Dual-energy x-ray absorptiometry scanner mismatch in follow-up bone mineral density testing.

Scanner mismatch occurs frequently with follow-up dual-energy x-ray absorptiometry (DXA) scans. Nearly one-in-five follow-up DXA scans were conducted on non-cross-calibrated scanners (scanner mismatch) and more than a quarter of patients who had a follow-up DXA scan had experienced scanner mismatch. INTRODUCTION: Detecting significant changes in bone mineral density (BMD) with dual-energy x-ray absorptiometry (DXA) scanners relies on the least significant change (LSC). Results from two different DXA scanners can only be compared, albeit with decreased sensitivity for change, if the LSC between the two scanners has been directly determined through cross-calibration. Performing follow-up DXA scans on non-cross-calibrated scanners (scanner mismatch) has safety and economic implications. This study aims to determine the proportion of scanner mismatch occurring at a population level. METHODS: All patients who completed at least two DXA scans between 1 April 2009 and 31 December 2018 in the province of Alberta, Canada, were identified using population-based health services databases. Scanner mismatch was defined as a follow-up DXA scan completed on a DXA scanner that differed from and was not cross-calibrated to the previous DXA scanner. Multivariate logistic regression models were used to assess predictive factors that may contribute to scanner mismatch. RESULTS: A total of 264,866 patients with 470,641 follow-up DXA scans were identified. Scanner mismatch occurred in 18.9% of follow-up DXA scans; 28.7% of patients experienced at least one scanner mismatch. Longer duration between scans (OR 1.25, 95% CI 1.24-1.26) and major osteoporotic fracture history before index scan (OR 1.06, 95% CI 1.03-1.08) increased risk of scanner mismatch. Osteoporosis medication use before index scan (OR 0.89; 95% CI 0.88-0.91), recency of follow-up scans (OR 0.98, 95% CI 0.73-0.98), female sex (OR 0.97, 95% CI 0.94-1.00), and age at last scan (OR 0.99, 95% CI 0.99-1.00) were associated with lower risk of scanner mismatch. CONCLUSION: Scanner mismatch is a common problem, occurring in one-in-five follow-up DXA scans and affecting more than a quarter of patients. Interventions to reduce this large proportion of scanner mismatch are necessary.

Size-adjustment techniques of lumbar spine dual energy X-ray absorptiometry measurements in assessing bone mineralization in children on maintenance hemodialysis.

OBJECTIVES: Growing skeleton is uniquely vulnerable to impaired mineralization in chronic kidney disease (CKD). Continued debate exists about the optimal method to adjust for body size when interpreting dual energy X-ray absorptiometry (DXA) scans in children with CKD given the burden of poor growth. The study aimed to evaluate the clinical usefulness of size-adjustment techniques of lumber-spine DXA measurements in assessing bone mineralization in children with kidney failure on maintenance hemodialysis (HD). METHODS: Case-control study included 93 children on maintenance HD (9-18 years; 48 males). Participants were subjected to spinal-DXA-scan to obtain areal bone mineral density (aBMD; g/cm2). Volumetric-BMD (vBMD; g/cm3) was mathematically estimated. Z-scores of aBMD for chronological age (aBMDZ-CA), aBMD adjusted for height age (aBMDZ-HA), and vBMDZ-score were calculated using mean and SD values of age subgroups of 442 healthy controls (7-18 years). RESULTS: In short-for-age CKD patients, aBMDZ-CA was significantly lower than vBMDZ-score, while aBMDZ-HA was significantly higher than aBMDZ-CA and vBMDZ-score. In normal height-for-age CKD patients, no significant difference between aBMDZ-scores and vBMDZ-score was detected. aBMDZ-CA was significantly lower and aBMDZ-HA was significantly higher in short-for-age compared to normal height-for-age patients without significant differences in vBMDZ-score. We observed age-related decrements in the percentage of HD patients with normal densitometric Z-scores, the effect of age was less pronounced in aBMDZ-HA than vBMDZ-score. vBMDZ-score correlated negatively with age, but not with heightZ-score. CONCLUSIONS: Estimated vBMD seems to be a convenient size-adjustment approach of spinal-DXA measurements in assessing BMD especially in older short-for-age children with CKD. aBMDZ-CA underestimates, while aBMDZ-HA overestimates BMD in such patients.

Fracture Risk Assessment: An Update.

➤: Our ability to accurately identify high fracture risk in individuals has improved as the volume of clinical data has expanded and fracture risk assessment tools have been developed. ➤: Given its accessibility, affordability, and low radiation exposure, dual x-ray absorptiometry (DXA) remains the standard for osteoporosis screening and monitoring response to treatment. ➤: The trabecular bone score (TBS) is a DXA software add-on that uses lumbar spine DXA imaging to produce an output that correlates with bone microarchitecture. It has been identified as an independent fracture risk factor and may prove useful in further stratifying fracture risk among those with a bone mineral density (BMD) in the osteopenic range (-1.0 to -2.4 standard deviations), in those with low-energy fractures but normal or only mildly low BMD, or in those with conditions known to impair bone microarchitecture. ➤: Fracture risk assessment tools, including the Fracture Risk Assessment Tool (FRAX), Garvan fracture risk calculator, and QFracture, evaluate the impact of multiple clinical factors on fracture risk, even in the absence of BMD data. Each produces an absolute fracture risk output over a defined interval of time. When used appropriately, these enhance our ability to identify high-risk patients and allow us to differentiate fracture risk among patients who present with similar BMDs. ➤: For challenging clinical cases, a combined approach is likely to improve accuracy in the identification of high-risk patients who would benefit from the available osteoporosis therapies.

Osteoporosis: Recent Recommendations and Positions of the American Society for Bone and Mineral Research and the International Society for Clinical Densitometry.

➤: Osteoporosis is common in orthopaedic patients, not only in those sustaining fragility fractures but also in patients ≥50 years old who are having elective orthopaedic surgery. ➤: The American Society for Bone and Mineral Research (ASBMR) has developed consensus-based recommendations for secondary fracture prevention for all patients who are ≥65 years old with a hip or spine fracture. ➤: The ASBMR encourages orthopaedic surgeons to "Own the Bone," by beginning prevention of a secondary fracture during hospitalization for a fragility fracture, if practicable, and arranging follow-up for continued bone health care after discharge. ➤: The International Society for Clinical Densitometry (ISCD) recognized that many poor outcomes and complications of elective orthopaedic surgery are related to osteoporosis. ➤: The ISCD used an evidence-based approach to create official positions to identify which patients ≥50 years old who are having elective orthopaedic surgery should undergo assessment of bone health and how this should be performed.

Bone Mineral Densitometry Reporting: Pearls and Pitfalls.

Dual-energy X-ray absorptiometry (DXA) is the method of choice for assessing bone mineral density (BMD). Unfortunately, the performance and interpretation of DXA can be challenging and errors are common. In fact, it has been reported that up to 90% of BMD reports contain at least 1 error. Errors can be the result of technique or interpretative in nature or both and can result in inappropriate diagnosis and management. In this article, we review the various types of pitfalls frequently encountered by physicians interpreting DXA studies. Being aware of these pitfalls will help readers recognize and avoid them when encountered in clinical practice.

Quantifying childhood fat mass: comparison of a novel height-and-weight-based prediction approach with DXA and bioelectrical impedance.

Accurate assessment of childhood adiposity is important both for individuals and populations. We compared fat mass (FM) predictions from a novel prediction model based on height, weight and demographic factors (height-weight equation) with FM from bioelectrical impedance (BIA) and dual-energy X-ray absorptiometry (DXA), using the deuterium dilution method as a reference standard. FM data from all four methods were available for 174 ALSPAC Study participants, seen 2002-2003, aged 11-12-years. FM predictions from the three approaches were compared to the reference standard using; R2, calibration (slope and intercept) and root mean square error (RMSE). R2 values were high from 'height-weight equation' (90%) but lower than from DXA (95%) and BIA (91%). Whilst calibration intercepts from all three approaches were close to the ideal of 0, the calibration slope from the 'height-weight equation' (slope = 1.02) was closer to the ideal of 1 than DXA (slope = 0.88) and BIA (slope = 0.87) assessments. The 'height-weight equation' provided more accurate individual predictions with a smaller RMSE value (2.6 kg) than BIA (3.1 kg) or DXA (3.4 kg). Predictions from the 'height-weight equation' were at least as accurate as DXA and BIA and were based on simpler measurements and open-source equation, emphasising its potential for both individual and population-level FM assessments.

Revisiting the radiographic assessment of osteoporosis-Osteopenia in children 0-2 years of age. A systematic review.

BACKGROUND: Imaging for osteoporosis has two major aims, first, to identify the presence of low bone mass (osteopenia), and second, to quantify bone mass using semiquantitative (conventional radiography) or quantitative (densitometry) methods. In young children, densitometry is hampered by the lack of reference values, and high-quality radiographs still play a role although the evaluation of osteopenia as a marker for osteoporosis is subjective and based on personal experience. Medical experts questioned in court over child abuse, often refer to the literature and state that 20-40% loss of bone mass is warranted before osteopenia becomes evident on radiographs. In our systematic review, we aimed at identifying evidence underpinning this statement. A secondary outcome was identifying normal references for cortical thickness of the skeleton in infants born term, < 2 years of age. METHODS: We undertook systematic searches in Medline, Embase and Svemed+, covering 1946-2020. Unpublished material was searched in Clinical trials and International Clinical Trials Registry Platform (ICTRP). Both relevant subject headings and free text words were used for the following concepts: osteoporosis or osteopenia, radiography, children up to 6 years. RESULTS: A total 5592 publications were identified, of which none met the inclusion criteria for the primary outcome; the degree of bone loss warranted before osteopenia becomes visible radiographically. As for the secondary outcome, 21 studies were identified. None of the studies was true population based and none covered the pre-defined age range from 0-2 years. However, four studies of which three having a crossectional and one a longitudinal design, included newborns while one study included children 0-2 years. CONCLUSIONS: Despite an extensive literature search, we did not find any studies supporting the assumption that a 20-40% bone loss is required before osteopenia becomes visible on radiographs. Reference values for cortical thickness were sparse. Further studies addressing this important topic are warranted.

Optimizing DXA to Assess Skeletal Health: Key Concepts for Clinicians.

CONTEXT: The diagnosis of osteoporosis and assessment of fracture risk prior to a sentinel fracture was transformed by the widespread clinical use of dual-energy X-ray absorptiometry (DXA) for the assessment of bone mineral density (BMD). EVIDENCE ACQUISITION: This review is based on a collection of primary and review literature gathered from a PubMed search of "dual energy X-ray absorptiometry," "trabecular bone score," and "atypical femur fracture" among other keywords. PubMed searches were supplemented by the authors' prior knowledge of the subject. EVIDENCE SYNTHESIS: While uncertainty exists for some aspects of osteoporosis care, patient and clinician familiarity with BMD assessment for screening and monitoring is firmly established. Beyond BMD, lateral spine images obtained with DXA can diagnose osteoporosis and refine fracture risk through the detection of unrecognized vertebral fractures. In addition, analysis of DXA lumbar spine images can reflect changes in trabecular bone microarchitecture, a component of bone "quality" that predicts risk of fracture independent of BMD. Finally, monitoring of bone health by DXA may be extended to include assessment of the femoral cortices for rare but serious adverse effects associated with antiresorptive therapies. CONCLUSIONS: Increasing technologic sophistication requires additional consideration for how DXA imaging is performed, interpreted and applied to patient care. As with any test, clinicians must be familiar with DXA performance, pitfalls in analysis, and interpretation within each clinical context in which DXA is applied. With this perspective, care providers will be well positioned to contribute to continuous improvement of DXA performance and, in turn, quality of osteoporosis care.

Deriving pQCT-Type Spatial Density from DXA Images.

INTRODUCTION: Musculoskeletal overuse injuries are a serious problem in the military, particularly in basic combat training, resulting in hundreds of millions of dollars lost because of limited duty days, medical treatment, and high rates of reinjury. Injury risk models have been developed using peripheral computed tomography (pQCT)-based injury correlates. However, pQCT image capture on large number of recruits is not practical for military settings. Thus, this article presents a method to derive spatial density pQCT images from much lower resolution but more accessible dual-energy X-ray absorptiometry (DXA). MATERIALS AND METHODS: Whole-body DXA images and lower leg pQCT images for 51 male military recruits were collected before a 40-day School of Infantry. An artificial neural network model was constructed to relate the DXA density profiles to spatial pQCT density at the 38% and 66% tibial locations. RESULTS: Strong correlation, R2 = 0.993 and R2 = 0.990 for the 38% and 66% pQCT slices, respectively, was shown between spatial density predicted by the artificial neural network model and raw data. CONCLUSIONS: High potential exists to create a practical protocol using DXA in place of pQCT to assess stress fracture risk and aid in mitigating musculoskeletal injuries seen in military recruits.

Common errors in dual-energy X-ray absorptiometry scans in imaging centers in Ecuador.

Dual-energy X-ray absorptiometry is recognized for measuring bone mineral density. The lack of knowledge can lead to errors both in the acquisition of information and in its analysis and subsequent interpretation. The main errors in Ecuadorian Centers were positioning of the patient to the equipment and incorrect analyzed area. PURPOSE/INTRODUCTION: Dual-energy X-ray absorptiometry (DXA) is recognized as the gold standard for measuring bone mineral density (BMD) with acceptable errors, good precision, and reproducibility. However, the training of operators in different centers and countries is not standardized, and the lack of knowledge can lead to errors both in the acquisition of information and in its analysis and subsequent interpretation. The purpose was to determine the most common errors in the performance of bone densitometry from different imaging centers in Ecuador. METHODS: Cross-sectional descriptive study. We collected DXA scans from different imaging centers in Ecuador. Data from the DXA scan included city of origin, type of specialist that requested it, and densitometry diagnosis. The DXA images provided were analyzed double blind by experts in the field from Argentina. RESULTS: From a total of 141 patients with a mean age of 61 ± 10 years, 93.6% were women. About 78% of the DXA scans came from private imaging centers and 22% from public centers, 95% of all came from the city of Guayaquil. The machines used were Hologic 50.4% and Lunar 49.6%. The densitometric diagnosis was 16.3% normal, 46.1% osteoporosis, and 37.6% osteopenia. A total of 112 left hip and 49 right hip scans were analyzed from which 31.2% and 22.4% had errors in patient positioning, respectively, mainly internal or external rotation. About 140 lumbar scans were analyzed from which 21.4% had patient positioning errors (not centered or not straight). Also in 38.5% the vertebral area did not correspond to L1-L4. About 3.5% had artifacts such as a metal bar or implant. The region of interest was misplaced in 24.1% of the lumbar scans and 19.9% of the femur. CONCLUSIONS: DXA quality standards exist but are often not implemented in clinical practice. When studies are performed incorrectly, it can lead to important errors in diagnosis and therapy. Physicians interested in the management of osteoporosis, although not directly involved in the performance and interpretation of DXA, should be familiar with the protocols to minimize errors and allow the proper use of bone densitometry.

Triglyceride Can Predict the Discordance between QCT and DXA Screening for BMD in Old Female Patients.

PURPOSE: This study is aimed at exploring which indicator can predict the discordance between DXA and QCT. METHODS: 192 female patients who took BMD screening tests by QCT and DXA were recruited, and the biomarkers were analyzed to study the relationship between the biomarkers and the discordance of two BMD screening methods. RESULTS: There are 42, 78, and 72 female patients in the normal, osteopenia, and osteoporosis groups defined by DXA and 6, 54, and 132 female patients in the corresponding group defined by QCT. DXA was less sensitive than QCT. Cholesterol (CHO) and triglyceride (TG) were all negatively correlated with the discordance between these two methods. When TG > 0.89 mmol/L, the QCT result would be the same as the DXA's; otherwise, there should be discordance between QCT and DXA. CONCLUSIONS: Triglyceride can be used to predict the discordance between QCT and DXA, and clinicians can evaluate patients' DXA results based on patient triglyceride or cholesterol results as a supplement to QCT results.

A Cross-Calibration Study of GE Lunar iDXA and GE Lunar DPX Pro for Body Composition Measurements in Children and Adults.

OBJECTIVE: To cross-calibrate dual energy X-ray absorptiometry machines when replacing GE Lunar DPX-Pro with GE Lunar iDXA. METHODS: A cross-sectional study was conducted in 126 children (3-19 years) and 135 adults (20-66 years). Phantom cross calibration was carried out using aluminum phantom provided with each of the machines on both machines. Total body less head (TBLH), lumbar spine (L2-L4) and left femoral neck bone mineral density (BMD), bone mineral content (BMC), and bone area were assessed for each patient on both machines. TBLH lean and fat mass were also measured. Bland-Altman analysis, linear regressions, and independent sample t test were performed to evaluate consistency of measurements and to establish cross-calibration equations. RESULTS: iDXA measured 0.33% lower BMD and 0.64% lower BMC with iDXA phantom as compared to DPX-Pro phantom (p < 0.001). In children, TBLH-BMC, femoral BMC and area were measured 10%-14% lesser, TBLH area was higher by 1%-2% and L2-L4 area by 10%-14% by iDXA as compared to DPX-Pro. iDXA measured higher TBLH fat [15% (girls), 31% (boys)] than DPX-Pro. In adults, TBLH-BMD (1.7%-3.4%), BMC (6.0%-10.9%) and area (4.2%-7.6%) were measured lesser by iDXA than DPX-Pro. L2-L4 BMD was higher [2.7% (men), 1.8% (women)] by iDXA than DPX-Pro. Femoral BMC was 2.11% higher in men and 4.1% lower in women by iDXA as compared to DPX-Pro. In children, R2 of cross-calibration equations, ranged from 0.91 to 0.96; in adults, it ranged from 0.93 to 0.99 (p < 0.01). After the regression equations were applied, differences in BMD values between both machines were negligible. CONCLUSION: A strong agreement for bone mass and body composition was established between both machines. Cross-calibration equations need to be applied to transform DPX-Pro measurements into iDXA measurements to avoid errors in assessment. This study documents a need for use of cross-calibration equations to transform DPX-Pro body composition data into iDXA values for clinical diagnosis.

Reproducibility of Metacarpal Bone Mineral Density Measurements Obtained by Dual-Energy X-Ray Absorptiometry in Healthy Volunteers and Patients With Early Arthritis.

Reduction in cortical bone mineral density at diaphysis of metacarpal bones of the hand, evaluated by dual X-ray radiogrammetry, has a bad prognostic value in patients with early arthritis. Nevertheless, this technique is hardly accessible in clinical practice. By contrast, evaluation of cortical bone mineral density at that location has not been previously assessed by conventional dual X-ray absorptiometry. The aim of this study is to evaluate the reproducibility of bone mineral density measurements at diaphysis of metacarpal bones using conventional dual X-ray densitometry in a population of healthy volunteers and patients with early arthritis. Nondominant hand dual X-ray densitometry was performed at three consecutive times with complete hand replacement in 27 subjects: 10 early arthritis and 17 healthy volunteers. Three different evaluators analyzed the 3 measurements of second to fourth metacarpal bones. To assess the reproducibility and accuracy of the measurements, intra- and interobserver agreement degrees, intra- and interclass correlation coefficients, smallest difference detectable assessment, and Bland Altman graphs were calculated. The coefficients of variation obtained for the different metacarpal evaluations were 2.25%, 2.91%, 2.85%, and 2.07% for metacarpal-2, metacarpal-3, metacarpal-4, and mean metacarpal-second to fourth, respectively, with a smallest difference detectable of 0.028, 0.034, 0.028, and 0.03 g/cm2, respectively. The mean intra- and interobserver correlation coefficients between of metacarpal second to fourth were 0.990 (95% confidence interval [CI]: 0.982-0.995) and 0.995 (95% CI: 0.991-0.997), respectively. As expected, women had lower bone mineral density at metacarpal bones, especially after menopause. The results obtained in this study show an excellent reproducibility of bone mineral density measurements at diaphysis of metacarpal bones of the hand, measured by conventional dual X-ray densitometry, in a mixed population of healthy subjects and patients with early arthritis. This is of great interest for longitudinal studies in patients with early arthritis.

DEXA sensitivity analysis in patients with adult spinal deformity.

BACKGROUND: Adult spinal deformity (ASD) is a debilitating condition that commonly requires surgical intervention. However, ASD patients may also present with osteoporosis, predisposing them to surgical complications and failure of instrumentation. As a result, proper detection of low bone mineral density (BMD) is critical in order to ensure proper patient care. Typically dual-energy x-ray absorptiometry (DEXA) scans are performed on the hip and spine. Unfortunately, in ASD patients, the latter is often inaccurate PURPOSE: In this study, we consider the value of obtaining a forearm DEXA scan in addition to a hip scan in patients suffering from ASD and osteoporosis in order to accurately detect low BMD. STUDY DESIGN: Retrospective study. PATIENT SAMPLE: Patient data between 2016 and 2018 from a single academic medical center was utilized. Two hundred eighty-six patients met the initial search criteria. OUTCOME MEASURES: No outcomes measures related to self-reporting, physiology, or functionality were evaluated in this study. Primary outcome measures analyzed included T-scores across various anatomic locations and diagnoses relating to low bone density (ie, osteopenia and osteoporosis). METHODS: This retrospective study examines patients that underwent DEXA studies between 2016 and 2018 and were previously diagnosed with both osteoporosis and adult spinal deformity. For each patient, age, gender, body mass index, and smoking history were noted, as well as whether there was long-term prednisone use. T-scores from both the forearm and hip were recorded and analyzed. Diagnoses from hip DEXA scans were compared with those obtained from forearm scans to identify which region was more sensitive in detecting low BMD. From this data, the frequency of a missed diagnosis, due to reliance on hip or spine T-scores for detection of low BMD, was extrapolated. No external funding source was received in support of this study. RESULTS: Two hundred eighty-six patients matched the initial search criteria. Only 68% had one T-score value. However, 24.8% of patients had data for both the hip and forearm, whereas 7.1% had data for the forearm, hip, and spine. Among the 85 patients with more than one anatomical site of study, the forearm was more sensitive than the hip in its ability to detect osteopenia or osteoporosis 41.2% of the time. A two-tailed t test showed no statistically significant difference between hip T-scores and forearm T-scores. However, for more than 17% of patients, the forearm allowed clinicians to detect osteoporosis or osteopenia in a setting where using only the hip data would have missed such a diagnosis. CONCLUSIONS: Clinicians need to ensure they survey at least two locations when conducting DEXA studies before precluding a diagnosis of osteopenia or osteoporosis. All ASD patients being evaluated for low bone density should receive DEXA scans that survey at least the hip and the forearm. Misdiagnoses can be costly in the setting of ASD. They occur frequently when only a single hip scan is relied upon to assess BMD.

Breast density measured volumetrically in a clinical environment: cross-sectional study with photon counting technology.

OBJECTIVE: Mammographic breast density (BDen), the ratio of glandular volume (GVol) to breast volume (BVol), is the second most prevalent risk factor for breast cancer (BC). Newly developed photon counting technology allows precise and systematic measurements in clinical practice. Our objective is to see how these parameters change with age in women with and without cancer. MATERIALS AND METHODS: This retrospective study analyzed results of BDen, GVol, and BVol in 64,182 mammograms performed with photon counting technology on 32,448 consecutive women from April 2014 to December 2015. Only their first study was included. We excluded women with incomplete data or with breast implants. RESULTS: Mean age of women without BC diagnosed during the study period was 52.1 ± 9.9. BC and was found in 263 women (0.81%). Mean age was 53.0 ± 10.4. BDen, GVol, and BVol were 14%, 24%, and 2% greater in women with BC (P < 0.001 for BDen and GVol and P = 0.02 for BVol). BDen and GVol diminished following similar patterns across age in both groups, with soft slopes before and after a steep drop from 50 to 60, probably due to menopause. CONCLUSION: BDen diminishes with age in women with or without BC, but it is generally higher in women with BC. GVol could be a more robust indicator associated with BC risk than BDen. This technology can ease the way to studies of interventions to diminish BDen (or GVol) in the hope of diminishing BC incidence or predict if longitudinal changes are indicative of impending cancer.

Agreement Between Bioelectrical Impedance and Dual-Energy X-Ray Absorptiometry to Track Changes in Fat-Free Mass After Resistance Training in Older Women.

Nascimento, MA, Silva, DRP, Ribeiro, AS, Pina, FLC, Gerage, AM, Gobbo, LA, Mayhew, JL, and Cyrino, ES. Agreement between bioelectrical impedance and dual-energy x-ray absorptiometry to track changes in fat-free mass after resistance training in older women. J Strength Cond Res 34(6): 1700-1708, 2020-The aim of our study was to compare the agreement between bioelectrical impedance (BIA) and dual-energy X-ray absorptiometry (DXA) to track changes on fat-free mass (FFM) after a resistance training (RT) program in older women. Forty-three older women (65.2 ± 4.6 years, 59.5 ± 9.2 kg, 156.4 ± 6.0 cm, 24.3 ± 3.3 kg·m) participated in a RT intervention (12 weeks, 8 exercises, 2 sets, 10-15 repetitions, 3 nonconsecutive days per week). Fat-free mass changes were determined by a single-frequency BIA device (EQ1), 6 BIA prediction equations for older women (EQ2, EQ3, EQ4, EQ5, EQ6, and EQ7), and DXA. At pretraining, 3 equations overpredicted, and 3 underpredicted DXA FFM (F = 244.63, p < 0.001), although all equations had high correlations with DXA (r = 0.78-0.83). After training, 4 equations overpredicted and one underpredicted DXA FFM (F = 176.25, p < 0.001). Dual-energy X-ray absorptiometry detected significant gains in FFM (0.65 ± 0.82 kg; p < 0.05), as did EQ3 (0.55 ± 1.69 kg; p < 0.05), and EQ4 (0.61 ± 1.88 kg; p < 0.05), whereas the remaining equations did not indicate significant changes in FFM. Low correlations between FFM and equation change values suggest that single-frequency BIA-derived equations may not provide sufficient accuracy to track changes in FFM after 12 weeks of RT in older women.

Impact of reference point selection on DXA-based measurement of forearm bone mineral density.

Few studies have systematically evaluated the technical aspects of forearm bone mineral density (BMD) measurement. We found that BMD remained stable regardless of the reference point; however, the ROI identified was not always consistent. Our study highlights the importance of using the same reference point for serial measurements of forearm BMD. BACKGROUND: Forearm fractures are clinically important outcomes from the perspective of morbidity, health care costs, and interruption of work. BMD of the forearm, as derived by dual-energy x-ray absorptiometry (DXA), is a better predictor of fracture at the forearm compared with BMD measured at other sites. However, very few studies have evaluated the technical aspects of selecting the ROI for forearm BMD measurement. This study aimed to compare the BMD values measured at the 1/3 radius site using three different reference points: the ulnar styloid process, the radial endplate, and the bifurcation of the ulna and radius. METHODOLOGY: Healthy Chinese patients participating in the control group of an ongoing study at Zhejiang Provincial People's Hospital were recruited for this study. For each patient, a DXA scan (GE Lunar Prodigy) of the forearm was performed and BMD values were separately calculated using each of the three reference points to identify the ROI. Pearson correlation coefficients were calculated to examine the correlation between the BMD measures derived from each reference point. The F test and independent t test were applied for more robust analysis of the differences in the variances and means. RESULTS: Sixty-eight healthy Chinese volunteers agreed to participate in this study. The root mean square standard deviation (RMS-SD) percentages of BMD values measured at the 1/3 radius site were 2.19%, 2.23%, and 2.20% when using the ulnar styloid process, radial endplate, and the bifurcation of the ulna and radius as the reference points, respectively. Pearson's correlation coefficients for all pairwise comparisons among these three groups were greater than 0.99. F tests and independent t tests showed p values ranging from 0.92 to 0.99. However, we observed that among 10% of patients, choosing an ROI at the ulnar styloid process led to an inability to accurately determine the BMD at the ultra-distal radius. CONCLUSIONS: Given equal ability to determine BMD at the 1/3 radius accurately, the radial endplate or the bifurcation of the ulna and radius should be preferentially selected as the reference point for routine forearm BMD measurements in order to avoid situations in which the ultra-distal radius BMD cannot be determined.

Predicting bone strength from CT data: Clinical applications.

In this review we summarise over 15 years of research and development around the prediction of whole bones strength from Computed Tomography data, with particular reference to the prediction of the risk of hip fracture in osteoporotic patients. We briefly discuss the theoretical background, and then provide a summary of the laboratory and clinical validation of these modelling technologies. We then discuss the three current clinical applications: in clinical research, in clinical trials, and in clinical practice. On average the strength predicted with finite element models (QCT-FE) based on computed tomography is 7% more accurate that that predicted with areal bone mineral density from Dual X-ray Absorptiometry (DXA-aBMD), the current standard of care, both in term of laboratory validation on cadaver bones and in terms of stratification accuracy on clinical cohorts of fractured and non-fractured women. This improved accuracy makes QCT-FE superior to DXA-aBMD in clinical research and in clinical trials, where the its use can cut in half the number of patients to be enrolled to get the same statistical power. For routine clinical use to decide who to treat with antiresorptive drugs, QCT-FE is more accurate but less cost-effective than DXA-aBMD, at least when the decision is on first line treatment like bisphosphonates. But the ability to predict skeletal strength from medical imaging is now opening a number of other applications, for example in paediatrics and oncology.