SAT Volumes Research Articles

Abstract 5818: Features of cancer cachexia in non-small cell lung cancer: Insights from the prospective TRACERx study

Abstract Introduction: Cancer cachexia (CC) is a major contributor to morbidity and mortality in patients with non-small cell lung cancer (NSCLC). It is characterized by loss of skeletal muscle (SM) tissue with or without adipose tissue loss. This analysis reports on the characteristics and outcomes of patients recruited into the prospective TRACERx study, who presented with or subsequently developed features of CC during follow-up. Approach: Using longitudinal CT imaging, total, subcutaneous and visceral adipose tissue (TAT, SAT, VAT) and SM volumes were manually quantified at the 3rd lumbar vertebrae level. Body weight was measured every 3-6 months and grouped according to BMI-adjusted weight loss grades. Multi-region primary tumour tissue was collected at the time of surgical resection and subjected to whole exome and RNA sequencing. Results: Patients in the TRACERx 421 cohort who presented with low SAT volume at diagnosis, represented by the lower 20% percentile of the cohort, had significantly shorter lung-cancer specific survival (LCSS) and overall survival (OS) compared with patients in the 80% percentile (3-y LCSS 61% vs 81%, p<0.001; 3-y OS 57% vs 69%, p=0.02). Patients presenting with low VAT had a significantly shorter LCSS (3-y-LCSS 66% vs 79%, p=0.01), but not OS (3-y OS 60% vs 69%). Low SM volume was not associated with LCSS or OS. However, loss of SM volume of ≥20% between diagnosis and disease relapse was associated with significantly reduced LCSS and OS (3-y LCSS 30% vs 49%, p=0.02; 3-y OS 26% vs 45%, p=0.03). Based on a multivariable model, low SAT volume at diagnosis and SM loss were independent prognostic factors for LCSS, but not OS. In addition, BMI-adjusted weight loss was associated with shorter OS and LCSS (3-y OS 7% for patients with weight loss grade 4 vs 54% in patients with stable weight, p<0.001 [LCSS 8% vs 61%, p<0.001]). Preliminary genomic data from patients with disease recurrence and with (n=47) or without (n=107) features of CC, defined as SAT or muscle loss >20% or weight loss grade 4, demonstrated distinct copy number alteration and differential gene expression profiles. Conclusion: In patients with early-stage NSCLC, both altered body composition and weight loss in keeping with CC was associated with poor survival outcomes. In particular, low SAT volume at diagnosis and loss of SM between diagnosis and relapse were independent prognostic factors for LCSS. Ongoing analyses in TRACERx will continue to investigate the potential tumour-intrinsic mediators of CC. Citation Format: Othman Al-Sawaf, Marcin Skrzypski, Jakob Weiss, Takahiro Karasaki, Nicolai Juul Birkbak, Francisco Zambrana, Alexander Frankell, Thomas B. Watkins, Carlos Martinez Ruiz, Selvaraju Veeriah, Cristina Naceur-Lombardelli, TRACERx Consortium, Nicholas McGranahan, Hugo Aerts, Charles Swanton, Mariam Jamal-Hanjani. Features of cancer cachexia in non-small cell lung cancer: Insights from the prospective TRACERx study [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5818.

Visceral adipose tissue phenotype and hypoadiponectinemia are associated with aortic Fluorine-18 fluorodeoxyglucose uptake in patients with familial dyslipidemias

BackgroundThe role of adipose tissue (AT) in arterial inflammation in familial dyslipidaemias is poorly studied. We investigated the relationship between AT and arterial inflammation in patients with heterozygous familial hypercholesterolemia (heFH) and familial combined hyperlipidemia (FCH). Methods and ResultsA total of 40 patients (20 heFH/20 FCH) and a subgroup of 20 of non-heFH/FCH patients were enrolled. Participants underwent blood sampling for serum adipokine measurements and Fluorine-18 fluorodeoxyglucose (18F-FDG) PET/CT imaging. Abdominal visceral (VAT) and subcutaneous (SAT) AT volumes and AT and abdominal aorta 18F-FDG uptake were quantified. FCH patients had increased VAT (pANOVA = 0.004) and SAT volumes (pANOVA = 0.003), lower VAT metabolic activity (pANOVA = 0.0047), and lower adiponectin levels (pANOVA = 0.007) compared to heFH or the control group. Log(Serum adiponectin) levels were correlated with aortic TBR (b = − 0.118, P = 0.038). In mediation analysis, VAT volume was the major determinant of circulating adiponectin, an effect partly mediated via VAT TBR. Clustering of the population of heFH/FCH by VAT volume/TBR and serum adiponectin identified two distinct patient clusters with significant differences in aortic TBR levels (2.11 ± 0.06 vs 1.89 ± 0.05, P= 0.012). ConclusionsVAT phenotype (increased VAT volume and/or high VAT TBR) and hypoadiponectinemia may account for the observed differences in arterial inflammation levels between heFH and FCH patients.

Assessment of the visceral adipose tissue by magnetic resonance imaging in patients with coronary artery disease: link to metabolism disorders and condition of the abdominal aorta

Abstract Aim MRI-quantification of the visceral and subcutaneous adipose tissue (AT) and investigation of its interconnections with anthropometric parameters of obesity, carbohydrate metabolism and condition of abdominal aorta in patients with chronic coronary artery disease (CAD). Methods The study included 55 patients (mean age 61.2±7.2 y.o.) with chronic CAD. All patients underwent MRI of the abdominal AT and abdominal aorta segment on a 1.5 T MRI in standard modes. Calculation of the area and volume of abdominal subcutaneous (SAT) and visceral adipose tissue (VAT) was conducted at L4-L5 level; the total volumes of abdominal SAT and VAT were calculated. Parameters of lipid and carbohydrate metabolism as well adipokines' profile were measured in blood serum. Results To eliminate gender bias the data in the total group was corrected for the sex, height and body weight. In the course of the multiple linear regression analysis, we detected the independent determinants, which described 95% of the total VAT volume variability and were represented by waist circumference and serum levels of HDL cholesterol and adiponectin. The model was characterized by the significance level p<0,ehab724.116501, the residues of the model were normal. The evaluation of the coefficients in the model was as following: 1,39 for waist circumference, −0.26 for HDL cholesterol and −0,19 for adiponectin. We detected direct correlation between the aorta diameter and total SAT volume (rs=0.30), which was independent from sex; and reverse correlations between the aorta diameter and HbA1c level (rs=−0.40) and postprandial glycemia (rs=−0.40). Patients with dilated aorta when compared to the patients with normal aorta diameter did not differ in the AT accumulation, but demonstrated decreased levels of HbA1c and postprandial glycaemia, which was dependent upon the lower numbers of patients with diabetes mellitus type 2. Conclusion We have identified the independent determinants of the total volume of the abdominal visceral AT increase, which appeared to be increment of the waist circumference and decrease of the serum adiponectin and HDL cholesterol. Results of the study indicate the presence of the interconnection between the processes of the abdominal aorta remodeling, accumulation of subcutaneous adipose tissue and carbohydrate metabolism impairments. Funding Acknowledgement Type of funding sources: None. MRI of the abdominal tissueMRI of the abdominal aorta

Classifying Abdominal Fat Distribution Patterns by Using Body Measurement Data

This study aims to explore new categorization that characterizes the distribution clusters of visceral and subcutaneous adipose tissues (VAT and SAT) measured by magnetic resonance imaging (MRI), to analyze the relationship between the VAT-SAT distribution patterns and the novel body shape descriptors (BSDs), and to develop a classifier to predict the fat distribution clusters using the BSDs. In the study, 66 male and 54 female participants were scanned by MRI and a stereovision body imaging (SBI) to measure participants’ abdominal VAT and SAT volumes and the BSDs. A fuzzy c-means algorithm was used to form the inherent grouping clusters of abdominal fat distributions. A support-vector-machine (SVM) classifier, with an embedded feature selection scheme, was employed to determine an optimal subset of the BSDs for predicting internal fat distributions. A five-fold cross-validation procedure was used to prevent over-fitting in the classification. The classification results of the BSDs were compared with those of the traditional anthropometric measurements and the Dual Energy X-Ray Absorptiometry (DXA) measurements. Four clusters were identified for abdominal fat distributions: (1) low VAT and SAT, (2) elevated VAT and SAT, (3) higher SAT, and (4) higher VAT. The cross-validation accuracies of the traditional anthropometric, DXA and BSD measurements were 85.0%, 87.5% and 90%, respectively. Compared to the traditional anthropometric and DXA measurements, the BSDs appeared to be effective and efficient in predicting abdominal fat distributions.

1471-P: Visceral and Subcutaneous Adipose Tissue Attenuation Differs by Type 1 and Type 2 Diabetes Status

Adipose tissue (AT) volume and quality may contribute to cardiovascular risk. AT volume and attenuation can be derived from computed tomography (CT) scans, with greater attenuation indicating poor AT quality and increased fibrosis. We examined whether AT quantity and quality were associated with coronary artery calcium (CAC) in a sample of adults without diabetes (non-DM), with type 1 diabetes (T1D), and with type 2 diabetes (T2D). 294 non-DM adults (mean age±SD 55±9 years), 226 adults with T1D (mean age±SD 52±9 years), and 52 adults with T2D (mean age±SD 53±9 years) completed CT scans for CAC measurement and abdominal CT scans at lumbar 4-5 for visceral (VAT) and subcutaneous (SAT) AT volume and attenuation measurement. Adults with T2D had significantly more VAT and SAT when adjusting for age and sex compared with T1D and non-DM adults, but after adjusting for BMI there was no difference in VAT volume by diabetes status. Adults with T2D had significantly lower SAT volume when adjusted for BMI as compared with both non-DM and T1D adults (157 cm3 vs. 177 cm3 and 183 cm3, p=0.0008). Adults with T1D had significantly higher SAT attenuation as compared with non-DM and T2D adults (p<0.0001 for both). Square root-transformed CAC volume was significantly higher in both T1D (mean volume±SD 10.4±14.7) and T2D (mean volume±SD 9.6±15.9) compared to non-DM adults (mean volume±SD 4.5±8.2). Greater attenuation of VAT and SAT was associated with increased CAC (p=0.03 for both), but there was no association between AT volume and CAC in this sample. AT attenuation was significantly higher in T1D and independently associated with subclinical atherosclerosis in a sample of non-DM, T1D, and T2D adults. AT fibrosis is associated with metabolic dysfunction, decreased angiogenesis, and increased inflammation; our results suggest that despite similar AT volume, T1D adults have adverse fat quality that may indicate fibrosis. This may be a mechanism through which T1D is associated with greater levels of CAC. Disclosure A. Keshawarz: None. A.C. Alman: None. C.C. Low Wang: Advisory Panel; Spouse/Partner; Bayer Healthcare, LLC, CSL Behring, Genentech/Roche, Hema Biologics, Novo Nordisk Pharmaceuticals, Inc, Octapharma Pharmazeutika, Shire. Speaker's Bureau; Self; Medical Education Resources. S. Mitchell: None. I.E. Schauer: Other Relationship; Spouse/Partner; Kestrel Labs. J.E.B. Reusch: Board Member; Self; American Diabetes Association. Other Relationship; Self; Merck & Co., Inc. J.G. Regensteiner: None. J.K. Snell-Bergeon: None. Funding American Diabetes Association (7-13-CD-10 to J.K.S-B.)

Quantification of fat and skeletal muscle tissue at abdominal computed tomography: associations between single-slice measurements and total compartment volumes

Body composition is of great prognostic value in several severe diseases, including different types of cancer as well as cardiometabolic disorders. We aimed to investigate the correlations of skeletal muscle mass and abdominal adipose tissue compartments between volumetric and single-slice measurements to study the usefulness of several anatomical landmarks for estimation of total compartment volumes using abdominal CT-scans. In this retrospective study volumetric quantifications of paraspinal skeletal muscles (SM) and adipose tissue compartments (visceral adipose tissue, VAT; subcutaneous adipose tissue, SAT) were performed in 50 consecutive patients (26 male; mean age, 63 ± 15years) who underwent abdominal multislice-CT for diagnostic purposes using an in-house software. Associations between total volumes of SM, VAT, and SAT with single-slice measurements at eight predefined anatomical landmarks (median intervertebral disk spaces T12/L1 to L5/S1; level of the umbilicus (U); level of the radix of the superior mesenteric artery (SMA)) were studied using correlation coefficients. Statistical analysis revealed a strong association between single-slice measurements of adipose tissue compartments with total VAT and SAT volume (VAT: all r > 0.89, P < 0.001; SAT: all r > 0.95, P < 0.001). The strongest associations with total SM volume were found for single-slice measurements obtained at L3/4 (r = 0.94, P < 0.001) and were further improved by normalization to height (r = 0.98, P < 0.001). Single-slice measurements of SM, VAT, and SAT at several anatomical landmarks are strongly associated with total compartment volumes and therefore allow for easy and simultaneous assessment of skeletal muscle mass and adipose tissue compartment volumes.

Sex dimorphism in the distribution of adipose tissue and its influence on proinflammatory adipokines and cardiometabolic profiles in motor complete spinal cord injury

Objective: We aimed to examine the influence of sex on the distribution of adipose tissue, as well as proinflammatory adipokine and cardiometabolic profiles, in chronic motor complete spinal cord injury (SCI).Design: Cross-sectional and correlational study.Setting: Academic rehabilitation hospital.Participants: Forty-seven individuals with chronic motor complete SCI classified according to sex (males: age 44.0 ± 10.9 y, body mass index (BMI) 27.2 ± 5.8, level of injury (LOI) C4 - L1; females: 42.0 ± 13.5 y, BMI 27.8 ± 6.6, LOI C4 - T11).Intervention: Not applicable.Outcome Measures: Visceral (VAT), subcutaneous (SAT), and total trunk (TTAT) adipose tissue volumes were assessed utilizing magnetic resonance imaging and a VAT:SAT ratio was calculated. Proinflammatory adipokines (tumor neurosis factor-α, interleukin-6, plasminogen activator inhibitor-1, thrombin-activatable fibrinolysis inhibitor, and high sensitivity c-reactive protein) and cardiovascular, carbohydrate, and lipid profiles were evaluated according to standard techniques.Results: VAT and VAT:SAT ratio were significantly greater in male participates with SCI (P ≤ 0.002), while SAT volume was significantly greater in female participants with SCI (P = 0.001). No difference was noted in TTAT between groups (P = 0.341). Male participants with SCI demonstrated lower high-density lipoprotein-cholesterol (HDLC) profiles and an elevated total cholesterol to HDLC ratio (P ≤ 0.003) compared with females. No other significant differences were found between groups concerning cardiometabolic profiles or proinflammatory adipokines; however, males exhibited poorer profiles overall. Proinflammatory adipokines significantly correlated with adipose tissue depots by sex (P < 0.05).Conclusion: The results show that sex influences the distribution of adipose tissue, and may influence proinflammatory and cardiometabolic profiles following SCI. The findings of this study highlight the need for further research with dietary modification and exercise to decrease health risks.

Caloric restriction lowers endocannabinoid tonus and improves cardiac function in type 2 diabetes

Background/ObjectivesEndocannabinoids (ECs) are associated with obesity and ectopic fat accumulation, both of which play a role in the development of cardiovascular disease (CVD) in type 2 diabetes (T2D). The effect of prolonged caloric restriction on ECs in relation to fat distribution and cardiac function is still unknown. Therefore, our aim was to investigate this relationship in obese T2D patients with coronary artery disease (CAD).Subjects/MethodsIn a prospective intervention study, obese T2D patients with CAD (n = 27) followed a 16 week very low calorie diet (VLCD; 450–1000 kcal/day). Cardiac function and fat accumulation were assessed with MRI and spectroscopy. Plasma levels of lipid species, including ECs, were measured using liquid chromatography-mass spectrometry.ResultsVLCD decreased plasma levels of virtually all measured lipid species of the class of N-acylethanolamines including the EC anandamide (AEA; −15%, p = 0.016), without decreasing monoacylglycerols including the EC 2-arachidonoylglycerol (2-AG). Baseline plasma AEA levels strongly correlated with the volume of subcutaneous white adipose tissue (SAT; R2 = 0.44, p < 0.001). VLCD decreased the volume of SAT (−53%, p < 0.001), visceral white adipose tissue (VAT) (−52%, p < 0.001), epicardial white adipose tissue (−15%, p < 0.001) and paracardial white adipose tissue (−28%, p < 0.001). VLCD also decreased hepatic (−86%, p < 0.001) and myocardial (−33%, p < 0.001) fat content. These effects were accompanied by an increased left ventricular ejection fraction (54.8 ± 8.7–56.2 ± 7.9%, p = 0.016).ConclusionsCaloric restriction in T2D patients with CAD decreases AEA levels, but not 2-AG levels, which is paralleled by decreased lipid accumulation in adipose tissue, liver and heart, and improved cardiovascular function. Interestingly, baseline AEA levels strongly correlated with SAT volume. We anticipate that dietary interventions are worthwhile strategies in advanced T2D, and that reduction in AEA may contribute to the improved cardiometabolic phenotype induced by weight loss.

Circulating selenoprotein P levels in relation to MRI-derived body fat volumes, liver fat content, and metabolic disorders.

Association studies of selenoprotein P (SELENOP) with cardiometabolic traits in humans are relatively scarce and, in part, conflicting. A general population sample from Northern Germany was evaluated for cross-sectional associations of circulating SELENOP concentrations with metabolic syndrome (MetS), total volumes of MRI-determined visceral (VAT) and subcutaneous (SAT) abdominal adipose tissue, liver signal intensity, and fatty liver disease (FLD). Nine hundred and five participants received comprehensive clinical and molecular phenotyping along with measurement of serum SELENOP; 584 individuals received MRI. Multivariable-adjusted restricted cubic regression splines displayed statistically significant inverse relations of SELENOP levels with MetS, VAT, and SAT (P < 0.0001 for all). Compared with the second quartile of SELENOP distribution, the MetS odds ratios for the first, third, and fourth quartiles were 1.62 (95% confidence interval [CI]: 1.08-2.43), 0.85 (95% CI: 0.57-1.26), and 0.41 (95% CI: 0.27-0.62), respectively. Furthermore, participants in the second, third, and fourth SELENOP quartiles had significantly lower VAT and SAT volumes as compared to those in the first biomarker quartile. A J-shaped relation was observed for SELENOP levels and liver signal intensity/FLD (P = 0.01). The findings suggest inverse associations of circulating SELENOP concentrations with several metabolic traits, to be further investigated in longitudinal studies.

Visceral and subcutaneous adipose tissue FDG uptake by PET/CT in metabolically healthy obese subjects.

ObjectiveTo measure FDG uptake in visceral (VAT) and subcutaneous (SAT) adipose tissue of metabolically healthy obese (MHO) and metabolically abnormal obese (MAO) compared to metabolically healthy lean (MHL) subjects. Given that MHO have increased metabolic risk, we hypothesized that MHO and MAO display similar VAT FDG uptake.Design and MethodsWe examined 18F-FDG-PET/CT studies of 141 adults (n=60 MHL, n=20 MHO, n=61 MAO) to determine VAT and SAT volumes and FDG uptake. Data on CVD risk factors (BMI, abdominal circumference, blood pressure, serum lipids, and fasting plasma glucose) were collected.ResultsMHO and MAO had similar VAT FDG uptake (P=0.74), both significantly lower than MHL (P<0.01) independent of age and gender. SAT FDG uptake was similar across all groups (P>0.2) independent of age and gender. In all groups, VAT FDG uptake was higher than SAT (P<0.0001). In separate sub-analyses of obese groups, VAT FDG uptake was more broadly negatively associated with whole-body adiposity than SAT FDG uptake, and FDG uptake in abdominal adipose depots was positively associated with liver density (P<0.05).ConclusionsFDG uptake in VAT of MHO is similar to MAO and lower than MHL, suggesting these subjects may present similar VAT dysfunction.

Relation of Visceral and Subcutaneous Adipose Tissue to Bone Mineral Density in Chinese Women

The relationship between adipose and bone tissues is still being debated. The purpose of our study was to evaluate whether the distribution and volume of abdomen adipose tissue are correlated to trabecular bone mineral density in the lumbar spine. In this cross-sectional study, 320 Chinese women, being divided into two groups according to age ≥55 years and <55 years, were evaluated with quantitative computed tomography (QCT) of the spine to simultaneously evaluate the average trabecular BMD of L2–L4, VAT, and SAT. Possible covariates of height, weight, age, and comorbidities were considered. In the <55-year-old sample, multiple linear regression analyses indicated that VAT volume was negatively correlated to trabecular BMD (P value = 0.0003) and SAT volume had no correlation to trabecular BMD. In contrast, there was no significant correlation between VAT or SAT and BMD in the ≥55-year-old sample. Our results indicate that high VAT volume is associated with low BMD in Chinese women aged <55 years and SAT has no relation with BMD.

A Single mri Slice Does Not Accurately Predict Visceral and Subcutaneous Adipose Tissue Changes During Weight Loss

Previous cross-sectional studies found that a single magnetic resonance imaging (MRI) slice predicts total visceral and subcutaneous adipose tissue (VAT and SAT) volumes well. We sought to investigate the accuracy of trunk single slice imaging in estimating changes of total VAT and SAT volume in 123 overweight and obese subjects who were enrolled in a 24-week CB-1R inverse agonist clinical trial (weight change, −7.7±5.3 kg; SAT change, −5.4±4.9 L, VAT change, −0.8±1.0 L). VAT and SAT volumes at baseline and 24 weeks were derived from whole body MRI images. The VAT area 5–10 cm above L4–L5 (A+5–10) (R2=0.59–0.70, P<0.001) best predicted changes in VAT volume but the strength of these correlations were significantly lower than those at baseline (R2=0.85–0.90, P<0.001). Furthermore, the L4–L5 slice poorly predicted VAT volume changes (R2=0.24–0.29, P<0.001). Studies will require 44–69% more subjects if (A+5–10) is used and 243–320% more subjects if the L4–L5 slice is used for equivalent power of multi slice total volume measurements of VAT changes. Similarly, single slice imaging predicts SAT loss less well than cross-sectional SAT (R2=0.31–0.49 vs. R2=0.52–0.68, p<0.05). Results stayed the same when examined in men and women separately. A single MRI slice 5–10 cm above L4–L5 is more powerful than the traditionally used L4–L5 slice in detecting VAT changes, but in general single slice imaging poorly predicts VAT and SAT changes during weight loss. For certain study designs, multi-slice imaging may be more cost effective than single slice imaging in detecting changes for VAT and SAT.

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

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. 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). 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). 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.

Between-slice intervals in quantification of adipose tissue and muscle in children

Magnetic Resonance Imaging (MRI) is increasingly being used in children to quantify adipose tissue (AT) and skeletal muscle (SM) in vivo. It is unclear whether the every 5 cm whole body MRI protocol used in adults is appropriate when applied in children. Whole body MRI continuous 1 cm thick slices were acquired in 73, aged 5-17-year-old healthy children. Images were segmented into subcutaneous (SAT), visceral (VAT), intermuscular AT (IMAT), and SM. The percentage difference between volumes measured by the continuous protocol and volumes estimated with protocols of different between-slice intervals (i.e., interval = 2, 3, 4 and 5 cm) was larger with an increase in interval size, depot size, weight and body mass index percentile. For group comparisons, studies will require less than 5.4% more subjects if an every 5 cm protocol is used for equivalent power as the every 1 cm protocol. For individual subject comparisons, interval protocols can be used to reliably distinguish between subjects who differ in SM or SAT volume by 0.14 to 0.64 L (i.e., 1 to 5% of SM or SAT volume) or more, or in VAT or IMAT volume by 0.06 to 0.21 L (i.e., 10 to 30% of VAT or IMAT volume) or more. The every 5 cm image acquisition protocol can be considered as accurate as the contiguous protocol for group comparisons in children, as well as for comparison of SM and SAT among individual children. However, a smaller slice interval protocol would be more accurate for comparison of VAT or IMAT among individual children.

Sexual dimorphism of adipose tissue distribution across the lifespan: a cross-sectional whole-body magnetic resonance imaging study

BackgroundDespite increasing research and clinical significance, limited information is available on how the visceral and subcutaneous adipose tissue (VAT and SAT) compartments develop during growth and maturation and then vary in volume across the adult lifespan. The present study aimed at exploring how adipose tissue compartments partition across the lifespan.MethodsTotal body VAT and SAT were quantified in an ethnically-diverse cross-sectional sample of healthy subjects ages 5 – 88 yrs [children (5–17 years): males n = 88, BMI percentile (X ± SD), 61.9 ± 27.1; females, n = 59, BMI percentile, 60.0 ± 28.4; adults (≥ 18 yrs): males, n = 164, BMI, 25.6 ± 3.7 kg/m2, and females, n = 188, BMI, 25.5 ± 5.4 kg/m2]. Subjects completed a whole-body magnetic resonance imaging scan and images were then segmented for VAT and SAT; total compartment volumes were calculated from respective slice areas. Sex and age distributions were evaluated by generating quadratic and cubic smoothing lines fitted to the data. Plots were developed with and without adjustment for total adipose tissue, ethnicity, and menopausal status in women. VAT and SAT volumes were both larger with greater age.ResultsIn adulthood, VAT was larger in males than in females with and without adjustment. In contrast, SAT volume was larger in females than in males after entering puberty and sex differences remained, with and without adjustment, across the remaining lifespan.ConclusionBased on observations made in this cross-sectional sample, VAT and SAT volumes were variably larger with greater age across most of the human lifespan, although the relatively small number of children warrants future larger scale studies to validate our observations. Moreover, the pattern and magnitude of adipose tissue "growth" differed between males and females, with the mechanistic basis of this sexual dimorphism only partially understood. These descriptive observations in a large cross-sectional cohort provide an initial foundation for future longitudinal and cohort studies.

Comparison of Low-Dose CT and MR for Measurement of Intra-Abdominal Adipose Tissue: A Phantom and Human Study

The aim of this study was to determine the accuracy and reproducibility of low-dose computed tomography (CT) and magnetic resonance (MR) for abdominal adipose tissue quantification on phantom and human studies. An adiposity phantom (with known internal/external oil volumes) was scanned at three different tube voltages (140, 120, and 90 kVp) using a 16-detector row CT scanner and was imaged using a T1-weighted spin echo MR sequence. For human studies, whole-volume coverage of the abdomen was obtained using CT (at 140 and 90 kVp) and T1-weighted spin echo MR imaging from five obese male volunteers (mean age, 40.6 years; mean body mass index, 30.2). The volumes of total, visceral, and subcutaneous adipose tissues (TAT, VAT, and SAT, respectively) were calculated independently by two radiologists for each CT scan and MR imaging using a computer-aided semiautomatic program. The estimated radiation dose could be reduced by approximately 75% with a 90-kVp protocol as compared with the 140-kVp protocol. Phantom studies showed that there was no statistically significant difference between the four methods in estimating the percentage predicted of the true volumes (measurement errors <4% for all methods, P > .05). In human studies, we found no statistically significant difference between the three methods in TAT, VAT, and SAT volumes (P > .05). Inter- and intraobserver reproducibilities of the CT volume estimates using the 90-kVp protocol were better than those obtained from MR imaging (kappa > 0.9 versus 0.4-0.5; coefficient of variation < 1% versus 15-22%). Low-dose CT provides accurate and reproducible measurement of abdominal adipose tissue volumes with a relevant dose reduction.