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  • 1
    Electronic Resource
    Electronic Resource
    Impact of Spinal Degenerative Changes on the Evaluation of Bone Mineral Density with Dual Energy X-Ray Absorptiometry (DXA) (1997)
    Springer
    Calcified tissue international 60 (1997), S. 430 -433 
    Details
    ISSN: 1432-0827
    Keywords: Key words: Dual-energy X-ray Absorptiometry — Degenerative factors — Postmenopausal women — Bone mineral density — Osteoporosis.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Abstract. The purpose of this study is to evaluate degenerative factors in a postmenopausal patient group and differentiate the influence on bone mineral density (BMD) measurements by dual-energy X-ray absorptiometry (DXA). The patients and methods included an investigation of 144 postmenopausal women (mean 63.3 years) with PA-DXA of the spine. Degenerative factors (osteophytes, osteochondrosis, scoliosis, and vascular calcification) were evaluated from plain lumbar radiographs, their estimated probability was analyzed as a function of age, and their influence on BMD measured by PA-DXA was determined. The results of the study revealed osteophytes in 45.8%, vascular calcifications in 24.3%, scoliosis in 22.2%, osteochondrosis in 21.5%. The estimated probability for degenerative factors increased from 35 to 80% in the 55- to 70- year age group. Osteophytes and osteochondrosis were associated with up to a 14% increase in BMD values (P 〈 0.001). Vascular calcifications showed a positive trend, whereas scoliosis did not show a discernible influence. We concluded that degenerative factors, except for scoliosis, showed an influence on BMD as measured by DXA. Their prevalence increased rapidly between 55 and 70 years of age. Interpretation of PA-DXA spine data for subjects of or above this age range should be complemented by plain film radiographs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002239900258
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  • 2
    Electronic Resource
    Electronic Resource
    Broadband ultrasound attenuation signals depend on trabecular orientation: An in vitro study (1993)
    Springer
    Osteoporosis international 3 (1993), S. 185-191 
    Details
    ISSN: 1433-2965
    Keywords: Bone densitometry ; Bone structure ; Osteoporosis ; Ultrasound
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Quantitative ultrasound (QUS) techniques have recently been introduced as alternative methods free of ionizing radiation for non-invasive assessment of skeletal status in osteoporosis. We carried out an in vitro study on bone specimens to investigate whether broadband ultrasound attenuation (BUA) signals are associated with bone structure, specifically with the orientation of the trabeculae, and whether this association is independent of the association between orientation and bone mineral density (BMD) as measured by dual-energy X-ray absorptiometry (DXA). BUA and BMD of 10 cubical specimens of purely trabecular bovine bone were examined along the three principal axes. The relative orientation of the trabeculae with respect to the direction of the ultrasound beam was evaluated on high-resolution conventional radiographs employing a semiquantitative ALIGNMENT score ranging from −2 (for perpendicular) to +2 (parallel). BUA variability was 27.6 dB/MHz, reflecting both inter-specimen (18.2 dB/MHz) and intra-specimen (19.4 dB/MHz) variability at comparable levels and to a much lesser extent reproducibility errors (1 dB/MHz). BUA was 44%–54% larger along the axis of the compressive trabeculae as compared with the two perpendicular axes. BMD and ALIGNMENT showed independent significant associations with BUA. A change in ALIGNMENT from perpendicular to parallel corresponded to a difference in BUA of 36.1 dB/MHz. The substantial level of intra-specimen variability suggests that BUA reflects anisotropical characteristics of trabecular bone. The association of BUA and ALIGNMENT indicates that BUA signals depend on trabecular orientation. This association is independent of BMD, indicating that BUA has considerable potential for non-invasive assessment of bone structure and strength, free of ionizing radiation, and for complementing existing bone densitometry examinations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01623674
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  • 3
    Electronic Resource
    Electronic Resource
    Quality assurance for bone densitometry research studies: Concept and impact (1993)
    Springer
    Osteoporosis international 3 (1993), S. 227-235 
    Details
    ISSN: 1433-2965
    Keywords: Bone densitometry ; Osteoporosis ; Quality assurance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract A concept for quality assurance (QA) in bone densitometry has been developed for clinical multicenter studies. Major elements provided by a coordinating center comprise (1) consulting services and certification of participating centers in the start-up phase of the study, (2) review of scan data acquired on QA standards for cross-calibration and longitudinal assessment of scanner stability, (3) review of selected patient data as well as of problem cases during the study, and (4) comprehensive review and correction of patient results based on QA data after conclusion of the study. Limitations of phantom-based QA data should be acknowledged. Typical problems encountered during research studies and guidelines for solutions are presented. Successful implementation of QA measures may yield substantial enhancement of statistical power. Depending on the study design and the variability of response within patient groups, improvement in precision due to QA measures may reduce the smallest detectable difference between subject groups or, alternatively, sample size by a few to more than 50%, and thus may contribute to a substantial reduction in study cost. Formulae for calculation of the magnitude of these effects are presented. To maximize the net benefit, QA efforts have to be limited to levels that assure reliability of the data at acceptable QA cost. While QA programs at individual clinical sites or for local practitioners may not need to be as extensive as for multicenter clinical trials, awareness of the potential problems and implementation of basic QA measures will help in obtaining high-quality bone densitometry results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01623825
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  • 4
    Electronic Resource
    Electronic Resource
    Spinal bone mineral assessment in postmenopausal women: A comparison between dual X-ray absorptiometry and quantitative computed tomography (1995)
    Springer
    Osteoporosis international 5 (1995), S. 433-439 
    Details
    ISSN: 1433-2965
    Keywords: Bone mineral density (BMD) ; Dual X-ray absorptiometry (DXA) ; Fracture risk ; Postmenopause ; Quantitative computed tomography (QCT)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We compared quantitative computed tomography (QCT) and dual X-ray absorptiometry (DXA) with respect to their ability to discriminate subjects with and without prevalent vertebral fractures. In 240 post-menopausal women (mean age 63.7±6.9 years) lateral spine radiographs (T4-L4) were reviewed for the presence of vertebral fracture. Using a semiquantitative technique to grade the severity of vertebral deformities, we classified fractures as mild, moderate or severe (grade 1 to 3, respectively). Postero-anterior DXA (PA-DXA) and lateral DXA (L-DXA) measurements (L2–4) as well as QCT measurements of the lumbar spine (T12-L3 or L1–14) were obtained in all women. Seventy-two women were diagnosed with at least one fracture, and of these 40 were graded as mild. Comparing normal women with fractured women, we found the area under the receiver operating characteristics (ROC) curves to be greatest for QCT (0.81), followed by L-DXA (0.72) and PA-DXA (0.65). The differences among all three techniques were significant. Comparing the normal women with women having only mild fractures, the areas under the ROC curves were 0.79, 0.73 and 0.63 for QCT, L-DXA and PA-DXA, respectively. Significant differences existed between QCT and PA-DXA as well as between L-DXA and PA-DXA. Logistic regression analysis also revealed the highest age-adjusted odds ratios for QCT (3.67; 2.25–5.97) while L-DXA and PA-DXA showed substantially lower odds ratios (2.00; 1.39–2.87, and 1.54; 1.11–2.15, respectively). We conclude that low bone density as measured by QCT, PA-DXA or L-DXA is significantly associated with the prevalence of vertebral fractures. Of the methods studied, QCT of trabecular bone offered the best discriminatory capability. L-DXA proved to be superior to PA-DXA in its diagnostic sensitivity, particularly in women with mild fracture. Mild vertebral fractures are associated with decreased spinal bone density and may be regarded as osteoporotic deformities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01626604
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  • 5
    Electronic Resource
    Electronic Resource
    An Update on the Diagnosis and Assessment of Osteoporosis with Densitometry (2000)
    Springer
    Osteoporosis international 11 (2000), S. 192-202 
    Details
    ISSN: 1433-2965
    Keywords: Key words:Definition of osteoporosis – Densitometry – Diagnosis – Risk assessment – Risk factors
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract: In 1994 the WHO proposed guidelines for the diagnosis of osteoporosis based on measurement of bone mineral density. They have been widely used for epidemiological studies, clinical research and for treatment strategies. Despite the widespread acceptance of the diagnostic criteria, several problems remain with their use. Uncertainties concern the optimal site for assessment, thresholds for men and diagnostic inaccuracies at different sites. In addition, the development of many new technologies to assess the amount or quality of bone poses problems in placing these new tools within a diagnostic and assessment setting. This review considers the recent literature that has highlighted the strengths and weaknesses of diagnostic thresholds and their use in the assessment of fracture risk, and makes recommendations for actions to resolve these difficulties.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001980050281
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  • 6
    Electronic Resource
    Electronic Resource
    Bone densitometry: Current assessment (1993)
    Springer
    Osteoporosis international 3 (1993), S. 91-97 
    Details
    ISSN: 1433-2965
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Conclusions Noninvasive measurements of bone mineral density allow the assessment of skeletal integrity, both centrally and peripherally, with high precision and accuracy and with relatively low radiation dose. When estimating skeletal status, it may be important to measure bone mineral density at more than one site to assess differential skeletal responses related to disease or therapy and to assess differential fracture risk. Due to technical differences between the various methods of bone mineral measurement, the quantitative results are typically expressed with differing calibration standards, such that direct comparisons must be carefully made. SPA measurements have been shown in several prospective studies to aid in the assessment of osteoporotic fracture risk. Limited data to date have shown spinal DPA to be at least comparable to peripheral SPA for fracture risk assessment, and current research with DXA indicates promising results for the X-ray-based bone densitometers. DXA has seen rapid growth in recent years, with current scanners able to measure the spine, hip, forearm and total body bone mineral density with a speed and precision previously unattainable with the isotope-based DPA systems. Longitudinal studies have shown QCT to be highly sensitive for detecting early and rapid bone loss and cross-sectional studies have shown QCT's capacity for separating normal and osteoporotic patient populations. though prospective studies are needed to confirm the latter result. QCT has the disadvantage of higher cost and radiation dose compared with the other methods currently in use, but it is the only noninvasive modality able preferentially to measure trabecular, cortical, or integral bone density at any skeletal site. All of the techniques in current clinical use, specifically SPA, DPA, DXA and QCT, represent major advances for the noninvasive measurement of bone mineral density at radiation doses significantly less than those due to yearly exposure from normal background radiation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01621875
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  • 7
    Electronic Resource
    Electronic Resource
    How To Use Ultrasound for Risk Assessment: A Need for Defining Strategies (1999)
    Springer
    Osteoporosis international 9 (1999), S. 193-195 
    Details
    ISSN: 1433-2965
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001980050135
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  • 8
    Electronic Resource
    Electronic Resource
    Assessment of the Geometry of Human Finger Phalanges Using Quantitative Ultrasound In Vivo (2000)
    Springer
    Osteoporosis international 11 (2000), S. 745-755 
    Details
    ISSN: 1433-2965
    Keywords: Key words: Bone geometry – Novel parameters – Phalanges – Quantitative ultrasound
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract: Quantitative Ultrasound (QUS) methods have been shown to be useful in the assessment of bone status. Nevertheless, ultrasound transmission depends on a variety of skeletal parameters, and a detailed understanding of ultrasound propagation through bone is important for the accurate interpretation of QUS results. In this study we wanted to elucidate the pathways of an ultrasound wave through finger phalanges and determine correlations between geometric and QUS parameters. Phalanges of a subject group were measured using QUS and magnetic resonance imaging (MRI). MRI was used for the derivation of the geometric parameters. Similar assessments were performed on cylindrical tubes and with a simulation program. New parameters related to speed of sound (SOS) and amplitude of the wave (A2P) were calculated. Strong correlations between QUS parameters and morphologic cross-sectional areas were observed in vivo and in phantoms. Similar correlations could be found in the calculations using the simulation software. Cross-sectional cortical area, medullary canal area and relative cortical area could be calculated from the QUS parameters (subjects: R 2= 0.71 for cortical area, R 2 = 0.45 for medullary canal area and R 2= 0.61 for relative cortical area; phantoms: R 2= 0.98 for cortical area, R 2= 0.78 for medullary canal area and R 2= 0.77 for relative cortical area). In vivo, phantom and simulation results consistently showed that SOS was correlated with cortical area but not with medullary canal area while the opposite was found for A2P. Pathways of the ultrasound wave through solid cortical bone and the medullary canal could be identified and the propagation of the wave could be depicted. These results help to interpret QUS findings and provide information that may be helpful in improving the performance of QUS.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001980070053
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  • 9
    Electronic Resource
    Electronic Resource
    Which vertebrae should be assessed using lateral dual-energy X-ray absorptiometry of the lumbar spine (1995)
    Springer
    Osteoporosis international 5 (1995), S. 196-204 
    Details
    ISSN: 1433-2965
    Keywords: Bone mineral density ; Diagnosis ; Dualenergy X-ray absorptiometry ; Osteoprosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The purpose of this study was to determine precision and diagnostic capability of bone mineral density measurements using lateral dual-energy X-ray absorptiometry (DXA) of the lumbar spine in supine position. Duplicate postero-anterior (PA) and lateral DXA measurements were performed in 60 women. Precision errors of the single vertebral levels using lateral DXA ranged from 3.3% to 4.9%. The combination of all levels improved the precision errors to 2.0%. Paired PA and lateral DXA measurements (Hologic QDR 2000) including the vertebral levels L2 to L4 were performed in 331 postmenopausal women. In 42 women an overlap of L4 by the pelvis was suspected on the lateral DXA images. Vertebral fractures were assessed as a fracture/non-fracture dichotomy. L4 and combinations of vertebrae including L4 showed the best discriminatory capabilities with respect to vertebral fractures in receiver operating characteristic (ROC) analyses,t-tests andZ-scores, with smaller variability of the results when multiple vertebral levels were used. The areas under the ROC curves were 0.662 and 0.639 for lateral and PA measurements of L2 to L4, respectively when all women were included. Excluding the women with pelvic overlap on lateral DXA scans improved the ROC area for lateral scans to 0.686 while that for PA scans remained almost constant (0.641). The differences between PA and lateral measurements were not statistically significant. In 162 women of our study cohort an additional quantitative computed tomography (QCT) measurement of the vertebral levels L2 to L4 was performed and overlapping bony structures at the three levels were studied. Overlapping bony structures were found on QCT slices in 96.9% at the L2 level and in 31.5% at the L3 level. At the L4 level an overlap was found in 5.6% of the women in addition to 31 women in whom L4 overlap had been suspected on DXA images. In total, the level L4 was overlapped in 24.7% of the women. Lateral DXA measurements of the lumbar spine with the patient in supine position are meaningful for diagnosis and follow-up of osteopenia. The inclusion of a maximum number of vertebrae, i.e. L2 to L4 (if L4 is not overlapped by pelvic bone), improves precision and diagnostic capability of the method.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02106100
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  • 10
    Electronic Resource
    Electronic Resource
    Accurate assessment of precision errors: How to measure the reproducibility of bone densitometry techniques (1995)
    Springer
    Osteoporosis international 5 (1995), S. 262-270 
    Details
    ISSN: 1433-2965
    Keywords: Bone densitometry ; Heteroscedasticity ; Precision error ; Reproducibility ; Statistics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Assessment of precision errors in bone mineral densitometry is important for characterization of a technique's ability to detect logitudinal skeletal changes. Short-term and long-term precision errors should be calculated as root-mean-square (RMS) averages of standard deviations of repeated measurements (SD) and standard errors of the estimate of changes in bone density with time (SEE), respectively. Inadequate adjustment for degrees of freedom and use of arithmetic means instead of RMS averages may cause underestimation of true imprecision by up to 41% and 25% (for duplicate measurements), respectively. Calculation of confidence intervals of precision errors based on the number of repeated measurements and the number of subjects assessed serves to characterize limitations of precision error assessments. Provided that precision error are comparable across subjects, examinations with a total of 27 degrees of freedom result in an upper 90% confidence limit of +30% of the mean precision error, a level considered sufficient for characterizing technique imprecision. We recommend three (or four) repeated measurements per individual in a subject group of at least 14 individuals to characterize short-term (or long-term) precision of a technique.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01774016
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