Technical principles of dual energy x-ray absorptiometry

Evaluating osteoporosis and bone quality in the aging spine: modern considerations for surgical management in the geriatric population

Surgical management paradigms of spinal pathologies in the aging population carry inherent substantial risks, with surgical complications being more prevalent among patients with osteoporosis compared to those with normal bone mineral density. In this narrative review, we aim to highlight important clinical understanding and considerations in perioperative evaluation and management of patients elected to undergo spinal surgery. Osteoporosis is a well-defined risk factor for mechanical complications following spinal surgery, and as such, perioperative optimization of bone health in the setting of surgery for geriatric patients remains a critical research area alongside intraoperative surgical augmentation techniques. Surgical techniques to circumvent challenges with instrumentation of poor bone mineral density have included augmentation of pedicle screw fixation, including segmental bicortical screw fixation techniques, cement augmentation with fenestrated screws, or use of expandable pedicle screws to improve bone-implant interface. Judicious selection of treatment modalities and subsequent perioperative optimization is paramount to minimize surgical complications. Contemporary guidelines and evolving paradigms in perioperative evaluation, optimization, and management of the aging spine include the advent of quantitatively evaluating computed tomography (CT) via assessment of the magnitude of Hounsfield units. Prescribing pharmacotherapeutic agents and monitoring bone health requires a multidisciplinary team approach, including endocrinologists and geriatricians to coordinate high-quality care for advanced-age patients who require surgical management of their spinal disorders.

A Study on Intelligent Optical Bone Densitometry

Osteoporosis is a prevalent chronic disease worldwide, particularly affecting the aging population. The gold standard diagnostic tool for osteoporosis is Dual-energy X-ray Absorptiometry (DXA). However, the expensive cost of the DXA machine and the need for skilled professionals to operate it restrict its accessibility to the general public. This paper builds upon previous research and proposes a novel approach for rapidly screening bone density. The method involves utilizing near-infrared light to capture local body information within the human body. Deep learning techniques are employed to analyze the obtained data and extract meaningful insights related to bone density. Our initial prediction, utilizing multi-linear regression, demonstrated a strong correlation (r = 0.98, p-value = 0.003**) with the measured Bone Mineral Density (BMD) obtained from Dual-energy X-ray Absorptiometry (DXA). This indicates a highly significant relationship between the predicted values and the actual BMD measurements. A deep learning-based algorithm is applied to analyze the underlying information further to predict bone density at the wrist, hip, and spine. The prediction of bone densities in the hip and spine holds significant importance due to their status as gold-standard sites for assessing an individual's bone density. Our prediction rate had an error margin below 10% for the wrist and below 20% for the hip and spine bone density.

Agaricus bisporus Extract Exerts an Anti-Obesity Effect in High-Fat Diet-Induced Obese C57BL/6N Mice by Inhibiting Pancreatic Lipase-Mediated Fat Absorption

Agaricus bisporus is well known as a source of polysaccharides that could improve human health. The objective of this study was to explore the anti-obesity effect of A. bisporus extract (ABE), abundant in polysaccharides, and its underlying mechanism. Pancreatic lipase inhibitory activity in vitro was determined after treatment with ABE and chitosan. Treatment with ABE and chitosan significantly decreased pancreatic lipase activity. Five-week-old male SD rats were randomly divided into three groups for acute feeding with vehicle, ABE at 80 mg/kg body weight (BW)/day, and ABE at 160 mg/kg BW/day. ABE dose-dependently increased plasma lipid clearance in an oral lipid tolerance test. Five-week-old male C57BL/6N mice were fed a control diet (CD), a high-fat diet (HFD), an HFD with ABE at 80 mg/kg BW/day, ABE at 160 mg/kg BW/day, or chitosan at 160 mg/kg BW/day for eight weeks. HFD-fed mice showed significant increases in body weight, fat mass, white adipose tissue, average lipid droplet size, and serum levels of glucose, triglyceride, ALT, and AST compared to those in the CD group. However, ABE or chitosan administration ameliorated these increases. ABE or chitosan significantly reduced dietary efficiency and increased fecal excretion levels of lipids, triglycerides, and total cholesterol. These in vitro and in vivo findings suggest that ABE might act as an anti-obesity agent by inhibiting pancreatic lipase-mediated lipid absorption, at least in part.

Feasibility of aluminum phantom radiography for osteoporosis detection in postmenopausal women with a fragility fracture of the distal radius compared to DXA and HR-pQCT

Recently, promising results have been reported for detection of osteoporosis with use of an aluminum phantom. Therefore, the aim of this study was to evaluate the feasibility of radiography-based bone mineral density (BMD) measurement using a graded aluminum phantom. This study included 27 postmenopausal women with a distal radius fracture. Aluminum phantom radiography of the healthy radius was conducted as well as high-resolution peripheral quantitative computed tomography (HR-pQCT) measurement of the ultradistal radius and dual energy X-ray absorptiometry (DXA) of the radius, spine, and hip. A strong correlation was observed between aluminum phantom radiography-based mean gray value (mGV) and DXA-derived BMD, especially for the ultradistal radius (ρ = 0.75; p < 0.001). A moderate correlation for the femoral neck (ρ = 0.61 and p < 0.001) between modalities was found. Radius mGV and HR-pQCT-derived BMD only showed a moderate correlation (ρ = 0.48; p < 0.09). Aluminum phantom radiography might serve as a cost efficient, highly available, low-radiation dose screening, and diagnostic method for osteoporosis additively to DXA measurements. Especially, an application in areas with constrained DXA availability and such as preoperative trauma settings would be beneficial. However, further investigation and assessment of specificity and sensitivity is needed.

Biomechanical structure-function relations for human trabecular bone - comparison of calcaneus, femoral neck, greater trochanter, proximal tibia, and vertebra

MicroCT-based finite element models were used to compute power law relations for uniaxial compressive yield stress versus bone volume fraction for 78 cores of human trabecular bone from five anatomic sites. The leading coefficient of the power law for calcaneus differed from those for most of the other sites (p < 0.05). However, after normalizing by site-specific mean values, neither the leading coefficient (p > 0.5) nor exponent (p > 0.5) differed among sites, suggesting that a given percentage deviation from mean bone volume fraction has the same mechanical consequence for all sites investigated. These findings help explain the success of calcaneal x-ray and ultrasound measurements for predicting hip fracture risk.

Associations Among Hip Structure, Bone Mineral Density, and Strength Vary With External Bone Size in White Women

Bone mineral density (BMD) is heavily relied upon to reflect structural changes affecting hip strength and fracture risk. Strong correlations between BMD and strength are needed to provide confidence that structural changes are reflected in BMD and, in turn, strength. This study investigated how variation in bone structure gives rise to variation in BMD and strength and tested whether these associations differ with external bone size. Cadaveric proximal femurs (n = 30, White women, 36-89+ years) were imaged using nanocomputed tomography (nano-CT) and loaded in a sideways fall configuration to assess bone strength and brittleness. Bone voxels within the nano-CT images were projected onto a plane to create pseudo dual-energy X-ray absorptiometry (pseudo-DXA) images consistent with a clinical DXA scan. A validation study using 19 samples confirmed pseudo-DXA measures correlated significantly with those measured from a commercially available DXA system, including bone mineral content (BMC) (R ²  = 0.95), area (R ²  = 0.58), and BMD (R ²  = 0.92). BMD-strength associations were conducted using multivariate linear regression analyses with the samples divided into narrow and wide groups by pseudo-DXA area. Nearly 80% of the variation in strength was explained by age, body weight, and pseudo-DXA BMD for the narrow subgroup. Including additional structural or density distribution information in regression models only modestly improved the correlations. In contrast, age, body weight, and pseudo-DXA BMD explained only half of the variation in strength for the wide subgroup. Including bone density distribution or structural details did not improve the correlations, but including post-yield deflection (PYD), a measure of bone material brittleness, did increase the coefficient of determination to more than 70% for the wide subgroup. This outcome suggested material level effects play an important role in the strength of wide femoral necks. Thus, the associations among structure, BMD, and strength differed with external bone size, providing evidence that structure-function relationships may be improved by judiciously sorting study cohorts into subgroups. © 2022 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Emerging Role of 18F-NaF PET/Computed Tomographic Imaging in Osteoporosis: A Potential Upgrade to the Osteoporosis Toolbox

Osteoporosis is a metabolic bone disorder that leads to a decline in bone microarchitecture, predisposing individuals to catastrophic fractures. The current standard of care relies on detecting bone structural change; however, these methods largely miss the complex biologic forces that drive these structural changes and response to treatment. This review introduces sodium fluoride (18F-NaF) positron emission tomography/computed tomography (PET/CT) as a powerful tool to quantify bone metabolism. Here, we discuss the methods of 18F-NaF PET/CT, with a special focus on dynamic scans to quantify parameters relevant to bone health, and how these markers are relevant to osteoporosis.

Dual X-ray absorptiometry-derived total and regional body volume

BACKGROUND & AIMS

Although dual X-ray absorptiometry (DXA) has been used to determine total body volume, using DXA to determine regional (i.e., arm and leg) volumes needs further assessment. Thus, the aim of the present study is to evaluate the validity of total and regional DXA-derived body volume compared to a traditional method for measuring body volume.

METHODS

A total of 30 males and females (Age: 25.9 ± 4.0 yrs; Height: 1.75 ± 0.10 m; Weight: 70.98 ± 14.02 kg) underwent one whole body DXA scan, underwater weighing, and regional measures of volume via water displacement. Manually created DXA region of interest boxes were used to determine regional DXA body composition. Total body volume was calculated by taking the participant's dry weight and dividing it by the average density from underwater weighing. Linear regression models with body volume from underwater weighing for total body volume and water displacement for regional volume as the dependent variable and DXA lean mass, fat mass, and bone mass as independent variables created total and regional DXA-derived body volume. T-tests assessed DXA-derived body volume to the traditional method of body volume assessment. Regression models were cross-validated using the Repeated k-fold Cross Validation method.

RESULTS

DXA-derived total body volume was not significantly (p = 0.999) different from total body volume measured via total body water displacement. In addition, both arm and leg regional DXA-derived volume was not significantly different (p = 0.999) compared to regional volume measured by regional water displacement. Cross-validation of each model produced R² values of 0.992, 0.923, and 0.932 for total body, arm, and leg, respectively.

CONCLUSIONS

The DXA may be used as valid method for estimating total and regional body volume. Thus, these results expand the DXA's capabilities and potentially allow for a convenient regional four-compartment model with DXA-derived regional volume.

Understanding entrance-air-kerma as a quality-control metric for dual-energy x-ray absorptiometry

Purpose

The low exposures, unique x‐ray beam geometry, and scanning design in dual‐energy x‐ray absorptiometry (DXA) make measurement and quality‐control strategies different from traditional x‐ray equipment. This study examines the dependence of measured entrance‐air‐kerma (EAK) on both dose sensor type and scan length. The feasibility of using EAK to compare scanner output between different scan modes, individual scanners, and scanner platforms was also established. Finally, the congruence between measured and vendor‐reported EAK was analyzed.

Methods

Four Hologic DXA scanners at two institutions and all four available scan modes were tested. EAK was measured directly by three types of Radcal dose sensors: 60‐cc pancake ion‐chamber (IC), 180‐cc pancake IC, and solid‐state detector. The coefficient of variation (COV) was used to assess the dependence of EAK on scan length. Variations in EAK between the types of dose sensors as well as measured versus vendor‐reported values were evaluated using Bland–Altman analysis: mean ±95% prediction interval (PI): 1.96σ.

Results

Dose sensor variations in EAK were minimal, with a −3.5 ± 3.5% (mean ±95% PI) percent difference between the two sizes of IC's. The solid‐state detector produced highly similar measurements to the 180‐cc IC. These small differences were consistent across all scanners and all scan modes tested. Neither measured nor vendor‐reported EAK values were found to show relevant dependence on scan length, with all COV values ≤4%. Differences between measured and reported EAK were higher at −6 ± 48%. Likely errors in vendor‐reported EAK calculations were also identified.

Conclusion

It is feasible to quantify DXA scanner stability using EAK as a quality‐control metric with a variety of solid‐state and IC dose sensors, and the scan length used is not critical. Although vendor‐reported EAK was consistent among scanners of the same platform, measured EAK varied significantly from scanner to scanner. As a result, measured and reported EAK may not always be comparable.

Muscle Mass Measurement Using Machine Learning Algorithms with Electrical Impedance Myography

Sarcopenia is a wild chronic disease among elderly people. Although it does not entail a life-threatening risk, it will increase the adverse risk due to the associated unsteady gait, fall, fractures, and functional disability. The import factors in diagnosing sarcopenia are muscle mass and strength. The examination of muscle mass must be carried in the clinic. However, the loss of muscle mass can be improved by rehabilitation that can be performed in non-medical environments. Electronic impedance myography (EIM) can measure some parameters of muscles that have the correlations with muscle mass and strength. The goal of this study is to use machine learning algorithms to estimate the total mass of thigh muscles (MoTM) with the parameters of EIM and body information. We explored the seven major muscles of lower limbs. The feature selection methods, including recursive feature elimination (RFE) and feature combination, were used to select the optimal features based on the ridge regression (RR) and support vector regression (SVR) models. The optimal features were the resistance of rectus femoris normalized by the thigh circumference, phase of tibialis anterior combined with the gender, and body information, height, and weight. There were 96 subjects involved in this study. The performances of estimating the MoTM used the regression coefficient (r²) and root-mean-square error (RMSE), which were 0.800 and 0.929, and 1.432 kg and 0.980 kg for RR and SVR models, respectively. Thus, the proposed method could have the potential to support people examining their muscle mass in non-medical environments.

The Interference of Gamma Rays With Bone Mineral Density Measurements in 177Lu-PSMA and DOTATATE Therapy

The main purpose was to describe the interference of gamma radiation emitted by ¹⁷⁷Lu with simultaneous bone mineral density BMD measures for patients undergoing ¹⁷⁷Lu-PSMA and ¹⁷⁷Lu DOTATATE therapy. A cohort of 9 patients underwent ¹⁷⁷Lu-PSMA therapy were randomly selected to speculate the activity in the abdominopelvic region. So that, SPECT/CT scan at 24 h was used with attenuation and scatter correction. The activities were derived from the delineated ROIs over the abdominopelvic zone showing a range of 34-274 MBq. Next, a water path was placed under spine phantom mimicking L1-L4 vertebrae and followed by consecutive DEXA scans made by Hologic 4500 W and GE-Lunar DPX-NT systems. Five scans were performed without/and with different Lu-177 activities 37, 185, 370 and 555 MBq under the same geometric conditions. The obtained BMD readings of L1-L4 by the Hologic device were 1.027, 1.024, 1.021, 1.013, and 1.006 g/cm² with presence of 0, 37, 185, 370, and 555 MBq ¹⁷⁷Lu activity, respectively. Whereas, in Lunar device, it was found as higher as 1.163, 1.121, 1.09, 1.072, and 1.043, respectively. There was no statistically significant difference between both devices (p_value ≥ 0.05). The fluctuation ranges in the L1-L4 BMD readings at the presence of 37-555 MBq were 0.3%-2%, and 3.6%-10.3% for Hologic and Lunar systems, respectively. It was emphasized that gamma radiation emitted by ¹⁷⁷Lu relatively influence DEXA scans and the yielded BMD measures. Postponing DEXA scans as early as 8 d after ¹⁷⁷Lu-PMSA and 11 d after ¹⁷⁷Lu-DOTATATE therapies is recommended to avoid the erroneous contribution of gamma radiation and provide precise bone assessment.

Bone Health Considerations in Breast Cancer

OBJECTIVES

The treatment of breast cancer requires the use of multiple modalities to achieve local control of disease and to prevent distant recurrence. Among patients whose tumors are hormone-receptor positive, endocrine therapy for up to 10 years in the adjuvant setting can be an important component of such therapy, but it is not without adverse events. Ovarian suppression or estrogen restriction can have a rapid and clinically significant detrimental effect on bone mineral density, leading to potential osteoporotic fracture. This article reviews the major causes of breast cancer treatment-induced bone loss and pharmacologic and nonpharmacologic management strategies to maintain bone health in this population.

DATA SOURCES

PubMed and international clinical practice guidelines were used.

CONCLUSION

A holistic, long-term approach is needed to identify and offer early intervention to patients at high-risk of significant bone density loss. A combination of routine screening, use of oral or intravenous bone-modifying agents, oral supplementation of calcium and vitamin D, and physical activity, including weight-bearing exercise, are required to maintain adequate bone health during treatment for breast cancer.

IMPLICATIONS FOR NURSING PRACTICE

Oncology nurses are well-situated in the primary and survivorship care teams for patients with breast cancer to provide proactive education on the need to assess and actively manage bone health. Nonpharmacologic interventions such as dietary supplementation and physical activity are essential to health promotion and are within the nursing scope of practice to emphasize with this patient population.

Effect of Strength Training Protocol on Bone Mineral Density for Postmenopausal Women with Osteopenia/Osteoporosis Assessed by Dual-Energy X-ray Absorptiometry (DEXA)

This study aims to introduce a resistance training protocol (6 repetitions × 70% of 1 maximum repetition (1RM), followed by 6 repetitions × 50% of 1RM within the same set) specifically designed for postmenopausal women with osteopenia/osteoporosis and monitor the effect of the protocol on bone mineral density (BMD) in the lumbar spine, assessed by dual-energy X-ray absorptiometry (DEXA). The subjects included in the study were 29 postmenopausal women (56.5 ± 2.8 years) with osteopenia or osteoporosis; they were separated into two groups: the experimental group (n = 15), in which the subjects participated in the strength training protocol for a period of 6 months; and the control group (n = 14), in which the subjects did not take part in any physical activity. BMD in the lumbar spine was measured by DEXA. The measurements were performed at the beginning and end of the study. A statistically significant increase (Δ% = 1.82%) in BMD was observed at the end of the study for the exercise group (0.778 ± 0.042 at baseline vs. 0.792 ± 0.046 after 6 months, p = 0.018, 95% CI [-0.025, -0.003]); while an increase was observed for the control group (Δ% = 0.14%), the difference was not statistically significant (0.762 ± 0.057 at baseline vs. 0.763 ± 0.059, p = 0.85, 95% CI [-0.013, 0.011]). In conclusion, our strength training protocol seems to be effective in increasing BMD among women with osteopenia/osteoporosis and represents an affordable strategy for preventing future bone loss.

Quantitative Breast Density in Contrast-Enhanced Mammography

Contrast-enhanced mammography (CEM) demonstrates a potential role in personalized screening models, in particular for women at increased risk and women with dense breasts. In this study, volumetric breast density (VBD) measured in CEM images was compared with VBD obtained from digital mammography (DM) or tomosynthesis (DBT) images. A total of 150 women who underwent CEM between March 2019 and December 2020, having at least a DM/DBT study performed before/after CEM, were included. Low-energy CEM (LE-CEM) and DM/DBT images were processed with automatic software to obtain the VBD. VBDs from the paired datasets were compared by Wilcoxon tests. A multivariate regression model was applied to analyze the relationship between VBD differences and multiple independent variables certainly or potentially affecting VBD. Median VBD was comparable for LE-CEM and DM/DBT (12.73% vs. 12.39%), not evidencing any statistically significant difference (p = 0.5855). VBD differences between LE-CEM and DM were associated with significant differences of glandular volume, breast thickness, compression force and pressure, contact area, and nipple-to-posterior-edge distance, i.e., variables reflecting differences in breast positioning (coefficient of determination 0.6023; multiple correlation coefficient 0.7761). Volumetric breast density was obtained from low-energy contrast-enhanced spectral mammography and was not significantly different from volumetric breast density measured from standard mammograms.

Assessment of Bone Density by DXA in Poorly Controlled Children With β-Thalassemia: Correction for Hepatic Iron Overload by Manual Analysis

INTRODUCTION

Beta thalassemia major (BTM) is characterized by anemia and iron overload, especially with inadequate chelation therapy. Dual energy x-ray absorptiometry software (DXA) may misanalyse bone measurements due to iron deposition in organs such as the liver. Our objective was to study difference between the posterior-anterior spine measurements of bone mineral content (BMC), area (BA) and density (BMD) in poorly chelated beta thalassemia patients with and without inclusion of the liver in the DXA analysis.

METHODS

We studied hemoglobin and serum ferritin concentrations in 208 patients with BTM (children n = 177, young adults n = 31). Posteroanterior spine measurements BMC, BA and areal BMD were performed using a GE iDXA. Using the tissue point typing feature (EnCore software, version 16), analysis was carried out including and excluding (manually) the iron overloaded liver. Machine generated Z-scores of L1-L4 BMD were used for analysis.

RESULTS

The mean age of the study group was 12.9 ± 5.4 yr. Mean hemoglobin and serum ferritin concentrations were 8.0 ± 1.7 g/dl and 2256.9 ± 1978.0 ng/ml, respectively. The mean BMC, BA, and aBMD at the lumbar spine were 23.2 ± 11.4 g, 29.9 ± 8.5 cm² and 0.736 ± 0.173 g/cm² respectively with inclusion of liver that is standard machine analysis. After the liver was excluded from the analysis, the mean BMC, BA, and aBMD were 23.9 ± 11.6 g, 30.0 ± 8.6 cm² and 0.757 ±0.173 g/cm^2, respectively and the BMC and aBMD were significantly greater (p < 0.05). Mean BMD Z-score was -1.5 ± 1.2, which significantly (p < 0.05) improved to -1.3 ± 1.2 after exclusion of the liver from the analysis.

CONCLUSION

In poorly chelated patients with thalassemia, inclusion of the iron-overloaded liver in the tissue analysis may exaggerate the deficit in bone parameters. Iron overloaded tissues need to be manually excluded during analysis of the PA spine.

Bone Mineral Density Testing in Patients Undergoing Total Ankle Arthroplasty: Should We Pay More Attention to the Bone Quality?

Total ankle arthroplasty (TAA) has become one of the standard treatments for end-stage ankle arthritis. Long-term TAA survivorship is reported from 63% to 95%, with aseptic loosening being the most common mode of failure. Several studies have shown that low bone mineral density (BMD) of the hip affects the longevity of prosthetic implants. The role of Dual energy X-ray absorptiometry for TAA has not been established. The purpose of this review was to define the role of BMD in TAA outcomes and the role of Dual energy X-ray absorptiometry in measuring periprosthetic BMD. There is a paucity of information and published literature regarding the relationship between BMD and TAA. From attempting this systematic review, we hope to highlight that much of the focus in total ankle arthroplasty has emphasized implants and relatively little has focused on the quality of bone into which the prostheses are implanted.

A novel algorithm for extracting soft-tissue and bone images measured using a photon-counting type X-ray imaging detector with the help of effective atomic number analysis

Most of the objects targeted for X-ray examination are composed of soft-tissue and bone. We aimed to develop an algorithm for generating X-ray images which can give quantitative information of soft-tissue and bone using an energy-resolving photon-counting type imaging detector. We used polychromatic X-rays for analysis in which both the beam hardening effect and detector response were properly corrected and then succeeded in virtually treating the amount of measured X-ray attenuation as if it were measured using monochromatic X-rays.

Feasibility and reliability of DEXA analysis after total ankle arthroplasty: A cadaver study

BACKGROUND

Although the outcomes of total ankle arthroplasty (TAA) have improved, unsolved problems such as stress shielding remain. Although dual energy X-ray absorptiometry (DEXA) is the "gold standard" for evaluation of these issues, it is rarely used in patients after TAA. This study aimed to establish a scan technique and to assess the mechanical changes in bone density caused by bone stock preparation.

METHODS

Eight fresh-frozen cadaver legs were investigated by DEXA before TAA, with implant in situ, and after implant removal. Scan surface, bone mineral content, and bone mineral density were analysed to assess mechanical bone mass changes.

RESULTS

We examined data for density changes by bone compression after TAA, and found "good" results for internal reliability but only "acceptable" results for external reliability.

CONCLUSIONS

The results were reliable and reproducible. Using the present data, mechanical and biological processes can be considered together to understand the postoperative phases of bone remodelling after TAA.

Adjustment of DXA BMD measurements for anthropometric factors and its impact on the diagnosis of osteoporosis

We compared the effect of anthropometric factors on osteoporosis diagnosis by quantitative computed tomography (QCT) and dual energy X-ray absorptiometry (DXA) and found QCT spine volumetric bone mineral density (vBMD) was not associated with body weight, body mass index (BMI) or DXA anteroposterior spine thickness. In contrast, DXA spine and hip areal bone mineral density (aBMD) were strongly associated with all three factors. Adjustment of DXA aBMD measurements improved consistency with QCT vBMD.

PURPOSE

Although the diagnosis of osteoporosis using DXA T scores preferentially targets patients with BMI, there is evidence that obesity is not protective against fractures. The aim of this study was to compare the effect of anthropometric factors on osteoporosis diagnosis by QCT and DXA and investigate whether adjustment of DXA aBMD can achieve a more even distribution of diagnoses between slimmer and heavier individuals consistent with QCT.

METHODS

The participants were 964 men and 682 women referred for low-dose chest CT and DXA examinations as part of their employers' health check-up programs. QCT vBMD was measured in the L1-L2 vertebrae and DXA aBMD in the spine and hip. The prevalence of osteoporosis in each tertile of BMI in participants aged > 50 years was evaluated based on their QCT and DXA findings, and then re-evaluated after adjustment to the mean BMI in each sex. Similar investigations were performed for body weight and DXA anteroposterior (AP) spine thickness. The effect of the adjustment of DXA aBMD for anthropometric factors on the correlation with QCT vBMD was also examined.

RESULTS

For spine QCT, correlations of age adjusted vBMD residuals against BMI were not statistically significant in men (P = 0.44) or women (P = 0.32). In contrast, slopes for aBMD residuals were all highly statistically significant (P < 0.001). There were similar findings for weight and AP spine thickness. Adjustment of DXA aBMD for anthropometric factors resulted in a more equal spread of diagnoses of osteoporosis and greater consistency with QCT.

CONCLUSION

Our study highlights differences between DXA and QCT in their correlation with anthropometric factors and its effect on the diagnosis of osteoporosis. Adjustment of DXA T scores for anthropometric factors gave greater consistency with QCT vBMD. Further studies are required into whether adjusting DXA aBMD for anthropometric factors has a beneficial impact on the discriminative or predictive power for vertebral fracture.

Effect of Positioning of the Region of Interest on Bone Density of the Hip

BACKGROUND

Large changes in positioning of the global region of interest (ROI) influence the measurement of bone mineral density (BMD) in the hip and forearm regions. However, it is unknown whether minor shifts in the positioning of the bottom of the global hip ROI affect the measurement of total hip BMD.

METHODS

The hip BMDs of 40 clinical densitometry patients were analyzed at baseline with the bottom of the global hip ROI positioned as usual, 10 mm distal to the base of the lesser trochanter (position 0). Then the hip was reanalyzed by shifting the bottom of the global hip ROI 1 mm proximally 10 times (positions +1 through +10) and then by shifting the bottom of the global hip ROI 1 mm distally 10 times (positions -1 through -10). The significance of the differences between mean values at the various distances from baseline was assessed using a Wilcoxon signed-rank test.

RESULTS

The mean total hip area, bone mineral content and BMD decreased as the bottom of the global hip ROI was shifted proximally; the decrease was significant when shifted by even 1 mm (p < 0.001). The mean total hip area, bone mineral content and BMD increased as the bottom of the global hip ROI was shifted distally; the increase was significant when shifted by even 1 mm (p < 0.001). The change in BMD with each 1 mm shift was uniform across the range studied from positions +10 through -10, and was approx 0.54%/mm. When the least significant change was based on 40 pairs of measurements, where each pair was comprised of the baseline scan and the same scan at -1 position, the least significant change was 0.01 g/cm².

CONCLUSIONS

The BMD of the total hip is sensitive to even minor changes in the positioning of the bottom of the global hip ROI. Although a 1 mm change in the bottom of the global hip ROI positioning would make little difference in the reported T-score, it could easily affect the determination of significance in changes in BMD over time.

Identification of Sarcopenia Components That Discriminate Slow Walking Speed: A Pooled Data Analysis

BACKGROUND

The Sarcopenia Definitions and Outcomes Consortium (SDOC) sought to identify cut points for muscle strength and body composition measures derived from dual-energy x-ray absorptiometry (DXA) that discriminate older adults with slow walking speed. This article presents the core analyses used to guide the SDOC position statements.

DESIGN

Cross-sectional data analyses of pooled data.

SETTING

University-based research assessment centers.

PARTICIPANTS

Community-dwelling men (n = 13,652) and women: (n = 5,115) with information on lean mass by DXA, grip strength (GR), and walking speed.

MEASUREMENTS

Thirty-five candidate sarcopenia variables were entered into sex-stratified classification and regression tree (CART) models to agnostically choose variables and cut points that discriminate slow walkers (<0.80 m/s). Models with alternative walking speed outcomes were also evaluated (<0.60 and <1.0 m/s and walking speed treated continuously).

RESULTS

CART models identified GR/body mass index (GRBMI) and GR/total body fat (GRTBF) as the primary discriminating variables for slowness in men and women, respectively. Men with GRBMI of 1.05 kg/kg/m2 or less were approximately four times more likely to be slow walkers than those with GRBMI of greater than 1.05 kg/kg/m2 . Women with GRTBF of less than 0.65 kg/kg were twice as likely to be slow walkers than women with GRTBF of 0.65 kg/kg or greater. Models with alternative walking speed outcomes selected only functions of GR as primary discriminators of slowness in both men and women. DXA-derived lean mass measures did not consistently discriminate slow walkers.

CONCLUSION

GR with and without adjustments for body size and composition consistently discriminated older adults with slowness. CART models did not select DXA-based lean mass as a primary discriminator of slowness. These results were presented to an SDOC Consensus Panel, who used them and other information to develop the SDOC Position Statements. J Am Geriatr Soc 68:1419-1428, 2020.

Distortion of dual energy X-ray images by faecal masses in a child with type 1 diabetes

Dual energy X-ray absorptiometry (DXA) scanning is the most common investigating modality used to assess bone mineral density (BMD). Conditions causing tissue calcification and artefacts such as metallic objects may mislead the results of the DXA scan. We present here a case of a child with diabetes where the DXA images were distorted by faecal lumps, leading to falsely elevated BMD and an error in interpretation of the DXA scans. Our case suggests that DXA software may not, at times, differentiate between bone and other high-attenuating material within the regions of interest. Thus, DXA images should also be visually examined and verified with the numeric data before report preparation in these patients.

The effects of microchipping C57BL/6N mice on standard phenotyping tests

The C57BL/6N inbred lines of mice are widely used in genetic research. They are particularly favoured in large scale studies such as the International Mouse Phenotyping Consortium (IMPC), where C57BL/6N mice are genetically altered to generate a collection of null alleles (currently more than 8500 null alleles have been generated). In this project, mice carrying null alleles are subjected to a pipeline of broad-based phenotyping tests to produce wide ranging phenotyping data on each model. We have previously described the development of a Home Cage Analysis system that automatically tracks the activity of group housed mice from a microchip inserted in the groin. This platform allows assessment of multiple biologically relevant phenotypes over long periods of time without experimenter interference, and therefore is particularly suited for high through-put studies. To investigate the impact of microchips on other tests carried out in the IMPC pipeline, we inserted microchips in 12 male and 12 female C57BL/6Ntac mice at seven weeks of age. Starting at nine weeks of age these mice underwent standard phenotyping tests, concurrently with 20 unchipped C57BL/6Ntac mice (10 females, 10 males). Tissues from a subset of the microchipped mice (six males and six females), chosen at random, were also sent for histopathological examination at the end of the phenotyping pipeline. No significant impact of insertion of microchip was observed in any of the phenotyping tests apart from bone mineral density measurement at DEXA due to the nature of the microchip. We therefore recommend that the microchip be inserted during the DEXA procedure, after the measurement is taken but before the mouse has recovered from the anaesthetic. This would avoid multiple anaesthetic exposures and prevent the potential variability in DEXA analysis output.

Dual Energy X-ray Methods for the Characterization, Quantification and Imaging of Calcification Minerals and Masses in Breast

Dual energy (DE) technique has been used by numerous studies in order to detect breast cancer in early stages. Although mammography is the gold standard, the dual energy technique offers the advantage of the suppression of the contrast between adipose and glandular tissues and reveals pathogenesis that is not present in conventional mammography. Both dual energy subtraction and dual energy contrast enhanced techniques were used in order to study the potential of dual energy technique to assist in detection or/and visualization of calcification minerals, masses and lesions obscured by overlapping tissue. This article reviews recent developments in this field, regarding: i) simulation studies carried out for the optimizations of the dual energy technique used in order to characterize and quantify calcification minerals or/and visualize suspected findings, and ii) the subsequent experimental verifications, and finally, the adaptation of the dual energy technique in clinical practice.

Framework for Photon Counting Quantitative Material Decomposition

In this paper, the accuracy of material decomposition (MD) using an energy discriminating photon counting detector was studied. An MD framework was established and validated using calcium hydroxyapatite (CaHA) inserts of known densities (50 mg/cm³, 100 mg/cm³, 250 mg/cm³, 400 mg/cm³), and diameters (1.2, 3.0, and 5.0 mm). These inserts were placed in a cardiac rod phantom that mimics a tissue equivalent heart and measured using an experimental photon counting detector cone beam computed tomography (PCD-CBCT) setup. The quantitative coronary calcium scores (density, mass, and volume) obtained from the MD framework were compared with the nominal values. In addition, three different calibration techniques, signal-to-equivalent thickness calibration (STC), polynomial correction (PC), and projected equivalent thickness calibration (PETC) were compared to investigate the effect of the calibration method on the quantitative values. The obtained MD estimates agreed well with the nominal values for density (mass) with mean absolute percent errors (MAPEs) 8 ± 11% (9 ± 15%) and 4 ± 6% (9 ± 14%) for STC and PETC calibration methods, respectively. PC displayed large MAPEs for density (27 ± 9%), and mass (25 ± 12%). Volume estimation resulted in large deviations between true and measured values with notable MAPEs for STC (40 ± 90%), PC (40 ± 80%), and PETC (40 ± 90%). The framework demonstrated the feasibility of quantitative CaHA mass and density scoring using PCD-CBCT.

Dual-energy X-ray absorptiometry is a reliable non-invasive technique for determining whole body composition of chickens

In this study, a Lunar Prodigy dual-energy X-ray absorptiometry (DEXA) scanner was validated as a technique to estimate chicken body composition in a non-invasive way. Former research has emphasized the importance of validation of every scanner and software version. In a first trial, DEXA estimated body composition for broilers was correlated with chemical carcass analysis to develop prediction equations. As such, those equations can be used in later experiments with chickens to correct DEXA estimations to estimate body composition accurately by DEXA. DEXA estimated fat mass, lean tissue mass, bone mineral content (BMC) and total body mass, which is the sum of fat, lean mass and BMC, were compared to chemically analyzed crude fat, lean mass as the sum of protein and water and body ash content and scale body weight, respectively. Those regression equations were then used in a second trial to determine body composition based upon DEXA for breeders at different ages. In this experiment, fat and lean tissue determined by DEXA, were compared to dissection parameters commonly used for assessing carcass quality, namely breast muscle and abdominal fat. The first trial showed that DEXA provides high correlations for body mass (ρ = 1) and the individual tissue masses separately (ρ ranging between 0.98 and 1). These high correlations allow for accurate prediction of those components with the developed regression equations. Proportional fat and lean tissue were correlated with their chemical counterparts, however, to a lower extent than absolute values due to lower variation between the proportional weights. BMC percentage was not significantly correlated with ash percentage. Furthermore, in trial 2 high correlations were observed between dissection parameters and DEXA-corrected estimations. These correlations show that DEXA can assess carcass quality in breeders without sacrificing the birds. In conclusion, DEXA is a reliable technique to estimate breeder and broiler body composition in a non-invasive way, hence allowing for longitudinal studies over longer periods of time while avoiding sacrificing of birds.

Acquisition of Quasi-Monochromatic Dual-Energy in a Microfocus X-ray Generator and Development of Applied Technology

In regenerative medicine, evaluation of bone mineral density using a microfocus X-ray generator could eventually be used to determine the degree of bone tissue regeneration. To evaluate bone mineral density against regenerated bone material, two low-energy X-rays are necessary. Herein, the acquisition of quasi-monochromatic, dual-energy soft X-ray and the subsequent medical application were examined using the K-absorption edges of two types of metal filters (i.e., zirconium and tin) in a microfocus X-ray generator. Investigation of the optimal tube voltage and filter thickness to form a quasi-monochromatic energy spectrum with a single filter revealed that a filter thickness of 0.3 mm results in an optimal monochromatization state. When a dual filter was used, the required filter thickness was 0.3 mm for tin and 0.2 mm for zirconium at a tube voltage of 35 kV. For the medical application, we measured quasi-monochromatic, dual-energy X-rays to evaluate the measurement accuracy of bone mineral density. Using aluminum as a simulated bone sample, a relative error of ≤5% was consistent within the aluminum thickness range of 1–3 mm. These data suggest that a bone mineral density indicator of recycled bone material can be easily obtained with the quasi-monochromatic X-ray technique using a microfocus X-ray generator.

Pitfalls in the measurement of muscle mass: a need for a reference standard

BACKGROUND

All proposed definitions of sarcopenia include the measurement of muscle mass, but the techniques and threshold values used vary. Indeed, the literature does not establish consensus on the best technique for measuring lean body mass. Thus, the objective measurement of sarcopenia is hampered by limitations intrinsic to assessment tools. The aim of this study was to review the methods to assess muscle mass and to reach consensus on the development of a reference standard.

METHODS

Literature reviews were performed by members of the European Society for Clinical and Economic Aspects of Osteoporosis and Osteoarthritis working group on frailty and sarcopenia. Face-to-face meetings were organized for the whole group to make amendments and discuss further recommendations.

RESULTS

A wide range of techniques can be used to assess muscle mass. Cost, availability, and ease of use can determine whether the techniques are better suited to clinical practice or are more useful for research. No one technique subserves all requirements but dual energy X-ray absorptiometry could be considered as a reference standard (but not a gold standard) for measuring muscle lean body mass.

CONCLUSIONS

Based on the feasibility, accuracy, safety, and low cost, dual energy X-ray absorptiometry can be considered as the reference standard for measuring muscle mass.

Comparative investigation of bone mineral density using CT and DEXA in a canine femoral model

Bone density measurements using computed tomography (CT) instead of dual-energy X-ray absorptiometry (DEXA) are currently of great interest in human and veterinary medical research as it would be beneficial to use CT scans obtained for other indications also for determining bone density. For Hounsfield units (HU) measured with CT in specific regions of interests (ROIs) in one or several slice/s a correlation with bone mineral density (BMD) measured by DEXA in humans and dogs of between 0.44 and 0.77 is reported in the literature. In the present study, instead certain volumes of interest (VOIs) obtained by CT scan and the corresponding HU to the respective VOIs were compared with the bone mineral density of the corresponding areas measured by DEXA. The aim of the study was to investigate whether this procedure gives more accurate information about bone density of the bones as three-dimensional objects of the respective patient. Correlation between measured HU in the respective VOI and BMD measured with DEXA in the corresponding ROI showed a very good correlation of 0.93. Linear regression with R²  = 0.85 (p = 0.0262) was calculated. Except for VOI5, similar distribution of values and significant differences (p < 0.0001-0.0087) between ROIs/VOIs were detected. Determining HU for assessing bone mineral density in a certain volume provides more accurate results than those previously reported from two-dimensional (2D) CT measurements. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:2667-2672, 2017.

Accuracy and Reliability of Assessing Lateral Compartmental Leg Composition Using Dual-Energy X-ray Absorptiometry

PURPOSE

This study aimed to investigate the accuracy and reliability of a novel dual-energy x-ray absorptiometry (DXA) scanning method in the frontal plane for total, fat, and lean mass quantification of the anterior and posterior upper leg compartments.

METHODS

Twenty-one (11 females; X¯age = 20.3 ± 1.3 yr) college athletes were assessed for total and regional body composition using DXA. The segmentation of anterior/posterior thigh compartments was measured with participants lying on their right and left sides and the scanned leg elevated with two foam pads. Custom regions of interest (ROIs) were created manually with enCore software for each scan using bony landmarks to quantify lean, fat, and total masses. Paired t-tests assessed this novel positioning method's accuracy against standard positioning. Intraclass correlation coefficients and coefficients of variation examined inter- and intrarater reliability for lateral scan measures of total, fat, and lean masses from manually created ROIs.

RESULTS

All mean ± SD differences between frontal and lateral DXA scans of right (R) and left (L) leg total mass (R: 8.42 ± 195.57 g; L: 19.47 ± 131.80 g), fat mass (R: 61.26 ± 215.66 g; L: -5.89 ± 239.97 g), and lean mass (R: -103.00 ± 302.54 g; L: -27.58 ± 288.14 g) were nonsignificant (P value range = 0.15-0.91). Intraclass correlation coefficients were high for all composition measures between and within raters, ranging from 0.983 to 0.999 and from 0.954 to 0.999, respectively, with low variation across measures (all coefficients of variation ≤ 5%).

CONCLUSION

The results of this study suggest that DXA measures using lateral subject positioning and custom ROIs to assess upper leg total, fat, and lean masses are accurate and reliable compared with total-body frontal subject positioning. Future studies are needed to determine the clinical usefulness of lateral view measures regarding prevention or rehabilitation of sports- or age-related injury.

Assessment of the effect of strontium, lead, and aluminum in bone on dual-energy x-ray absorptiometry and quantitative ultrasound measurements: A phantom study

PURPOSE

Dual-energy X-ray absorptiometry (DXA) is the gold standard technique to measure areal bone mineral density (aBMD) for the diagnosis of osteoporosis. Because DXA relies on the attenuation of photon to estimate aBMD, deposition of bone-seeking metallic elements such as strontium, lead, and aluminum that differ in atomic numbers from calcium can cause inaccurate estimation of aBMD. Quantitative ultrasound (QUS) is another technique available to assess bone health by measuring broadband ultrasound attenuation (BUA), speed of sound (SOS), and an empirically derived quantity called stiffness index (SI). Because the acoustic properties are not prone to significant change due to changes in microscopic atomic composition of bone, it is hypothesized that QUS is unaffected by the presence of bone-seeking elements in the bone. The objective of this study was to investigate the effect of strontium, lead, and aluminum on DXA-derived aBMD and QUS parameters using bone-mimicking phantoms compatible with both techniques.

METHODS

Bone-mimicking phantoms were produced by homogeneously mixing finely powdered hydroxyapatite compounds that contain varying concentrations of strontium, lead, or aluminum with porcine gelatin solution. Seven strontium-substituted phantoms were produced with varying molar ratio of Sr/(Sr + Ca) ranging from 0% to 2%. Four lead-doped phantoms and four aluminum-doped phantoms were constructed with the respective analyte concentrations ranging from 50 to 200 ppm. An additional 0 ppm phantom was produced to be used as a baseline for the lead and aluminum phantom measurements. All phantoms had uniform volumetric bone mineral density (vBMD) of 200 mg/cm³ , and were assessed using a Hologic Horizon^® DXA device and a Hologic Sahara^® QUS device. Furthermore, theoretical aBMD bias for mol/mol% substitution of calcium with the three bone-seeking elements was calculated.

RESULTS

Strong positive linear relationship was found between aBMD measured by DXA and strontium concentration (P < 0.001, r = 0.995). From the measurement of lead and aluminum phantoms using DXA, no statistically significant relationship was observed between aBMD and the analyte concentrations. For the QUS system, with an exception of BUA and lead concentration that exhibited statistically significant relationship (P < 0.038, r = 0.899), no statistically significant change was observed in all QUS parameters with respect to the clinically relevant concentration of all three elements. The calculated theoretical aBMD bias induced by 1 mol/mol% substitution of calcium with strontium, lead, and aluminum were 10.8%, 4.6%, and -0.7%, respectively.

CONCLUSION

aBMD measured by DXA was prone to overestimation in the presence of strontium, but acoustic parameters measured by QUS are independent of strontium concentration. The deviation in aBMD induced by the clinically relevant concentrations of lead and aluminum under 200 ppm could not be detected using the Hologic Horizon^® DXA device. Furthermore, the SI measured by the QUS system was not affected by lead or aluminum concentrations used in this study.

Comparative measurements of bone mineral density and bone contrast values in canine femora using dual-energy X-ray absorptiometry and conventional digital radiography

BACKGROUND

Aseptic loosening due to bone remodelling processes after total hip replacement is one common cause for revision surgery. In human medicine, dual-energy X-ray absorptiometry (DEXA) is the gold standard for quantitative evaluation of bone mineral density, whereas in veterinary medicine conventional radiography is used for follow-up studies. Recently, a method has been described using digital X-ray images for quantitative assessment of grey scale values of bone contrast. Therefore, the aim of the present study was to evaluate the correlation of bone mineral density (BMD) measured by DEXA with grey scale values (GV) measured in digital X-ray images (RX50, RX66) ex vivo.

RESULTS

The measured GV in the chosen X-ray settings showed on average a good correlation (r = 0.61) to the measured BMD with DEXA. Correlation between the two X-ray settings was very good (r = 0.81). For comparisons among regions of interests (ROIs) a difference of 8.2% was found to be statistically significant, whereas in the case of RX50 and RX66 differences of 5.3% and 4.1% were found to be statistically significant.

CONCLUSIONS

Results indicate that measuring absolute changes in bone mineral density might be possible using digital radiography. Not all significant differences between ROIs detectable with DEXA can be displayed in the X-ray images because of the lower sensitivity of the radiographs. However, direct comparison of grey scale values of the periprosthetic femur in one individual patient during the follow-up period, in order to predict bone remodelling processes, should be possible, but with a lesser sensitivity than with DEXA. It is important that the same X-ray settings are chosen for each patient for follow-up studies.

Advances in imaging approaches to fracture risk evaluation

Fragility fractures are a growing problem worldwide, and current methods for diagnosing osteoporosis do not always identify individuals who require treatment to prevent a fracture and may misidentify those not a risk. Traditionally, fracture risk is assessed using dual-energy X-ray absorptiometry, which provides measurements of areal bone mineral density at sites prone to fracture. Recent advances in imaging show promise in adding new information that could improve the prediction of fracture risk in the clinic. As reviewed herein, advances in quantitative computed tomography (QCT) predict hip and vertebral body strength; high-resolution HR-peripheral QCT (HR-pQCT) and micromagnetic resonance imaging assess the microarchitecture of trabecular bone; quantitative ultrasound measures the modulus or tissue stiffness of cortical bone; and quantitative ultrashort echo-time MRI methods quantify the concentrations of bound water and pore water in cortical bone, which reflect a variety of mechanical properties of bone. Each of these technologies provides unique characteristics of bone and may improve fracture risk diagnoses and reduce prevalence of fractures by helping to guide treatment decisions.

Osteoporosis Imaging in the Geriatric Patient

Given the expected rapid growth of the geriatric world population (=individuals aged >65 years) to 1.3 billion by 2050, age-related diseases such as osteoporosis and its sequelae, osteoporotic fractures, are on the rise. Areal bone mineral density (aBMD) by dual-energy X-ray absorptiometry (DXA) is the current gold standard to diagnose osteoporosis, to assess osteoporotic fracture risk, and to monitor treatment-induced BMD changes. However, most fragility fractures occur in patients with normal or osteopenic aBMD, indicating that factors beyond BMD impact bone strength. Recent developments in DXA technology such as TBS, VFA, and hip geometry analysis are now available to assess some of these non-BMD parameters from the DXA image. This review will discuss the use of DXA and DXA-assisted technologies and their respective advantages and disadvantages. Special attention is given to if and how each method is indicated in the geriatric population, and the latest ISCD 2015 guidelines have been incorporated.

A Candidate Gene Association Study of Bone Mineral Density in an Iranian Population

The genetic epidemiology of variation in bone mineral density (BMD) and osteoporosis is not well studied in Iranian populations and needs more research. We report a candidate gene association study of BMD variation in a healthy cross-sectional study of 501 males and females sampled from the Iranian Multi-Centre Osteoporosis Study, Shiraz, Iran. We selected to study the association with 21 single nucleotide polymorphisms (SNPs) located in the 7 candidate genes LRP5, RANK, RANKL, OPG, P2RX7, VDR, and ESR1. BMD was measured at the three sites L2-L4, neck of femur, and total hip. Association between BMD and each SNP was assessed using multiple linear regression assuming an allele dose (additive effect) on BMD (adjusted for age and sex). Statistically significant (at the unadjusted 5% level) associations were seen with seven SNPs in five of the candidate genes. Two SNPs showed statistically significant association with more than one BMD site. Significant association was seen between BMD at all the three sites with the VDR SNP rs731246 (L2-L4 p = 0.038; neck of femur p = 0.001; and total hip p < 0.001). The T allele was consistently associated with lower BMD than the C allele. Significant association was also seen for the P2RX7 SNP rs3751143, where the G allele was consistently associated with lower BMD than the T allele (L2-L4 p = 0.069; neck of femur p = 0.024; and total hip p = 0.045).

Stochastic predictors from the DXA scans of human lumbar vertebrae are correlated with the microarchitecture parameters of trabecular bone

The purpose of this study was to provide a novel stochastic assessment of inhomogeneous distribution of bone mineral density (BMD) from the Dual-energy X-ray Absorptiometry (DXA) scans of human lumbar vertebrae and identify the stochastic predictors that were correlated with the microarchitecture parameters of trabecular bone. Eighteen human lumbar vertebrae with intact posterior elements from 5 cadaveric spines were scanned in the posterior-anterior projection using a Hologic densitometer. The BMD map of human vertebrae was obtained from the raw data of DXA scans by directly operating on the transmission measurements of low- and high-energy X-ray beams. Stochastic predictors were calculated by fitting theoretical models onto the experimental variogram of the BMD map, rather than grayscale images, from DXA scans. In addition, microarchitecture parameters of trabecular bone were measured from the 3D images of human vertebrae acquired using a Micro-CT scanner. Significant correlations were observed between stochastic predictors and microarchitecture parameters. The sill variance, representing the standard deviation of the BMD map to some extent, had significantly positive correlations with bone volume, trabecular thickness, trabecular number and connectivity density. The sill variance was also negatively associated with bone surface to volume ratio and trabecular separation. This study demonstrates that the stochastic assessment of the inhomogeneous distribution of BMD from DXA scans of human lumbar vertebrae can reveal microarchitecture information of trabecular bone. However, future studies are needed to examine the potential of stochastic predictors from routine clinical DXA scans in providing bone fragility information complementary to BMD.

Photoacoustic and ultrasound imaging of cancellous bone tissue

We used ultrasound (US) and photoacoustic (PA) imaging modalities to characterize cattle trabecular bones. The PA signals were generated with an 805-nm continuous wave laser used for optimally deep optical penetration depth. The detector for both modalities was a 2.25-MHz US transducer with a lateral resolution of ~1 mm at its focal point. Using a lateral pixel size much larger than the size of the trabeculae, raster scanning generated PA images related to the averaged values of the optical and thermoelastic properties, as well as density measurements in the focal volume. US backscatter yielded images related to mechanical properties and density in the focal volume. The depth of interest was selected by time-gating the signals for both modalities. The raster scanned PA and US images were compared with microcomputed tomography (μCT) images averaged over the same volume to generate similar spatial resolution as US and PA. The comparison revealed correlations between PA and US modalities with the mineral volume fraction of the bone tissue. Various features and properties of these modalities such as detectable depth, resolution, and sensitivity are discussed.

Type 1 diabetes patients have lower strength in femoral bone determined by quantitative computed tomography: A cross-sectional study

AIMS/INTRODUCTION

Previous studies have reported osteoporosis measured by dual-energy X-ray absorptiometry in younger patients with type 1 diabetes. Limitations of 2-D imaging, however, limit the precision of dual-energy X-ray absorptiometry for the measurement of bone mineral density and bone strength.

MATERIALS AND METHODS

Three-dimensional quantitative computed tomography was used to calculate volumetric-bone mineral density (vBMD) and strength in femoral bone subfractions. A total of 17 male type 1 diabetes patients and 18 sex-matched healthy controls aged from 18 to 49 years were investigated in the present cross-sectional study. Patients with overt nephropathy were excluded.

RESULTS

Type 1 diabetes patients had significantly lower cortical vBMD in the femoral neck, and significantly lower total vBMD, cortical thickness and cortical cross-sectional area (cortical CSA) in the intertrochanter. Bone strength estimated by the buckling ratio (an index of cortical instability) of the intertrochanter was significantly higher in type 1 diabetes patients. The following serum bone markers were comparable between the two groups: bone-specific alkaline phosphatase, N-terminal propeptide of type 1 procollagen, osteocalcin, pentosidine and homocysteine. Serum insulin-like growth factor-1 values were significantly lower in the type 1 diabetes patients than in controls. Serum insulin-like growth factor-1values were positively correlated with serum bone formation markers, and the total vBMD of the femoral neck and lumbar spine in type 1 diabetes patients.

CONCLUSIONS

The present study is the first investigation by quantitative computed tomography measurement to show cortical instability and lower vBMD in the intertrochanter of young and middle-aged type 1 diabetes patients. Low insulin-like growth factor-1 might be a causative factor for osteoporosis in type 1 diabetes.

Spine Trabecular Bone Score Precision, a Comparison Between GE Lunar Standard and High-Resolution Densitometers

Trabecular bone score (TBS) is related to microarchitecture and fracture risk independently of bone mineral density (BMD) and clinical risk factors. Widespread clinical TBS use requires documentation of reproducibility and ideally comparability across scanners. This study evaluated TBS reproducibility and explored differences between Lunar Prodigy and iDXA densitometers. Reproducibility was assessed from replicate scans in 210 men and women participating in various dual-energy X-ray absorptiometry (DXA) precision assessments. iDXA-to-Prodigy comparability was evaluated using 155 participants from 3 study groups. L1-L4 BMD and TBS precision was similar on iDXA and Prodigy (BMD coefficient of variation = 1.9% and 1.5% and TBS coefficient of variation = 1.4% and 1.6%, respectively). Precision did not differ between men and women; however, between-technologist differences (p < 0.05) of similar magnitude were observed for both BMD and TBS. Prodigy-to-Prodigy TBS values were highly correlated (R(2) = 0.85 with bias of -0.010 TBS units). Agreement was less robust comparing Prodigy with iDXA instruments (TBS R(2): 0.72-0.81 with biases of 0.012-0.034 TBS units). In conclusion, TBS precision is comparable to that of BMD and does not differ between men and women. Additionally, in these cohorts, slight TBS differences were observed between iDXA and Prodigy scans. These data suggest a potential difference between densitometer models perhaps due to higher iDXA image resolution.

Random field assessment of inhomogeneous bone mineral density from DXA scans can enhance the differentiation between postmenopausal women with and without hip fractures

Bone mineral density (BMD) measurements from Dual-energy X-ray Absorptiometry (DXA) alone cannot account for all factors associated with the risk of hip fractures. For example, the inhomogeneity of bone mineral density in the hip region also contributes to bone strength. In the stochastic assessment of bone inhomogeneity, the BMD map in the hip region is considered as a random field and stochastic predictors can be calculated by fitting a theoretical model onto the experimental variogram of the BMD map. The objective of this study was to compare the ability of bone mineral density and stochastic assessment of inhomogeneous distribution of bone mineral density in predicting hip fractures for postmenopausal women. DXA scans in the hip region were obtained from postmenopausal women with hip fractures (N=47, Age: 71.3±11.4 years) and without hip fractures (N=45, Age: 66.7±11.4 years). Comparison of BMD measurements and stochastic predictors in assessing bone fragility was based on the area under the receiver operating characteristic curves (AUC) from logistic regression analyses. Although stochastic predictors offered higher accuracy (AUC=0.675) in predicting the risk of hip fractures than BMD measurements (AUC=0.625), this difference was not statistically significant (p=0.548). Nevertheless, the combination of stochastic predictors and BMD measurements had significantly (p=0.039) higher prediction accuracy (AUC=0.748) than BMD measurements alone. This study demonstrates that stochastic assessment of bone mineral distribution from DXA scans can serve as a valuable tool in enhancing the prediction of hip fractures for postmenopausal women in addition to BMD measurements.

Does the precision of dual-energy X-ray absorptiometry for bone mineral density differ by sex?

Given larger bone size in men, bone mineral density (BMD) precision might differ between sexes. This study compared dual-energy X-ray absorptiometry BMD precision of 3 International Society for Clinical Densitometry-certified technologists in older men and women. Each technologist scanned a cohort of 30 men and 30 women (total n = 180) by using a Lunar iDXA densitometer (GE Healthcare, Madison, WI). Each volunteer had 2 lumbar spine and bilateral hip scans with repositioning between examinations. BMD least significant change was calculated. Age and body mass index did not differ between men and women. Mean height and weight were greater in men, 174.6 cm ± 6.9 and 81.6 kg ± 11.1 respectively, (p < 0.0001) than in women, 161.5 cm ± 5.9/69.1 kg ± 14.2, respectively. Bone area was greater in men (p < 0.0001) at all sites. BMD least significant change was statistically better (p < 0.05) in women at the mean total femur (0.014 vs 0.018 g/cm(2)) and left femoral neck (0.025 vs 0.038 g/cm(2)), but not different at either total femur, the right femoral neck, or lumbar spine (all p > 0.05). In conclusion, statistically significant male/female differences in BMD precision were observed at the mean total femur and left femoral neck. Given the small magnitude of difference in g/cm(2) and inconsistent pattern, that is, no right femoral neck difference, there is virtually no clinical difference in BMD precision between sexes. These data do not support a need for sex-specific precision analyses.

Bone mineralization in children with Wilson's disease

BACKGROUND

The goal of this study was to determine bone mineralization in children with Wilson's disease (WD).

METHODS

Twenty-seven patients (16 males) and two age- and gender-matched healthy children for each patient were enrolled in the study. Bone mineral content (BMC, grams) and density (BMD, g/cm(2)) at lumbar 1-4 vertebrae were measured by dual-energy X-ray absorptiometry. Urinary calcium excretion was calculated in 19 patients. The effect of cirrhosis and hypercalciuria on BMC and BMD was also evaluated in WD patients.

RESULTS

There was no statistically significant difference between patients and healthy controls regarding mean BMC (33.0 ± 13.9 vs. 35.8 ± 13.8 g) (p = 0.940) and mean BMD values (0.66 ± 0.16 vs. 0.71 ± 0.18 g/cm(2)) (p = 0.269), respectively. Nine (47.4 %) patients had hypercalciuria. Hypercalciuric patients had statistically significant lower BMC and BMD values than those without hypercalciuria. A significant difference continued to be present after age, weight, height, and pubertal stage adjustment was done, but disappeared after weight, height, follow up duration, and pubertal stage adjustment was done. The presence of cirrhosis did not affect BMC and BMD significantly in WD patients.

CONCLUSIONS

BMC and BMD in children with WD were normal. The presence of hypercalciuria but not cirrhosis may affect BMC and BMD negatively in the patients.