Dual-energy X-ray Absoptiometry Research Articles

Cole-Impedance Model Representations of Right-Side Segmental Arm, Leg, and Full-Body Bioimpedances of Healthy Adults: Comparison of Fractional-Order

The passive electrical properties of a biological tissue, referred to as the tissue bioimpedance, are related to the underlying tissue physiology. These measurements are often well-represented by a fractional-order equivalent circuit model, referred to as the Cole-impedance model. Objective: Identify if there are differences in the fractional-order (α) of the Cole-impedance parameters that represent the segmental right-body, right-arm, and right-leg of adult participants. Hypothesis: Cole-impedance model parameters often associated with tissue geometry and fluid (R∞, R1, C) will be different between body segments, but parameters often associated with tissue type (α) will not show any statistical differences. Approach: A secondary analysis was applied to a dataset collected for an agreement study between bioimpedance spectroscopy devices and dual-energy X-ray absoptiometry, identifying the Cole-model parameters of the right-side body segments of N=174 participants using a particle swarm optimization approach. Statistical testing was applied to the different groups of Cole-model parameters to evaluate group differences and correlations of parameters with tissue features. Results: All Cole-impedance model parameters showed statistically significant differences between body segments. Significance: The physiological or geometric features of biological tissues that are linked with the fractional-order (α) of data represented by the Cole-impedance model requires further study to elucidate.

Analiza telesnog sastava - najčešći modeli i metode ispitivanja

Accurate and valid analysis of body composition is important for the diagnosis of nutritional status, training impact assessment, the body's response to nutritional and therapeutic interventions, growth and development of the organism, and health risk assessment. With the increasing prevalence of chronic non-communicable diseases, obesity, the need for different models and methods of body composition analysis has also increased. This review paper aimed to show the most commonly used methods for body composition analysis and to give a brief insight into the current techniques. The methods for analysing body composition vary in their accuracy and reliability and in practice the use of appropriate methods depends on the interest and the required accuracy, e.g. dual-energy X-ray absoptiometry (DXA) as the gold standard for determining bone mineral density, or magnetic resonance imaging (MRI) as the gold standard for soft tissue and organ analysis. These methods, along with computed tomography (CT), hydrodensitometry and plethysmography, are routinely used in clinical medicine, and due to their complexity, availability and high prices, they are mostly used in sports medicine for research purposes. In sports medicine, the anthropometric method and bioelectrical impedance analysis (BIA) are mostly used, due to their simplicity and comfort for the examinees. The best assessment of body composition can be obtained by a combination of several methods - a multi-component model, which can increase the accuracy and reliability of the obtained data, and health risk can be assessed with greater certainty.

Zoledronic Acid for Treatment of Low Bone Mineral Density in Patients with Beta Thalassemia Major.

To determine the efficacy of zoledronic acid (ZA) in thalassemia major associated low bone mineral density. Prospective, open label, single arm trial. Bone mineral density (BMD) at lumbar, hip and forearm region were performed at baseline and after 1year of therapy. Initial, 9 patients received a first dose of 4mg. Due to severe adverse effects, further doses for these patients and all new recruited patients were 1mg once every 3months for 4 doses. All patients were receiving 500mg of calcium carbonate twice daily and 0.25μg alfacalcidol once daily before and during the entire study period. Dual energy X-ray absoptiometry was performed at baseline and after 1year. Twenty-seven patients with transfusion dependent thalassemia with a median age 19.5year (15-38years) were eligible for ZA treatment. Seven patients had bony pains. Four patients developed grade 4 hypocalcemia (3 developed tetany) and 2 developed infusion related toxicity with initial dose of 4mg. One mg dose was well tolerated. At the end of 1year, bone pains had completely resolved. There was significant increase in BMD at lumbar (p = 0.002) and forearm regions (p = 0.04) and intertrochantric area (p = 0.041). The % change in BMD at 1year was +3.7 ± 3.2%. ZA is an efficacious agent in treatment of low BMD in these patients. ZA produces significant adverse reactions at 4mg dose but 1mg dose is well tolerated and is efficacious.

Racial Differences in Bone Microarchitecture and Estimated Strength at the Distal Radius and Distal Tibia in Older Adolescent Girls: a Cross-Sectional Study.

Previous studies have demonstrated that an individual's race and ethnicity are important determinants of their areal bone mineral density (aBMD), assessed by dual-energy X-ray absorptiometry. However, there are few data assessing the impact of race on bone microarchitecture and strength estimates, particularly in older adolescent girls and young adults. We hypothesized that bone microarchitecture and strength estimates would be superior in Blacks compared to White and Asian American adolescent girls and young adults of similar age based on reports of higher aBMD in Blacks. We assessed BMD using dual-energy X-ray absoptiometry (DXA), bone microarchitecture at the distal radius and distal tibia using high-resolution peripheral quantitative computed tomography (HRpQCT) and estimated measures of bone strength using micro-finite element analysis (FEA) in 35 White, 15 Asian American, and 10 Black girls 14-21years. After controlling for height, most DXA measures of aBMD and aBMD Z scores were higher in Black girls compared with Whites and Asian Americans. HRpQCT and FEA showed that at the distal radius, Blacks had greater cortical perimeter, cortical area, trabecular thickness, trabecular BMD, estimated failure load, and stiffness than the other two groups. For the distal tibia, trabecular number and BMD were higher in Blacks than Asian Americans. Particularly at the distal radius, adolescent and young adult White and Asian American girls have less favorable bone microarchitecture and lower bone strength than Blacks, possibly explaining the lower risk of fracture seen in Blacks. Level II.

Body composition changes in elite soccer players along the competitive season

Changes in body composition were investigated in 30 elite (serie A) soccer players (age, 25.2±4.26y; stature,1821±6,39cm; body mass 78.7±6.38kg; BMI, 23.7±1,24kg/m2) along the competitive season. Body composition was assessed with Dual-energy X-ray absoptiometry (DXA) at pre-season (July), mid-season (January-March), and end-season (May).Results show that body mass and BMI did not change to a significant extent along the season; however, fat mass and percent fat mass showed significant reduction (p=0,017; p=0,014). Significant reduction was already found in the latter at mid-season vs. pre-season (p=0.032 for both). The decrease in fat mass and percent fat mass was similar across the playing positions. Instead, lean mass and bone mineral content did not change significantly. To our knowledge, this work is the first report of season-related body composition changes in elite soccer players using the reliable DXA technique. Results are in partial agreement with previous finding showing changes in both fat and lean mass along the season in elite soccer players [1] using skinfolds measurement and predictive equations. The results of this work should be of interest to soccer professionals because they will help improve athletes’ performance.

Whole-body vibration slows the acquisition of fat in mature female rats

To evaluate the effects of whole-body vibration on fat, bone, leptin and muscle mass. Thirty 7-month-old female 344 Fischer rats were randomized by weight into three groups (baseline, vibration or control; n=8-10 per group). Rats in the vibration group were placed inside individual compartments attached to a Pneu-Vibe vibration platform (Pneumex, Sandpoint, ID, USA) and vibrated at 30-50 Hz (6 mm peak to peak) for 30 min per day, 5 days per week, for 12 weeks. The vibration intervention consisted of six 5-min cycles with a 1-min break between cycles. There were significant body composition differences between the whole-body vibration and the control group. The whole-body vibration group weighed approximately 10% less (mean+/-s.d.; 207+/-10 vs 222+/-15 g, P<0.03) and had less body fat (20.8+/-3.8 vs 26.8+/-5.9 g, P<0.05), a lower percentage of body fat (10.2+/-1.7 vs 12+/-2.0%, P<0.05), and lower serum leptin levels (1.06+/-0.45 vs 2.27+/-0.57 ng ml(-1), P<0.01) than the age-matched controls. No differences were observed for total lean mass, bone mineral content (BMC), bone mineral density (BMD), insulin-like growth factor-I (IGF-I) or soleus (SOL) and extensor digitorum longus (EDL) mass or function. Regional high-resolution dual-energy X-ray absoptiometry scans of the lumbar spine (L1-4) revealed that the whole-body vibration group had significantly greater BMC (0.33+/-0.05 vs 0.26+/-0.03 g, P<0.01) and BMD (0.21+/-0.01 vs 0.19+/-0.01 g cm(-2), P<0.01) than the control group. No differences between the groups were observed in the amount of food consumed. These findings show that whole-body vibration reduced body fat accumulation and serum leptin without affecting whole body BMC, BMD or lean mass. However, the increase in vertebral BMC and BMD suggests that vibration may have resulted in local increases in bone mass and density. Also, whole-body vibration did not affect muscle function or food consumption.

Bone health in children and adolescents after allogeneic stem cell transplantation

This cross-sectional study evaluated the overall bone health and the prevalence of vertebral complications after stem cell transplantation (SCT) in prepubertal children and adolescents. A total of 44 children and adolescents (median age, 10 years) were evaluated at a median of 3.8 years after SCT for areal bone mineral density (aBMD) with dual-energy X-ray absoptiometry and for vertebral fractures with instant vertebral assessment. Pretransplant and posttransplant medications and nutritional parameters were recorded, and plasma levels of vitamin D, calcium, phosphate, and parathormone were measured. Of the 44 patients, 16 (36%) had a BMD Z-score of <-1.0. The patients with low BMD did not differ from the others with regard to their clinical or biochemical characteristics. Prepubertal patients had better BMD Z-scores at all sites compared with pubertal or postpubertal subjects. This was evident especially at the hip, in which the median aBMD Z-score in prepubertal patients (-0.2; range, -0.5 to +1.7) was found to be significantly higher than in pubertal (-1.1; range, -1.5 to +0.4) and postpubertal (-1.1; range, -2.6 to +0.5) patients (P = .03). Five patients (11%) had a history of peripheral fractures. Nine patients (20%) had vertebral compression fractures, which were asymptomatic in 7 patients. Approximately one-third of patients who had undergone allogeneic SCT in childhood were found to have a reduced BMD before reaching adulthood. This was due in part to inadequate BMD gain during the pubertal years. The high prevalence of asymptomatic vertebral compression fractures calls for the systematic assessment of spinal health during the posttransplantation follow-up.

A seasonal variation of calcitropic hormones, bone turnover and bone mineral density in early and mid-puberty girls – a cross-sectional study

The importance of the seasonal variation of calcitropic hormones to growing skeleton has not been established. We studied whether there exists a seasonal variation in calcitropic hormones, bone mineral density (BMD) and bone remodelling markers in early puberty girls. One hundred and ninety-six girls, mean age 11.4 (sd 0.4) years, in Tanner stage 2 (early puberty) and 3 (mid-puberty) were studied during September to March. The BMD was measured from the lumbar vertebrae and the left femur by dual-energy X-ray absoptiometry. Their serum 25-hydroxyvitamin D (S-25-OHD), serum intact parathyroid hormone (S-iPTH), serum osteocalcin, urinary pyridinoline and urinary deoxypyridinoline were analysed from fasting samples. The concentration of S-25-OHD and serum osteocalcin differed among months (P < 0.01), reflecting a seasonal variation. The parathyroid hormone correlated negatively with S-25-OHD (r -0.325, P < 0.001). Moreover, the BMD in the femur (P = 0.047) and to a lesser extent in vertebrae (P = 0.057) differed between months in early puberty girls but this was not seen in mid-puberty. Seasonal variation in S-25-OHD and bone remodelling markers accompanied by negative correlation between S-25-OHD and S-iPTH was seen in this cross-sectional study of adolescent girls. In addition, the seasonal rhythm contributed 7.0-7.6 % difference in the BMD of lumbar vertebrae and left femur in early puberty girls. This variation should be avoided since it could hamper peak bone mass attainment.

IZMENENIYa KOSTNOY TKANI ChELOVEKA V KOSMIChESKOM POLETE II. NEKOTORYE ZAKONOMERNOSTI I OSOBENNOSTI

There are considered possible mechanisms of some peculiarities of cosmonauts bone tissue changes after space flights 5-7 month duration, that were diagnosed using dual energy X-ray absoptiometry (DEXA). Local osteopenia in spongy bone of the body lower part may be connected with big weight bearing load in 1g conditions. Increasing of mineral content in upper part of the skeleton and hypermineralization of vertebrae body spongy bone, that were showed by computer tomography possible are the secondary effects and are connected with fluid redistribution to cranial direction, including abdomen. Additional negative gradient of bone mass in bones of lower part of skeleton, that is observed in early period of readaptation (till 1 month) may be explained as result of acceleration of bone remodeling (resorption and formation of bone), as reaction to recover of loading. Individual variability of above mentioned reactions is connected with genetically determined initial bone mass and phenotype of bone metabolism. There are considered possibilities of genetic prediction of osteopenia in discussed conditions.

A cellular-level approach to predicting resting energy expenditure across the adult years

We previously derived a whole-body resting energy expenditure (REE) prediction model by using organ and tissue mass measured by magnetic resonance imaging combined with assumed stable, specific resting metabolic rates of individual organs and tissues. Although the model predicted REE well in young persons, it overpredicted REE by approximately 11% in elderly adults. This overprediction may occur because of a decline in the fraction of organs and tissues as cell mass with aging. The aim of the present study was to develop a cellular-level REE prediction model that would be applicable across the adult age span. Specifically, we tested the hypothesis that REE can be predicted from a combination of organ and tissue mass, the specific resting metabolic rates of individual organs and tissues, and the cellular fraction of fat-free mass. Fifty-four healthy subjects aged 23-88 y had REE, organ and tissue mass, body cell mass, and fat-free mass measured by indirect calorimetry, magnetic resonance imaging, whole-body (40)K counting, and dual-energy X-ray absoptiometry, respectively. REE predicted by the cellular-level model was highly correlated with measured REE (r = 0.92, P < 0.001). The mean difference between measured REE (x+/- SD: 1487 +/- 294 kcal/d) and predicted REE (1501 +/- 300 kcal/d) for the whole group was not significant, and the difference between predicted and measured REE was not associated with age (r = 0.009, NS). The present approach establishes an REE-body composition link with the use of a model at the cellular level. The combination of 2 aging-related factors (ie, decline in both the mass and the cellular fraction of organs and tissues) may account for the lower REE observed in elderly adults.

Longitudinal study of bone mineral density in patients with Crohn's disease.

Osteoporosis is frequent in Crohn's disease. The aim of the study was to assess the rate of bone loss over time retrospectively and the influence of disease-related factors on bone loss. Twenty-nine patients (8 male), admitted for repeated bone mineral density assessments (BMD) were enrolled. BMD measured by dual energy x-ray absoptiometry was expressed in grams per square centimeter, and as sex- and age-matched Z score. The mean interval between BMD assessments was 41 months, during which period 27 patients used corticosteroids (mean dose 8.6 g) and 21 patients some form of bone protective medication. Initial Z scores at a mean age of 41 years were significantly below zero (spine -1.6 +/- 1.4; femur -1.4 +/- 1.4). Over time, no change in absolute BMD was observed accompanied by an improvement in Z scores. At the same time, an increase in body weight and a decrease in erythrocyte sedimentation rate (ESR) was observed. Multilinear regression analysis demonstrated change in ESR as independent predictor for change in femoral Z score. In conclusion, low BMD is frequent in Crohn's disease, but decline of BMD over time was not found, despite ongoing use of corticosteroids.