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PubMed1989

Bone densitometry of the peripheral skeleton with a new photon counting and imaging device.

We present a new method for the assessment of bone mineral content of the peripheral skeleton. The method employs a new photon counting and imaging area device, the multi-wire proportional counter. The system can work as a single photon absorptiometer at the energies of both I-125 and Gd-153. It can work also as a dual photon absorptiometer using one of the two pairs of isotopes (I-125, Gd-153) or (I-125, Am-241). Both the calcaneus and the forearm can be imaged in a few minutes, with either single or dual photon absorptiometry. To test this new method in a clinical environment we compared it with the standard dual photon absorptiometry of the forearm. The data collected in a cross-sectional study of bone mineral content and bone mineral density in a group of 76 patients show a good correlation between the two measurement techniques (r = 0.931). The multi-wire proportional counter, due to its imaging capabilities, has a much lower repositioning error. This allows its use in regions with a large gradient of bone mineral density, such as the calcaneus or the very distal site of the forearm, which recent data have indicated to be superior to more proximal measurements in identifying osteoporosis.

Absorptiometry, Photon↗
PubMed1994

Statistical concepts in the interpretation of serial bone densitometry.

The precision of a measurement can be expressed as the variance of multiple measurements. The coefficient of variation is a dimensionless expression of precision that is prevalent in the radiology literature. However, the coefficient of variation has important limitations. The question whether measured change is significant arises whenever any quantitative clinical parameter is followed over time. When serial bone mineral density measurements are made, change is commonly estimated as the slope of a line fitted to the serial data by linear regression. Confidence intervals for change based on this method usually assume that the precision error in measurement remains constant over time and that change is truly linear. Estimates of long-term precision may be elusive, and if constant, may vary for different individuals. If separate measurement precisions are known or are indeed constant, one can assess the level of statistical agreement of longitudinal data to linear, or other theoretical, models.

Absorptiometry, Photon↗
PubMed2001

Do ultrasound measurements reflect bone microarchitecture rather than bone mass?: An in vitro study of the rat femur with the use of ultrasound, densitometry, and histomorphometry.

RATIONALE AND OBJECTIVES: In an experimental study in 40 rat femurs, the authors correlated the amplitude-dependent speed of bone ultrasound (Ad-SOS) with the bone mineral content and density and with the bone trabecular connectivity: trabecular bone volume, trabecular number, trabecular thickness, and trabecular separation to evaluate and compare the usefulness of the Ad-SOS to determine bone quantity and/or quality. METHODS: Bone mineral content and density were determined with dual-energy x-ray absorptiometry. Trabecular connectivity was determined with histomorphometric techniques. RESULTS: There was a strong correlation between the Ad-SOS and the other parameters studied, with a particularly high positive correlation with trabecular bone volume and trabecular thickness, and an inverse correlation with trabecular separation. The correlation was weaker with the bone mineral content and bone mineral density and with the trabecular number. For the trabecular separation, the correlation was significant in all cases, but it was negative. CONCLUSIONS: Bone ultrasound, in this case Ad-SOS, defines the quality of the bone in terms of trabecular architecture rather than bone density; however, this conclusion is valid only for the rat femur model that the authors used.

Absorptiometry, Photon↗
PubMed2002

Bone densitometry, steroids and osteoporosis.

PURPOSE OF REVIEW: Scans to measure bone mineral density at the spine and hip have an important role in the evaluation of patients at risk of osteoporosis. Oral corticosteroid use is an important risk factor for a fragility fracture and the relative risk is particularly high for vertebral and hip fractures. In Europe and the USA, guidelines have been published for the investigation of patients at risk of corticosteroid-induced osteoporosis, with recommendations on the diagnostic use of bone mineral density scans and the initiation of treatment based on the findings. RECENT FINDINGS: Large trials of bisphosphonates, selective oestrogen receptor modulators and parathyroid hormone have addressed the issue of fracture prevention in women with postmenopausal osteoporosis and there is a growing consensus that the World Health Organization definition of osteoporosis of a -score=-2.5 is an appropriate threshold for preventive treatment in these patients. For most agents separate studies have been conducted of their use for the prevention and treatment of corticosteroid-induced osteoporosis. SUMMARY: There is increased awareness of the importance of preventive treatment for osteoporosis in patients taking high doses of oral corticosteroids (daily dose of 7.5 mg prednisolone or greater). In view of evidence that corticosteroid use is an independent risk factor for fracture over and above bone mineral density, guidelines for intervention set a higher threshold than the World Health Organization figure ( -score=-1.5 rather than -2.5) for intervention with bone sparing treatment in these patients.

Aged↗
PubMedDate not supplied

Thin-section and low-dose volumetric computed tomographic densitometry of the lung in systemic sclerosis.

OBJECTIVE: To correlate lung density measurements with the results of visual assessment of thin-section computed tomography (CT) and of pulmonary function tests (PFT) in Systemic Sclerosis (SSc). METHODS: Thirty-nine SSc patients underwent sequential thin-section CT and spiral low-dose whole-lung acquisitions. The thin-section CT scans were evaluated with a dedicated visual scale. Mean lung density, skewness, and kurtosis were calculated from the lung density histogram. In addition from the spiral low-dose acquisition, the lung volume was computed. The visual score, the densitometric parameters, and the lung volume were correlated with the PFT. RESULTS: Mean lung density, skewness, and kurtosis computed from thin-section (R = 0,66; R = -0,74; R = -0,75) and low-dose volumetric (R = 0,72; R = -0,71; R = -0,71) CT and the lung volume (R = -0.54) correlated with the visual score. Densitometric values and lung volume consistently better correlated with PFT than the visual score. CONCLUSIONS: In SSc the histogram results are more closely correlated to PFT than the visual score. The low-dose spiral CT seems ideal for longitudinal studies.

Adolescent↗
PubMed2004

Influence of long-term cigarette smoking on immunoglobulin E-mediated allergy, pulmonary function, and high-resolution computed tomography lung densitometry in elderly patients with asthma.

BACKGROUND: Smoking is the most important cause of chronic obstructive pulmonary disease (COPD). However, the influence of cigarette smoking on the pathogenesis of asthma in the elderly remains controversial. This study attempted to clarify the influence of cigarette smoking on elderly asthmatics. METHODS: Forty-eight asthmatics over 70 years old (25 ex-smokers and 23 never-smokers) and 20 patients with COPD over 70 years old (all ex-smokers) were studied to determine the influence of cigarette smoking on IgE-mediated allergy (total IgE, IgE antibodies against inhalant allergens, bronchial hyper-responsiveness (BHR), generation of leukotriene (LT) B4 and C4), pulmonary function, and the relative area of lung showing attenuation values less than -950 Hounsfield units (RA950) on high-resolution computed tomography scans. RESULTS: The incidence of positive IgE antibodies against inhalant allergens, BHR, and the generation of leukotriene B4 (LTB4) by leucocytes were significantly increased in patients with a history of smoking compared with those without. Residual volume (%RV) was significantly increased, and diffusing capacity for carbon monoxide was significantly decreased in ex-smokers with asthma and COPD compared with never-smokers with asthma. Inspiratory RA950 and ratio of expiratory RA950 to inspiratory RA950 were significantly larger in asthmatics with a smoking history than in those without, and in COPD patients than in asthmatics. CONCLUSION: Cigarette smoking enhances the production of IgE antibodies, BHR, and generation of LTB4 by leucocytes in elderly asthmatics. Increased hyper-inflation or emphysematous changes of the lungs expressed by increased RA950, closely related to %RV, was more frequently observed in ex-smokers compared with never-smokers.

Aged↗
PubMed1996

Assessment of bone involvement in patients with multiple myeloma using bone densitometry.

To evaluate the use of dual energy X-ray absorptiometry (DXA) in multiple myeloma (MM) we performed a prospective study of 34 patients with newly diagnosed MM. Most patients had advanced disease and all but two patients had osteolytic bone destructions and/or pathological fractures. Bone mineral content (BMC) and bone mineral density (BMD) of the lumbar spine (L1-L4) and hip were measured using a Hologic QDR-1000 scanner. Collapsed vertebrae were not excluded from analysis. Data from 289 healthy Danish volunteers aged 21-79 yr were used for calculation of Z-scores. Lumbar spine BMC (Z-score -0.46 +/- 0.23, p = 0.05) and lumbar spine BMD (Z-score -0.56 +/- 0.23, p = 0.02) were significantly reduced in MM patients, whereas no reduction was seen in hip BMC or BMD. Collapsed vertebrae had marked reduced BMD (Z-score -1.34 +/- 0.22, p < 0.001), as had non-fractured vertebrae in the same individuals (Z-score -1.42 +/- 0.25, p < 0.001). Lumbar spine BMD correlated with radiologically assessed bone morbidity (r -0.37, p = 0.03) and stronger with the incidence of vertebral fractures (r -0.64, p < 0.001). Thus, osteopenia of the back is common in multiple myeloma and correlates with an increased incidence of fractures. DXA may identify subjects with increased risk of vertebral fractures for more intensive chemotherapeutic or anti-resorptive treatment.

Absorptiometry, Photon↗
PubMed1990

Image analysis of endodontic radiographs: digital subtraction and quantitative densitometry.

In this study computerized image analysis procedures were applied to endodontic radiographs. Kontron IBAS 2000 is a commercially available image analysis system with processing routines applicable to radiograph digitizing and transformations. The system was evaluated for: its ability to harmonize blackening and contrast in endodontic radiographs; its ability to compensate for angulation distortion of sequential exposures of individual teeth; its potential for application of digital subtraction methods; and its use in automated gray-level analyses of diseased and healthy bone areas in endodontic radiographs. The Kontron IBAS 2000 system proved suitable for all applications. However, the specificity of the subtraction procedure was limited by some inherent problems in the harmonization of blackening and in the subtraction process itself. On the other hand, automated gray level measurements proved to be a robust method for unbiased and quantitative assessment of healing of apical periodontitis.

Absorptiometry, Photon↗
PubMedDate not supplied

Bone mineral densitometry with x-ray and radionuclide sources: a theoretical comparison.

Two methods of dual-photon absorptiometry (DPA) utilizing an x-ray tube instead of a radionuclide source have recently been introduced. In one method kVp switching is employed and two transmitted intensities at each pixel are determined. In the other method, K-edge filtration combined with a single kVp spectrum is used, but photons in two energy windows are counted. We present a theoretical analysis of the two methods, focusing on a figure of merit which is essentially the exposure efficiency (the precision for a given entrance exposure) and tube loading. We also compare their exposure efficiencies to theoretical limits that no DPA system can exceed. Our study indicates that the K-edge-filtered method is more exposure efficient by about a factor of 2. The switched-kVp method requires less heat units per scan by about a factor of 3. A hybrid K-edge switched-kVp method is suggested which achieves the same exposure efficiency as the K-edge-filtered method at lesser tube loading. Our theoretical model is based on published x-ray spectra and attenuation coefficients and is in good agreement with other simulation work. It is of interest that a point source of Gd-153 would be even more exposure efficient, achieving about 90% of the theoretical limit. However, in practice, the Gd source is of finite size and limited strength, and consequently the radionuclide method cannot achieve as good a precision as either x-ray method in similar scan times.

Bone Density↗
PubMed1998

Assessment of bone in Ehlers Danlos syndrome by ultrasound and densitometry.

OBJECTIVE: Ehlers Danlos syndrome (EDS) is an inherited disorder of connective tissue characterised by hyperextensible skin, joint laxity, and easy bruising. There are phenotypic similarities with osteogenesis imperfecta, but in EDS a tendency to fracture or altered bone mass has not previously been considered to be a cardinal feature. METHOD: This case-control design study investigates whether 23 patients with EDS had differences in fracture rates, bone mass, and calcaneal ultrasound parameters compared with age and sex matched controls. RESULTS: 23 cases of EDS (mean (SD) age 38.5 (15.5)) were compared with 23 controls (mean age 37.8 (14.5)). A significant reduction in bone density measured by dual energy x ray absorptiometry was found at the neck of femur by 0.9 SD, p = 0.05, and lumbar spine by 0.74 SD, p = 0.02. At the calcaneum, broad band ultrasound attenuation and speed of sound were significantly reduced compared with controls by 0.95 SD (p = 0.004) and 0.49 SD (p = 0.004) for broad band ultrasound attenuation and speed of sound respectively. Broad band ultrasound attenuation and speed of sound remained significantly reduced after adjusting for bone mineral density (BMD). After adjusting for functional status (HAQ), age and sex, hypermobility was inversely correlated with broad band ultrasound attenuation and SOS, but not BMD at hip or spine. Previous fracture was 10 times more common in EDS (p < 0.001), with 86.9% of patients reporting a total of 47 low impact fractures, compared with 8.7% of controls. CONCLUSION: This study has identified a tendency of EDS patients to fracture, have low bone mass and abnormal bone structure. The aetiology is likely to be multifactorial, with an inherited structural element, accentuated by immobility or reduced exercise. This is one of the first clinical studies to suggest ultrasound can detect structural differences in bone, independent of dual energy x ray absorptiometry.

Absorptiometry, Photon↗
PubMed2001

Value of clinical factors in selecting postmenopausal women with rheumatoid arthritis for bone densitometry.

OBJECTIVE: Criteria to decide which patients with rheumatoid arthritis (RA) should be examined by dual energy x ray absorptiometry (DXA) are currently not available. The rheumatologists from Amsterdam have proposed preliminary criteria based on clinical risk factors (age, disease activity, and functional status). These criteria are preliminary and not widely accepted but might be helpful in practice. The value of the proposal in a group of Spanish postmenopausal women with RA is analysed. METHODS: DXA (lumbar spine and femoral neck) was performed in 128 patients recruited from a clinical setting, and the proposed criteria were applied. T and Z scores were established for a Spanish reference population. RESULTS: The mean (SD) age of the patients was 61.3 (10.7) and mean duration of the postmenopausal period 14.5 (10.1) years. Mean duration of RA was 13.7 (7.7) years. Mean C reactive protein was 22 (21) mg/l; mean erythrocyte sedimentation rate 26 (18) mm/1st h; and mean Health Assessment Questionnaire score 1.25 (0.79). Ninety (70%) patients fulfilled the proposed criteria. Their sensitivity for the diagnosis of osteoporosis (T score < or =-2.5 SD) was 86% and their specificity, 43%. Positive predictive value was 54% and negative predictive value, 79%. CONCLUSIONS: The proposed criteria seem a good screening method for the selection of those patients with RA whose bone mineral density should be assessed as the sensitivity and negative predictive value are acceptable.

Absorptiometry, Photon↗
PubMed2003

Hand bone densitometry in rheumatoid arthritis, a five year longitudinal study: an outcome measure and a prognostic marker.

OBJECTIVE: To investigate whether hand bone mineral content (BMC) measurement is an outcome measure for RA and whether the early changes in hand BMC predict functional disability. METHODS: Tender and swollen joints in hands and body, HAQ score, Larsen score on hand radiographs, serum CRP, and hand BMC measurement by DXA were studied every six months for five years in 40 patients with early RA. At the final visit, patients completed the SF-36 and Duruoz hand function questionnaires. RESULTS: All patients completed two years and 29 completed five years' follow up. Hand BMC worsened over the first three years (percentage loss from baseline: mean (SD) -5.5 (7.2), -7.5 (8.4), -9.8 (9.4)) and stabilised over last two years (-9.9 (8.8), -10 (7.8)). Baseline disease activity and function correlated with hand BMC loss at five years (swollen joints in hands: r=-0.38, p=0.043; swollen joints in body: r=-0.47, p=0.01; HAQ: r=-0.52, p=0.004). Percentage change in hand BMC over five years correlated with SF-36 physical function (r=0.61, p<0.01), hand function (r=-0.64, p<0.01), HAQ score (r=-0.63, p<0.01) at five years. Relative risk of bad hand functional outcome at five years was significantly higher for patients with hand BMC loss of >/=1.17 g (smallest detectable difference) than for patients with less bone loss within the first six months (OR=6.9, 95% CI 1.3 to 34.5, p<0.02). CONCLUSION: Early loss of hand BMC in patients with RA is a composite marker of disease activity and functional status and can predict poor functional outcome.

Absorptiometry, Photon↗