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At least 1,333 records · Page 74Linked to original sources
PubMed2001

[The development of SPA bone densitometry for heel bone].

The design principles of a bone densitometer for heel bone based on SPA are introduced here, which include the principles of mechanical system and control system. The main technical index and advantages of the device have also been discussed in the paper.

Absorptiometry, Photon↗
PubMed2003

Densitometry identifies women in whom treatment will reduce fracture risk.

Despite lack of research on the effectiveness of osteoporosis screening to reduce fractures, there is sufficient evidence that bone density measurements accurately predict short-term fracture risk and that treating asymptomatic women with osteoporosis reduces fracture risk. According to this report, a reasonable recommendation is to screen all women older than 65 years and postmenopausal women younger than 65 years who have low weight (or body mass index) or who have never used hormone replacement therapy. The US Preventive Services Task Force noted that the optimal screening frequency has not been studied, but suggested a frequency of not more than every 2 years for older women or every 5 years for younger postmenopausal women. Also of note: other sources, notably the bisphosphonates package labeling, advise against monitoring therapy with repeated dual-energy x-ray absorptiometry or other methods.

Comment↗
PubMed2003

[Manufacture and evaluation of a spine phantom used in the cross-calibration of DXA bone densitometry].

OBJECTIVE: To design and manufacture a reliable spine phantom used in the cross calibration and quality control of dual X-ray absorptiometry (DXA). METHODS: A hydroxyapatite quality control phantom was designed and made through three steps: solid water, bone phantom material and integration, then evaluated the phantom on four different types of DXA machines made by LUNAR company. RESULTS: Among the four DXA densitometers, the Expert fan beam densitometer had the biggest accuracy errors of bone mineral density (BMD), bone mineral content(BMC) and area values while the other three one narrow fan beam (Prodigy) and two pencil beam densitometers-had small errors. Of the three indexes measured by all the machines, BMD error was the smallest (-15.4%-11.5%), with the Prodigy's BMD was most outstanding. BMD errors at the higher density ends were small, tend to be positive values while the errors at the lower ends were big, tend to be negative. In cross calibration, giving consideration to the differences between the both ends, it is better to use the regression equation to correct. The base line of precision error derived by scanning the phantom once a day for consecutive 25 days was better than that derived by scanning the phantom 25 times consecutively on the same day. As to precision error, the coefficient of variation (CV) of scanning-25 times-a day was the smallest (0.0043) while the CV of 12 adults measurements was the biggest (0.0078). CONCLUSIONS: This phantom can be used in the quality control and cross-calibration of different types of DXA machines.

Absorptiometry, Photon↗
PubMedDate not supplied

[Computed tomographic densitometry in the diagnosis of chronic obstructive lung diseases].

The capacities of spiral computed tomography (CT) synchronized with a patient's respiration in the diagnosis of chronic obstructive lung diseases (COLD) were studied. Normal lung parenchymal density was clarified in different parts. The densitometric changes typical of bronchial asthma (BA) and COLD were studied in relation to the severity of an obstructive process. The differential diagnostic criteria of BA and COLD, including those at the early stage of the disease, are proposed. The optimized procedure of spiral CT synchronized with the patient's respiration is presented.

Absorptiometry, Photon↗
PubMed1992

Osteoporosis and bone mineral densitometry.

Osteoporosis is a common cause of vertebral and hip fractures and although their occurrence depends on a variety of factors, bone mineral density (BMD) is the most important determinant. Methods of measuring BMD are therefore pertinent to identify individuals with reduced bone mass and at increased risk of fracture, and current techniques provide accurate and precise BMD measurements with low radiation dose. The methods most widely used are single photon absorptiometry; dual photon absorptiometry, which has been replaced by dual energy x-ray absorptiometry; and quantitative CT. Dual energy x-ray absorptiometry permits BMD measurement in the lumbar spine, femoral neck, forearm, and whole body. Bone strength is also related to trabecular width and arrangement. The newer techniques of broadband ultrasound attenuation and MR imaging (T2*) offer potential for investigating both trabecular bone mass and structure, as does high-resolution CT. These methods provide powerful tools for the study of the skeleton in health and disease and have established roles in appropriate clinical circumstances. Although BMD measurement can provide an estimate of fracture risk, there are limitations to fracture prediction in an individual subject, but efforts are being made to improve the discriminatory and predictive aspects of BMD.

Absorptiometry, Photon↗
PubMedDate not supplied

[Methodological basis and clinical applications of total-body densitometry].

With the advent of dual-energy x-ray absorptiometry (DXA) total body scans can be done in only 10-20 minutes rather than the 60-80 minutes required by dual-photon absorptiometry (DPA). The DXA approach replace the Gd153 radionuclide source of DPA and provides substantially greater output intensity. The higher radiation flux achievable provides several advantages over conventional DPA: this makes total body scans routinely accessible. The measures of the entire skeleton and its major subregions cut down the problems of representativeness and relocation. The short term precision (coefficient of variation) was 0.5% for total body-bone mineral density (BMD) and about 1% for regional-BMD. We studied 885 women; study cohort consisted of 161 healthy postmenopausal women, 357 healthy postmenopausal women and 367 osteoporotic women with one or more vertebral crushes. The results indicate that bone mass begin decreasing during the last period of the premenopausal phase; the advent of menopause brings about a dramatic reduction of both total body and single area BMD: this phenomenon is particularly marked in subjects with osteoporosis. The single most important factor in determining BMD changes, is years since menopause. In order to assess the ability of DXA total body to distinguish women with postmenopausal osteoporosis of variable radiological degress from healthy postmenopausal women, we studied 330 postmenopausal females aged 42-85 years. There were 63 healthy women who were considered controls (Group 1).(ABSTRACT TRUNCATED AT 250 WORDS)

Absorptiometry, Photon↗
PubMedDate not supplied

[Radiologic densitometry in the evaluation of disorders of bone mineral density in patients with diabetes mellitus].

Presents a quantitative assessment of the total content of minerals in bones of 50 diabetics and 50 controls, carried out by a modified photodensitometric procedure. The data evidence a significant reduction of the mineral content in the bones of diabetes mellitus patients, this permitting an earlier detection of osteoporosis in the course of diabetes.

Absorptiometry, Photon↗