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At least 1,117 records · Page 62Linked to original sources
PubMed1996

Quantitative assessment of radiation-induced lung changes by computerized optical densitometry of routine chest x-rays.

PURPOSE: To develop a quantitative assay of radiological lung changes after postmastectomy radiotherapy applicable for analysis of routine chest x-rays. METHODS AND MATERIALS: The assay relies on measurement of the optical density of chest x-rays by means of a standard personal computer-controlled film densitometer used for scanning dosimetry films. Density profiles were recorded at 1 mm steps along two reference lines in each lung. The crossing between the clavicula and the first rib in the x-ray projection was used as an easily identifiable anatomical landmark and was used to establish two parallel cranio-caudal reference lines separated by 20 mm. The starting point for recording optical densities was 5 mm below a line perpendicular to the reference lines and tangent to the top of the lung. Data were stored in a computer file for subsequent processing. The optical film densities in the apex of the lungs were converted into equivalent absorber thickness (EAT). To minimize the dependency on technical factors, the unirradiated lung was used as a control. Lung density changes were quantified by the relative change in EAT (REAT), which was evaluated as the difference between the summed EATs along the reference lines in the two lungs, corrected for any pretreatment difference in lung density, and taken as a percentage of the pretreatment EAT value of the lung. RESULTS: Four different test were carried out to investigate the reproducibility and validity of the proposed assay. (a) An anthropomorphic phantom was used to test the relationship between REAT and the layer of plastic absorber placed in front of one lung. A linear relationship was found with a correlation coefficient of 0.9993. (b) A series of 10 repeat measurements of the same arbitrarily chosen x-ray showed a mean REAT value of 9.8%, with a standard deviation of 0.21%. (c) Forty-three chest x-rays exposed on the same day were available from the clinical series. These were treated as double determinations of REAT values, and the standard deviation was estimated at 1.35%. (d) REAT values estimated with this assay were significantly correlated with the scores of two experienced specialists, an oncologist and a radiologist (Spearman's rank correlation coefficient being 0.605, p < 10(-8)). CONCLUSION: This assay quantifies radiation-induced lung injury from routine chest x-rays. Thus, it is possible to take advantage of the very large retrospective materials available in most oncological institutions. The assay has been validated in a phantom experiment and shown to be reproducible. Furthermore, it is technically easy to perform.

Female↗
PubMed1995

Recent developments in DXA. Quality of new DXA/MXA-devices for densitometry and morphometry.

The introduction of new devices demands the assessment of their capabilities in established terms. The accuracy, reproducibility and spatial resolution of in vitro (phantom) osteodensitometric and morphometric measurements of QDR 2000 Plus and EXPERT are presented. Design details of these DXA/MXA-devices are listed and discussed in combination with the data acquired in the test measurements and calculations. The image quality will improve with further software developments. The long-term reproducibility and in vivo reliability remains to be evaluated.

Absorptiometry, Photon↗
PubMed1992

Evaluation of the Lawrence Livermore National Laboratory (LLNL) torso phantom by bone densitometry and x-ray.

The recent Workshop on Standard Phantoms recommended that the LLNL torso phantom be adopted as a calibration standard for the quantitation of in vivo radioactivity. This phantom was designed for the calibration of systems for the detection of x-rays of less than 20 keV. The anthropomorphic characteristics and tissue substitute composition of the phantom were assessed with techniques using photons of higher energy. Dual photon absorptometry at 42 and 100 keV showed that the phantom was representative of in vivo tissue composition. Chest radiography showed that the phantom was representative of a human even though the stomach, GI tract and the scapulae were not present and air gaps were observed at organ boundaries.

Absorptiometry, Photon↗
PubMed1995

Predicting vertebral deformity using bone densitometry at various skeletal sites and calcaneus ultrasound.

We investigated the usefulness of bone density measurements from multiple skeletal sites and calcaneus ultrasound for evaluating the probability of vertebral deformation. Bone mineral density (BMD) was measured at the second metacarpal and middle phalanges using radiographic absorptiometry of hand radiographs, and at the lumbar spine using dual-energy x-ray absorptiometry. Distal radius and proximal radius were measured using single-energy x-ray absorptiometry (SXA), expressed as bone mineral content (BMC, grams per centimeter), and as BMD (grams per square centimeter). The calcaneus was measured using both SXA (BMD) and broadband ultrasound attenuation (BUA). Among the women in this study (mean age 74, SD = 5), 84 women developed new vertebral deformations (57 cases with one and 27 cases with two or more deformations), which were identified on serial radiographs during an average of 9 years prior to the measurements of bone density. Logistic regression analysis was used to calculate odds ratios for risk of deformation corresponding to a 1-SD difference in density or ultrasound, adjusted for age. All bone measurements were significantly associated with vertebral deformation, with odds ratios (95% confidence intervals) ranging from 1.40 (1.10, 1.78) for proximal radius BMD to 1.88 (1.45, 2.44) for calcaneus BMD measurements. Measurements of calcaneal BUA, calcaneal BMD, and hand BMD generally remained significant when included simultaneously with another measurement in the same model, suggesting that spine or radius BMD may not provide much additional information about risk of deformation. It appears that all of the measurements of bone density and ultrasound provide useful information regarding the probability of deformation. These findings await confirmation in a prospective study.

Absorptiometry, Photon↗
PubMedDate not supplied

Bone mineral densitometry in dialyzed patients: quantitative computed tomography versus dual photon absorptiometry.

Reduced bone mineral density (BMD) increases risk of fractures, thus making it necessary to monitor patients suffering from chronic renal failure and consecutive disturbance of bone metabolism. In order to evaluate the reliability of available methods, bone mineral density of the lumbar spine assessed with single energy computed tomography (QCT) was compared with bone mineral density of the lumbar spine, femoral neck, Ward's triangle and trochanteric region measured by dual energy photon absorptiometry (DPA) in 45 hemodialyzed patients with a mean hemodialysis duration of 35 +/- 26 months (SD). Depending on the measurement site and method 4-34% of dialyzed patients suffered from reduced BMD (z-score < -2). The highest correlation (r = 0.61, p < 0.01) was found between QCT of the spine, trabecular bone, and DPA of Ward's triangle. One year after baseline measurement bone mineral density was reassessed after randomization to either QCT or DPA in 14 and 18 patients, respectively. Whereas lumbar spine and femoral neck did not change, mean BMD showed a decrease at the measurement sites of Ward's triangle (DPA), trochanteric region (DPA) and trabecular bone of the spine (QCT), which, however, was statistically not significant. Cortical BMD of the spine assessed with QCT showed an increase. Although there is some reduction in bone density at most sites in hemodialyzed patients, no significant bone loss could be demonstrated over the course of 1 year.

Absorptiometry, Photon↗
PubMed1995

Comparative x-ray densitometry of bones from ovariectomized rats.

Comparative analysis of dual energy x-ray absorptiometry (DXA) and quantitative computed tomography (QCT) with phantoms and rat bones showed that both are necessary to adequately quantitate ovariectomy induced bone changes, in vivo. Precision and accuracy analysis of a Hologic QDR 1000/W and a Stratec 960 QCT showed that the latter is a highly precise, modestly accurate device that is more suited to the analysis of small bones. Specifically, smaller error was achieved by threshold optimization for the QCT in the analysis of phantoms 1.04-9.6 mm in diameter, with precision comparable to or better than DXA. Additionally, the QCT measured significant differences between groups in proximal tibiae when DXA could not; and measured a larger difference between sham and ovariectomized controls which was suitable for analysis of the dose dependent effects of a pharmacological test compound, raloxifene. This may reflect the ability of the QCT to measure volumetric mineral density (VMD, mg/cc), compared to two dimensional analyses by DXA. However, QCT was not able to analyze vertebrae in vivo, a site of considerable clinical interest. Therefore, DXA is useful to analyze the axial skeleton in vivo, while the appendicular skeleton is better analyzed in vivo by QCT. By both techniques, a similar dose response was observed for raloxifene, with ED50 = 0.3 mg/kg for both axial and appendicular skeleton. Comparative analysis of rat L1-4 by the Hologic QDR 1000/W and Lunar DPXL showed 12-14% higher BMD and BMC values for the Hologic, which is the opposite relationship between these instruments to that observed clinically for this site.

Absorptiometry, Photon↗
PubMed2006

Standards and measurements for assessing bone health-workshop report co-sponsored by the International Society for Clinical Densitometry (ISCD) and the National Institute of Standards and Technology (NIST).

This article reports and discusses the results of the recent ISCD-NIST Workshop on Standards and Measurements for Assessing Bone Health. The purpose of the workshop was to assess the status of efforts to standardize and compare results from dual-energy X-ray absorptiometry (DXA) scans, and then to identify and prioritize ongoing measurement and standards needs.

Absorptiometry, Photon↗
PubMed2005

Bone densitometry in pediatric populations: discrepancies in the diagnosis of osteoporosis by DXA and CT.

OBJECTIVES: To test the hypothesis that because of errors associated with growth and development, osteoporosis is frequently overdiagnosed in children when using dual-energy x-ray absorptiometry (DXA). This study compared bone density values obtained by DXA with those from computed tomography (CT), which is not influenced by body or skeletal size. STUDY DESIGN: Vertebral bone density was measured by using both DXA and CT in 400 children (100 each, healthy and sick boys and girls). Regression analysis was used to compare DXA and CT Z scores, and the agreement between DXA and CT classifications of Z scores below -2.0 was examined. RESULTS: DXA and CT Z scores were moderately related (r2 = 0.55 after accounting for age and anthropometric measures). DXA Z scores predicted CT Z scores below -2.0 with reasonable sensitivity (72%), specificity (85%), and negative predictive value (98%), but positive predictive value was low (24%). Many more subjects were classified as having bone density lower by DXA (76/400) than by CT (25/400), particularly subjects below the 5 th percentile of height and/or weight for age. CONCLUSIONS: The inability of DXA to account for the large variability in skeletal size and body composition in growing children greatly diminishes the accuracy of this projection technique for assessing bone acquisition and diagnosing osteoporosis in pediatric populations.

Absorptiometry, Photon↗
PubMed2003

Plasma low-density lipoprotein cholesterol and bone mass densitometry in postmenopausal women.

OBJECTIVE: The prevalence and the clinical and social importance of osteopenia and osteoporosis are increasing in western societies. To improve knowledge of the risk factors associated with these conditions, we assessed the relationship between bone mass density and plasma lipid profile in a cohort of postmenopausal women. METHODS: We studied 1303 postmenopausal women who attended a menopause outpatient clinic. All women underwent bone mineral density determination at the level of the lumbar spine. Plasma lipids and lipoproteins and bone metabolic markers were assessed on a blood sample obtained after a 12-hour fast. RESULTS: Statistically significant associations were found by univariate analysis between prevalence of osteopenia and age, time since menopause, body mass index, and low-density lipoprotein (LDL) cholesterol. Specifically, women with plasma LDL cholesterol levels of at least 160 mg/dL had a more than doubled probability of being osteopenic compared with women with lower LDL cholesterol (47.9% versus 21.2%, respectively). Time since menopause, body mass index, and LDL cholesterol were the only variables significantly associated with the prevalence of osteopenia, by multivariable analysis. CONCLUSION: Postmenopausal women with increased plasma LDL cholesterol levels had a greater probability of being classified as osteopenic than women with normal plasma LDL cholesterol levels. Our data, if confirmed, suggest that elevated levels of plasma LDL cholesterol should be regarded as an additional risk factor for reduced bone mineral density.

Aged↗
PubMed2005

Differences in stability and bone remodeling between a customized uncemented hydroxyapatite coated and a standard cemented femoral stem A randomized study with use of radiostereometry and bone densitometry.

The custom made Unique stem is designed to fit closely to the metaphyseal region of the femur in order to obtain maximum mechanical stability and optimal load transfer. Thirty-seven patients (38 hips) with non-inflammatory arthritis were randomized to the uncemented custom made Unique stem or the Elite Plus stem inserted with cement. The patients have been followed clinically as well as with radiostereometry (RSA) and Dual-energy X-ray Absorptiometry (DXA) for 2 years. After 2 years the RSA result showed minimal translation and rotation for the Unique stem while the Elite Plus rotated slightly (mean 1.05 degrees) into retroversion. Compared to previous studies the Elite Plus was as stable as the Charnley prosthesis. The DXA results showed a significantly higher proximal and total (10% for the Unique versus 5% for Elite) bone loss for the Unique stem compared to the Elite Plus. Thus the optimal proximal press-fit of the custom made stem did secure a stable fixation, but did not decrease the proximal bone loss.

Absorptiometry, Photon↗
PubMed1997

Interpretation of bone densitometry studies.

Dual-energy x-ray absorptiometry (DXA) is widely used for identifying patients with osteoporosis, making decisions about the commencement of preventive therapy, and following up response to treatment. It is important that radiologists and nuclear medicine physicians issuing clinical reports present clear interpretations that aid the primary care physician in making decisions affecting treatment. This review discusses the principles behind the interpretation of bone mineral density (BMD) studies. After a World Health Organization report published in 1994, osteoporosis is often diagnosed on the basis of the patient's T-score value (difference of BMD from young adult mean normalized to the population SD). T-scores are a measure of current fracture risk. There are problems relating to the use of T-scores in the elderly, and we argue that decisions about treatment are generally best made on the basis of the Z-score value (difference of BMD from age-matched mean normalized to the population SD) because this measures the patient's fracture risk relative to his or her peers. Recent studies confirm that the posteroanterior (PA) projection lumbar spine scan is still the optimum measurement site for monitoring response to treatment. A BMD change of 4.5% is required to register a statistically significant change.

Absorptiometry, Photon↗
PubMed2003

Importance of lean mass in the interpretation of total body densitometry in children and adolescents.

OBJECTIVE: Most studies that use total body dual energy x-ray absorptiometry (DEXA) in children rely on areal bone mineral density (BMD=bone mineral content [BMC]/bone area [BA]) and compare the output with age- and sex-specific normative data. Because this approach is prone to size-related misinterpretation, this study focuses on the interrelations among BMC, body size (height), and lean tissue mass (LTM). STUDY DESIGN: This cross-sectional study presents normative total body LTM data in relation to height and BMC for 459 healthy white subjects (249 female), 3 to 30 years of age. Guidelines for DEXA interpretation in children are provided and illustrated for patients with growth hormone deficiency (n=5) and anorexia nervosa (n=5). RESULTS: LTM/height tended to be greater in male than in girls. The BMC/LTM ratio was greater in female than in boys (P<.001), even after adjustment for age and height. Sex-specific reference curves were created for LTM/height, the BMC/LTM ratio, BA/height, and BMC/BA. CONCLUSIONS: We recommend that total body DEXA in children should be interpreted in 4 steps: (1) BMD or BMC/age, (2) height/age, (3) LTM/height, and (4) BMC/LTM ratio for height. This allows differentiation of the origin of a low BMD or BMC/age, for example, short stature and primary, secondary, and mixed bone defects.

Absorptiometry, Photon↗