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Results for “Absorptiometry, Photon”

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PubMed1977

Diagnosis of osteoporosis: usefulness of photon absorptiometry at the radius.

The photon-absorption method (Cameron-Sorenson) is commonly used in the diagnosis of osteoporosis to measure bone mineral in appendicular bones. Although this method gives accurate and reproducible results when applied to the distal radius and midradius, separation between osteoporotic patients and age-matched normals was less than satisfactory because of a large overlap. By contrast, a radiographic index based on the pattern of trabecular bone at the proximal femur (Singh index) gave a better separation between the two populations. The Singh index discriminates better, probably because osteoporotic patients have a greater proportion of loss of trabecular bone of the axial skeleton than of cortical bone of the appendicular skeleton.

Age Factors↗

PubMed1987

Dual-photon absorptiometry of the proximal tibia.

Dual-photon absorptiometric bone-mineral assay, penetration tests, and axial compression tests of the proximal tibial epiphyses were carried out in 18 human cadaver knees. The reproducibility of bone mineral assay was within +/- 12% (95% tolerance limits). Linear regression analysis with bone-mineral content as the independent variable showed a good correlation to the ultimate force obtained from the compression tests on the medial (r = 0.81) and the lateral (r = 0.90) condyles. The correlation between bone mineral content and an average of three condylar penetration tests was somewhat weaker (medical condyle: r = 0.65, lateral condyle: r = 0.62). It is concluded that dual-photon absorptiometric bone-mineral assay may be a suitable noninvasive alternative to bone-strength measurement and thus suitable for monitoring the changes in tibial condylar bone during follow-up studies.

Humans↗

PubMed1977

Photon absorptiometry of bone after successful renal transplantation.

Photon absorptiometric measurements of the right lower femur were carried out at regular intervals of one to three months in 58 recipients of renal transplant. (1) During the first six months after transplant 57% showed a significant and abnormal rate of loss of bone mineral (mean 11.7% per year. +/- 1.1% S.E.M.) while 30 months' after transplantation only 17% showed such a significant loss (p=0.025). (2) Eighteen months after transplantation both male and female recipients of transplants had a significantly lower mean bone mineral index than controls (p less than 0.001). (3) Male patients who developed new post-transplant fractures had a lower mean bone mineral content compared with age and sex-matched controls taken from transplant recipients without such fractures (p less than 0.01). Similarly male patients with post-transplant fractures had a significantly longer mean period on regular haemodialysis (p less than 0.05) compared with patients without such fractures. Regular photon absorptiometric measurements provide an accurate, informative and non-invasive technique for following changes of bone mineral content after successful renal transplantation.

Bone Diseases↗

PubMed1990

Bone mass measured by photon absorptiometry: comparison of forearm, heel, and spine.

We assessed bone mass quantification at different skeletal sites by single and dual photon absorptiometric (SPA and DPA) methods. Improved DPA measurement of spinal bone mineral density in young healthy subjects showed a short- and long-term precision of 1.2% and 1.6%. Compared to the conventional DPA method the imprecision was reduced by more than 50%. The appendicular measurements were more precise (0.5-1.2%). We present the intercorrelations and predictive errors between peripheral measurements and improved spinal and total body bone measurements in early postmenopausal women (n = 144) recruited in 1988. To compare the improved system with the conventional methods, we retrieved data on age-matched early postmenopausal women (n = 151) recruited in 1983. In the 1988 population all peripheral methods had similar predictive errors in estimation of spinal bone mineral density (SEE = 11-13%) and total body bone mineral density (SEE = 4-5%). Measurement of trabecular bone in the heel and distal forearm did not improve the validity of predicting spinal bone mass. In a cadaver study (n = 11) the predictive error in estimation of the spinal ash weight from forearm measurements was of the same magnitude (15%) as that in estimation of the spinal BMC from the forearm (16%). We conclude that the predictive error in estimation of spinal bone mass from peripheral bone measurements is more likely to be caused by intra-skeletal variation in bone mass than by precision errors. However, this does not reflect the inability of peripheral bone mass measurements to predict fracture risk.

Absorptiometry, Photon↗

PubMed1989

Body composition measurement by dual photon absorptiometry: comparison with body density and total body potassium measurements.

Body composition was measured in 29 healthy adults (12 men and 17 women) by three different methods: Dual photon (153Gd) absorptiometry (DPA), body density measurements (BD) and measurements of total body potassium (TBK). Correlation and regression analysis with the body fat percentage (Fat%) measured by the three different methods gave r values between 0.83 and 0.90 and SEEs between 4.0 and 6.0 (Fat%). We conclude that DPA provides a new method of measuring body composition with precision and accuracy errors in the same range as the more established methods.

Adult↗

PubMed1987

Single- and dual-photon absorptiometry in osteoporosis and osteomalacia.

Single- and dual-photon absorptiometric methods have been used in the past to identify populations at risk for bone loss, to define the osteoporotic syndrome in terms of bone mass, and to evaluate treatment regimens to prevent bone loss. Technical improvements have made these procedures available for the nontraumatic measurement of bone mineral in the management of the individual patient suspected of having osteoporosis or other bone loss. This requires a different approach to data interpretation because decisions have to be made on the basis of a single measurement. Osteoporosis and osteomalacia cannot be distinguished by bone mineral measurements because both are characterized by a decrease in content of bone mineral. Bone mineral measurements can be used to assess the risk of fracture and, with it, the severity of bone loss. This allows treatment decisions to be made. Repeated measurements made under well-defined conditions allow estimation of long-term rate of bone loss and monitoring of treatment effect.

Bone and Bones↗

PubMed1989

X-ray dual-photon absorptiometry: a new method for the measurement of bone density.

A recently introduced method (dual-photon X-ray absorptiometry, DEXA) capable of measuring skeletal density in man (at present in the spine and hips, but ultimately for the whole body) has been evaluated in terms of its ability to perform long-term assessment of bone density changes. The method, which uses X rays rather than gamma rays as its photon source, represents a significant improvement over present systems both in image quality and precision (reproducibility) of results, which is better than 1% in vivo. Scanning time is approximately halved compared with present techniques and the radiation dose is reduced by 25%. First data on long-term drift of results and effects of changes in patient composition (i.e. thickness and fat content) are given and show the new method to be superior to present radionuclide systems. It is likely that this new method will become the standard for bone density measurements.

Bone and Bones↗

PubMed1999

[Dual photon absorptiometry in full-term newborns].

BACKGROUND: There is scanty information about bone mineral density in newborns. Normal values are needed to assess the effects of diseases and drugs used during the neonatal period. AIM: To assess bone mineral density in normal newborns. PATIENTS AND METHODS: Total body bone mineral density was measured in 16 newborns with 39 +/- 1.2 weeks of gestational age, using a Norland dual photon densitometer. RESULTS: The mean weight of newborns was 3.366 +/- 325 g. Bone mineral content was 58.3 +/- 10.8 g and bone mineral density was 0.369 +/- 9.6 g/cm2. RESULTS: The availability of normal bone mineral content values in newborns will be useful for the assessment of conditions that affect bone mineralisation.

Absorptiometry, Photon↗

PubMed1987

Errors in longitudinal measurements of bone mineral: effect of source strength in single and dual photon absorptiometry.

The effect of changing strength during the useful life of a radiation source was evaluated in studies performed on four dual photon (DPA) and two single photon (SPA) bone absorptiometry instruments. Two DPA units and one SPA unit did not show any systematic dependence of measured bone mineral content or bone mineral areal density (BMD) on source activity when evaluated over an entire source life. One DPA and one SPA instrument, however, showed significant time trends associated with source activity. The fourth DPA instrument had a significant linear decrease in BMD over a source life in the automatic mode but performed better in the manual mode.

Bone and Bones↗

PubMed1979

Osteoporosis in hyperthyroidism estimated by photon absorptiometry.

The degree of osteoporosis in hyperthyroidism before and during treatment with carbimazole was studied by photon absorption technique of the right forearm and calcaneus. In addition serum total calcium, serum ionized calcium, serum phosphorus and serum alkaline phosphatase were determined. A group of 96 patients suffering from untreated hyperthyroidism (85 women and 11 men) was studied (79 of these patients were also followed during treatment) and compared to a control group of 157 persons (107 women and 50 men). The women were divided into two groups: less than or equal to 45 years old and more than 45 years old. In all groups untreated hyperthyroid patients showed lower bone densities compared to the control group, but this was only significant in women. During treatment all groups showed a significant increase in density. After 3-6 months of treatment bone density in the calcaneus increased 12% and in the forearm 1.5%; after 6 months - 3 years 33% and 31%, respectively. At that time bone density was normalized. There was no correlation between bone density in hyperthyroid patients and duration and severity of the disease. The biochemical changes were characterised by increases in serum alkaline phosphatase (26%), serum total calcium (16%) and serum ionized calcium concentration (17%) in cases of untreated hyperthyroidism. Serum phosphorus concentration did not change. A correlation was found between elevation of the alkaline phosphatase and decreased bone density.

Adult↗

PubMed1983

Comparison between 153Gd and 241Am, 137Cs for dual-photon absorptiometry of the spine.

The bone mineral content (BMC) of the spine can be measured from the attenuation of two photon beams. An equation was derived for the theoretical precision of BMC measurement and validated experimentally. Though 153Gd was found to possess the better energy combination, the precision due to the photon energy levels using 241Am, 137Cs was only 1.5 times the value obtained from 153Gd. The available photon outputs from 241Am and 153Gd were investigated and with a 12 mm diameter disc source a theoretical precision of 1% could be obtained with source strengths 20 GBq 241Am or 5GBq 153Gd in a 40 min and 20 min patient scan respectively. There was no great advantage in either energy combination when the problems of fat or patient dose were considered. Given the disadvantages of 153Gd, its cost and availability, 241Am, 137Cs can be used as a practical alternative to measure spine BMC from a reconstructed bone mineral image.

Americium↗

PubMed1988

Long-term precision of dual photon absorptiometry in the lumbar spine in clinical settings.

We have investigated the long-term in vivo precision of a dual photon spine scanner using three different Gd sources and compared it with that of the single photon scanner. Standard values were significantly different with the three Gd sources. With the second there was also a systematic increase of 2% per 60,000 cps in the 44 KeV channel as the source decayed, whereas no such shift was found with the other two sources. This resulted in a significant in vivo intrasource (P less than 0.05) and intersource (P less than 0.01) variation and a six-month reproducibility ranging from 3.7 to 8.1%. After correction for these systematic errors the clinically important 2-year reproducibility in 26 premenopausal women was 3.4 +/- 1.3% for spinal BMC and 3.7 +/- 1.7% for spinal BMD. In comparison, the forearm single photon scanner had a long-term precision of 1.0 +/- 0.3%. With the presented techniques spinal measurements may therefore require 11.6 times (3.4(2):1.0(2] as many participants as the forearm measurements to detect the same changes in bone mass.

Adult↗

PubMed1975

Dual photon absorptiometry in lumbar vertebrae. II. Precision and reproducibility.

Bone mineral content in lumbar vertebrae is determined by the attenuation of 59.6 keV (241Am) and 662 keV (137Cs) photons using the intermittent scanning technique. The precision, mainly influenced by decay variations, is analyzed mathematically. The reproducibility in patient measurements is also affected by variations in positioning, movements during measurement and base line errors. In four normal subjects the reproducibility ranged from 3.4 to 5.7%. The long-term stability was better than 1% during a five-month period as tested by phantom measurements.

Americium↗

PubMed1981

Bone mineral content in relation to age and menopause in middle-aged women. A study of bone density in lumbar vertebrae by dual photon absorptiometry in a population sample of women.

As one phase of a comprehensive population study of women, bone density was determined in the third lumbar vertebra by dual photon absorptiometric technique. The method involves the use of two radionuclides, which both emit gamma radiation but with different energies (241Am with 59.6 keV and 137Cs with 662 keV). Women in three age strata were studied: 46, 54 and 62 years. The bone mineral content was higher in premenopausal or recently postmenopausal 54-year-old women than in women of the same age who had been postmenopausal for a long time (p less than 0.02). A similar trend was found for women aged 62. The differences could not be explained by differences in other factors studied, such as body height, body weight, smoking habits, numbers of pregnancies or physical inactivity. No significant differences were found when women with similar menstrual status in different age-groups were compared. In the ages studied, hormonal factors seem to be more important than the age per se for the development of oeteoporosis.

Aging↗

PubMed1983

Dual photon absorptiometry of the spine with a low activity source of gadolinium 153.

Apparatus and data-processing techniques were developed to measure the bone mineral content (BMC) of the lumbar spine. 153Gd was used as the dual photon source with an activity down to 7 GBq, lower than that adopted by other workers. The compromise between resolution and sensitivity was optimised. A reproducibility in normal subjects of 1.5% (coefficient of variation) was obtained. Normalisation procedures using parameters of the scan image and other indicators of body size such as span were developed, and reduced the coefficient of variation between normal subjects to 10% for men and 8% for pre-menopausal women. The absolute values of BMC are similar to those reported by others. Cross-sectional studies in women demonstrated an accelerated loss of BMC after the menopause.

Adult↗

PubMed1988

Nuclear medicine studies of aging--VI. Dual photon absorptiometry and bone scans in "at risk" women with back pain.

We studied 20 women who were at risk for osteoporosis (postmenopausal, or on dialysis, or on steroids), who presented with severe back pain. Patients underwent a dual photon (153Gd) densitometry study of the L2-L4 vertebrae, as well as an emission bone scan (99mTc-MDP). The dual photon method revealed abnormal results (20% or more below the mean expected value) in 13/20 patients (65%), and below the "fracture threshold" in 15/20 (75%). The emission bone scan delineated abnormal foci of uptake in 15/19 (79%). We conclude that women at risk for osteoporosis, who present with severe back pain, are likely to have a positive bone scan due to compression fracture or other derangements related to bone demineralization.

Adult↗

PubMed1986

Single photon absorptiometry for the measurement of bone mineral content in horses.

A safe, non-invasive method for the accurate measurement of bone mineral content in the third metacarpal bone of the horse is described. The technique involves scanning the bone with a single photon beam from an Americium-241 source. Data were obtained from the excised metacarpal bones from both forelimbs of 50 normal and seven lame horses. Measurements were made in vivo on eight normal and seven lame horses and on one experimental horse with osteopenia induced by partial weightlessness in a flotation tank. In the normal horses bone mineral content altered with age, particularly in the first six months of life. There were also differences according to the site of scanning on the metacarpus. The contribution of the splint bones to the total bone mineral content was less than 2 per cent distal to the mid-point of the metacarpus, but in the proximal shaft it increased to 12 per cent. No significant differences were noted either between right and left limbs, or between male and female animals. A reduction in bone mineral content was demonstrated in the affected leg of horses with chronic lameness and with osteopenia induced by weightlessness. The bone mineral content (g/cm) correlated well with the ash content (mg/100 mg dry bone weight), the specific gravity and the apparent transverse velocity of ultrasound (m/sec) through the bone. A measure of bone mineral density (g/cm3) was calculated from the bone mineral content and cross sectional area of the bone to overcome the individual differences in size of the metacarpus.

Age Factors↗

PubMed1985

In vivo measurement of bone mineral content of mandibles by dual-photon absorptiometry.

The purpose of this study was 1) to reveal the short- and long-term precision of noninvasive in vivo measurements of bone mineral content (BMC) in larger and smaller parts of mandibles and in forearm bones by a new two-dimensional dual-photon attenuation system GT45; 2) to develop normal reference values and ranges for mandibular BMC in individuals between 20-40 yr of age without known systemic diseases and with normal oral state, (n = 56, F:M = 1:1), and 3) to relate mandibular BMC with forearm bone BMC, sex and age, by comparing BMC values of a well-defined normal old test group (n = 24, F:M = 1:1, 70-81 yr of age) with the normal reference values. The analyses indicated: 1) the in vivo short- and long-term precision of the methods is high. 2) BMC of mandibles and forearm bones is significantly related to sex and age (P less than 0.01, and in mandibles of young females/males: P = 0.02). 3) BMC in mandibles and forearm bones is significantly correlated in both age groups (P less than 0.01) with relatively weak coefficients of correlation. GT45 may be used to follow BMC changes in mandibles in groups or single individuals after surgical treatment and to evaluate sex and age dependent BMC changes in mandibles and forearm bones.

Adult↗