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PubMed1991

The effect of positioning on dual energy X-ray bone densitometry of the proximal femur.

The influence of subject repositioning on the precision of bone mineral densitometry of the proximal femur using dual energy X-ray absorptiometry was estimated by determining the variation in the bone mineral density (BMD) of subjects scanned with their foot and leg position varying from that routinely used in clinical scanning. The mean variations in BMD of the femoral neck, Ward's triangle and trochanter were 2.7, 4.1 and 1.7%, respectively, in eight subjects scanned with the foot internally rotated by 0, 13 and 27 degrees. The mean variations in BMD in four subjects scanned with the leg in the customary position and abducted +/- 6 degrees from the conventionally used scanning position were 3.6, 2.8 and 1.6% for the same respective regions of interest. For diagnostic applications, the orientation of the leg and foot during scanning is relatively unimportant since the variations in BMD introduced by the different foot and leg orientations likely to be encountered in routine clinical scanning are small compared to the intrapopulation variation in BMD. However, for monitoring changes in BMD longitudinally, careful repositioning of the foot and leg will be necessary to achieve precision in vivo of less than 1%.

Absorptiometry, Photon↗
PubMed1981

Receptor autoradiography with tritium-sensitive film: potential for computerized densitometry.

Benzodiazepine receptors mounted tissue sections of brain were localized by autoradiography using a tritium-sensitive sheet film (3H-Ultrofilm, LKB). The use of the film had many advantages compared to a previous technique utilizing emulsion-coated coverslips. A major advantage is the adaptability of the film to microdensitometric techniques for measurement of receptors. The densitometry can be carried out by computerized, color-coded image analysis.

Animals↗
PubMed1989

The use of CT densitometry to predict lung toxicity in bone marrow transplant patients.

Total body irradiation (TBI) is considered an integral part of the preparation of patients with hematological malignancies for marrow transplantation. One of the major causes of death following bone marrow transplantation is interstitial pneumonia. Its pathogenesis is complex but radiation may play a major role in its development. Computed tomography (CT) has been used in animal and human studies as a sensitive non-invasive method for detecting changes in the lung following radiotherapy. In the present study CT scans are studied before and up to 1 year after TBI. Average lung densities measured before TBI showed large variations among the individual patients. On follow-up scans, lung density decreases were measured for patients who did not develop lung complications. Significant lung density increases were measured in patients who subsequently had lung complications. These lung density increases were observed prior to the onset of respiratory complications and could be correlated with the clinical course of the patients, suggesting the possibility for the usage of CT lung densitometry to predict lung complications before the onset of clinical symptoms.

Adolescent↗
PubMed1989

The use of CT densitometry in the assessment of radiation-induced damage to the rat lung: a comparison with other endpoints.

Changes in rat lung following irradiation have been assessed on the basis of survival, histopathology, function (breathing rate assay), and density changes measured by computed tomography (CT) scanning. CT densitometry is a non-invasive procedure which may be used without modification to assess lung damage in experimental animals and in man. An increase in the breathing rate is seen following irradiation of the thorax, the time of onset and severity of which are dose dependent and correlate with histopathological changes occurring at the same time. Lung density changes occurring after irradiation are more complex. For the lowest dose used (10.75 Gy) no density increase was observed and in fact density decreased with time after irradiation to a slightly greater extent than in non-irradiated controls. A post-irradiation increase in lung density was seen for rats given 13.0 Gy, but values fluctuated with maxima at 50 and 225 days after irradiation. Higher radiation doses (14.5, 16.0 Gy) were followed by a transient decrease in density before a dose-related density increase was observed. Density averaged over the whole lung proved to be a sub-optimal index of radiation-induced lung damage because of the focal nature of radiation-induced lung lesions and because of the apparently anomalous changes in post-irradiation damage which are observed. Further studies are being made to determine if regional density values will provide a more sensitive index.

Animals↗
PubMed2006

Comparison of two hydroxyapatite-coated femoral stems: clinical, functional, and bone densitometry evaluation of patients randomized to a regular or modified hydroxyapatite-coated stem aimed at proximal fixation.

Clinical function, bone mineral density (BMD), and radiographs of 80 randomly allocated, hydroxyapatite-coated femoral stems of two differing lengths were studied for 2 years. The short stem was optimized for proximal fixation. The predictive value of bone densitometry was also studied. After 2 years, significantly more bone apposition and a higher BMD percentage were observed in Gruen zone 7 of the short stem. We conclude that stem design can be enhanced to achieve more proximal fixation. However, we found a higher incidence of pain with the short stem, indicating a trade-off between increased proximal fixation and diminished overall mechanical stability. No strong correlations between clinical function and radiographic evaluation of remodeling were found with BMD, suggesting that dual-energy x-ray absorptiometry has no predictive value for short-term clinical outcome.

Absorptiometry, Photon↗
PubMed2005

Bone densitometry and bone biopsy.

Bone densitometry is one of the most frequently used investigations in the assessment and management of patients suspected to have osteoporosis. The current method of choice for measuring BMD is dual-energy X-ray absorptiometry, because of its high precision and low radiation dose. The initiation and choice of treatment in patients with osteoporosis is critically dependent on the availability of BMD measurements and BMD can also be used to monitor the response to therapy. Transiliac bone biopsy is indicated for selected patients with metabolic bone disease where less invasive investigations have yielded inconclusive results. Under these circumstances it is an invaluable investigation that can be used to differentiate infiltrative disorders from primary abnormalities of osteoblast or osteoclast function.

Absorptiometry, Photon↗
PubMed1994

A prospective study of heparin-induced osteoporosis in pregnancy using bone densitometry.

OBJECTIVE: Our purpose was to evaluate the subclinical occurrence of heparin-induced osteoporosis in pregnancy, by means of bone densitometry. STUDY DESIGN: A prospective, consecutive cohort of 14 pregnant women requiring heparin therapy and 14 pregnant controls matched for age, race, and smoking status was identified by 20 weeks' gestation at a university medical center. Proximal femur bone density measurements were taken at baseline, immediately post partum, and 6 months post partum in the cases and controls. Vertebral measurements were also obtained on both groups immediately post partum and 6 months post partum. Bone density as a function of heparin dosing and duration was examined. Nonparametric statistical tests were used for all comparisons. RESULTS: Five of 14 cases (36%) had a > or = 10% decrease from the baseline proximal femur measurements to immediate postpartum values versus none of the 14 matched controls (p = 0.04). Mean proximal femur bone density measurements also decreased in the cases (p = 0.01); this difference continued to be statistically significant 6 months post partum (p = 0.03). No dose-response relationship could be demonstrated. CONCLUSION: Heparin adversely affected bone density in about one third of exposed patients.

Absorptiometry, Photon↗
PubMed2002

Cross-sectional structural parameters from densitometry.

Bone densitometry has previously been used to obtain cross-sectional properties of bone from a single X-ray projection across the bone width. Using three unique projections, we have extended the method to obtain the principal area moments of inertia and orientations of the principal axes at each scan cross-section along the length of the scan. Various aluminum phantoms were used to examine scanner characteristics to develop the highest accuracy possible for in vitro non-invasive analysis of cross-sectional properties. Factors considered included X-ray photon energy, initial scan orientation, the angle spanned by the three scans (included angle), and I(min)/I(max) ratios. Principal moments of inertia were accurate to within +/-3.1% and principal angles were within +/-1 degrees of the expected value for phantoms scanned with included angles of 60 degrees and 90 degrees at the higher X-ray photon energy (140 kVp). Low standard deviations in the error (0.68-1.84%) also indicate high precision of calculated measurements with these included angles. Accuracy and precision decreased slightly when the included angle was reduced to 30 degrees. The method was then successfully applied to a pair of excised cadaveric tibiae. The accuracy and insensitivity of the algorithms to cross-sectional shape and changing isotropy (I(min)/I(max)) values when various included angles are used make this technique viable for future in vivo studies.

Absorptiometry, Photon↗
PubMed2000

[Usefulness of bone densitometry in the evaluation of primary hyperparathyroidism].

BACKGROUND: In recent years, the clinical profile of primary hyperparathyroidism (PH) is predominantly characterized by mild or asymptomatic forms. In this context, the effects of the PH on bone metabolism reach a growing importance in the adoption of therapeutic decisions. PATIENTS AND METHODS: 116 patients with PH were studied, 95 women (25 premenopausal, 70 postmenopausal) and 21 males. In all cases parathyroidectomy criteria were evaluated. Bone mineral density (BMD) was determined in 71 patients in lumbar spine (LS) and femoral neck by dual-X-Ray absorptiometry (DXA) and the influence of this measurement in the decision of surgical treatment was analyzed. RESULTS: The patients with PH showed a significant reduction of BMD at all sites (p < 0.001) and 71.8% met osteoporosis densitometric criteria. The most frequent parathyroidectomy criteria was the presence of specific clinical manifestations (51.7%) followed by decrease of the BMD in LS (49.3%). The probability of meeting criteria for surgical treatment was significantly higher in patients in which BMD was measured (odds ratio: 3.09 [1.03-9.22]; p = 0.036). CONCLUSIONS: In its current presentation, PH presents a significant decrease of bone mass. The systematic performance of bone densitometry has a decisive influence in its appropriate management.

Absorptiometry, Photon↗
PubMed1994

Precise accurate mineral measurements of excised sheep bones using X-ray densitometry.

An Hologic QDR 1000-W dual energy X-ray absorptiometer (DXA) was used to make a densitometric evaluation and to optimize ex vivo scanning and analysis conditions for excised sheep bones. Articulated lumbar spines and femora, removed at autopsy from eight 1-2-year-old cross-bred merino ewes, were studied using standard lumbar spine and hip protocols (version 4.20). Spine data were analysed with the ultra-high resolution (UHR) protocol (version 4.25). Preliminary hip measurements also were made using the lumbar spine (version 4.20) and scoliosis protocols (version 4.25). Bone mineral density (BMD) precision for the total hip (n = 5) was 0.4% using version 4.20, and 0.8% using the scoliosis protocol (version 4.25) but was 1.2-3.4% for femoral sub-regions. Precision for the lumbar spine was 0.8% (version 4.20). There was considerable variation in BMD and bone mineral content (BMC) at the same site between animals. Right and left hip BMD were highly correlated (r = 0.98, P < 0.00001). Measurement variables evaluated to determine the optimal conditions included: Hologic scanning protocols, depth of water immersion of bone and dimensions of the region of interest. Accuracy was determined by ashing. Use of the scoliosis protocol (version 4.25) gave the best results for proximal femur measurement. Measured BMC decreased by 4.4% as the water depth increased from 0 to 22.5 cm. At 5 cm water, BMC accuracy was 99% for the total hip, and BMD precision values (n = 3) were 0.3% (total hip) and 0.4% (femoral neck, trochanteric region and femoral shaft). The much-improved precision was attributed to use of a positioning device and to optimizing of the depth of water immersion. Rib segments (length 2.5 cm) were measured using the ultra-high resolution protocol (version 4.25). BMC accuracy determined using 6 ribs was best (100 +/- 2%) at 5 cm water. BMD precision (n = 5) was best (0.3%) at 0 cm water depth and was 0.5% at 4.5 cm water depth. Rib sample BMC (n = 15, 4.5 cm water depth) and ash weight were highly correlated (r = 0.985, P < 0.001). It is concluded that highly precise, accurate densitometry can be performed on excised small and large sheep bones. This technique will support studies evaluating the sheep as an animal model of human osteoporosis.

Absorptiometry, Photon↗
PubMed1998

Bone mineralization status measured by dual energy radiographic densitometry in preterm infants fed commercial formulas.

We have studied the effect of two preterm commercial infant formulas with different calcium and phosphorus contents on the mineral balance and bone mineralization of 30 preterm infants at 1 month of age. Bone mineralization was measured by dual energy X-ray densitometry. The formula supplying a higher content of calcium and phosphorus promoted higher mineral retention (P<0.01) as well as higher bone mineral content (1.556 vs. 1.073 g, P<0.01) and bone mineral density (0.458 vs. 0.424 g/cm2, P<0.05), approaching values of the control group, which comprised a cohort of 15 preterm newborns whose gestational age was 4 weeks older than the subjects selected to be fed with the formulas. The intake of calcium correlated with retention (r=0.69); the phosphorus intake also correlated with phosphorus retention (r=0.95). Intakes of calcium and phosphorus correlated with the bone mineral content (r=0.65) and with bone mineral density (r=0.49). We conclude that formulas for preterm infants should not have a calcium content lower than 120 mg/100 kcal and should have a calcium/phosphorus ratio of about 2 to promote adequate bone mineralization.

Absorptiometry, Photon↗
PubMed2000

The Tromsø study: determinants of precision in bone densitometry.

Studies of precision determinants in bone densitometry are scarce. A total of 111 subjects recruited from the population-based multipurpose Tromsø Study (Norway), 27-75 years of age, had repeated forearm bone single X-ray absorptiometry (SXA) measurements. Measurement conditions were systematically varied in series up to eight scans. Median coefficients of variation (CV) for two scans performed 1 week apart, by two different operators were 0.79% and 0.98% at distal and ultradistal sites, respectively. The CV distribution was skewed: 5% of the subjects had individual CVs above 2.2% (distal) and 3.4% (ultradistal). Age (P = 0.0097) and repositioning were important determinants of precision. The SXA bone mineral density (BMD)-measurement method is sufficiently precise to establish BMD level. The minimal individual percentage BMD change that can be detected with 95% certainty was 2% and 3% at distal and ultradistal sites, respectively. Detection of BMD changes less than this should rely on multiple repeat measurements at each point in time.

Absorptiometry, Photon↗
PubMed1989

Stress shielding effect of rigid internal fixation plates on mandibular bone grafts. A photon absorption densitometry and quantitative computerized tomographic evaluation.

The use of rigid internal fixation reconstruction plates in combination with bone grafts provides many advantages in mandibular reconstruction. These advantages include ease of adaptability at the time of surgery as well as immediate postoperative function for the patient. Disadvantages may include a "stress shielding" or disuse osteoporosis effect on the underlying bone graft as a result of the rigidity of the reconstruction plate. This study evaluated the stress shielding effects on bone grafts in primate mandibles. Bilateral bone grafts stabilized with rigid fixation plates were performed in 4 Macaca fascicularis monkeys. Three months after the bone grafting procedure one plate was removed from each monkey. The monkeys were then killed 1, 4, 6 and 8 months after plate removal. Photon absorption densitometry and computerized tomography were used to evaluate stress shielding. The results of this study indicate that the stress shielding effect occurs if the plate is not removed from the area of bone grafting postoperatively.

Absorptiometry, Photon↗
PubMed2001

Prospective X-ray densitometry and ultrasonography study of the hand bones of patients with rheumatoid arthritis of recent onset.

OBJECTIVE: Bone demineralization observed in early rheumatoid arthritis is not easily measured. To measure bone loss and to discriminate between rheumatoid arthritis and other rheumatic diseases, we used two methods: dual-energy X-ray absorptiometry and ultrasonography. METHODS: From a population-based recruitment, 32 patients with early peripheral polyarthritis (median disease duration: 4 months) were studied. Clinical, laboratory, functional, hand-bone assessments were made at the entry an at months 6 and 12. Bone X-ray densitometry measurements were made on 16 areas of the hand. Speed of sound was measured across the proximal phalanges of the four fingers. X-rays of both hands were scored according to the modified Sharp's score. At 12 months, patients were classified as rheumatoid arthritis (N = 15; 9 F) or as other rheumatic diseases. RESULTS: We found: 1) significantly decreased bone mineral density (BMD) of the whole hand, in the rheumatoid arthritis group versus the other rheumatic diseases group, at 6 and 12 months (P < 0.05); 2) no significant decrease of bone mineral density (BMD) in other areas in the rheumatoid arthritis group; 3) no significant change of ultrasounds in either group; and 4) no significant correlation between the decrease of BMD in the rheumatoid arthritis group and clinical, biological or radiologic parameters, except for IFNgamma, whose production in whole blood cell culture was lower at entry in the rheumatoid arthritis group. CONCLUSION: DEXA bone assessment in rheumatoid arthritis was able t detect bone loss in the whole hand at 6 months.

Absorptiometry, Photon↗
PubMed2003

Is ultrasound of bone relevant for corticosteroid-treated patients? A comparative study with bone densitometry measured by DEXA.

Corticosteroid treatment diminishes bone mass and alters bone quality. The objective was to evaluate bone in corticosteroid-treated patients and controls and in fractured and non-fractured patients treated with corticosteroids using both X-ray densitometry (DEXA) and ultrasound. We evaluated 34 women aged 58 +/- 14 years (X +/- SD), who had been on long-term low dose prednisone therapy for at least 6 months, and who had never received specific treatment for osteoporosis. Bone mineral density of total skeleton (TS), lumbar spine (LS), femoral neck (FN), and vertebral morphometry (MXA) were measured by DEXA. Speed of sound (SOS), broadband ultrasound attenuation (BUA) and stiffness were measured using an Achilles Plus system. Forty-two healthy women served as controls. Both densitometric and ultrasound parameters in the patients were significantly diminished compared with controls: TS: P < 0.002, LS: P < 0.025, FS: P < 0.005, Stiffness: P < 0.001, BUA: P < 0.002 and SOS: P < 0.002. The percentage of patients with a Z score below -2 was higher in Stiffness and BUA: 38% and 47%, respectively, compared with a range of 16-24% in the other parameters (P < 0.05 BUA vs. DEXA measurements). Eleven patients with previous bone fracture had values lower than the non-fractured patients, both according to DEXA and ultrasound measurements, but the difference was only significant for BUA (P < 0.02). BUA of the calcaneus was more effective in detecting the specific skeletal alterations and fracture risk of the group of patients receiving chronic corticosteroid treatment.

Absorptiometry, Photon↗
PubMed2002

Bone densitometry: applications and limitations.

Osteoporosis is clinically diagnosed in its advanced stages, usually following a fracture. Accurate, precise, and noninvasive skeletal assessment is now possible for early detection of osteoporosis at a preclinical stage. Currently, the gold standard in bone mass measurement and fracture prediction is dual energy X-ray absorptiometry (DEXA) of the hip and spine. Exponential increases in fracture risk have been observed with small decreases in bone mineral density. Bone mineral density (BMD) should be considered in conjunction with independent clinical risk factors for fracture, including: low body weight, history of postmenopausal fracture, family history of fracture, and poor neuromuscular function. The World Health Organization (WHO) diagnostic criteria for osteoporosis and osteopenia are appropriate for postmenopausal Caucasian women and are applicable to DEXA assessments at the hip, spine, or forearm. This review explores the relationship between BMD and fracture risk, the principles of bone densitometry interpretation, and the applications as well as the limitations of DEXA technology, and presents cases illustrating common errors seen in the interpretation of DEXA studies.

Absorptiometry, Photon↗
PubMed2001

Inaccuracies inherent in dual-energy X-ray absorptiometry in vivo bone mineral densitometry may flaw osteopenic/osteoporotic interpretations and mislead assessment of antiresorptive therapy effectiveness.

New, anatomically realistic simulation studies based on a cadaveric lumbar vertebra and a broad range of soft tissue anthropometric representations have quantitatively delineated inaccuracies inherent in dual-energy X-ray absorptiometry (DXA) in vivo bone mineral density (BMD) methodology. It is found that systematic inaccuracies in DXA BMD measurements may readily exceed +/-20% at typical in vivo lumbar vertebral sites, especially for osteopenic/osteoporotic, postmenopausal, and elderly patients. These findings are quantitatively compared with extensive clinical evidence of strong, positive correlations between soft tissue anthropometrics and DXA in vivo BMD upon which prior significant bone biology interpretations and implications have been based. The agreement is found to be both qualitatively and quantitatively excellent. Moreover, recent extensive multicenter clinical studies have also exposed new facets of strong linkages between body mass/percent body fat/body mass index (BMI) and DXA-measured BMD that are particularly relevant to osteopenia/osteoporosis and remedial effectiveness of antiresorptive drug therapy. These seemingly disparate and unrelated diagnostic and prognostic aspects of clinically observed associations between soft tissue anthropometrics and measured vertebral BMD are, in this study, self-consistently shown to share the common origin of being manifestations of systematic inherent inaccuracies in DXA in vivo BMD methodology, without the need to invoke any underlying biologically causal mechanism(s). These inaccuracies arise principally from absorptiometric disparities between the intra- and extraosseous soft tissues within the DXA scan region of interest. The present evaluative comparisons are based exclusively on an incisive and diverse body of clinical data that appears difficult to dismiss or discount. Previous invocations of biologically causal mechanisms responsible for this broad range of observations linking body mass, percent body fat, and/or BMI to measured BMD now appear questionable. This doubtful status has also been extended in the present work to previously reported relationships between antiresorptive therapies and observed changes in DXA-derived BMD. These findings strongly indicate that critical and insightful reassessments of diagnostic/prognostic imputations underpinned by DXA in vivo BMD measurements are warranted. It is suggested that a good deal of what is known of bone fragility, bone densitometry, antiresorptive drug efficacy, and/or other therapeutic regimens, if based on patient-specific in vivo DXA methodology, may prove to be equivocal and tenuous.

Absorptiometry, Photon↗