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At least 1,171 records · Page 65Linked to original sources
PubMed1998

Clinical evaluation of a high-resolution new peripheral quantitative computerized tomography (pQCT) scanner for the bone densitometry at the lower limbs.

Precision, long-term stability, linearity and accuracy of the x-ray peripheral quantitative computerized tomographic (pQCT) bone scanner XCT 3000 (Norland-Stratec Medical Sys.) were evaluated using the European Forearm Phantom (EFP). In vivo measurements were assessed using a standardized procedure at the distal femur and the distal tibia. In the patient-scan mode, the spatial resolution of the system was 1.04 +/- 0.05 lp/mm as measured at the 10% level of the modulation transfer function (MTF). The contrast-detail diagram (CDD) yielded a minimal difference in attenuation coefficient (AC) of 0.07 cm(-1) at an object size of 0.5 mm. The effective dose for humans was calculated to be less than 1.5 microSv per scan. Short-term precision in vivo was expressed as root mean square standard deviation of paired measurements of 20 healthy volunteers (RMSSD = 0.5%). At the distal femur total volumetric density (ToD) and total cross-sectional area (ToA) were found to be less sensitive to positioning errors than at the distal tibia. Structural parameters like the polar cross-sectional moment of inertia (CSMIp) or the polar cross-sectional moment of resistance (CSMRp) showed a good short-term precision at the distal femur (RMSSD = 1.2 and 1.4%). The relation between the two skeletal sites with respect to CSMIp or CSMRp showed a high coefficient of determination (r2 = 0.77 and 0.74).

Bone Density↗
PubMed2006

Photon absorptiometry, bone densitometry and the challenge of osteoporosis.

During the lifetime of Physics in Medicine and Biology, osteoporosis has been recognized as the cause of a major health burden for societies, particularly within developed countries. The health detriment is associated with the consequences of bone fractures and the subsequent increases in morbidity and mortality. Much of the credit for the current availability of means for identifying groups of subjects at risk of fracture and the provision of means for the effective treatment of excessive bone loss can be attributed to the technique of dual photon absorptiometry. In this review, the history of the development of techniques based on the interactions of x- and gamma-rays with bone is considered and the ultimate dominance of x-ray based absorptiometry is described. The advantages and disadvantages of current absorptiometric techniques are presented and the likely future path for bone measurement is outlined.

Absorptiometry, Photon↗
PubMed1993

Factors influencing lung density in experimental models: results of studies using CT densitometry.

Lung density measurements using computed tomography have been made in mice, rats, and pure-bred beagles and mongrel dogs. Density was found to be dependent on a number of factors including the location of the area scanned, and the age and species of the animal. Lung density was found to decrease by approximately 40% from initial values in a group of rats scanned at intervals between 30 and 800 days old. Age-related density changes were not seen for the lungs of mice or dogs; however measurements were not made over a prolonged period. A gradient of increasing density from the base to apex of the lung was seen for 30 and 175-day-old rats (scanned in the prone position) while an apex to base density gradient was seen for both types of dog studied (scanned in the supine position). In none of the species studied was there a systematic difference in density of the right and left lungs. Differences in average lung density between the mice, rats and dogs reported here are consistent with the relationship between lung morphology, metabolic rate and body size which obtains for a range of mammalian species.

Absorptiometry, Photon↗
PubMed2003

Bone densitometry as an indicator of percentage tibia ash in broiler chicks fed varying dietary calcium and phosphorus levels.

The relative sensitivity of tibia bone mineral content (BMC) and density (BMD), percentage ash (ash), and shear force as indicators for dietary Ca and P was compared in 3-wk-old broiler chicks. One hundred eight 7-d-old chicks were grouped by weight into 6 blocks of 3 cages each with 6 birds per cage. Three corn-soybean meal-based diets were randomly assigned to cages within each block. The diets were low P, medium P, and adequate P and were formulated to contain 4.0, 5.1, and 7.8 g of total P/kg feed, respectively; and 5.1, 6.7, and 10.0 g of Ca/kg feed, respectively. The chicks were fed the experimental diets for 14 d. On d 22, chicks were killed, and tibiae were removed from 3 birds/cage. Weight gain, feed intake, feed efficiency, BMC, BMD, shear force, and ash were determined. The BMC and BMD were determined using dual energy x-ray absorptiometry. Correlations among the various bone status variables and dietary Ca and P were determined. Growth performance criteria and ash increased linearly, and BMC and BMD increased linearly and quadratically as dietary concentrations of Ca and P increased. The correlation coefficient between dietary Ca and BMC, BMD, shear force, or ash was 0.89, 0.91, 0.50, or 0.89, respectively; and between dietary P and BMC, BMD, shear force, or ash was 0.88, 0.91, 0.48, or 0.89, respectively. The correlation coefficient between ash and BMC, BMD, or shear force was 0.92, 0.93, or 0.67, respectively. The correlation coefficients for linear regression between shear force and BMC or BMD was 0.56. The regression model for predicting percentage ash using BMD was as follows: percentage ash = 24 + (240 x BMD) with an r2 of 86%. It is concluded that in broiler chicks, tibia ash, BMC, and BMD may be more sensitive than shear force as indicators of dietary Ca and P concentrations and that BMD as measured by dual energy x-ray absorptiometry may be used to predict percentage of tibia ash.

Absorptiometry, Photon↗
PubMed2006

Dose evaluation in paediatric radiology and adult bone densitometry examinations.

Dose measurements are acknowledged to be a vital part of the quality assurance process in diagnostic radiology, and the use of thermoluminescence dosemeters (TLDs) is a recommended method of entrance dose evaluation. Measurement of doses in radiographic examinations is widely adopted in clinical practice for adults as well as for children. Phantoms can be used to simulate different parts of the body, depending on the materials used to build them. In this work two different sets of phantoms have been prepared with acrylic blocks. The first set was used to simulate children of different ages. The second set was used to simulate the adult spine. The dosimetric measurements have been carried out using TLD and an ionising chamber. Measurements were performed in three X-ray equipments in Aracaju, Brazil. The entrance, half thickness and exit surface doses were analysed.

Absorptiometry, Photon↗
PubMed1993

DEXA bone densitometry measurements in adults with X-linked hypophosphatemia.

Bone mineral densities in adults with X-linked hypophosphatemia are variable, and while most are reportedly normal some can be very high. Eighteen patients with adult X-linked hypophosphatemia underwent bone mineral determinations of the lumbar spine and femoral neck with dual energy x-ray absorptiometry (DEXA). Most of them were on various treatment regimens. Ten of 18 patients (55%) had spinal bone mineral densities that were greater than two standard deviations above the age-matched mean, and 3 of 11 patients (27%) had bone mineral densities of the femoral neck in excess of two standard deviations. Eight patients (median age 41.5 years) were followed serially for 24 to 42 months, and they exhibited a spinal bone loss of 0.019 gm/cm2/year.

Absorptiometry, Photon↗
PubMed1995

Image analysis DNA densitometry measurements on complete and partial hydatidiform mole and nonmolar products of conception.

Most spontaneous first trimester abortions have an abnormal karyotype, some being triploid; the latter are said to show characteristic histological changes, including focal villous hydropic change, focal trophoblast hyperplasia, cisternal cavitation of larger villi, irregular outline to villi, and trophoblast inclusions. To date, DNA-ploidy profiles have been derived from flow cytometry and cytogenetic karyotyping, both methods being time-consuming and expensive. This study has assessed DNA ploidy on products of conception using a simple video image analysis system. It is concluded that diploid, triploid, aneuploid, and hyperdiploid states can be ascertained on archival paraffin-embedded material using interactive image analysis morphometry. However, the stated histological criteria for triploidy (which has previously been equated with partial mole) appear to be unreliable, with only three of eight histological partial moles having this DNA pattern. In addition, there were six diploid, five triploid, seven hyperdiploid, and two aneuploid DNA ploidy profiles in the spontaneous nonmolar pregnancies. We found that of the 11 complete moles, five were aneuploid and six were hyperdiploid, with none being either diploid or triploid. This finding is contrary to the commonly held view that all complete moles have a diploid DNA profile.

Abortion, Missed↗
PubMedDate not supplied

Measurement of atherosclerotic luminal irregularity and obstruction by radiographic densitometry.

This report describes a procedure to quantify stenosis and to detect enface plaques in single plane angiograms. We derived an optical density function proportional to local arterial chord length from arteriographs over a wide range of conditions. Standard radiographs were made of silicone rubber bolus used as the radiopaque medium in cadaver arteries. Replicate arterial casts filled with iodine-bearing contrast medium were radiographed for comparison. Identical atherosclerotic areas in both film sets were scanned with a microdensitometer and vessel chord lengths used to construct arterial cross sections for comparison with vessel casts. Cross-sectional areas derived from cadaver and phantom films were highly correlated with those derived from cast slices (r = 0.997). Thus, luminal cross-sectional areas were accurately estimated independent of plaque location, and accuracy of chord length measurement was +/- 0.28 mm in vessels four to 10 mm in diameter.

Absorptiometry, Photon↗