Jan-Erik Angelhed

Whole-body adipose tissue analysis : Comparison of MRI, CT and dual energy X-ray absorptiometry

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.

Pubertal Timing Is an Independent Predictor of Central Adiposity in Young Adult Males: The Gothenburg Osteoporosis and Obesity Determinants Study

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/m2) 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.

Whole-body T1 mapping improves the definition of adipose tissue: consequences for automated image analysis.

To determine whether a whole‐body T1‐mapping acquisition method improves the definition of adipose tissue (AT) and simplifies automated AT segmentation compared to an image‐based method.

Obesity is accompanied by disturbances in peripheral glucocorticoid metabolism and changes in FA recycling

The glucocorticoid activating enzyme 11β‐hydroxysteroid dehydrogenase type 1 (11βHSD1) is of major interest in obesity‐related morbidity. Alterations in tissue‐specific cortisol levels may influence lipogenetic and gluco/glyceroneogenetic pathways in fat and liver. We analyzed the expression and activity of 11βHSD1 as well as the expression of phosphoenolpyruvate carboxykinase (PEPCK), sterol regulatory element binding protein (SREBP), and fatty acid synthase (FAS) in adipose and liver and investigated putative associations between 11βHSD1 and energy metabolism genes. A total of 33 obese women (mean BMI 44.6) undergoing gastric bypass surgery were enrolled. Subcutaneous adipose tissue (SAT), omental fat (omental adipose tissue (OmAT)), and liver biopsies were collected during the surgery. 11βHSD1 gene expression was higher in SAT vs. OmAT (P = 0.013), whereas the activity was higher in OmAT (P = 0.009). The SAT 11βHSD1 correlated with waist circumference (P = 0.045) and was an independent predictor for the OmAT area in a linear regression model. Energy metabolism genes had AT depot–specific expression; higher leptin and SREBP in SAT than OmAT, but higher PEPCK in OmAT than SAT. The expression of 11βHSD1 correlated with PEPCK in both AT depots (P = 0.05 for SAT and P = 0.0001 for OmAT). Hepatic 11βHSD1 activity correlated negatively with abdominal adipose area (P = 0.002) and expression positively with PEPCK (P = 0.003). In human obesity, glucocorticoid regeneration in the SAT is associated with central fat accumulation indicating that the importance of this specific fat depot is underestimated. Central fat accumulation is negatively associated with hepatic 11βHSD1 activity. A disturbance in peripheral glucocorticoid metabolism is associated with changes in genes involved in fatty acid (FA) recycling in adipose tissue (AT).

Weight Loss after Gastric Bypass Surgery in Women Is Followed by a Metabolically Favorable Decrease in 11β-Hydroxysteroid Dehydrogenase 1 Expression in Subcutaneous Adipose Tissue

BACKGROUND AND AIMS The role of 11beta-hydroxysteroid dehydrogenase 1 (11beta-HSD1) in the pathogenesis of obesity has been elucidated in humans and in various rodent models. Obesity is accompanied by disturbances in glucocorticoid metabolism, circulating adipokine levels, and fatty acid (FA) reesterification. This study was undertaken to evaluate glucocorticoid metabolism in sc fat before and after weight loss and to explore putative associations between 11beta-HSD1 and leptin, adiponectin, and FA recycling. SUBJECTS AND METHODS Twenty-seven obese (mean body mass index 44.4 + or - 4.4 kg/m(2)) women underwent gastric bypass surgery. Subcutaneous fat biopsies were collected before and 2 yr after surgery. The expression of 11beta-HSD1, leptin, adiponectin, and phosphoenolpyruvate carboxykinase (PEPCK) mRNA was evaluated with real-time PCR. Serum leptin and adiponectin protein levels were estimated by ELISA. RESULTS Two years after gastric bypass surgery, significant reductions were observed in the mean body mass index (from 44.4 to 30.8 kg/m(2)) and mean waist circumference (from 121.9 to 90.6 cm). After weight loss, 11beta-HSD1 mRNA expression decreased 4-fold (P < 0.001). Both leptin and adiponectin mRNA expression decreased, with concomitantly decreased circulating leptin and increased circulating adiponectin levels. PEPCK mRNA expression did not change. CONCLUSION Weight loss after gastric bypass surgery was followed by metabolically favorable changes in insulin sensitivity, circulating leptin and adiponectin, and peripheral glucocorticoid metabolism. A significant reduction in 11beta-HSD1 expression was observed in sc adipose tissue after weight loss. This suggests that up-regulation of 11beta-HSD1 is a consequence, rather than a cause, of obesity.

Optimization and evaluation of an image intensifier TV system for digital chest imaging

The quality of the digital image acquired with an image intensifier-TV system depends on a number of parameters. The present work describes procedures to take into account and control the major parameters that influence the image, and how it is perceived by a viewer. This is done both by adjustment of the equipment and by digital image restoration. To further increase the diagnostic yield of chest images, image processing routines for local contrast enhancement were developed and evaluated. Digital images were compared to conventional radiograms by ROC analysis of simulated nodules and line structures on an anthropomorphic phantom. The digital, 1024 matrix, image-intensifier system was found to be well suited for chest imaging, provided optimized equipment and processed images were used.

Measurement of lower-leg volume change by quantitative computed tomography

Background: Lower-leg edema is a common symptom in many diseases. A precise method with low variability for measurement of edema is warranted in order to obtain optimal conditions for investigation of treatment effects. Purpose: To evaluate computed tomography for precise measurement of lower-leg muscle and adipose tissue volumes using a very low level of effective radiation dose. Material and Methods: Eleven volunteers were examined three times during 1 day, either as two consecutive examinations in the morning and one single examination in the afternoon, or as one examination in the morning and two in the afternoon. Eleven scans with computed tomography were made at each examination, and lower-leg volumes were calculated from automatically measured scan areas and interscan distances. Volumes for muscle, adipose tissue, and bone were calculated separately. Minimal radiation dose was used. Results: Mean difference between the repeated examinations was −0.1 ml for total volume, −1.4 ml for muscle, and 1.6 ml for adipose tissue volume. The corresponding 95% confidence intervals were −6.5 to 6.0 ml, −3.5 to 6.5 ml, and −7.0 to 4.0 ml, respectively. The resulting effective dose was 0.5 µSv to one leg. Conclusion: Computed tomography can be used as a precise quantitative method to measure small volume changes of the lower leg as a whole, and separately for muscle and adipose tissue. The results were obtained with a negligible effective dose, lower than that delivered by modern fan-beam dual-energy X-ray absorptiometry whole-body examinations and equal to a few hours of background radiation.

Image Intensifier Based Digital Chest Radiography Visibility of Lesions and Anatomy

Contrast- and edge-enhanced digital monitor images from an image intensifier system for chest radiography were compared to conventional radiograms using visual grading analysis. Eleven observers graded the visibility of rounded opacities, the carinal region, fine line structures, and also compared the overall quality of images from 20 patients. The results showed significantly better visibility on the digital monitor for the rounded opacities and the mediastinum compared to the conventional radiograms. The overall quality of the digital images was also considered better. However, the digital images showed significantly inferior visibility for the line structures in comparison with the conventional radiograms. Our study indicates that the present contrast- and edge-enhanced digital images, with a spatial resolution of 1 024 × 1024 pixels and a contrast resolution of 8 bits, are superior to conventional radiograms for the visualization of mediastinal anatomy and rounded opacities. The clinical importance of the inferior visibility of fine line structures is not clear.

Image selection for volume calculations in digital ventriculography

The author describes a computer-assistance program for the selection of images to use in the calculation of cardiac parameters. Heart cycles with varying time intervals from end-systole to end-diastole may have end-diastolic volume variations, even though the contraction and relaxation patterns are normal. Thus it may be difficult to select the optimal beat from visual inspection of the image sequence only. The program calculates the points of time for end-diastole using image data. Using criteria for RR-intervals, the optimal images are found. The program needs minimal operator intervention and takes three minutes for a calculation based on 200 images. The quality of the computer output can be checked by inspection of the time-density diagram.<<ETX>>