Accuracy Of Dual-energy X-ray Absorptiometry Research Articles

Bone mineral density and microarchitecture change during skeletal growth in harbor seals (Phoca vitulina) from the German coast

Across species, the skeletal system shares mutual functions, including the protection of inner organs, structural basis for locomotion, and acting as an endocrine organ, thus being of pivotal importance for survival. However, insights into skeletal characteristics of marine mammals are limited, especially in the growing skeleton. Harbor seals (Phoca vitulina) are common marine mammals in the North and Baltic Seas and are suitable indicators of the condition of their ecosystem. Here, we analyzed whole-body areal bone mineral density (aBMD) by dual-energy X-ray absorptiometry (DXA) and lumbar vertebrae by high-resolution peripheral quantitative computed tomography (HR-pQCT) in neonate, juvenile, and adult harbor seals. Along skeletal growth, an increase in two-dimensional aBMD by DXA was paralleled by three-dimensional volumetric BMD by HR-pQCT, which could be attributed to an increasing trabecular thickness while trabecular number remained constant. Strong associations were observed between body dimensions (weight and length) and aBMD and trabecular microarchitecture (R2 = 0.71–0.92, all p < 0.001). To validate the results of the DXA measurement (i.e., the standard method used worldwide to diagnose osteoporosis in humans), we performed linear regression analyses with the three-dimensional measurements from the HR-pQCT method, which revealed strong associations between the two imaging techniques (e.g., aBMD and Tb.Th: R2 = 0.96, p < 0.0001). Taken together, our findings highlight the importance of systematic skeletal investigations in marine mammals during growth, illustrating the high accuracy of DXA in this context. Regardless of the limited sample size, the observed trabecular thickening is likely to represent a distinct pattern of vertebral bone maturation. As differences in nutritional status, among other factors, are likely to affect skeletal health, it appears essential to routinely perform skeletal assessments in marine mammals. Placing the results in the context of environmental exposures may allow effective measures to protect their populations.

Alternatives to DEXA for the assessment of bone density: a systematic review of the literature and future recommendations.

Osteoporosis has significant implications in spine fusion surgery, for which reduced spinal bone mineral density (BMD) can result in complications and poorer outcomes. Currently, dual-energy x-ray absorptiometry (DEXA) is the gold standard for radiographic diagnosis of osteoporosis, although DEXA accuracy may be limited by the presence of degenerative spinal pathology. In recent years, there has been an evolving interest in using alternative imaging, including CT and MRI, to assess BMD. In this systematic review of the literature, the authors assessed the use and effectiveness of MRI, opportunistic CT (oCT), and quantitative CT (qCT) to measure BMD. In accordance with the PRISMA guidelines, the authors conducted a systematic search for articles posted on PubMed between the years 2000 and 2022 by using the keywords "opportunistic CT, quantitative CT, MRI" AND "bone density" AND "spine." Inclusion criteria consisted of articles written in English that reported studies pertaining to human or cadaveric subjects, and studies including a measure of spinal BMD. Articles not related to spinal BMD, osteoporosis, or spinal surgery or reports of studies that did not include the use of spinal MRI or CT were excluded. Key study outcomes were extracted from included articles, and qualitative analysis was subsequently performed. The literature search yielded 302 articles. Forty-two articles reported studies that met the final inclusion criteria. Eighteen studies utilized MRI protocols to correlate spinal BMD with vertebral bone quality scores, M-scores, and quantitative perfusion markers. Eight studies correlated oCT with spinal BMD, and 16 studies correlated qCT with spinal BMD. With oCT and qCT imaging, there was consensus that Hounsfield unit (HU) values > 160 demonstrated significant reduction in risk of osteoporosis, whereas HU values < 110 were significantly correlated with osteoporosis. Osteoporosis is increasingly recognized as a significant risk factor for complications after spinal fusion surgery. Consequently, preoperative assessment of BMD is a critical factor to consider in planning surgical treatment. Although DEXA has been the gold standard for BMD measurement, other imaging modalities, including MRI, oCT, and qCT, appear to be viable alternatives and may offer cost and time savings.

Dual energy X-ray absorptiometry produces larger measurement error in non-Hispanic Caucasians than Hispanics

Dual energy X-ray absorptiometry (DXA) is often used as a criterion measure in body composition research and in clinical settings for the estimate of body fat percent (%Fat). The accuracy of DXA for predicting %Fat has primarily been conducted in non-Hispanic populations. The purpose of this study was to determine the agreement of DXA-derived %Fat in Hispanic and non-Hispanic Caucasian adults. The sample consisted of Hispanic males (n=96) and females (n=102) and non-Hispanic Caucasian males (n=145) and females (n=161). The %Fat of a whole-body DXA scan was compared against a criterion 4-compartment (4C) model via constant error (CE=DXA - 4C model) and 95% limits of agreement. Also, a 2×2 factorial ANOVA, using CE as a dependent variable, was conducted to examine the main and interaction effects of sex and ethnicity. When compared to the 4C model, DXA overestimated %Fat by 4.0% in Hispanics and 5.5% in non-Hispanic Caucasians (all p<0.05). The 95% limits of agreement ranged from ±5.5% to ±5.9% for all group comparisons. The 2×2 factorial ANOVA indicated the CE was greater in non-Hispanic Caucasians than Hispanics (CE difference=1.5%; p<0.05). Our findings revealed that DXA significantly overestimates %Fat in both populations (Hispanics and non-Hispanic Caucasians), when compared to a 4C model, regardless of sex (male or female). However, the error is more profound in non-Hispanic Caucasian adults. It is worth nothing that DXA may be useful for tracking changes in body composition that occur throughout a lifestyle intervention. Nonetheless, practitioners should be aware that the estimate of %Fat from DXA may be larger than the actual values obtained from a 4C model.

Accuracy of dual-energy x-ray absorptiometry for assessing longitudinal change in visceral adipose tissue in patients with coronary artery disease.

Visceral adipose tissue (VAT) is a key target of interventions for obesity-related diseases. Dual-energy x-ray absorptiometry (DXA) can estimate VAT, however its accuracy to measure longitudinal change in VAT compared to gold-standard techniques such as magnetic resonance imaging (MRI), has not been studied in adults. This study aimed to determine the accuracy of DXA compared with gold-standard MRI for cross-sectional VAT assessment, and for detecting longitudinal change in VAT. Adults with coronary artery disease (64 ± 8 years; BMI 27.8 ± 3.5 kg/m2; 88% male) were assessed for VAT by DXA and MRI at baseline (n = 34) and during implementation of an exercise intervention study at 3- and 12-months (n = 29). To match the 5.2 cm DXA measurement site for Hologic software (InnerCoreTM), VAT cross-sectional area (CSA) was measured by MRI using a single slice at L4/L5 junction, and VAT volume measured by 10 × 5 mm slices over the L4/L5 junction. MRI slices were quantified for VAT using semi-automated specialised software. Relationships between DXA and MRI for cross-sectional VAT and longitudinal change in VAT were determined by linear regression. Accuracy between the methods was assessed by Bland-Altman analysis, with data presented as mean difference (95% confidence interval), lower and upper limits of agreement (LoA). Strong correlations were found between DXA-VAT and MRI-VAT at baseline (r = 0.90; p < 0.001), and longitudinal change in DXA-VAT and MRI-VAT over 3- and 12-months (r = 0.67; p < 0.001). In contrast, Bland-Altman analysis revealed significant overestimation by DXA-VAT volume at baseline by 13% [-104 cm3 (-157, -52 cm3), p < 0.001; LoA (-398, 189 cm3)], and underestimation of change in DXA-VAT volume over 3-months by 33% [-41 cm3 (-77, -4 cm3), p = 0.030; LoA (-228, 147 cm3)] and 12-months by 47% [-65 cm3 (-114, -17 cm3), p = 0.010; LoA (-316, 185 cm3)]. Results were similar for VAT CSA. Compared with MRI, DXA substantially underestimated longitudinal changes in VAT. Therefore, DXA is not currently a valid alternative to MRI for quantifying VAT changes and may under-represent the effectiveness of interventions for obesity management.

Validation of Dual Energy X-Ray Absorptiometry and Nuclear Magnetic Resonance in the Analysis of Body Composition in Mice.

BackgroundAs an instrument for measuring body composition in experimental animals, dual energy X-ray absorptiometry (DXA) is ideal for accuracy, cost, and measurement efficiency. However, there is too little insight into the effectiveness of the various aspects of applying DXA to experimental animals. We investigated whether to compare and verify the precision and accuracy of DXA and nuclear magnetic resonance (NMR) animal body composition analyzers.MethodsWe used 30 Institution of Cancer Research mice in the study. First, in order to evaluate the reproducibility of DXA and NMR, we did repeated measurements by repositioning each mouse in anesthesia and euthanasia states. Subsequently, the accuracy of each device was evaluated by comparing the weight measured before the experiment, the weight of the tissue extracted from the mice after the experiment, and the measured DXA and NMR. In addition, when measuring the body composition of animals, we compared the time and the measurable body composition parameters and summarized the advantages and disadvantages of the 2 devices.ResultsCompared to NMR, DXA had the advantage of a fast measurement of bone composition and rapid image analysis. In addition, DXA showed a higher correlation (>95%) with fat mass, lean mass baseline than did NMR (>85%).ConclusionsIn conclusion, DXA was confirmed to have higher precision and measurement accuracy than did NMR. Therefore, DXA is an effective method for evaluating the body composition of experimental animals.

A new finite element based parameter to predict bone fracture.

Dual Energy X-Ray Absorptiometry (DXA) is currently the most widely adopted non-invasive clinical technique to assess bone mineral density and bone mineral content in human research and represents the primary tool for the diagnosis of osteoporosis. DXA measures areal bone mineral density, BMD, which does not account for the three-dimensional structure of the vertebrae and for the distribution of bone mass. The result is that longitudinal DXA can only predict about 70% of vertebral fractures. This study proposes a complementary tool, based on Finite Element (FE) models, to improve the DXA accuracy. Bone is simulated as elastic and inhomogeneous material, with stiffness distribution derived from DXA greyscale images of density. The numerical procedure simulates a compressive load on each vertebra to evaluate the local minimum principal strain values. From these values, both the local average and the maximum strains are computed over the cross sections and along the height of the analysed bone region, to provide a parameter, named Strain Index of Bone (SIB), which could be considered as a bone fragility index. The procedure is initially validated on 33 cylindrical trabecular bone samples obtained from porcine lumbar vertebrae, experimentally tested under static compressive loading. Comparing the experimental mechanical parameters with the SIB, we could find a higher correlation of the ultimate stress, σULT, with the SIB values (R2adj = 0.63) than that observed with the conventional DXA-based clinical parameters, i.e. Bone Mineral Density, BMD (R2adj = 0.34) and Trabecular Bone Score, TBS (R2adj = -0.03). The paper finally presents a few case studies of numerical simulations carried out on human lumbar vertebrae. If our results are confirmed in prospective studies, SIB could be used—together with BMD and TBS—to improve the fracture risk assessment and support the clinical decision to assume specific drugs for metabolic bone diseases.

Accuracy of Longitudinal Assessment of Visceral Adipose Tissue by Dual-Energy X-Ray Absorptiometry in Children with Obesity.

Background Increased visceral adipose tissue (VAT) is strongly associated with cardiometabolic risk factors. Accurate quantification of VAT is available through magnetic resonance imaging (MRI), which incurs a significant financial and time burden. We aimed to assess the accuracy of dual-energy X-ray absorptiometry- (DXA-) derived VAT (DXA-VAT) against a gold standard MRI protocol (MRI-VAT) in children with normal weight and obesity cross-sectionally, and over the course of a lifestyle intervention. Methodology MRI-VAT and DXA-VAT were quantified in 61 children (30 normal weight and 31 with obesity) at baseline. Children with obesity entered a three-month exercise and/or nutrition intervention after which VAT was reassessed. MRI- and DXA-VAT cross-sectional area, volume, and mass were quantified, and associations were calculated at baseline (n = 61) and pre-post intervention (n = 28, 3 participants dropped out). Method agreement was assessed through Bland–Altman analysis, linear regression, and Passing–Bablok regression. Results At baseline, all DXA- and MRI-VAT outcomes were strongly associated (r = 0.90, P < 0.001). However, there were no significant associations between absolute or relative change in DXA- and MRI-VAT outcomes (r = 0.25–0.36, P > 0.05). DXA significantly overestimated VAT CSA (cross-sectional area), volume, and mass when compared with MRI (P < 0.001) at baseline. Significant proportional bias was observed for all DXA-VAT outcomes at baseline and for relative longitudinal changes in DXA-VAT. Conclusions Although DXA-VAT outcomes were strongly associated with MRI-VAT outcomes at baseline, estimates were subject to proportional bias in children with obesity and normal weight. DXA lacks validity for detecting changes in VAT among children with obesity. This trial is registered with NCT01991106.

Changes in DXA-derived lean mass and MRI-derived cross-sectional area of the thigh are modestly associated

Dual-energy X-ray absorptiometry (DXA) derived measures of lean mass demonstrate strong associations with magnetic resonance imaging (MRI) derived measures of muscle volume (MV) in cross-sectional studies, however, few studies have compared changes in response to an intervention. The purpose of this study was to determine the accuracy of DXA at detecting changes in lean mass, using MRI-derived MV as a reference standard. 10 male and 16 female subjects (29.2 ± 9.5 years) underwent DXA and MRI scans before and after a 10-week resistance training intervention. DXA thigh lean mass was compared to MRI mid-thigh MV, and percent change in size was compared between MRI and DXA. There was a strong correlation between measures cross-sectionally (r = 0.89) in agreement with previous investigations. However, there was a modest correlation of percentage change over time between methods (r = 0.49). Bland-Altman plots revealed that the amount of random error increased as the magnitude of the change from baseline increased. DXA measures of change in lean mass were modestly associated with MRI measures of change in MV. While there are several advantages to using DXA for the measurement of lean mass, the inability to accurately detect changes over time calls into question its use in clinical trials.

Comparison of Dual Energy X-ray Absorptiometry and Bioimpedance in Assessing Body Composition and Nutrition in Peritoneal Dialysis Patients

Peritoneal dialysis (PD) patients are characterized by protein malnutrition and muscle wasting. Reliable, easy, and cheap methods for evaluating nutrition are desirable. Three methods are commonly available: dual-energy X-ray absorptiometry (DXA), bioimpedance (BI), and subjective global assessment (SGA).The objective of the study was to compare the previously mentioned methods for assessment of body composition and nutritional status in PD patients. The study is cross-sectional and consisted of 72 PD patients from a single center PD ambulatorium. Participants were measured twice by DXA, twice by BI, and once by SGA. Measurements included lean tissue mass (LTM), fat tissue mass (FT) and, for BI, overhydration (OH), intracellular water (ICW), and extracellular water (ECW). LTM and FT were indexed to body area (Lean Tissue Index [LTI] and Fat Tissue Index [FTI], respectively), and ICW for height (ICW/ht). We assessed conventional biochemical and clinical variables, using values for normal individuals as a reference. There was good overall agreement between BI and DXA but considerable intra-individual variation (1 standard deviation: FT 5.7kg; LTM 5.6kg). Factors affecting the differences were FT, ICW, LTM, and ICW. Obesity (DXA 43%; BI 54%) and muscle wasting (BI 28%; SGA 53%) were common. Agreement between BI and SGA was poor. Thirty-eight percent of patients judged malnourished by SGA also had a low LTI; 23% with normal SGA had low LTI. SGA was closer related to LTI (BI) than LTI (DXA). Plasma albumin was correlated to LTI, FTI, and ICW/ht, and comorbidity to OH, clinical malnutrition, reduced FTI, but not LTI. Agreement between DXA and BI was high on a population basis but not at an individual level. Obesity and muscle wasting were common in this population. OH might reduce DXA accuracy in PD patients. LTI and ICW may be useful measures to supplement SGA in assessing nutrition.

Diagnostic accuracy of DXA compared to conventional spine radiographs for the detection of vertebral fractures in children

ObjectivesIn children, radiography is performed to diagnose vertebral fractures and dual energy x-ray absorptiometry (DXA) to assess bone density. In adults, DXA assesses both. We aimed to establish whether DXA can replace spine radiographs in assessment of paediatric vertebral fractures.MethodsProspectively, lateral spine radiographs and lateral spine DXA of 250 children performed on the same day were independently scored by three radiologists using the simplified algorithm-based qualitative technique and blinded to results of the other modality. Consensus radiograph read and second read of 100 random images were performed. Diagnostic accuracy, inter/intraobserver and intermodality agreements, patient/carer experience and radiation dose were assessed.ResultsAverage sensitivity and specificity (95 % confidence interval) in diagnosing one or more vertebral fractures requiring treatment was 70 % (58–82 %) and 97 % (94–100 %) respectively for DXA and 74 % (55–93 %) and 96 % (95–98 %) for radiographs. Fleiss’ kappa for interobserver and average kappa for intraobserver reliability were 0.371 and 0.631 respectively for DXA and 0.418 and 0.621 for radiographs. Average effective dose was 41.9 μSv for DXA and 232.7 μSv for radiographs. Image quality was similar.ConclusionGiven comparable image quality and non-inferior diagnostic accuracy, lateral spine DXA should replace conventional radiographs for assessment of vertebral fractures in children.Key Points• Vertebral fracture diagnostic accuracy of lateral spine DXA is non-inferior to radiographs.• The rate of unreadable vertebrae for DXA is lower than for radiographs.• Effective dose of DXA is significantly lower than radiographs.• Children prefer DXA to radiographs.• Given the above, DXA should replace radiographs for paediatric vertebral fracture assessment.

Effects of bariatric surgery on bone

Bariatric surgery currently relies on combinations of restrictive and malabsorptive procedures. Early decreases in bone mineral density (BMD) have been reported. However, the accuracy of dual-energy X-ray absorptiometry used to measure BMD can be diminished by the major weight loss, whereas quantitative computed tomography (QCT) measurements are less affected. The nutritional deficiencies induced by mixed bariatric surgery procedures, together with changes in hormones produced by adipocytes and/or the gastrointestinal tract, are often associated with elevations in serum levels of bone resorption markers. Although the data are limited, the incidence of fractures does not seem higher after bariatric surgery than in non-operated obese patients.

Body composition in young female eating-disorder patients with severe weight loss and controls: evidence from the four-component model and evaluation of DXA.

Background/Objectives:Whether fat-free mass (FFM) and its components are depleted in eating-disorder (ED) patients is uncertain. Dual energy X-ray absorptiometry (DXA) is widely used to assess body composition in pediatric ED patients; however, its accuracy in underweight populations remains unknown. We aimed (1) to assess body composition of young females with ED involving substantial weight loss, relative to healthy controls using the four-component (4C) model, and (2) to explore the validity of DXA body composition assessment in ED patients.Subjects/Methods:Body composition of 13 females with ED and 117 controls, aged 10–18 years, was investigated using the 4C model. Accuracy of DXA for estimation of FFM and fat mass (FM) was tested using the approach of Bland and Altman.Results:Adjusting for age, height and pubertal stage, ED patients had significantly lower whole-body FM, FFM, protein mass (PM) and mineral mass (MM) compared with controls. Trunk and limb FM and limb lean soft tissue were significantly lower in ED patients. However, no significant difference in the hydration of FFM was detected. Compared with the 4C model, DXA overestimated FM by 5±36% and underestimated FFM by 1±9% in ED patients.Conclusion:Our study confirms that ED patients are depleted not only in FM but also in FFM, PM and MM. DXA has limitations for estimating body composition in individual young female ED patients.

SAT0491 Accuracy of A New Ultrasonic Method for Osteoporosis Diagnosis on Lumbar Spine

BackgroundOsteoporosis is a systemic skeletal disease characterized by low bone mass and microarchitectural deterioration of bone tissue with a consequent increase in bone fragility and susceptibility to fracture. Fractures associated...

Validation of Dual Energy X-Ray Absorptiometry Measures of Abdominal Fat by Comparison with Magnetic Resonance Imaging in an Indian Population

ObjectiveAbdominal adiposity is an important risk factor for diabetes and cardiovascular disease in Indians. Dual energy X-ray absorptiometry (DXA) can be used to determine abdominal fat depots, being more accessible and less costly than gold standard measures such as magnetic resonance imaging (MRI). DXA has not been fully validated for use in South Asians. Here, we determined the accuracy of DXA for measurement of abdominal fat in an Indian population by comparison with MRI.Design146 males and females (age range 18–74, BMI range 15–46 kg/m2) from Hyderabad, India underwent whole body DXA scans on a Hologic Discovery A scanner, from which fat mass in two abdominal regions was calculated, from the L1 to L4 vertebrae (L1L4) and from the L2 to L4 vertebrae (L2L4). Abdominal MRI scans (axial T1-weighted spin echo images) were taken, from which adipose tissue volumes were calculated for the same regions.ResultsIntra-class correlation coefficients between DXA and MRI measures of abdominal fat were high (0.98 for both regions). Although at the level of the individual, differences between DXA and MRI could be large (95% of DXA measures were between 0.8 and 1.4 times MRI measures), at the sample level, DXA only slightly overestimated MRI measures of abdominal fat mass (mean difference in L1L4 region: 2% (95% CI:0%, 5%), mean difference in L2L4 region:4% (95% CI: 1%, 7%)). There was evidence of a proportional bias in the association between DXA and MRI (correlation between difference and mean −0.3), with overestimation by DXA greater in individuals with less abdominal fat (mean bias in leaner half of sample was 6% for L1L4 (95%CI: 2, 11%) and 7% for L2L4 (95% CI:3,12%).ConclusionsDXA measures of abdominal fat are suitable for use in Indian populations and provide a good indication of abdominal adiposity at the population level.

S.P.49 Cautions regarding subcapital whole body DXA scan interpretation among boys with Duchenne muscular dystrophy (DMD)

Abstract Lumbar and subcapital whole body Dual-energy X-ray absorptiometry (DXA) scans are recommended for monitoring bone mass (BMD) in boys with DMD. Complications of DMD and corticosteroids include: obesity, contractures, loss of ambulation and fractures contributing to errors in subcapital DXA accuracy and reproducibility. DXA scans in DMD boys frequently contain technical artifacts influencing BMD interpretation. We report the frequency of positioning and acquisition issues influencing subcapital DXA scan interpretation of DMD boys. Subcapital DXA scans (n = 189) of 64 DMD boys on Deflazacort were reviewed for motion artifact, contractures, obesity, suboptimal positioning, missing body segments, and orthopaedic hardware. Artifact-free scans with optimal positioning were obtained in the 64 boys when ambulatory, age 8.1 ± 2.2, BMI 16.7 ± 2.3 and 18.9 ± 3.9% subcapital body fat. 25% of the boys (16/64) when non-ambulatory, age 16.1 ± 2.1 had scans with motion artifact. 47% of the boys (30/64) developed contractures precluding optimal positioning. 14% of the boys (9/64) age 17.0 ± 2.5 when non-ambulatory, BMI 28.3 ± 4.0 and 52.8 ± 5.9% subcapital body fat had scans missing body segments; 6/9 missing digits, 1/9 both elbows, 1/9 ulna and 1/9 foot. 8% of the boys (5/64) age 17.1 ± 2.8 had hardware which increased BMD (g/cm2) from 8% to 124% (52.3 ± 50.6%) from their previous hardware-free scan. In general there are no technical issues with subcapital DXA in young ambulatory boys with DMD. As boys with DMD age, subcapital DXA scans contain a higher frequency of scan acquisition and interpretation errors from multiple sources. Attention to positioning for scan acquisition and analysis of scans in array mode may limit the potential for reproducibility and accuracy errors. Despite technical limitations DXA can identify boys with high fat mass and fracture risk. Future studies should compare the diagnostic yield of serial pQCT to DXA, to avoid the technical pitfalls of subcapital DXA.

Vertebral morphometry by dual-energy X-ray absorptiometry (DXA) for osteoporotic vertebral fractures assessment (VFA)

This study was done to evaluate the diagnostic accuracy of dual-energy X-ray absorptiometry (DXA) compared with conventional radiography for identifying vertebral fractures. A total of 930 postmenopausal women underwent conventional radiography and DXA imaging of the spine. The images were evaluated by two expert skeletal radiologists using the semiquantitative (SQ) method for conventional radiography and the morphometric vertebral fracture assessment (VFA) for DXA. The SQ method for radiography (SQ-Rx) analysed 99.1% of vertebrae, identifying 442 vertebral fractures; VFA analysed 97.5% vertebrae, detecting 420 vertebral fractures. Agreement between SQ-Rx and VFA reached 98.76%, and the κ-score was 0.96 [95% confidence interval (CI), 0.95-0.98]. Assessing the grading of vertebral fractures, agreement reached 97.5% and the κ-score was 0.841 (95% CI, 0.821-0.891). Considering SQ-Rx method as "gold standard", VFA had a sensitivity of 97.85 % and a specificity of 99.81%. The negative (NPV) and positive (PPV) predictive value for VFA were 99.83 % and 98.15%, respectively. Fractures were identified in 251 (27 %) and 242 (26 %) of patients on SQ-Rx and VFA, respectively. On a per-patient basis, the agreement between the two methods was 97% and the κ-score was 0.95 (95% CI, 0.920-0.968). The diagnostic parameters for VFA were 97.23% sensitivity, 98.86% specificity, 97.60% PPV and 98.84% NPV. This study demonstrated that VFA with DXA may reach a high level of accuracy for diagnosing vertebral fractures, suggesting that VFA should be introduced in the screening of individuals with a risk of osteoporosis and in the follow-up of osteoporotic patients receiving treatment.

Vertebral fracture assessment by new dual-energy X-ray absorptiometry

The aim of this study was to investigate the diagnostic performance of new dual-energy X-ray absorptiometry (DXA) technologies in the detection of vertebral fractures (VFs). Sixty-eight patients were submitted to DXA and conventional radiography (XR) on the same day. Lateral images of the spine were independently evaluated by three radiologists with different experience in skeletal imaging, in two sessions with 7days between evaluations of the same anonymous images. The most expert physician repeated the analysis in a subsequent reading session after further 7days. Results from expert XR evaluation were considered as gold standard. A semiquantitative approach was used to interpret images and morphometric analysis was performed when a VF was suspected. Seventy vertebrae (70/884, 7.9%) were excluded from the lesion-based analysis, as not evaluable: 11/70 (15.7%) missed by XR only, 56/70 (80.0%) missed by DXA only, 3/70 (4.3%) missed by both techniques (upper thoracic spine). Forty “true” fractures were detected (4.9% out of 814 vertebrae) in 26 patients (38.2% of the 68 studied patients). Twenty-five (62.5%) were mild fractures. DXA sensitivity and specificity were 70.0% and 98.3% on a lesion-based analysis, 73.1% and 90.5% on a patient-based analysis. Intra-observer agreement was excellent with no significant difference between the two techniques. Inter-observer agreement among the 3 observers was higher for XR (k=0.824 versus 0.720 in the detection of VFs, p=0.011). DXA accuracy was not influenced by radiologist experience; T4-L4 assessability as well as reproducibility and repeatability of the two techniques and accuracy of DXA were independent from sex, age, body mass index, grade of arthrosis. However DXA sensitivity was affected by mild VFs. Vertebral level did not affect the diagnostic performance with exception of vertebral body assessability. Latest improvements make VFs assessment by DXA competitive with traditional radiographic gold standard, providing consistent advantages and attractions. Few limitations still affect DXA performance and need to be overcome.

Lumbar spine and total-body dual-energy X-ray absorptiometry in children with severe neurological impairment and intellectual disability: a pilot study of artefacts and disrupting factors

BackgroundChildren with severe neurological impairment and intellectual disability (ID) are susceptible for developing low bone mineral density (BMD) and fractures. BMD is generally measured with dual-energy X-ray absorptiometry (DXA).ObjectiveTo describe the occurrence of factors that may influence the feasibility of DXA and the accuracy of DXA outcome in children with severe neurological impairment and ID.Materials and methodsBased on literature and expert opinion, a list of disrupting factors was developed. Occurrence of these factors was assessed in 27 children who underwent DXA measurement.ResultsDisrupting factors that occurred most frequently were movement during measurement (82%), aberrant body composition (67%), small length for age (56%) and scoliosis (37%). The number of disrupting factors per child was mean 5.3 (range 1–8). No correlation was found between DXA outcomes and the number of disrupting factors.ConclusionFactors that may negatively influence the accuracy of DXA outcome are frequently present in children with severe neurological impairment and ID. No systematic deviation of DXA outcome in coherence with the amount of disrupting factors was found, but physicians should be aware of the possible influence of disrupting factors on the accuracy of DXA.

Individual trabecula segmentation (ITS)-based morphological analyses and microfinite element analysis of HR-pQCT images discriminate postmenopausal fragility fractures independent of DXA measurements.

Osteoporosis is typically diagnosed by dual-energy X-ray absorptiometry (DXA) measurements of areal bone mineral density (aBMD). Emerging technologies, such as high-resolution peripheral quantitative computed tomography (HR-pQCT), may increase the diagnostic accuracy of DXA and enhance our mechanistic understanding of decreased bone strength in osteoporosis. Women with (n = 68) and without (n = 101) a history of postmenopausal fragility fracture had aBMD measured by DXA, trabecular plate and rod microarchitecture measured by HR-pQCT image-based individual trabecula segmentation (ITS) analysis, and whole bone and trabecular bone stiffness by microfinite element analysis (µFEA) of HR-pQCT images at the radius and tibia. DXA T-scores were similar in women with and without fractures at the spine, hip, and 1/3 radius, but lower in fracture subjects at the ultradistal radius. Trabecular microarchitecture of fracture subjects was characterized by preferential reductions in trabecular plate bone volume, number, and connectivity over rod trabecular parameters, loss of axially aligned trabeculae, and a more rod-like trabecular network. In addition, decreased thickness and size of trabecular plates were observed at the tibia. The differences between groups were greater at the radius than the tibia for plate number, rod bone volume fraction and number, and plate-rod and rod-rod junction densities. Most differences between groups remained after adjustment for T-score by DXA. At a fixed bone volume fraction, trabecular plate volume, number, and connectivity were directly associated with bone stiffness. In contrast, rod volume, number, and connectivity were inversely associated with bone stiffness. In summary, HR-pQCT-based ITS and µFEA measurements discriminate fracture status in postmenopausal women independent of DXA measurements. Moreover, these results suggest that preferential loss of plate-like trabeculae contribute to lower trabecular bone and whole bone stiffness in women with fractures. We conclude that HR-pQCT-based ITS and µFEA measurements increase our understanding of the microstructural pathogenesis of fragility fracture in postmenopausal women.

Comparison of DXA and CT in the Assessment of Body Composition in Premenopausal Women With Obesity and Anorexia Nervosa

Accurate methods for assessing body composition in subjects with obesity and anorexia nervosa (AN) are important for determination of metabolic and cardiovascular risk factors and to monitor therapeutic interventions. The purpose of our study was to assess the accuracy of dual-energy X-ray absorptiometry (DXA) for measuring abdominal and thigh fat, and thigh muscle mass in premenopausal women with obesity, AN, and normal weight compared to computed tomography (CT). In addition, we wanted to assess the impact of hydration on DXA-derived measures of body composition by using bioelectrical impedance analysis (BIA). We studied a total of 91 premenopausal women (34 obese, 39 with AN, and 18 lean controls). Our results demonstrate strong correlations between DXA- and CT-derived body composition measurements in AN, obese, and lean controls (r = 0.77-0.95, P < 0.0001). After controlling for total body water (TBW), the correlation coefficients were comparable. DXA trunk fat correlated with CT visceral fat (r = 0.51-0.70, P < 0.0001). DXA underestimated trunk and thigh fat and overestimated thigh muscle mass and this error increased with increasing weight. Our study showed that DXA is a useful method for assessing body composition in premenopausal women within the phenotypic spectrum ranging from obesity to AN. However, it is important to recognize that DXA may not accurately assess body composition in markedly obese women. The level of hydration does not significantly affect most DXA body composition measurements, with the exceptions of thigh fat.