heart failure, leading to cardinal symptoms such as dyspnea, pulmonary congestion, and pitting edema. Edema index (EI) recently emerged as a surrogate for extracellular volume status and has been proven to be able to reflect one's congestion status. In this study, we aimed to evaluate the prognostic value of EI in patients with chronic heart failure (CHF).

Methods

A total of 401 consecutive patients with CHF between August 2019 and October 2021 were prospectively enrolled. EI was obtained by InBody S10. The primary endpoint was long-term all-cause and cardiovascular mortality.

Results

Patients with high EI (>0.397) tended to be older, presented with atrial fibrillation, have higher N-terminal brain natriuretic peptide, and have higher creatinine (all p < 0.05). During a median follow-up of 1200 days, the all-cause and cardiovascular mortality rate was significantly higher in the high EI group compared to the low EI group (all-cause mortality rate 43.8% vs. 30.3%, p < 0.001, and cardiovascular mortality rate 17.5% vs. 13.0%, p < 0.001, respectively). In the multivariate Cox proportional hazard analysis, EI > 0.397 was an independent predictor for both all-cause mortality (HR 1.959; 95% CI 1.304, 2.944; p = 0.001) and cardiovascular mortality (HR 2.051; 95% CI 1.276, 3.296; p = 0.003).

Conclusions

Admission EI could be used as a marker for predicting long-term mortality in patients with CHF, and higher EI was associated with an increased risk of all-cause and cardiovascular mortality. Furthermore, EI-guided management could be a promising therapy in patients with CHF.

Skeletal muscle mass in competitive physique-based athletes (bodybuilding, 212 bodybuilding, bikini, and physique divisions): A case series

OBJECTIVES

(1) To examine the muscle thickness of various muscle groups of the body to estimate the absolute and relative skeletal muscle mass (SM) in competitive physique-based athletes (Bodybuilding, 212 Bodybuilding, Bikini, and Physique divisions) and (2) to compare values across various divisions of competition and to resistance trained and non-resistance trained individuals.

METHODS

Eight competitive physique-based athletes (2 M and 6 F), two recreationally resistance trained (1 M and 1 F) and two non-resistance trained (1 M and 1 F) participants had muscle thickness measured by ultrasound at nine sites on the anterior and posterior aspects of the body. SM was estimated from an ultrasound-derived prediction equation and SM index was used to adjust for the influence of standing height (i.e., divided by height squared).

RESULTS

SM values ranged from 19.6 to 60.4 kg in the eight competitive physique-based athletes and 16.1 to 32.6 kg in the four recreationally resistance trained and non-resistance trained participants. SM index ranged from 7.2 to 17.9 kg/m2 in the eight competitive physique-based athletes and 5.8 to 9.3 kg/m2 in the four recreationally resistance trained and non-resistance trained participants.

CONCLUSION

Overall, varying magnitudes of SM and SM index were present across competitors and their respective divisions of bodybuilding. The Men's Open Bodybuilder in the present study had greater values of total SM and SM index compared to previously published values in the literature. Our data provides insight into the extent of SM present in this population and further extends the discussion regarding SM accumulation in humans.

The Prevalence and Agreement of Sarcopenic Obesity Using Different Definitions and Its Association with Mild Cognitive Impairment

BACKGROUND

The consistent definition of sarcopenic obesity (SO) is limited, its association with mild cognitive impairment (MCI) has not been clarified.

OBJECTIVE

This study aimed to evaluate the prevalence and agreement of SO using different definitions and the association between SO and MCI.

METHODS

SO was diagnosed by the co-existence of sarcopenia defined by the Asia Working Group for Sarcopenia (AWGS) and obesity by body mass index (BMI), visceral fat area (VFA), waist circumference (WC), or body fat percentage (BF%). Cohen's kappa was used to assess the agreement between the different definitions. The association between SO and MCI was assessed using multivariable logistic regression.

RESULTS

Among 2,451 participants, the prevalence of SO ranged from 1.7% to 8.0% under different definitions. SO defined by AWGS and BMI (AWGS+BMI) showed fair agreements with the other three criteria (κ ranged from 0.334 to 0.359). The other criteria showed good agreements with each other. The κ statistics were 0.882 for AWGS+VFA and AWGS+BF%, 0.852 for AWGS+VFA and AWGS+WC, and 0.804 for AWGS+BF% and AWGS+WC, respectively. When using different diagnoses of SO, compared with the health group, the adjusted ORs of MCI for SO were 1.96 (95% CI: 1.29-2.99, SO: AWGS+WC), 1.75 (95% CI: 1.14-2.68, SO: AWGS+VFA), 1.94 (95% CI: 1.29-2.93, SO: AWGS+BF%), and 1.45 (95% CI: 0.67-3.12, SO: AWGS+BMI), respectively.

CONCLUSION

Using different obesity indicators combined with AWGS to diagnose SO, BMI had lower prevalence and agreement compared with other three indicators. SO was associated with MCI under different methods (WC, VFA, or BF%).

Assessment of clinical measures of total and regional body composition from a commercial 3-dimensional optical body scanner

BACKGROUND

The accurate assessment of total body and regional body circumferences, volumes, and compositions are critical to monitor physical activity and dietary interventions, as well as accurate disease classifications including obesity, metabolic syndrome, sarcopenia, and lymphedema. We assessed body composition and anthropometry estimates provided by a commercial 3-dimensional optical (3DO) imaging system compared to criterion measures.

METHODS

Participants of the Shape Up! Adults study were recruited for similar sized stratifications by sex, age (18-40, 40-60, >60 years), BMI (under, normal, overweight, obese), and across five ethnicities (non-Hispanic [NH] Black, NH White, Hispanic, Asian, Native Hawaiian/Pacific Islander). All participants received manual anthropometry assessments, duplicate whole-body 3DO (Styku S100), and dual-energy X-ray absorptiometry (DXA) scans. 3DO estimates provided by the manufacturer for anthropometry and body composition were compared to the criterion measures using concordance correlation coefficient (CCC) and Bland-Altman analysis. Test-retest precision was assessed by root mean square error (RMSE) and coefficient of variation.

RESULTS

A total of 188 (102 female) participants were included. The overall fat free mass (FFM) as measured by DXA (54.1 ± 15.2 kg) and 3DO (55.3 ± 15.0 kg) showed a small mean difference of 1.2 ± 3.4 kg (95% limits of agreement -7.0 to +5.6) and the CCC was 0.97 (95% CI: 0.96-0.98). The CCC for FM was 0.95 (95% CI: 0.94-0.97) and the mean difference of 1.3 ± 3.4 kg (95% CI: -5.5 to +8.1) reflected the difference in FFM measures. 3DO anthropometry and body composition measurements showed high test-retest precision for whole body volume (1.1 L), fat mass (0.41 kg), percent fat (0.60%), arm and leg volumes, (0.11 and 0.21 L, respectively), and waist and hip circumferences (all <0.60 cm). No group differences were observed when stratified by body mass index, sex, or race/ethnicity.

CONCLUSIONS

The anthropometric and body composition estimates provided by the 3DO scanner are precise and accurate to criterion methods if offsets are considered. This method offers a rapid, broadly available, and automated method of body composition assessment regardless of body size. Further studies are recommended to examine the relationship between measurements obtained by 3DO scans and metabolic health in healthy and clinical populations.

Validation of skeletal muscle mass estimation equations in active young adults: A preliminary study

We analyzed the validity of the estimation equations for skeletal muscle mass (SMM) using mass of appendicular lean soft tissue (ALST), evaluated by dual-energy X-ray absorptiometry (DXA), in healthy young males undergoing training, and compared it with the results obtained using whole-body magnetic resonance imaging (MRI). We hypothesized that a novel variable, that is, trunk and trunk-to-appendicular ratio of lean soft tissues (trunk/ALST), would be useful in reducing estimation errors in athletes or physically active participants. We analyzed the data of 30 participants (mean age 19.9 ± 1.8 years). SMM was measured using whole-body MRI, while mass of trunk and ALST was assessed using DXA. Three previously utilized estimation equations were retrieved from the literature and used for comparison. The estimated SMM values using previous equations highly correlated with measured SMM, which was determined by MRI, but the mean estimated SMM values were significantly lower than the measured-SMM values. Stepwise regression analysis revealed that mass of ALST, trunk/ALST ratio, and percent body fat were significant predictors of SMM and were incorporated as the new suggested variables. This equation accounted for 90.3% of the variance in SMM. While the previous equations' estimated SMM correlated with measured-SMM in participants with trunk/ALST ratios ≤1.05, they underestimated SMMs in those with trunk/ALST ratios >1.05. The present study confirms that the previously used equations underestimate the actual SMM, particularly in participants with high trunk/ALST ratios (>1.05). The current equation may be used in healthy and active young males, including athletes, as a preliminary tool.

Skeletal muscle fat quantification by dual-energy computed tomography in comparison with 3T MR imaging

Objectives

To quantify the proportion of fat within the skeletal muscle as a measure of muscle quality using dual-energy CT (DECT) and to validate this methodology with MRI.

Methods

Twenty-one patients with abdominal contrast-enhanced DECT scans (100 kV/Sn 150 kV) underwent abdominal 3-T MRI. The fat fraction (DECT-FF), determined by material decomposition, and HU values on virtual non-contrast-enhanced (VNC) DECT images were measured in 126 regions of interest (≥ 6 cm²) within the posterior paraspinal muscle. For validation, the MR-based fat fraction (MR-FF) was assessed by chemical shift relaxometry. Patients were categorized into groups of high or low skeletal muscle mean radiation attenuation (SMRA) and classified as either sarcopenic or non-sarcopenic, according to the skeletal muscle index (SMI) and cut-off values from non-contrast-enhanced single-energy CT. Spearman’s and intraclass correlation, Bland-Altman analysis, and mixed linear models were employed.

Results

The correlation was excellent between DECT-FF and MR-FF (r = 0.91), DECT VNC HU and MR-FF (r = - 0.90), and DECT-FF and DECT VNC HU (r = − 0.98). Intraclass correlation between DECT-FF and MR-FF was good (r = 0.83 [95% CI 0.71–0.90]), with a mean difference of - 0.15% (SD 3.32 [95% CI 6.35 to − 6.66]). Categorization using the SMRA yielded an eightfold difference in DECT VNC HU values between both groups (5 HU [95% CI 23–11], 42 HU [95% CI 33–56], p = 0.05). No significant relationship between DECT-FF and SMI-based classifications was observed.

Conclusions

Fat quantification within the skeletal muscle using DECT is both feasible and reliable. DECT muscle analysis offers a new approach to determine muscle quality, which is important for the diagnosis and therapeutic monitoring of sarcopenia, as a comorbidity associated with poor clinical outcome.

Key Points

• Dual-energy CT (DECT) material decomposition and virtual non-contrast-enhanced DECT HU values assess muscle fat reliably.

• Virtual non-contrast-enhanced dual-energy CT HU values allow to differentiate between high and low native skeletal muscle mean radiation attenuation in contrast-enhanced DECT scans.

• Measuring muscle fat by dual-energy computed tomography is a new approach for the determination of muscle quality, an important parameter for the diagnostic confirmation of sarcopenia as a comorbidity associated with poor clinical outcome.

DXA Measured Visceral Adipose Tissue, Total Fat, Anthropometric Indices and its Association With Cardiometabolic Risk Factors in Mother-Daughter Pairs From India

Visceral fat is the pathogenic fat depot associated with diabetes, dyslipidemia, and cardiovascular diseases. Estimation of visceral adipose tissue (VAT) by dual energy-X-ray absorptiometry (DXA) is a newer technique with less radiation exposure, shorter scanning time, and lower cost. In this study, we attempted to look at relationship between cardiometabolic risk factors and VAT, total body fat percent (TBF%) and anthropometry. We also studied the changes in body composition and metabolic parameters with menopause. The familial resemblance of VAT and TBF% in mother-daughter pair was also compared. This was a cross sectional community study of 300 women (150 postmenopausal mothers and 150 premenopausal daughters). Body composition indices by DXA and metabolic parameters were assessed. The association between DXA-VAT, TBF%, anthropometric measures, and cardiometabolic risk factors were studied by correlation, receiver operating characteristics curves, and logistic regression analysis. VAT indices were significantly higher and lean indices lower in postmenopausal women as compared to premenopausal women. One fourth of postmenopausal women were categorized as metabolically obese normal weight. DXA-VAT was a better predictor of cardiometabolic risk factors as compared to waist circumference, body mass index, and TF% in postmenopausal women (AUC:0.68 vs 0.62, 0.60 & 0.5, respectively), whereas body mass index had a better prediction in premenopausal women(AUC:0.68). VAT area >100 cm² had a significant association with the presence of ≥2 cardiometabolic risk factors (p = 0.04, OR: 2.2, CI:1.0-4.7) in the postmenopausal women. Daughters of the mothers with higher TBF% were found to have a higher TBF% compared to daughters of mothers with normal TBF% (36.2 ± 4.2 vs 32.2 ± 4.4, p = 0.03), similar resemblance was not seen for VAT. The study showed that the VAT increases and lean mass decreases with age and menopause. DXA measured VAT is a better predictor of cardiometabolic risk in postmenopausal women but not in premenopausal women. Total body fat may have a familial resemblance, but not the VAT which is determined by age, menopause, and probable life style factors.

Obesity Phenotypes, Diabetes, and Cardiovascular Diseases

This review addresses the interplay between obesity, type 2 diabetes mellitus, and cardiovascular diseases. It is proposed that obesity, generally defined by an excess of body fat causing prejudice to health, can no longer be evaluated solely by the body mass index (expressed in kg/m²) because it represents a heterogeneous entity. For instance, several cardiometabolic imaging studies have shown that some individuals who have a normal weight or who are overweight are at high risk if they have an excess of visceral adipose tissue-a condition often accompanied by accumulation of fat in normally lean tissues (ectopic fat deposition in liver, heart, skeletal muscle, etc). On the other hand, individuals who are overweight or obese can nevertheless be at much lower risk than expected when faced with excess energy intake if they have the ability to expand their subcutaneous adipose tissue mass, particularly in the gluteal-femoral area. Hence, excessive amounts of visceral adipose tissue and of ectopic fat largely define the cardiovascular disease risk of overweight and moderate obesity. There is also a rapidly expanding subgroup of patients characterized by a high accumulation of body fat (severe obesity). Severe obesity is characterized by specific additional cardiovascular health issues that should receive attention. Because of the difficulties of normalizing body fat content in patients with severe obesity, more aggressive treatments have been studied in this subgroup of individuals such as obesity surgery, also referred to as metabolic surgery. On the basis of the above, we propose that we should refer to obesities rather than obesity.

Assessment of Body Composition in Health and Disease Using Bioelectrical Impedance Analysis (BIA) and Dual Energy X-Ray Absorptiometry (DXA): A Critical Overview

The measurement of body composition (BC) represents a valuable tool to assess nutritional status in health and disease. The most used methods to evaluate BC in the clinical practice are based on bicompartment models and measure, directly or indirectly, fat mass (FM) and fat-free mass (FFM). Bioelectrical impedance analysis (BIA) and dual energy X-ray absorptiometry (DXA) (nowadays considered as the reference technique in clinical practice) are extensively used in epidemiological (mainly BIA) and clinical (mainly DXA) settings to evaluate BC. DXA is primarily used for the measurements of bone mineral content (BMC) and density to assess bone health and diagnose osteoporosis in defined anatomical regions (femur and spine). However, total body DXA scans are used to derive a three-compartment BC model, including BMC, FM, and FFM. Both these methods feature some limitations: the accuracy of BIA measurements is reduced when specific predictive equations and standardized measurement protocols are not utilized whereas the limitations of DXA are the safety of repeated measurements (no more than two body scans per year are currently advised), cost, and technical expertise. This review aims to provide useful insights mostly into the use of BC methods in prevention and clinical practice (ambulatory or bedridden patients). We believe that it will stimulate a discussion on the topic and reinvigorate the crucial role of BC evaluation in diagnostic and clinical investigation protocols.

Ankle strength, muscle size, and adipose content following unilateral tibiotalar arthrodesis

Tibiotalar arthrodesis is commonly used to treat end-stage ankle osteoarthritis. Post-operative impairments are often attributed to limited ankle motion. However, whether muscular deficits also exist, thereby potentially contributing to impairments, is unknown. This study aimed to identify post-operative deficits in ankle musculature by examining range of motion, strength (maximum isometric ankle joint torque), and leg composition (cross-sectional area of individual tissue types: bone, subcutaneous adipose, intramuscular adipose, muscle). Ten individuals with unilateral tibiotalar arthrodesis participated. Paired t-tests (p < 0.05) identified differences between the fused and contralateral, control limb. The results indicate that individuals with tibiotalar arthrodesis have profound losses of range of motion and strength. Across participants, range of motion in the fused limb was 53.5 ± 11.7%, 66.8 ± 6.3%, 38.2 ± 18.7%, 37.8 ± 13.6% less than the control for dorsiflexion, plantarflexion, inversion, and eversion, respectively. The largest strength deficit was in dorsiflexion, with the fused limb producing 47.2 ± 9.4% less torque than the control. The quantity and quality of muscle tissue was also negatively affected in individuals following tibiotalar arthrodesis. The total cross-sectional area of the fused limb was 11.4 ± 5.4% smaller than the control limb. This change was primarily due to the 16.1 ± 6.7% decrease in muscle cross-sectional area. However, intramuscular adipose was significantly increased. Although the posterior compartment demonstrated a significant decrease in cross-sectional area, when accounting for differences in total cross-sectional area, the relative sizes of the four muscle compartments were consistent between limbs. This cross-sectional study motivates longitudinal research examining muscular deficits and whether these deficits are reversible with exercise and rehabilitation. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res.

Measuring body composition in the preterm infant: Evidence base and practicalities

Preterm birth and body composition have demonstrable effects on growth and later health outcomes. Preterm infants reach term equivalent age with a lower proportion of lean mass and higher body fat percentage than their term equivalent counterparts. Weight and length do not give an accurate assessment of body composition. Tracking body composition rather than just weight is a fundamental part of improving nutritional outcomes. This is important given the ongoing controversies regarding the nutritional needs of preterm infants, as well as establishing suitable targets for their growth. In this review we describe current methodologies used in the measurement of body composition of the preterm infant and the review the recent published evidence for their accuracy and utility. Current measurement techniques employed include air displacement plethysmography, bioelectrical impedance analysis, isotope dilution techniques, MRI and a combination of manual measurements including skinfold thickness, body mass index and mid upper arm/mid-thigh circumference. These measures allow for the estimation of fat mass, fat-free mass and regional assessment of adiposity. Some methods, such as dual-energy X-ray absorptiometry and air displacement plethysmography do allow for comparison of change in body composition over time in cohorts of preterm infants that may be studied over a longer period of time and into adult life. However, none of the currently described methods give an accurate and practically achievable method of obtaining body composition measures in preterm infants in day to day routine clinical practise, although this remains a key priority when decisions are being made about how best to feed.

Rapid compositional mapping of knee cartilage with compressed sensing MRI

More than a decade after the introduction of compressed sensing (CS) in MRI, researchers are still working on ways to translate it into different research and clinical applications. The greatest advantage of CS in MRI is the reduced amount of k-space data needed to reconstruct images, which can be exploited to reduce scan time or to improve spatial resolution and volumetric coverage. Efficient data acquisition using CS is extremely important for compositional mapping of the musculoskeletal system in general and knee cartilage mapping techniques in particular. High-resolution quantitative information about tissue biochemical composition could be obtained in just a few minutes using CS MRI. However, in order to make this goal a reality, some issues still need to be addressed. In this article we review the current state of the art of CS methods for rapid compositional mapping of knee cartilage. Specifically, data acquisition strategies, image reconstruction algorithms, and data fitting models are discussed. Different CS studies for T2 and T1ρ mapping of knee cartilage are reviewed, with illustrative results. Future directions, opportunities, and challenges of rapid compositional mapping techniques are also discussed. Level of Evidence: 4 Technical Efficacy: Stage 6 J. Magn. Reson. Imaging 2018;47:1185-1198.

Magnetic resonance imaging-measured skeletal muscle mass to fat-free mass ratio increases with increasing levels of fat-free mass

BACKGROUND

To investigate the skeletal muscle mass to fat-free mass (SM-FFM) ratio in female and male athletes, as well as to examine the relationship between ultrasound predicted SM and magnetic resonance imaging (MRI)-measured SM.

METHODS

Seven female track and field athletes (female), 8 male collegiate swimmers (male-G1) and 8 male collegiate Olympic weightlifters (male-G2) volunteered. Whole-body SM volume was measured using MRI images obtained from the first cervical vertebra to the ankle joints. The volume of SM tissue was calculated and the SM volume was converted into mass units by an assumed skeletal muscle density. Muscle thickness was measured using ultrasound at nine sites and SM was estimated using an ultrasound-derived prediction equation.

RESULTS

Percent body fat was similar among the groups. FFM, MRI-measured SM and SM-FFM ratio were greater in Males-G2 compared to the other two groups and those variables of Male-G1 were higher than the Female group. There was an excellent correlation (r=0.976) between MRI-measured and ultrasound-predicted SM (total error=1.52 kg). No significant difference was observed between MRI-measured and ultrasound-predicted SM in the overall sample or within each group. The SM-FFM ratio was positively correlated (r=0.708) with FFM in female and male athletes.

CONCLUSIONS

We provide evidence for how the MRI-measured SM-FFM ratio changes with increasing levels of FFM and provide data that the ultrasound may be useful in estimating SM in athletes. Given the size limitations with MRI, both of these findings may be useful for future research investigating large sized athletes.

Fat-Free Mass and Skeletal Muscle Mass Five Years After Bariatric Surgery

OBJECTIVE

This study investigated changes in fat-free mass (FFM) and skeletal muscle 5 years after surgery in participants from the Longitudinal Assessment of Bariatric Surgery-2 trial.

METHODS

A three-compartment model assessed FFM, and whole-body magnetic resonance imaging (MRI) quantified skeletal muscle mass prior to surgery (T0) and 1 year (T1), 2 years (T2), and 5 years (T5) postoperatively in 93 patients (85% female; 68% Caucasian; age 44.2 ± 11.6 years) who underwent gastric bypass (RYGB), sleeve gastrectomy, or adjustable gastric band. Repeated-measures mixed models were used to analyze the data.

RESULTS

Significant weight loss occurred across all surgical groups in females from T0 to T1. FFM loss from T0 to T1 was greater after RYGB (mean ± SE: -6.9 ± 0.6 kg) than adjustable gastric band (-3.5 ± 1.4 kg; P < 0.05). Females with RYGB continued to lose FFM (-3.3 ± 0.7 kg; P < 0.001) from T1 to T5. A subset of males and females with RYGB and MRI-measured skeletal muscle showed similar initial FFM loss while maintaining FFM and skeletal muscle from T1 to T5.

CONCLUSIONS

Between 1 and 5 years following common bariatric procedures, FFM and skeletal muscle are maintained or decrease minimally. The changes observed in FFM and muscle during the follow-up phase may be consistent with aging.

Skeletal muscle mass in human athletes: What is the upper limit?

OBJECTIVES

To examine the amount of absolute and relative skeletal muscle mass (SM) in large sized athletes to investigate the potential upper limit of whole body muscle mass accumulation in the human body.

METHODS

Ninety-five large-sized male athletes and 48 recreationally active males (control) had muscle thickness measured by ultrasound at nine sites on the anterior and posterior aspects of the body. SM was estimated from an ultrasound-derived prediction equation. Body density was estimated by hydrostatic weighing technique, and then body fat percentage and fat-free mass (FFM) were calculated. We used the SM index and FFM index to adjust for the influence of standing height (ie, divided by height squared).

RESULTS

Ten of the athletes had more than 100 kg of FFM, including the largest who had 120.2 kg, while seven of the athletes had more than 50 kg of SM, including the largest who had 59.3 kg. FFM index and SM index were higher in athletes compared to controls and the percentage differences between the two groups were 44% and 56%, respectively. The FFM index increased linearly up to 90 kg of body mass, and then the values leveled off in those of increasing body mass. Similarly, the SM index increased in a parabolic fashion reaching a plateau (approximately 17 kg/m² ) beyond 120 kg body mass.

CONCLUSIONS

SM index may be a valuable indicator for determining skeletal muscle mass in athletes. A SM index of approximately 17 kg/m² may serve as the potential upper limit in humans.

IMM-H007, a new therapeutic candidate for nonalcoholic fatty liver disease, improves hepatic steatosis in hamsters fed a high-fat diet

Nonalcoholic fatty liver disease (NAFLD), the most common chronic liver disease in humans, is characterized by the accumulation of triacylglycerols (TGs) in hepatocytes. We tested whether 2′,3′,5′‐tri‐acetyl‐N6‐(3‐hydroxylaniline) adenosine (IMM‐H007) can eliminate hepatic steatosis in hamsters fed a high‐fat diet (HFD), as a model of NAFLD. Compared with HFD‐only controls, IMM‐H007 treatment significantly lowered serum levels of TG, total cholesterol, and free fatty acids (FFAs) in hamsters fed the HFD, with a prominent decrease in levels of serum transaminases and fasting insulin, without affecting fasting glucose levels. Moreover, ¹H‐MRI and histopathological analyses revealed that hepatic lipid accumulation and fibrosis were improved by IMM‐H007 treatment. These changes were accompanied by improvement of insulin resistance and oxidative stress, and attenuation of inflammation. IMM‐H007 reduced expression of proteins involved in uptake of hepatic fatty acids and lipogenesis, and increased very low density lipoprotein secretion and expression of proteins responsible for fatty acid oxidation and autophagy. In studies in vivo, IMM‐H007 inhibited fatty acid import into hepatocytes and liver lipogenesis, and concomitantly stimulated fatty acid oxidation, autophagy, and export of hepatic lipids. These data suggest that IMM‐H007 resolves hepatic steatosis in HFD‐fed hamsters by the regulation of lipid metabolism. Thus, IMM‐H007 has therapeutic potential for NAFLD.

Bedside Ultrasound of Quadriceps to Predict Rehospitalization and Functional Decline in Hospitalized Elders

Objective

To evaluate the capacity of total anterior thigh thickness, quadriceps muscle thickness, and quadriceps contractile index, all measured by bedside ultrasound, to predict rehospitalization, functional decline, and death in elderly patients 3 months after hospital discharge. To evaluate intra and interobserver reproducibility of the dominant thigh evaluation method by point of care ultrasound.

Methods

Cohort study of patients aged 65 years or more admitted to a medium complexity unit in a teaching hospital in southern Brazil. Comprehensive geriatric assessment and ultrasound evaluation of the dominant thigh of each participant were performed. After 3 months of hospital discharge, telephone contact was made to evaluate the outcomes of rehospitalization or death and functional decline—assessed by the 100 points Barthel scale and defined as a decrease of five or more points.

Results

100 participants were included. There was no statistically significant difference between intraobserver measurements in the GEE method analysis (p > 0.05), and the mean bias obtained in Bland–Altman plots was close to zero in all four analyses performed, suggesting good intra and interobserver agreement. There was a significant correlation between the echographic measurements (quadriceps thickness and contractile index) and gait speed, timed up and go, and handgrip tests. There was a significant association between contractile index (quadriceps thickness over total anterior thigh thickness multiplied by 100) lower than 60% and functional decline (relative risk 1.35; CI 95% 1.10–1.65; p = 0.003) as well as between the thickness of the quadriceps and rehospitalization or death, in both individuals with preserved walking capacity and in bedridden elders (relative risk 1.34; CI 95% 1.02–1.75; p = 0.04).

Conclusion

The ultrasonographic method to evaluate thigh thickness was easily applicable and reproducible. The thickness of the quadriceps could predict rehospitalization or death, even in those patients without walking capacity—unable to perform gait speed and timed up and go tests. Additionally, the contractile index was associated with functional decline after 3 months of hospital discharge. This is a promising result, which highlights the bedside ultrasound of the quadriceps as a potential tool for the prognosis evaluation of bedridden hospitalized elderly patients.

Estimation of Body Fat Mass Using Dual-Energy X-Ray Absorptiometry, Bioelectric Impedance Analysis, and Anthropometry in HIV-Positive Male Subjects Receiving Highly Active Antiretroviral Therapy

BACKGROUND

The purpose of this pilot study was to compare estimates of percentage body fat mass (FM) by bioelectric impedance analysis (BIA) and skinfold measurements (SF) with estimates obtained from dual-energy x-ray absorptiometry (DEXA) in 47 HIV-infected male subjects receiving highly active antiretroviral therapy (HAART). As different patterns of abdominal fat accumulation might affect the body FM estimation, correlation and agreement of these methods were also compared in patients with waist to hip ratio (WHR) < or =0.9 and >0.9.

METHODS

Body FM was estimated by BIA and by measuring skinfold thickness at biceps, triceps, and subscapular area, and was compared with DEXA as the reference method using paired t-test.

RESULTS

Estimates by SF were significantly higher and by BIA were significantly lower compared with DEXA for all subjects. This relationship persisted only in those with WHR >0.9. Both BIA and SF correlated significantly with DEXA, but they did not agree. However, both techniques showed a small intermethod bias, and the precision was within the acceptable range. This relationship persisted in those with WHR >0.9. In comparison with measurement by BIA, SF showed poorer agreement (larger bias and error).

CONCLUSION

For population studies and perhaps to monitor changes over time for intervention studies, the bias for both BIA and SF methods is relatively small and errors and precisions are within the acceptable range when compared with DEXA, and thus all 3 techniques can be used for routine monitoring of total body FM in male subjects with HIV infection.

Quantification of intermuscular and intramuscular adipose tissue using magnetic resonance imaging after neurodegenerative disorders

Ectopic adiposity has gained considerable attention because of its tight association with metabolic and cardiovascular health in persons with spinal cord injury (SCI). Ectopic adiposity is characterized by the storage of adipose tissue in non-subcutaneous sites. Magnetic resonance imaging (MRI) has proven to be an effective tool in quantifying ectopic adiposity and provides the opportunity to measure different adipose depots including intermuscular adipose tissue (IMAT) and intramuscular adipose tissue (IntraMAT) or intramuscular fat (IMF). It is highly important to distinguish and clearly define these compartments, because controversy still exists on how to accurately quantify these adipose depots. Investigators have relied on separating muscle from fat pixels based on their characteristic signal intensities. A common technique is plotting a threshold histogram that clearly separates between muscle and fat peaks. The cut-offs to separate between muscle and fat peaks are still not clearly defined and different cut-offs have been identified. This review will outline and compare the Midpoint and Otsu techniques, two methods used to determine the threshold between muscle and fat pixels on T1 weighted MRI. The process of water/fat segmentation using the Dixon method will also be outlined. We are hopeful that this review will trigger more research towards accurately quantifying ectopic adiposity due to its high relevance to cardiometabolic health after SCI.

Imaging methods for analyzing body composition in human obesity and cardiometabolic disease

Advances in the technological qualities of imaging modalities for assessing human body composition have been stimulated by accumulating evidence that individual components of body composition have significant influences on chronic disease onset, disease progression, treatment response, and health outcomes. Importantly, imaging modalities have provided a systematic method for differentiating phenotypes of body composition that diverge from what is considered normal, that is, having low bone mass (osteopenia/osteoporosis), low muscle mass (sarcopenia), high fat mass (obesity), or high fat with low muscle mass (sarcopenic obesity). Moreover, advances over the past three decades in the sensitivity and quality of imaging not just to discern the amount and distribution of adipose and lean tissue but also to differentiate layers or depots within tissues and cells is enhancing our understanding of distinct mechanistic, metabolic, and functional roles of body composition within human phenotypes. In this review, we focus on advances in imaging technologies that show great promise for future investigation of human body composition and how they are being used to address the pandemic of obesity, metabolic syndrome, and diabetes.

Long-term risperidone treatment induces visceral adiposity associated with hepatic steatosis in mice: a magnetic resonance approach

Although atypical antipsychotic drugs (APDs) have led to significant advances in the treatment of psychotic disorders, they still induce metabolic disturbances. We aimed at characterizing the metabolic consequences of a risperidone treatment and at establishing a link with noninvasive MR markers, in order to develop a tool for predicting symptoms of the metabolic syndrome. Fat deposition and liver morphometry were assessed by T1-weighted imaging. Fatty acid composition and fat accumulations in tissues were determined using MR spectroscopy with and without water suppression, respectively. Risperidone treatment induced a weight gain accompanied with metabolic disturbances such as hyperglycemic status, an increase in visceral adipose tissue (VAT), and liver fat depositions. Correlations using Methylene-Water Ratio (MWR) and Polyunsaturated Index (PUI) demonstrated a concomitant increase in the weight gain, VAT and liver fat depositions, and a decrease in the quantity of polyunsaturated fatty acids. These results were consistent with a hepatic steatosis state. We evaluated the ability of MR techniques to detect subtle metabolic disorders induced by APDs. Thus, our model and methodology offer the possibility to investigate APDs side effects in order to improve the health conditions of schizophrenic patients.

Influence of body adiposity on structural characteristics of skeletal muscle in men and women

The structure of skeletal muscle (SM) can be characterized by quantitative (size) and qualitative (composition) attributes, which are disparately reported to be influenced by body adiposity. This study tests the hypothesis that body adiposity exerts a systematic influence on these muscle characteristics and evaluates the possible functional implications for movements. Lower limb SM volume (VSM) and attenuation (ATTSM), an inverse measure of lipid infiltration in muscle, were determined with computed tomography in 21 men (BMI = 21-36 kg m(-2) ; age = 31-71 years.) and 18 women (BMI = 19-35 kg m(-2) ; age = 32-76 years.). After adjusting for age, a multivariate regression analysis revealed that body adiposity positively correlated (P<0·05-0·001) with absolute VSM and cross-sectional area (CSA) in both genders, while VSM per unit body mass (VSM/BM) decreased with adiposity (P<0·001) in women and was constant in men. ATTSM was higher in men (P<0·05) and decreased (P<0·05) with adiposity in both genders. The product of ATTSM by average muscle CSA (predictor of maximal strength) and by VSM/BM (predictor of maximal dynamic performance) was lower in women (P<0·001) and was reduced by age in both genders (P<0·05-0·01), while obesity had a negative effect (P<0·001) only on the predictor of performance. In conclusion, body adiposity significantly increases SM size and reduces ATTSM. Structural indicators accounting for both quantitative and qualitative characteristics of SM may be useful predictors of the effects of obesity on motor function at different ages. With rising body adiposity and advancing age, women appear mostly affected by the decline of SM features relevant for motor performance.

MRI quantification of fatty infiltration and muscle atrophy in a mouse model of rotator cuff tears

Rotator cuff pathology is the most common shoulder problem seen by orthopedic surgeons. Rotator cuff muscle fatty infiltration and muscle atrophy are common in larger tears and are considered predicting factors for the prognosis of cuff repair. Clinically, MRI is the gold standard in determining fatty infiltration and muscle atrophy; however, analysis for MRI imaging is primarily qualitative in nature with the results lacking further validation. We have recently developed a mouse model of rotator cuff tears. The goal of this study is to quantify and verify rotator cuff muscle atrophy and fatty infiltration using high-resolution MRI in our mouse model. The rotator cuff muscles were analyzed for fat using a triglyceride quantification assay (TQA), muscle volume was measured through water displacement (WD), and histology. The study revealed that MRI had a high correlation with fat as measured with histology and TQA (R(2)  =098). MRI also correlated well with atrophy measured with WD and wet weight. This suggests that MRI is a reliable modality in evaluating the progression of fatty infiltration and muscle atrophy following rotator cuff tears in a small animal model.

Clinical, ethical and financial implications of incidental imaging findings: experience from a phase I trial in healthy elderly volunteers

Background

The detection of incidental findings (IF) in magnetic resonance imaging (MRI) studies is common and increases as a function of age. Responsible handling of IF is required, with implications for the conduct of research and the provision of good clinical care.

Aim

To investigate the prevalence and clinical significance of IF in a prospective cohort of healthy elderly volunteers who underwent MRI of the torso as a baseline investigation for a phase I trial. We assessed the follow-up pathway with consequent cost implications and impact on trial outcomes.

Methods

A total of 29 elderly healthy volunteers (mean age 67, range 61–77, 59% female) were eligible at screening and underwent MRI for assessment of visceral and subcutaneous fat.

Results

IF were detected in 19 subjects (66%). Suspected IF of high and low clinical significance were found in 14% and 52% of participants, respectively. Follow up of IF was conducted in 18 individuals, confirming abnormalities in 13 subjects, 3 of whom were recommended for deferred clinical re-evaluation. The remaining 5 subjects had false positive IF based on second line imaging tests. Costs of follow-up medical care were considerable.

Conclusion

MRI abnormalities are common in elderly individuals, as a result of age and non-diagnostic quality of research scans. In the presence of IF in the context of clinical trials, immediate referrals and follow up assessments may be required to rule out suspected pathology prior to exposing trial participants to investigational medicine products (IMP). Unanticipated costs, ethical implication and the possible impact of IF on trial outcomes need to be taken into account when designing and conducting trials with an IMP.

Automatic intra-subject registration-based segmentation of abdominal fat from water-fat MRI

PURPOSE

To develop an automatic registration-based segmentation algorithm for measuring abdominal adipose tissue depot volumes and organ fat fraction content from three-dimensional (3D) water-fat MRI data, and to evaluate its performance against manual segmentation.

MATERIALS AND METHODS

Data were obtained from 11 subjects at two time points with intermediate repositioning, and from four subjects before and after a meal with repositioning. Imaging was performed on a 3 Tesla MRI, using the IDEAL chemical-shift water-fat pulse sequence. Adipose tissue (subcutaneous--SAT, visceral--VAT) and organs (liver, pancreas) were manually segmented twice for each scan by a single trained observer. Automated segmentations of each subject's second scan were generated using a nonrigid volume registration algorithm for water-fat MRI images that used a b-spline basis for deformation and minimized image dissimilarity after the deformation. Manual and automated segmentations were compared using Dice coefficients and linear regression of SAT and VAT volumes, organ volumes, and hepatic and pancreatic fat fractions (HFF, PFF).

RESULTS

Manual segmentations from the 11 repositioned subjects exhibited strong repeatability and set performance benchmarks. The average Dice coefficients were 0.9747 (SAT), 0.9424 (VAT), 0.9404 (liver), and 0.8205 (pancreas); the linear correlation coefficients were 0.9994 (SAT volume), 0.9974 (VAT volume), 0.9885 (liver volume), 0.9782 (pancreas volume), 0.9996 (HFF), and 0.9660 (PFF). When comparing manual and automated segmentations, the average Dice coefficients were 0.9043 (SAT volume), 0.8235 (VAT), 0.8942 (liver), and 0.7168 (pancreas); the linear correlation coefficients were 0.9493 (SAT volume), 0.9982 (VAT volume), 0.9326 (liver volume), 0.8876 (pancreas volume), 0.9972 (HFF), and 0.8617 (PFF). In the four pre- and post-prandial subjects, the Dice coefficients were 0.9024 (SAT), 0.7781 (VAT), 0.8799 (liver), and 0.5179 (pancreas); the linear correlation coefficients were 0.9889, 0.9902 (SAT, and VAT volume), 0.9523 (liver volume), 0.8760 (pancreas volume), 0.9991 (HFF), and 0.6338 (PFF).

CONCLUSION

Automated intra-subject registration-based segmentation is potentially suitable for the quantification of abdominal and organ fat and achieves comparable quantitative endpoints with respect to manual segmentation.

The importance of body composition and dry weight assessments in patients with chronic kidney disease

Chronic volume overload is the major cause of hypertension and other cardiovascular morbidity in dialysis patients. One of the most important goals of physicians who take care of patients with chronic renal failure is to obtain near euvolemia or "dry body weight" in order to maintain or normalize blood pressure and prevent further cardiovascular events. In clinical practice, exact estimation of dry weight in hemodialysis patients remains a major challenge. Alterations in body composition, particularly malnutrition, are common in patients receiving long-term hemodialysis and contribute to a high mortality rate. In contrast, obesity - a known risk factor for cardiovascular morbidity and mortality - is prevalent amongst kidney allograft recipients in - long term after renal transplantation. Several technological tools and biochemical markers for estimation of plasma volume and body composition are available for clinical use. Our aim was to highlight the importance of control of body fluid volume and body composition in patients with chronic kidney disease and to describe the different methods available for such measurements.

Assessment of abdominal adipose tissue and organ fat content by magnetic resonance imaging

As the prevalence of obesity continues to rise, rapid and accurate tools for assessing abdominal body and organ fat quantity and distribution are critically needed to assist researchers investigating therapeutic and preventive measures against obesity and its comorbidities. Magnetic resonance imaging (MRI) is the most promising modality to address such need. It is non-invasive, utilizes no ionizing radiation, provides unmatched 3-D visualization, is repeatable, and is applicable to subject cohorts of all ages. This article is aimed to provide the reader with an overview of current and state-of-the-art techniques in MRI and associated image analysis methods for fat quantification. The principles underlying traditional approaches such as T(1) -weighted imaging and magnetic resonance spectroscopy as well as more modern chemical-shift imaging techniques are discussed and compared. The benefits of contiguous 3-D acquisitions over 2-D multislice approaches are highlighted. Typical post-processing procedures for extracting adipose tissue depot volumes and percent organ fat content from abdominal MRI data sets are explained. Furthermore, the advantages and disadvantages of each MRI approach with respect to imaging parameters, spatial resolution, subject motion, scan time and appropriate fat quantitative endpoints are also provided. Practical considerations in implementing these methods are also presented.

Sonographic measurements of subcutaneous fat in obese individuals may correlate better with peripheral artery disease indices

PURPOSE

The purpose of this study was to investigate the association of various methods for body fat assessment with indices of peripheral artery disease in the deep and superficial femoral arteries.

METHODS

The intima-media thickness (IMT), maximal IMT (max IMT), femoral wall thickness (FWT), maximal FWT (max FWT), cross-sectional intima media area (CIMA), and atherosclerotic burden score (ABS) were measured sonographically in 26 subjects. The minimum thickness of the abdominal subcutaneous fat layer (Smin) was measured sonographically close to the xyphoid process, and body fat percentage was calculated using various formulas.

RESULTS

Smin correlated significantly with body fat percentage calculated with all formulas and was the sole parameter that was associated significantly with all the femoral artery atherosclerotic indices IMT: r = 0.74, p < 0.001; max IMT: r = 0.53, p < 0.05; FWT: r = 0.78, p < 0.001; max FWT: r = 0.57, p < 0.005; ABS: r = 0.52, p < 0.05; CIMA: r = 0.86, p < 0.001; Smin was the major independent predictor of femoral IMT on a multiple stepwise regression analysis (beta = 0.02; SE = 0.008, R(2) = 0.35, p < 0.05).

CONCLUSIONS

Smin correlates better than indirect indices and formulas of body fat estimation with markers of extracoronary atherosclerosis. Sonographic measurement of Smin may serve in the future as a useful tool in everyday clinical practice.

Quantitative comparison and evaluation of software packages for assessment of abdominal adipose tissue distribution by magnetic resonance imaging

OBJECTIVE

To examine five available software packages for the assessment of abdominal adipose tissue with magnetic resonance imaging, compare their features and assess the reliability of measurement results.

DESIGN

Feature evaluation and test-retest reliability of softwares (NIHImage, SliceOmatic, Analyze, HippoFat and EasyVision) used in manual, semi-automated or automated segmentation of abdominal adipose tissue.

SUBJECTS

A random sample of 15 obese adults with type 2 diabetes.

MEASUREMENTS

Axial T1-weighted spin echo images centered at vertebral bodies of L2-L3 were acquired at 1.5 T. Five software packages were evaluated (NIHImage, SliceOmatic, Analyze, HippoFat and EasyVision), comparing manual, semi-automated and automated segmentation approaches. Images were segmented into cross-sectional area (CSA), and the areas of visceral (VAT) and subcutaneous adipose tissue (SAT). Ease of learning and use and the design of the graphical user interface (GUI) were rated. Intra-observer accuracy and agreement between the software packages were calculated using intra-class correlation. Intra-class correlation coefficient was used to obtain test-retest reliability.

RESULTS

Three of the five evaluated programs offered a semi-automated technique to segment the images based on histogram values or a user-defined threshold. One software package allowed manual delineation only. One fully automated program demonstrated the drawbacks of uncritical automated processing. The semi-automated approaches reduced variability and measurement error, and improved reproducibility. There was no significant difference in the intra-observer agreement in SAT and CSA. The VAT measurements showed significantly lower test-retest reliability. There were some differences between the software packages in qualitative aspects, such as user friendliness.

CONCLUSION

Four out of five packages provided essentially the same results with respect to the inter- and intra-rater reproducibility. Our results using SliceOmatic, Analyze or NIHImage were comparable and could be used interchangeably. Newly developed fully automated approaches should be compared to one of the examined software packages.

Neuromuscular electrical stimulation and volitional exercise for individuals with rheumatoid arthritis: a multiple-patient case report

BACKGROUND AND PURPOSE

Muscle atrophy is common in patients with rheumatoid arthritis (RA). Although neuromuscular electrical stimulation (NMES) is a viable treatment for muscle atrophy, there is no evidence about the use of NMES in patients with RA. The purposes of this multiple-patient case report are: (1) to describe the use of NMES applied to the quadriceps femoris muscles in conjunction with an exercise program in patients with RA; (2) to report on patient tolerance and changes in lean muscle mass, quadriceps femoris muscle strength (force-producing capacity), and physical function; and (3) to explore how changes in muscle mass relate to changes in quadriceps femoris muscle strength, measures of physical function, and patient adherence.

CASE DESCRIPTION

Seven patients with RA (median age=61 years, range=39-80 years) underwent 16 weeks of NMES and volitional exercises. Lean muscle mass and strength of the quadriceps femoris muscle and physical function were measured before and after treatment.

OUTCOMES

One patient did not tolerate the NMES treatment, and 2 patients did not complete at least half of the proposed treatment. Patients who completed the NMES and volitional exercise program increased their lean muscle mass, muscle strength, and physical function.

DISCUSSION

Because of the small sample, whether NMES combined with exercises is better than exercise alone or NMES alone could not be determined. However, the outcomes from this multiple-patient case report indicate that NMES is a viable treatment option to address muscle atrophy and weakness in patients with RA. Strategies to increase tolerance and adherence to NMES are warranted.

IRM du tissu adipeux abdominal et lipodystrophie VIH, étude cas-témoin

PURPOSE

To characterize intra-abdominal adipose tissue changes in HIV patients with clinical lipodystrophy using a reproducible imaging technique. Materials and methods. 89 HIV patients with clinical lipodystrophy were included. A single axial T1W image was acquired at the mid L4 vertebral level. Two radiologists measured subcutaneous (SAT) and visceral (VAT) adipose tissues using a semi-automated method. Measurements were compared to a matched population (race, sex, age and BMI).

RESULTS

Measurements of abdominal adipose tissue on MRI are reproducible. Three clinical types of lipodystrophy are described in males with increased visceral (VAT) and reduced subcutaneous (SAT) adipose tissues compared to control subjects. Two clinical types of lipodystrophy are described in females with increased visceral (VAT) and unchanged subcutaneous (SAT) adipose tissues.

CONCLUSION

MRI with comparison between HIV patients and normal control subjects is a reproducible method to characterize adipose tissue changes of lipodystrophy and evaluate its severity. Evaluation of a adipose tissue distribution in a large control population would be helpful to the study of metabolic disorders.

Laboratory and field measurements of body composition

Objective

This background paper was prepared in response to a request to review the concepts related to measurement of body composition, to discuss laboratory and field methods of assessing body composition and to discuss the practical applications of the methods – how they might be used singly or in combination to provide data for a selected population.

Design

The common laboratory and field methods are described and discussed, with particular attention to the assumptions involved and the applicability of the methods to the different population groups. Most measurements of body composition are made in the field, at the bedside or clinic as opposed to in the laboratory. The laboratory methods have a role to play in their own right, in research into new concepts, models and methods. However, they are particularly important in establishing the accuracy of the field methods.

Setting

Field, bedside and laboratory studies.

Subjects

Children, adults, the elderly, ethnic groups.

Results

Laboratory estimates of body compositions are best performed by multi-component methods or by 2-component methods adjusted for to the populations under investigation. There is a scarcity of data for most of the populations in the world.

Conclusions

Energy requirements based on body weight are an approximation since they do not take into account differences in body composition, which will better determine the true requirements. The measurement of body composition occurs in many branches of biology and medicine. It is used in the assessment of nutritional and growth status and in disease states and their treatment. Energy stores, skeletal muscle and protein content can be determined and changes monitored. In human energetics, body composition is widely used for the standardisation of other variables, such as basal metabolic rate (BMR), in the assessments of ethnic and environmental differences and of variability and adaptation to different levels of nutrition. Choosing a method is very problematic. Users want simple, inexpensive, rapid, safe accurate methods to measure body composition but speed and simplicity come at the expense of accuracy. Recommendations are made for age, sex, and in some cases, fatness and ethnic specific methods.

Validation of hand-held bioelectrical impedance analysis with magnetic resonance imaging for the assessment of body composition in overweight women

Methods of assessing body composition suitable for use in clinical trials should be accurate, reliable, and easy to perform. One such technique routinely implemented is hand-held bioelectrical impedance analysis (BIA). The validity of this method, however, in body composition assessment of overweight women is not known. The aim of this study was to validate the hand-held BIA technique with magnetic resonance imaging (MRI) for the assessment of body composition in overweight women. Fat mass, percent fat mass, fat-free mass, and percent fat-free mass values estimated by hand-held BIA were compared to those measured by MRI. Thirty-one Caucasian women (50.1 +/- 8.2 years, body mass index of 26.9 +/- 3.1 kg/m(2)) participated in the study. BIA measurements were highly reproducible (technical error (TE) was 0.06 +/- 0.07 kg for fat mass and 0.08 +/- 0.11% for percent fat mass), but were significantly different (P < 0.0001) for each body composition parameter when compared to MRI. BIA underestimated fat mass by 2.3 +/- 3.3 kg and percent fat mass by 5.6 +/- 3.9%. Likewise, BIA overestimated fat free mass by 7.4 +/- 2.7 kg and percent fat free mass by 5.6 +/- 3.2%. No relationship between the bias and the mean of the two measurements was noted suggesting that bias is not related to measurement size. Although hand-held BIA gives reproducible findings, the bias noted for all body composition parameters puts into question the validity of this regional impedance device for use in clinical trials in overweight women.

Abdominal fat-water separation with SSFP at 3 Tesla

The ability of the phase-sensitive steady-state free precession (SSFP) technique to distinguish subcutaneous and visceral adipose tissue in the abdomen at 3 T was evaluated. A phased array receiver radiofrequency coil and a commercially available SSFP sequence were used for imaging. The raw image data were postprocessed to generate fat-only and water-only images. A postprocessing algorithm that is computationally efficient and robust is presented. The postprocessing technique separates the fat and water pixels automatically without any user interference. The feasibility of the technique is demonstrated in vivo with breath-hold abdomen images. The short scan time and the ease of use of this technique are well suited to the quantification of body fat distribution in children.

Skeletal muscle atrophy and increased intramuscular fat after incomplete spinal cord injury

STUDY DESIGN

Cross-sectional and longitudinal design.

OBJECTIVES

(1) To quantify skeletal muscle cross-sectional area (CSA) after correcting for intramuscular fat (IMF) in thigh muscle groups 6 weeks after incomplete spinal cord injury (SCI), (2) to monitor the changes in muscle CSA and IMF after 3 months from the initial measurement.

SETTING

Academic institution Athens, GA, USA.

METHODS

Six incomplete SCI patients (28+/-4 years, 178+/-5 cm and 78+/-6 kg, mean+/-SE, C7 to L3, American Spinal Injury Association B or C) were tested at 5+/-1 weeks and 3 months after the initial measurement. T1-weighted magnetic resonance images were taken of both thighs. Six able-bodied (AB) controls were matched in age, sex, height and weight (29+/-4 years, four male and two female subjects, 179+/-5 cm and 77+/-6 kg).

RESULTS

At 6 weeks post-injury, muscle CSA was 82+/-4 cm(2) in incomplete SCI and 123+/-21 cm(2) in AB controls (P=0.04). IMF CSA was 5.2+/-1.3 and 2.3+/-0.6 cm(2) in incomplete SCI and AB controls, respectively (P=0.03). Relative IMF was three-fold higher (P=0.03) in the SCI group versus AB controls (5.8+/-1.4 versus 2.0+/-0.6%). After 3 months, IMF increased 26% in the SCI group compared to the initial measurement (P=0.02).

CONCLUSIONS

Skeletal muscle atrophy is associated with greater IMF accumulation in SCI group 6 weeks post-injury compared to AB controls. Moreover, IMF continues to increase over time in incomplete SCI.

Fully automated large-scale assessment of visceral and subcutaneous abdominal adipose tissue by magnetic resonance imaging

OBJECTIVE

To describe and evaluate a fully automated method for characterizing abdominal adipose tissue from magnetic resonance (MR) transverse body scans.

METHODS

Four MR pulse sequences were applied: SE, FLAIR, STIR, and FRFSE. On 39 subjects, each abdomen was traversed by 15 contiguous transaxial images. The total abdominal adipose tissue (TAAT) was calculated from thresholds obtained by slice histogram analysis. The same thresholds were also used in the manual volume calculation of TAAT, subcutaneous abdominal adipose tissue (SAAT) and visceral abdominal adipose tissue (VAAT). Image segmentation methods, including edge detection, mathematical morphology, and knowledge-based curve fitting, were used to automatically separate SAAT from VAAT in various 'nonstandard' cases such as those with heterogeneous magnetic fields and movement artefacts.

RESULTS

The percentage root mean squared errors of the method for SAAT and VAAT ranged from 1.0 to 2.7% for the four sequences. It took approximately 7 and 15 min to complete the 15-slice volume estimation of the three adipose tissue classes using automated and manual methods, respectively.

CONCLUSION

The results demonstrate that the proposed method is robust and accurate. Although the separation of SAAT and VAAT is not always perfect, this method could be especially helpful in dealing with large amounts of data such as in epidemiological studies.

Role of a critical visceral adipose tissue threshold (CVATT) in metabolic syndrome: implications for controlling dietary carbohydrates: a review

There are likely many scenarios and pathways that can lead to metabolic syndrome. This paper reviews mechanisms by which the accumulation of visceral adipose tissue (VAT) may contribute to the metabolic syndrome, and explores the paradigm of a critical VAT threshold (CVATT). Exceeding the CVATT may result in a number of metabolic disturbances such as insulin resistance to glucose uptake by cells. Metabolic profiles of patients with visceral obesity may substantially improve after only modest weight loss. This could reflect a significant reduction in the amount of VAT relative to peripheral or subcutaneous fat depots, thereby maintaining VAT below the CVATT. The CVATT may be unique for each individual. This may help explain the phenomena of apparently lean individuals with metabolic syndrome, the so-called metabolically normal weight (MONW), as well as the obese with normal metabolic profiles, i.e., metabolically normal obese (MNO), and those who are "fit and fat." The concept of CVATT may have implications for prevention and treatment of metabolic syndrome, which may include controlling dietary carbohydrates. The identification of the CVATT is admittedly difficult and its anatomical boundaries are not well-defined. Thus, the CVATT will continue to be a work in progress.

A longitudinal magnetic resonance imaging (MRI) study of differences in abdominal fat distribution between normal mice, and lean overexpressers of mitochondrial uncoupling protein-3 (UCP-3)

AIM

To characterize evolution and distribution of abdominal adipose fat between 6 and 18 weeks of age in an animal model of energy consumption based on mice overexpressing the mitochondrial uncoupler protein 3 (UCP-3).

METHODS

T2-weighted multislice MRI was performed six times during the 12 week study; visceral, subcutaneous and intermuscular fat depots were quantified.

RESULTS

The overexpressor (UCP-3tg) mice consistently have less subcutaneous, visceral, interskeletal muscle and total fat throughout the experiment. Mean (standard error) volumes (ml) of the three distinct depots change between week 6 and week 18 as follows: wild type: subcutaneous 1.93 (0.28) to 6.18 (0.47), visceral 2.15 (0.34) to 6.37 (0.64), intermuscular 0.23 (0.04) to 0.53 (0.03); UCP-3tg: subcutaneous 1.47 (0.17) to 4.07 (0.57), visceral 1.18 (0.04) to 3.69 (0.59), intermuscular 0.23 (0.01) to 0.32 (0.04). Although they eat more (4.3 g compared with 3.4 g per day) the UCP-3tg's always weigh less than controls. In wild-type control animals, increases of all fat pools between week 6 and week 18 is highly significant, as it is for subcutaneous, visceral and total pools in the UCP-3tg animals. The UCP-3tg mice, however, show no significant absolute or relative increase in intermuscular fat; UCP-3 is predominantly overexpressed in skeletal muscle.

CONCLUSION

MRI provides an excellent approach to comparative studies of fat distribution in animal models of energy expenditure such as the UCP-3tg mouse.

Skeletal muscle triglyceride: marker or mediator of obesity-induced insulin resistance in type 2 diabetes mellitus?

The inability of insulin to stimulate glucose metabolism in skeletal muscle is a classic characteristic of type 2 diabetes, but this insulin resistance entails altered patterns of lipid metabolism as well. An association between intracellular triglyceride and insulin resistance has been well established in both human and animal studies of obesity-related insulin resistance and type 2 diabetes. Skeletal muscle's ability to select substrate for fuel metabolism, a metabolic flexibility, is also lost in insulin resistance, and defects in fatty acid metabolism during fasting or postabsorptive conditions likely play an important role in lipid oversupply to insulin-resistant muscle. These impairments appear to be at least indirectly centered on the ability of mitochondria to oxidize fatty acids, possibly through mediation of lipid metabolite levels such as ceramide or diacylglycerol, which are known to directly attenuate insulin signaling. Moreover, periodic use of muscle triglyceride by exercise may mediate the association between muscle triglyceride and insulin resistance. Thus, it appears that skeletal muscle triglyceride is perhaps a surrogate for other lipid species having a more direct effect on insulin action. Defining mechanisms by which dysregulation of fatty acid metabolism and persistent lipid oversupply alter insulin action may help to target more effective strategies to prevent or treat type 2 diabetes.

New bioimpedance model accurately predicts lower limb muscle volume: validation by magnetic resonance imaging

Conventional bioimpedance analysis (BIA) methods now simplify the representation of lower limb geometry and electrical properties for body composition estimation. In the present study, a three-dimensional model of the lower limb was assembled by segmentation of magnetic resonance cross-sectional images (MRI) for adipose tissue, skeletal muscle, and bone. An electrical network was then associated with this model. BIA and MRI measurements were made in six lean subjects (3 men and 3 women, age 32.2 +/- 6.9 yr). Assuming 0.85 S/m for the longitudinal conductivity of the muscle, the model predicted in the examined subjects an impedance profile that conformed well to the BIA impedance profile; predicted and measured resistances were similar (261.3 +/- 7.7 vs. 249 +/- 9 Omega; P = not significant). The resistance profile provided, through a simpler model, muscle area estimates along the lower limb and total leg muscle volume (mean 4,534 cm(3) for men and 4,071 cm(3) for women) with a mean of the absolute value of relative error with respect to MRI of 6.2 +/- 3.9. The new approach suggests that BIA can reasonably estimate the distribution and volume of muscles in the lower extremities of lean subjects.

Methods of assessing body shape and composition in HIV-associated lipodystrophy

Although HIV-associated lipodystrophy can be diagnosed just from clinical examination, criteria for diagnosis and judgement of severity are not clearly defined. Clinical assessment can be systematized with questionnaires for patients and physicians. Computed tomography, nuclear magnetic imaging and dual-energy X-ray absorptiometry are objective reference methods but are expensive for routine follow-up and diagnosis. Therefore, anthropometry and other non-invasive bedside methods deserve further validation studies.

Assessment of contractile and noncontractile components in human skeletal muscle by magnetic resonance imaging

A magnetic resonance imaging (MRI) technique for the assessment of contractile and noncontractile components of human skeletal muscle is described, and the inter-rater and intra-rater test-retest reliability for repeated measurements from the same MR image are examined. Twenty cross-sectional MR images from the right lower leg were obtained from 30 healthy young men and women (mean age 24.1 years, SD 3.3). The anatomical cross-sectional area (aCSA; cm2), the cross-sectional area of noncontractile components (Noncon; cm2), the contractile cross-sectional area (cCSA = aCSA minus Noncon; cm2), and the relative amount of Noncon (%), of the ankle dorsiflexor muscle compartment were determined for each slice using a computer-based image analysis system. Reliability for repeated measurements of the slice with the largest aCSA for the 30 subjects was analyzed by two raters on two different occasions. Inter-rater reliability on both occasions, assessed by the intraclass correlation coefficient (ICC), was excellent for cCSA (ICC3.1 = 0.99) and Noncon (ICC(3.1) > 0.82). Intra-rater (between occasions) reliability was excellent for the two raters for measurements of cCSA (ICC1.1 = 0.99) and Noncon (ICC1.1 > 0.94). Bland and Altman analyses did not identify any clinically relevant bias in the measurements. Method errors were acceptable: within subjects coefficients of variation (CV) was less than 1.8% for cCSA and less than 16.3% for Noncon. It is concluded that repeated measurements of contractile and noncontractile components of the ankle dorsiflexor muscle compartment, obtained from the same MR image, are highly reliable.