| 1. |
- Brandberg, John, 1966, et al.
(författare)
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Accurate tissue area measurements with considerably reduced radiation dose achieved by patient-specific CT scan parameters
- 2008
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Ingår i: British Journal of Radiology. - : British Institute of Radiology. - 1748-880X .- 0007-1285. ; 81:970, s. 801-8
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Tidskriftsartikel (refereegranskat)abstract
- A low-dose technique was compared with a standard diagnostic technique for measuring areas of adipose and muscle tissue and CT numbers for muscles in a body composition application. The low-dose technique was intended to keep the expected deviation in the measured area of adipose and muscle tissue to <1% of the total tissue area. The largest diameter of the patient determined the parameters for the low-dose technique. 17 patients - chosen to cover a wide range of diameters (31-47 cm) for both abdomen and thighs - were examined using both techniques. Tissue areas were compared, as were CT numbers for muscle tissue. Image noise was quantified by standard deviation measurements. The area deviation was <1%, except in the smallest subjects, in whom it was <2%. The integral radiation dose of the low-dose technique was reduced to 2-3% for diameters of 31-35 cm and to 7.5-50% for diameters of 36-47 cm as compared with the integral dose by the standard diagnostic technique. The CT numbers of muscle tissue remained unchanged with reduced radiation dose. Image noise was on average 20.9 HU (Hounsfield units) for subjects with diameters of 31-35 cm and 11.2 HU for subjects with diameters in the range of 36-47 cm. In conclusion, for body composition studies with CT, scan protocols can be adjusted so that the integral dose is lowered to 2-60% of the standard diagnostic technique at our centre without adversely altering area measurements of adipose and muscle tissue and without altering CT numbers of muscle tissue.
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| 2. |
- Brandberg, John, 1966
(författare)
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Computed Tomography and Magnetic Resonance Imaging in Determination of Human Body Composition. Methodological and Applied Studies
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Background: Computed tomography (CT) and magnetic resonance imaging (MRI) provide important research opportunities due to their unique capability of characterizing and quantifying tissues and organs. Ionizing radiation is a limitation using CT, and recent developments aiming to improve MRI for determination of body composition have not been validated. An area with special interest in body composition is obesity research. The prevalence of obesity is increasing and abdominal, in particular visceral, obesity is associated with the metabolic syndrome and type 2 diabetes. Aims: I. To evaluate if the radiation dose to the subject can be substantially reduced in assessment of body composition using CT while maintaining accurate measurements of adipose and muscle tissue areas and muscle tissue attenuation. II. To validate a T1 mapping whole-body MRI method, used for assessment of body composition, by comparing it with a whole-body CT method. III. To examine within-scanner reproducibility and between-scanner performance of CT measurements of adipose and muscle tissue areas and liver attenuation. IV. To study the effects of GH treatment on body composition and insulin sensitivity in postmenopausal women with abdominal obesity. Methods: I. Seventeen subjects, covering a wide range of body diameters, were examined using scan parameters chosen to reduce radiation dose as well as standard clinical scan parameters. Tissue areas and muscle CT-numbers were measured. II. Ten patients were examined both by MRI and CT to validate the T1 mapping whole-body MRI method. MRI and CT results were compared regarding tissue areas and volumes, slice by slice, and for the whole body, respectively. III. Reproducibility of the two CT scanners was investigated using duplicates from 50 patients. Between-scanner performance was evaluated by comparison of results from 40 patients. IV. The effects of GH treatment were studied in 40 women in a randomized, placebo-controlled 12-month trial. Changes in body composition and insulin sensitivity were evaluated using CT and clamp-technique, respectively. Results and conclusions: I. In assessment of body composition using CT, the radiation dose to the subject was reduced to 2-60 % of standard dose used for diagnostic purposes while maintaining accurate measurements of adipose and muscle tissue areas and muscle tissue attenuation,. The resulting effective dose for a single slice examination is <0.1mSv, a dose level associated with trivial risk. Therefore, CT can be justified for body composition assessment even in large populations or for repeated examinations. II. Compared with CT, the MRI method slightly overestimated subcutaneous adipose tissue volume and slightly underestimated visceral adipose tissue volume, but it can be considered sufficiently accurate for whole-body measurements of adipose tissue volumes. III. Within-scanner reproducibility and between-scanner agreement were high for measurements of adipose and muscle tissue area. For measurements of liver attenuation, within-scanner reproducibility was high while a systematic bias was revealed in comparison between scanners. Therefore, comparison of CT numbers for liver from different scanners may be unreliable. IV. GH treatment of postmenopausal women with abdominal obesity reduced visceral adipose tissue and improved insulin sensitivity. CT revealed adipose tissue changes not detectable by waist-to-hip ratio, sagittal diameter, or waist circumference.
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| 3. |
- Franco Ramos, Celina, 1956, et al.
(författare)
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Growth hormone treatment reduces abdominal visceral fat in postmenopausal women with abdominal obesity: a 12-month placebo-controlled trial.
- 2005
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Ingår i: The Journal of clinical endocrinology and metabolism. - : The Endocrine Society. - 0021-972X .- 1945-7197. ; 90:3, s. 1466-74
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Tidskriftsartikel (refereegranskat)abstract
- Abdominal obesity is associated with blunted GH secretion and a cluster of cardiovascular risk factors that characterize the metabolic syndrome. GH treatment in abdominally obese men reduces visceral adipose tissue and has beneficial effects on the metabolic profile. There are no long-term data on the effects of GH treatment on postmenopausal women with abdominal obesity. Forty postmenopausal women with abdominal obesity participated in a randomized, double-blind, placebo-controlled, 12-month trial with GH (0.67 mg/d). The primary aim was to study the effect of GH treatment on insulin sensitivity. Measurements of glucose disposal rate (GDR) using a euglycemic, hyperinsulinemic glucose clamp; abdominal fat, hepatic fat content, and thigh muscle area using computed tomography; and total body fat and fat-free mass derived from (40)K measurements were performed at baseline and at 6 and 12 months. GH treatment reduced visceral fat mass, increased thigh muscle area, and reduced total and low-density lipoprotein cholesterol compared with placebo. Insulin sensitivity was increased at 12 months compared with baseline values in the GH-treated group. In the GH-treated group only, a low baseline GDR was correlated with a more marked improvement in insulin sensitivity (r = -0.68; P < 0.001). A positive correlation was found between changes in GDR and liver attenuation as a measure of hepatic fat content between baseline and 12 months (r = 0.7; P < 0.001) in the GH-treated group. In postmenopausal women with abdominal obesity, 1 yr of GH treatment improved insulin sensitivity and reduced abdominal visceral fat and total and low-density lipoprotein cholesterol concentrations. The improvement in insulin sensitivity was associated with reduced hepatic fat content.
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| 4. |
- Franco Ramos, Celina, 1956, et al.
(författare)
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The reduction in visceral fat mass in response to growth hormone is more marked in men than in oestrogen-deficient women.
- 2009
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Ingår i: Growth hormone & IGF research : official journal of the Growth Hormone Research Society and the International IGF Research Society. - : Elsevier BV. - 1096-6374. ; 19:2, s. 112-120
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Tidskriftsartikel (refereegranskat)abstract
- CONTEXT: Women with severe growth hormone (GH) deficiency have a less marked response to GH replacement than men. This has mostly been attributed to the attenuating effects of oestrogen replacement therapy. OBJECTIVE: To study gender related differences in the response to GH treatment in men and postmenopausal women. METHODS: Fifteen men and 15 age- and BMI-matched women with abdominal obesity (mean age: 58; range 51-64 years) were treated for one year with similar doses (0.47 vs. 0.51mg/day) of GH. All women were postmenopausal not receiving oestrogen treatment. Insulin sensitivity was assessed using a hyperinsulinemic euglycemic clamp and body composition by computed tomography (CT) scans and from total body potassium, K(40). RESULTS: Men and women were comparable at baseline in terms of waist circumference, IGF-1 and lipid levels. After one year of GH treatment, there was a 18% reduction in visceral adipose tissue (VAT) in men and a 5% reduction in women (P=0.0001 men vs. women). Although the magnitude of the difference was small, men increased more in thigh muscle mass (P<0.0001 vs. women). A reduction in thigh intermuscular adipose tissue (IMAT) and diastolic blood pressure was seen only in men (both p<0.05 vs. baseline). A decrease in LDL cholesterol, and an increase in serum insulin, was observed only in women (both p<0.05 vs. baseline). CONCLUSION: Low dose GH treatment reduced VAT more markedly in men as compared with women. As all women were postmenopausal and oestrogen-deficient, this gender difference in responsiveness was not due to an antagonistic effect of oestrogen on peripheral GH action.
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| 5. |
- Franco Ramos, Celina, 1956, et al.
(författare)
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Thigh intermuscular fat is inversely associated with spontaneous GH release in post-menopausal women with abdominal obesity.
- 2006
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Ingår i: European journal of endocrinology / European Federation of Endocrine Societies. - : Oxford University Press (OUP). - 0804-4643. ; 155:2, s. 261-8
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Tidskriftsartikel (refereegranskat)abstract
- CONTEXT: The metabolic syndrome is characterized by an increased accumulation of visceral adipose tissue (VAT) and blunted GH secretion. There are, however, no data on the association between GH secretion and other fat depots (in liver and muscle). OBJECTIVE/DESIGN: The aim of this cross-sectional study, which included 20 post-menopausal women with abdominal obesity, was to determine the association between GH secretion and regional adipose tissue (AT) distribution. Twelve-hour GH profiles (2000-0800 h) were performed by blood sampling every 20 min. GH was analyzed using an ultra-sensitive assay followed by approximate entropy (ApEn) and deconvolution analysis. RESULTS: In simple regression analyses, both basal and pulsatile GH secretions correlated negatively with VAT and thigh intermuscular adipose tissue (IMAT), but not with hepatic fat content. There was no correlation between ApEn and the AT depots studied. In multiple regression analysis, pulsatile GH secretion correlated inversely with thigh IMAT (B-coefficient=-0.67; P<0.01), whereas the correlation with VAT became non-significant. Furthermore, in multiple regression analysis, basal GH secretion correlated negatively with VAT (B-coefficient=-0.77; P=0.001), but not significantly with thigh IMAT. CONCLUSION: In post-menopausal women with abdominal obesity, pulsatile GH secretion demonstrated an independent, negative association with thigh IMAT, whereas basal GH secretion showed an independent, negative association with VAT. These findings suggest that the neuroendocrine association between fat mass and somatotropic axis is depot-dependent. We have identified thigh IMAT to be important in this interplay.
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| 6. |
- Karlsson, Martin, et al.
(författare)
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Serum phospholipid fatty acids, adipose tissue, and metabolic markers in obese adolescents
- 2006
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Ingår i: Obesity (Silver Spring). - 1930-7381. ; 14:11, s. 1931-9
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE: Fatty acid (FA) composition has a role in adipogenesis. The objective was to study serum phospholipid (PL) FAs in adolescents and their relation to abdominal adipose tissue (AT) compartments and metabolic markers. RESEARCH METHODS AND PROCEDURES: Abdominal AT was measured by magnetic resonance imaging and FA pattern was determined in serum PL of 10 obese adolescents (5 females), median age 12.0 years (range, 10.4 to 16.4) and BMI 30.7 (26.8 to 40.4), and 15 lean control subjects (9 females), median age 12.6 years (range, 11.3 to 15.4), and BMI 19.5 (17.1 to 23.4). RESULTS: Obese adolescents had relatively higher levels of saturated FA (SFA) and nervonic acid compared with controls. Serum PL concentration of n-3 polyunsaturated fatty acids (PUFA) was lower in the obese vs. lean females (p = 0.01), including docosahexaenoic acid (DHA) (p = 0.01). The ratios of arachidonic acid to DHA and total n-6/n-3 FA were increased in obese children (p = 0.02 and 0.01, respectively). n-3 PUFAs were inversely correlated to all subcutaneous AT compartments except visceral AT. The homeostasis model assessment index of beta-cell function related inversely to DHA concentration (p = 0.03). All changes were more marked in the females. DISCUSSION: Serum FA pattern in obese adolescents differed significantly from that in age-matched lean controls, reflecting a decrease in n-3 PUFA, especially DHA, and an increase in SFA. The subcutaneous AT, but not visceral AT, correlated to the changes in PUFA and SFA, suggesting an abnormal essential FA metabolism in obese adolescents.
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| 7. |
- Kindblom, Jenny, 1971, et al.
(författare)
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BMI Changes during Childhood and Adolescence as Predictors of Amount Adult Subcutaneous and Visceral Adipose Tissue in Men - the GOOD Study.
- 2009
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Ingår i: Diabetes. - : American Diabetes Association. - 1939-327X .- 0012-1797. ; 58:4, s. 867-874
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Tidskriftsartikel (refereegranskat)abstract
- Objective. The amount of visceral adipose tissue is a risk factor for the metabolic syndrome. It is unclear how body mass index (BMI) changes during childhood and adolescence predict adult fat distribution. We hypothesized that there are critical periods during development for the prediction of adult subcutaneous and visceral fat mass by BMI changes during childhood and adolescence. Research Design and Methods. Detailed growth charts were retrieved for the men participating in the population-based Gothenburg Osteoporosis and Obesity Determinants (GOOD) study (n=612). Body composition was analysed using Dual X-Ray Absorptiometry and adipose tissue areas using abdominal computed tomography at 18-20 years of age. Results. The main finding in the present study was that subjects with increases in BMI Z-score of >1 SD during adolescence had, independent of prepubertal BMI, both larger subcutaneous (+138%; p<0.001) and visceral adipose tissue areas (+91%; p< 0.001) than subjects with unchanged BMI Z-score. In contrast, subjects with increases in BMI Z-score of >1 SD during late childhood had larger amount adult subcutaneous adipose tissue (+83%; p< 0.001) than subjects with unchanged BMI Z-score, but unaffected amount of visceral adipose tissue. BMI changes during adolescence predict both visceral and subcutaneous adipose tissue of the abdomen while BMI changes during late childhood predict only the subcutaneous adipose tissue. Conclusions. The amount of visceral adipose tissue in young adult men was associated with BMI changes specifically during adolescence, while the amount of subcutaneous adipose tissue was associated with BMI changes during both late childhood and adolescence.
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| 8. |
- Kindblom, Jenny, 1971, et al.
(författare)
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Pubertal timing is an independent predictor of central adiposity in young adult males: the Gothenburg osteoporosis and obesity determinants study
- 2006
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Ingår i: Diabetes. - : American Diabetes Association. - 0012-1797 .- 0012-1797 .- 1939-327X. ; 55:11, s. 3047-52
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Tidskriftsartikel (refereegranskat)abstract
- The role of puberty and normal variations in pubertal timing for the development of obesity in men is unclear. The aim of the current study was to investigate the impact of pubertal timing and prepubertal BMI (kg/m(2)) for young adult BMI and fat mass distribution. Detailed growth charts from birth to age 18-20 years were retrieved for the men participating in the population-based Gothenburg Osteoporosis and Obesity Determinants study. Age at peak height velocity (PHV) and BMI at age 10 years were estimated for 579 subjects, and PHV was used as an assessment of pubertal timing. The fat mass characterization and distribution were analyzed using dual X-ray absorptiometry and peripheral as well as abdominal computed tomography at age 18.9 +/- 0.5 years. We demonstrate that age at PHV is an independent negative predictor of young adult BMI and whole-body fat mass. Interestingly, age at PHV is an independent negative predictor of central, but not peripheral, fat mass. In contrast, BMI at 10 years of age predicts both central and peripheral subcutaneous fat mass. In conclusion, we demonstrate that early pubertal onset specifically predicts a central fat mass distribution, while a predominantly subcutaneous obese phenotype is strongly predicted by a high prepubertal BMI.
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| 9. |
- Kullberg, Joel, et al.
(författare)
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Whole-body adipose tissue analysis: comparison of MRI, CT and dual energy X-ray absorptiometry.
- 2009
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Ingår i: The British journal of radiology. - : British Institute of Radiology. - 1748-880X .- 0007-1285. ; 82:974, s. 123-30
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to validate a recently proposed MRI-based T(1)-mapping method for analysis of whole-body adipose tissue (AT) using an established CT protocol as reference and to include results from dual energy X-ray absorptiometry (DEXA). 10 subjects, drawn from the Swedish Obese Subjects Sibling-pairs study, were examined using CT, MRI and DEXA. The CT analysis was based on 28 imaged slices. T(1) maps were calculated using contiguous MRI data from two different gradient echo sequences acquired using different flip angles. CT and MRI comparison was performed slice-wise and for the whole-body region. Fat weights were compared between all three modalities. Strong correlations (r > or = 0.977, p<0.0001) were found between MRI and CT whole-body and AT volumes. MRI visceral AT volume was underestimated by 0.79 +/- 0.75 l (p = 0.005), but total AT was not significantly different from that estimated by CT (MRI - CT = -0.61+/-1.17 l; p = 0.114). DEXA underestimated fat weights by 5.23 +/- 1.71 kg (p = 0.005) compared with CT. MRI underestimated whole-body volume by 2.03 +/- 1.61 l (p = 0.005) compared with CT. Weights estimated either by CT or by DEXA were not significantly different from weights measured using scales. In conclusion, strong correlations were found between whole-body AT results from CT, MRI-based T(1) mapping and DEXA. If the differences between the results from T(1)-mapping and CT-based analysis are accepted, the T(1)-mapping method allows fully automated post-processing of whole-body MRI data, allowing longitudinal whole-body studies that are also applicable for children and adolescents.
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| 10. |
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