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At least 19 recordsLinked to original sources
PubMed1992

Influence of oophorectomy on serum levels of sex steroids and bone metabolism and assessment of bone mineral density in lumbar trabecular bone by QCT-C value.

The present cross-sectional study was carried out to determine the influence of oophorectomy (OPX) on serum levels of sex steroids and bone metabolism, as well as bone mineral density (BMD), in OPX subjects in comparison with age- and body size-matched controls. Quantitative computed tomography (QCT) and dual-photon absorptiometry (DPA) demonstrated a remarkable reduction in BMD in OPX subjects. In particular, the QCT of the centrum of vertebral bone (QCT-C) in these subjects was no more than 69.33 +/- 3.40% (X +/- SEM) of the control value, and this parameter was much lower than the QCT integral (QCT-I) value of total lumbar vertebrae. This means that BMD decreases specifically in spongy portions after OPX. The serum level of estrone (E1) was significantly lower in OPX subjects than in controls. The hormonal action of E1 on target organs has been thought to be only one-third of that of estradiol (E2), but the marked reduction in serum E1 level seemed to be a significant cause of the reduction in BMD. The serum level of androstenedione (delta 4) significantly decreased in OPX subjects and appeared to affect bone metabolism negatively. Both bone formation and bone resorption were found to be stimulated following OPX, but the rate of bone resorption was found to be higher than that of bone formation: there was an imbalance between bone formation and bone resorption in OPX subjects. However, it was not possible to prove a relationship between Ca regulating hormone and this phenomenon. In conclusion, the QCT-C value reflects the changes in spongy vertebral BMD more sensitively than the QCT-I value or DPA.(ABSTRACT TRUNCATED AT 250 WORDS)

Androgens↗
PubMed1990

Quantification of bone healing. Comparison of QCT, SPA, MRI, and DEXA in dog osteotomies.

Four noninvasive imaging modalities were used to quantitatively evaluate and compare tibial osteotomy healing in dogs. Quantitative computed tomography (QCT), magnetic resonance imaging (MRI), single-photon absorptiometry (SPA), and dual-energy x-ray absorptiometry (DEXA) were the four techniques examined. Bilateral tibial osteotomies were performed in 32 dogs divided into four groups. The osteotomies were stabilized with a 2-mm gap using unilateral external skeletal fixation. Dogs were anesthetized, imaged with the four noninvasive techniques, and killed at 2-12 weeks. Invasive techniques were used to determine: 1) the torsional properties of the bone; and 2) the local stiffness properties and calcium content within the bone. The techniques which had the strongest associations with the torsional properties of the osteotomies were QCT, SPA and DEXA. Generally, QCT and SPA had marginally stronger correlations than DEXA; but, overall, there were no differences between the techniques. MRI had the poorest associations with the torsional properties of the osteotomies. Generally, QCT had the strongest correlations with local material properties, such as indentation stiffness and calcium content. SPA had the second strongest correlations with calcium content and had the third strongest correlations with indentation stiffness behind DEXA. DEXA had the third strongest correlations for calcium content. With the exception of some of the correlations with indentation stiffness, MRI had the poorest associations with the local parameters studied.

Absorptiometry, Photon↗
PubMed1991

A new set of calibration standards for estimating the fat and mineral content of vertebrae via dual energy QCT.

A new set of calibration standards has been developed for implementing a dual-energy (DE) quantitative CT technique for estimating the fat and bone content of vertebrae. The QCT technique is based upon a three-component model of bone and utilizes calibration materials that mimic those components in their X-ray attenuation properties. The three components we chose to simulate are bone (mineral plus collagen), fat and a fat-free red marrow. This choice was predicated upon our desire to employ materials that would facilitate later experimental verification of the method. The calibration standards and a set of test samples were manufactured of tissue-simulating epoxy resins. They were employed in studies of the accuracy (consistency) and precision of the technique and in a study of 21 normal postmenopausal women. Estimates of the bone and fat content of the test samples were consistent with the manufacturer's specifications to within 13 mg/ml and 7 vol%, respectively. Long-term reproducibility (coefficient of variation) for both quantities was about 3%. The average bone content of the T12-L3 vertebrae of the human subjects was 262 +/- 32 mg/ml (152 +/- 18 mg/ml calcium hydroxyapatite or mineral) and the average fat content was 63 +/- 8%. Conventional single energy (SE) QCT measurements of these vertebrae were about 23% less than the DE mineral measurements, which is consistent with the differences between SEQCT and ash content that others have determined via chemical analysis. The DE fat content is, in absolute terms, about 15% greater than values reported in the literature and may be due to an error in the assumed composition of red marrow. The true accuracy of the bone and fat estimates is to be determined in a planned human vertebral specimen study.

Bone Density↗
PubMed1991

[The comparative measurement of the bone marrow dose in quantitative computed tomography (QCT), dual-photon radiography (DPX) and conventional x-rays of the LS].

One of the issues in the discussion on the best method for measuring the bone mineral content is the relevance of the applied dose. We used highly sensitive thermoluminescent dosimeters (TLD) to directly compare bone marrow doses in a human phantom. DPX gave a bone marrow dose in the lumbar spine of 4 mu Gy, in QCT the dose corrected to the same amount of irradiated marrow was about 1 mGy. This value is in the same range as conventional a.p. plus lateral view x-rays of the lumbar spine. Corrected to the total body dose, the QCT dose is as low as 10% of the yearly background irradiation. It should therefore be radiobiologically irrelevant.

Absorptiometry, Photon↗
PubMed1992

Measurement of bone mineral density (BMD) with quantitative computed tomography (QCT) in postmenopausal osteoporosis: effect of estrogen.

UNLABELLED: To determine the efficacy of the estrogen replacement therapy (ERT) on the bone mineral density (BMD) measured with quantitative computed tomography (QCT) in postmenopausal osteoporosis 16 women aged 46-72 were examined. They were divided into two groups: 8 women treated with conjugated estrogens (Group I) and 8 who did not received ERT (Group II). In all 16 patients the serum hormonal concentrations (LH, FSH and estradiol) were measured with radioimmunological methods. The bone densitometry was performed in all of them using the single-energy computed tomography (QCT) with the computer Picker 1200. Bone mineral density was measured in three lumbar vertebra (L1-L3) and expressed in milligrams K2HPO4 per ml. The bone mineral density (BMD) was statistically significantly higher in the estrogen treated group (Group I) in every vertebra compared with that of controls (Group II). The serum FSH concentration was statistically significantly lower in the ERT group (Group I) and a statistically significant correlation between FSH level and average BMD (Lmean) was present. IN CONCLUSION: 1. the ERT is very efficacious in preventing bone loss in postmenopausal women; 2. measurement of BMD in lumbar vertebra L1 or L3 may be a sufficiently reliable and accurate, cost-effective and time-saving method of screening for osteoporosis; 3. the serum FSH determination seems to be useful in monitoring of the estrogen therapy for postmenopausal osteoporosis.

Aged↗
PubMed1989

[Clinical application of skeletal scintigraphy and quantitative computed tomography (QCT) to osteoarthritis of the knee].

Skeletal scintigraphy and QCT were performed to determine changes of subchondral bone tissues in osteoarthritis of the knee and findings were compared with plain X-ray findings, knee pain and femoro-tibial angle. Results on blood pool study were especially related to pain. Results on delayed study using single photon emission computed tomography revealed high uptake on the medial side of the femur and tibia parallel to plain X-rays and pain. The QCT value was slightly decreased as osteoarthritic changes progressed without a significant change. In addition, delayed study in cases with previous surgical intervention by high tibial osteotomy revealed a lower uptake on the medial side of the femur and tibia. When skeletal scintigraphy accurately reflects blood flow through the subchondral bone tissues and is closely related to morbidity and pain, this modality is valuable in analysis of signs and symptoms as well as postoperative outcome.

Aged↗
PubMed1991

[Peripheral quantitative computed tomography for bone mineral measurement using a new special QCT-scanner. Methodology, normal values, comparison with manifest osteoporosis].

Some years ago we designed a special purpose gamma-ray QCT scanner for bone mineral measurements at the forearm. Currently, the first commercially built scanners (Stratec SCT 900) are being tested and clinically evaluated. The scanner uses an 125I photon source with a multidetector translate rotate fan beam geometry and newly developed semiconductor crystals. Quantification of trabecular bone and total bone at a standardized radial cross section gives an in-vivo reproducibility of less than 1%, which is superior compared to all other bone mineral measurement techniques. In-vitro reproducibility is between 0.2 and 0.4%, measured with calibration phantoms. The high in vivo reproducibility is ensured by automatic contour finding algorithms to determine the bone mass within a forearm cross sectional slice. A number of healthy men (n = 201) and women (n = 400) were examined to obtain a reference population for comparison to patients with generalized bone disease. We compared 182 osteoporotic females with healthy subjects. The high precision of the device and the high sensitivity of the measurement site considering changes of trabecular bone mass provide a very powerful means for monitoring bone mineral loss or changes due to therapy, as well as high diagnostic sensitivity.

Adult↗
PubMed1989

Peripheral QCT: a low-risk procedure to identify women predisposed to osteoporosis.

A low-risk procedure is described for the precise quantitation of changes of trabecular and cortical bone density at peripheral measuring sites. The method is based on quantitative computed tomography (QCT). Bone parameters are calculated for a sample volume common to all examinations of a patient. This is achieved by matching stacks of tomograms according to the cross sectional area of the bone measured. With the help of a special-purpose CT system the described procedure enables a reproducibility for trabecular and cortical bone parameters of 0.3% (1 SD) at a local radiation dose of 0.1 mSv (10 mrem). The method was used to assess the individual changes in bone density of 39 perimenopausal women during an observation period of 2 to 3 years. The results are grouped according to their menstrual state. Regularly menstruating women experience minute or no changes in bone density. After menopause the interindividual differences are considerable: some women lose bone excessively, others remain relatively stable. The frequency distribution of the rate of bone loss appears to be bimodal. Hence women can be classified in fast losers and slow losers. We conclude that the rate of bone loss may be most helpful in the identification of those women predisposed to osteoporosis.

Disease Susceptibility↗
PubMed1990

Dual energy radiography versus quantitative computer tomography for the diagnosis of osteoporosis.

In this study we compared dual energy radiography (DER), a new, highly precise x-ray densitometric technique recently devised for measurements of vertebral mineral density and quantitative computer tomography (QCT), a densitometric technique that selectively measures the trabecular compartment of the vertebra. DER and QCT measurements were obtained in 56 healthy (H) and 48 fractured osteoporotic (OP) women using a Hologic QDR 1000 bone densitometer and a GE 9800 scanner, respectively. DER was significantly correlated with QCT in both the H (r = 0.75; P less than 0.0001) and the OP subjects (r = 0.58; P less than 0.0001). DER decreased significantly with age in the H (P less than 0.05), but not in the OP women, whereas QCT was related to age in both the H (P less than 0.0001) and the OP subjects (P less than 0.01). The rate of bone loss with age was also higher with QCT than with DER in both normal and osteoporotic women. The difference in bone density between the H and the OP subjects was larger (P less than 0.05) with QCT than with DER. Receiver operating characteristic analysis revealed that QCT was a better predictor of vertebral fractures than DER. A larger percentage of OP subjects were 2 SD or more below the normal predicted value with QCT (41%) than with DER (29%). Furthermore, the slopes of the regressions of bone density with age for normal and osteoporotic women were significantly different (P less than 0.05) with QCT but not with DER. These findings are consistent with a disproportionate loss of trabecular bone with age in osteoporosis.(ABSTRACT TRUNCATED AT 250 WORDS)

Absorptiometry, Photon↗
PubMed1991

[The early changes in bone mineral metabolism due to radiation--measurement of bone mineral density in lumbar vertebra by quantitative computed tomography].

Osteosclerosis, osteonecrosis and compression fracture are commonly observed several years after radiation. Since lumbago usually occurs several months after radiation, the possibility that bone mineral metabolism is disturbed during and immediately after radiation cannot be ruled out. However, there have been no reports concerning early changes in bone mineral metabolism due to radiation. The bone mineral density was measured by QCT (Quantitative Computed Tomography) in 30 normal non-radiated cases and 14 radiated cases to investigate the changes in bone mineral metabolism due to radiation. The bone mineral density (QCT-Value: QCT-V) in the 3rd lumbar vertebra (L3) of normal non-radiated subjects decreased linearly with age (Y = 291.114447-3.01473X). The QCT-V of the 5th lumbar vertebra (L5) of normal cases also decreased linearly with age (Y = 309.641397-3.03986X), resembling that of L3. The ratio of the QCT-V of L5 to L3 (L5/L3, expressed as a percentage) definitely increased with age (Y = 86.5657441 + 0.58885064X). In radiated cases, the QCT-V of L3 in the non-radiated field did not change appreciably. The QCT-V of L5 in the radiated field was decreased from 20GY and reached 53.08 +/- 17.37% of the pre-radiation value after 50GY. The L5/L3 ratio was also decreased from 20GY and reached 55.47 +/- 15.32% of the pre-radiation value after 50GY. It becomes apparent that the QCT-V of the radiated lumbar vertebra is decreased during radiation. It is suggested that bone mineral metabolism may be disturbed in the early phase of radiation.

Bone Density↗
PubMed1991

Biomechanics of fracture risk prediction of the hip and spine by quantitative computed tomography.

In this review, we have made use of some simple engineering concepts to summarize current efforts relating QCT measures to bone density and strength. From a variety of in vitro experiments on cadaveric vertebrae and femora, it is evident that both apparent and ash densities are strong linear functions of QCT measures, with coefficients of determination ranging from 0.49 to 0.90 and relative errors from 44.9% to 7.1%. QCT data also can be used (with somewhat less confidence) to determine the compressive modulus (R2s from 0.36 to 0.68, relative errors from 45.0% to 35.5%) and compressive strength (R2s from 0.58 to 0.70, relative errors from 56.5% to 39.9%) of trabecular bone from the proximal femur and vertebral body. In cortical bone, material properties are only correlated weakly with QCT measures. Experiments designed to relate QCT data to failure loads for the proximal femur and vertebral body have been remarkably successful. Coefficients of determination have ranged from 0.32 to 0.93, with relative errors from 31.1% to 13.9%. However, when the in vitro failure loads determined in these experiments are compared against available estimates of in vivo loads on the spine and hip, it is apparent, at least in the elderly, that in vivo loads are relatively close to those that cause fracture in vitro. To assess the possibility of developing QCT-based clinical predictors of fracture risk for individual patients, we have introduced the concept factor of risk often used in engineering design to account for uncertainties in estimates of service loads and component strength. The factor of risk for a particular loading condition is defined as the ratio of expected service loads to the known failure loads. To extend this concept to densitometric fracture risk prediction in vivo, it is important to recognize that densitometric data must not only be used to predict the ultimate load carrying capacity of the region of interest, but that this ultimate load must then be compared to the forces expected in vivo under comparable loading conditions. One difficulty with this approach is that little is known about the in vivo forces that are associated with atraumatic age-related fractures of the hip and vertebrae and even less about the forces applied to the hip and spine during traumatic events such as falls. However, from available estimates of in vivo loads during bending and lifting, it is apparent that in the elderly, factors of risk for the spine can easily approach 1.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1989

[Participation of osteoporosis in femoral neck fracture--bone mineral measurement of proximal femur using quantitative computed tomography].

Quantitative computed tomography (QCT) was used to measure bone mineral contents of the proximal femur. First, 62 specimens of cancellous bones of the proximal femur obtained at operation were burnt for mineral determination after preoperative QCT measurement to evaluate the relationship between QCT values and ash weight. The findings indicated that QCT measurement of proximal femur was as useful as that of the lumbar spine. Next, 10 groups of 50 men and 50 women ranging in age from the 5th to the 9th decade were tested to define the control mean and range of QCT mineral content of proximal femur, to compare with 32 cases of femoral neck fracture. In women with femoral neck fracture, QCT values of the femoral neck were less than those of the same normal age group except for cases of medial fracture in the 9th decade. This measurement might provide an index for fracture risk.

Aged↗
PubMed1989

Prediction of vertebral strength by dual photon absorptiometry and quantitative computed tomography.

We measured the lumbar bone mineral of 19 cadavers (10 women, 9 men) by dual photon absorptiometry (DPA) and quantitative computed tomography (QCT). In addition, we determined the ultimate load and stress of each vertebra, and finally ash content and volumetric ash density of the vertebral body. We found that single energy QCT was inferior to DPA and dual energy QCT in the prediction of the ultimate load or stress of vertebrae (P less than 0.001). The ultimate stress was best predicted by using the dual energy QCT results (r = 0.71; SEE = 36.3 N/cm2) whereas the ultimate vertebral load was best predicted by using the DPA (BMC) results (r = 0.80; SEE = 740 N). If the QCT finding was multiplied with the surface area of the vertebral body it could be used to predict the ultimate load with good accuracy (r = 0.74; SEE = 841 N). All the above correlations were higher in women than in men. The frequency of vertebral compression fractures in the material was well correlated with the bone mineral findings. A nonlinear (third degree) relationship between mineral content and mechanical characteristics is proposed but within the area of measurement used in clinical practice a linear (first degree) equation is preferred.

Aged↗
PubMed1991

Bone densitometry of excised vertebrae; anatomical relationships.

Bone mineral density (BMD) was determined in 32 excised vertebrae using three methods: (1) dual-energy quantitative computed tomography (QCT), (2) dual-photon absorptiometry (DPA) with 153-Gd in an anteriorposterior projection and (3) scanning slit X-ray absorptiometry (SSXA) in both AP and lateral projections. The QCT region-of-interest in the anterior vertebral body had a lower density than that of the total trabecular portion of the body, but was highly correlated to this larger region (r = 0.96; SEE = 8 mg/cm3). The anterior QCT region also correlated moderately with BMD from DPA (r = 0.77; SEE = 18 mg/cm3). Measurements of the vertebral body in lateral projection were less well correlated (r = 0.5-0.7) to QCT densities. Both the anterior QCT region (r = 0.81; SEE = 18 mg/cm3) and the BMD from DPA (r = 0.86; SEE = 16 mg/cm3) and the BMD from DPA (r = 0.86; SEE = 16 mg/cm3) were similarly predictive of density of the integral vertebral body. Differences among densitometric methods on the spine depend on the projection used and the region examined.

Absorptiometry, Photon↗
PubMed1991

Quantitative computed tomography: comparative study using different scanners with two calibration phantoms.

To assess computed tomography (CT) scanners in vertebral quantitative computed tomography (QCT) measurement, five cadaveric vertebrae fixed in a water phantom were measured using 16 CT scanners of 10 different models using two types (CaCO3 and K2HPO4) of reference phantom. Although the same reference phantoms were used, the QCT values varied markedly depending on the CT scanner employed. The differences in QCT values were greater in the equivalent amount of CaCO3 than in that of K2HPO4. The largest difference between CT scanners was 40 mg/cm3 in the equivalent amount of CaCO3 and 28 mg/cm3 in that of K2HPO4. These differences were reflected among CT scanners by different slopes and intercepts of the reference lines of CaCO3, K2HPO4 and ash density depending on the CT scanner used. However, good correlations (r greater than 0.97) were observed for the QCT values obtained by various CT scanners. These results show that QCT values on one machine can be compared more closely with those of another machine if conversion formulae, determined by using materials equivalent to human vertebral bone, are employed.

Bone Density↗
PubMed1989

Quantitative computed tomography reflects vertebral fracture morbidity in osteopenic patients.

We studied the relationship between spontaneous vertebral compression fractures and lumbar vertebral trabecular bone density in 69 consecutive patients with suspected osteopenia. Seven had biopsy-confirmed osteomalacia. The remaining 62 were divided into three groups: group 1--asymptomatic patients suspected of having osteopenia on plain films, but with no vertebral compression fractures (N = 24); group II--those with one to five vertebral compression fractures (N = 16); and group III--those with six or more vertebral compression fractures (N = 22). A quantitative computed tomographic (QCT) scan of the lumbar spine was performed on all patients. Patients in group I had QCT values of 94 +/- 23 mg/cm3 (mean +/- SE); those in group II had QCT values of 66 +/- 28 mg/cm3; and those in group III had values of 34 +/- 28 mg/cm3. There were significant differences among all groups (P less than .001), although there was considerable overlap of individuals among the groups. There was no significant difference between the mean QCT value of patients with one compression fracture and the value of those with between two and five compression fractures. Patients with biopsy-proven osteomalacia had higher vertebral trabecular bone density than patients with osteoporosis and compression fractures. Our study provides evidence suggesting a strong inverse relationship between QCT-measured vertebral bone density and the presence of vertebral compression fractures in a group of osteopenic patients.

Absorptiometry, Photon↗