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Biomedical subjects

R B Mazess

Publications and source records attributed to R B Mazess.

At least 109 records · Page 6Linked to original sources
PubMed1984

Total body and regional bone mineral by dual-photon absorptiometry in metabolic bone disease.

Dual-photon absorptiometry (153Gd) was used to measure bone mineral of the total body and major anatomical areas. Patients with osteoporosis (male = 11, female = 18) and with renal osteodystrophy (n = 17) were significantly below (20%) normal females (n = 72) and males (n = 13) at most sites. In the osteoporotic patients, but not the renal patients, there was preferential osteopenia of the spine. Bone loss in all anatomical areas became evident after the menopause with an annual loss rate of about 0.7%.

Absorption↗
PubMed1984

Effects of 1,25(OH)2D3 on bone tissue in the rabbit: studies on fracture healing, disuse osteoporosis, and prednisone osteoporosis.

A closed tibial fracture, which was controlled by an intramedullary stainless steel pin, was created in 16 rabbits. Eight rabbits were treated with 75 ng of 1,25(OH)2D3 daily as subcutaneous (s.c.) injections. After three weeks, the fractured tibia resisted a force of 101.7 +/- 21.0 Newtons in the control group and 57.3 +/- 8.0 Newtons in animals given 1,25(OH)2D3 (m +/- SE, P less than 0.05). In another group of eight rabbits, the left hindleg was immobilized in a plastic splint. Four rabbits were given 75 ng of 1,25(OH)2D3/day s.c. and the effect of immobilization was studied on the calcaneus. Bone ash/cm3 of the calcaneus on the immobilized side was decreased by 11 +/- 2% in control rabbits and by 20 +/- 2% in the group treated with 1,25(OH)2D3 indicating a more advanced immobilization osteoporosis (m +/- SE, P less than 0.05), which was also demonstrated by studies of bone density. Eighteen rabbits were used in a study of the effects of 1,25(OH)2D3 on the development of prednisolone osteoporosis. The dose of prednisolone was 2.5 mg per day, given by the oral route. After four months, the density of the femur was 1.53 +/- 0.02 g/cm2 in control rabbits and 1.42 +/- 0.01 in prednisolone-treated animals (P less than 0.01). In rabbits additionally given 1,25(OH)2D3, the mean value for bone density was further lowered (n.s.). It appears that 1,25(OH)2D3 exaggerates disuse osteoporosis and prednisolone osteoporosis and impairs fracture healing in rabbits. These results differ from what has been shown earlier with 1,25(OH)2D3 treatment in the rat.

Animals↗
PubMed1984

Total body composition by dual-photon (153Gd) absorptiometry.

The lean-fat composition (%FATR) of soft tissue and the mineral mass of the skeleton were determined in vivo using dual-photon (153Gd) absorptiometry (dose under 2 mrem). A rectilinear raster scan was made over the entire body in 18 subjects (14 female, 4 male). Single-photon absorptiometry (125I) measured bone mineral content on the radius. Percentage fat (%FATD) was determined in the same subjects using body density (from underwater weighing with correction for residual lung volume). Lean body mass (LBM) was determined using both %FATR and %FATD. Percentage fat from absorptiometry and from underwater density were correlated (r = 0.87). The deviation of %FATD from %FATR was due to the amount of skeletal mineral as a percentage of the LBM (r = 0.90). Therefore, skeletal variability, even in normal subjects, where mineral ranges only from 4 to 8% of the LBM, essentially precludes use of body density as a composition indicator unless skeletal mass is measured. Anthropometry (fatfolds and weight) predicted %FATR and LBM at least as well as did underwater density. The predictive error of %FATR from fatfolds was 5% while the predictive error in predicting LBM from anthropometry was 2 to 3 kg (3%).

Adipose Tissue↗
PubMed1984

Total body bone mineral in vivo by dual photon absorptiometry. I. Measurement procedures.

A dual photon scanner using a 1 Ci 153Gd source, a NaI detector, traditional electronics and a desktop computer, was constructed. Software for the computation of the total body bone mineral (TBBM) was developed. Non-linear influences such as deadtime due to high count rates, patient scatter and Compton effects were investigated and correction algorithms were introduced in order to obtain exponential attenuation. System precision was measured on a bone-aluminium standard (CV = 2.6%) and system linearity was assessed on aluminium pieces (r = 0.999, SEE = 3.0%). Short-term precision in vivo was tested on 15 healthy subjects scanned twice with a 2-month interval (CV = 2.4%). Long-term reproducibility in vivo was tested on two healthy subjects scanned eight times with 1-month intervals (CV = 1.9% and 3.2%). The influence of patient orientation was investigated on two skeletons. No significant difference was found between anatomical and random orientation. It was concluded that the precision errors were small, therefore making the method applicable not only in cross-sectional studies but also in longitudinal studies designed to investigate the loss or gain of total bone mass in patients suffering from calcium metabolic disorders.

Bone and Bones↗
PubMed1984

Total body bone mineral in vivo by dual photon absorptiometry. II. Accuracy.

We investigated the accuracy of total body mineral (TBBM) measured by dual photon absorptiometry (1 Ci 153Gd source, 44 and 100 KeV) using skeletons, soft tissue equivalent materials and whole cadaver extremities. The accuracy was assessed on five skeletons (r = 0.99, SEE = 1.5%). The influence of the soft tissue composition on the TBBM measurement was investigated in the same five skeletons. They were scanned in a 16 cm thickness of ethanol solutions of different concentration (0, 20, 40, 60, 80, 100% ethanol) and only a 2% difference (non-significant) was found between measuring 100% ethanol and 100% water. Furthermore, seven whole cadaver extremities were scanned before and after removal of the soft tissues (r = 0.995, SEE = 6.3%). The slope was not different from one and the intercept not different from zero. Equipment at the University of Wisconsin, Madison, and at Glostrup Hospital, Denmark, was compared by measuring the same healthy subjects and skeletons on both scanners. The Glostrup and Madison TBBM values correlated well (r = 0.99, SEE = 5.8%) and the intercept (345 Glostrup arbitrary units) was not significantly different from zero (P greater than 0.05). The TBBM results were calibrated into total body calcium (TBCa) and no significant difference was found between Glostrup and Madison TBCa values (P greater than 0.20).

Bone and Bones↗
PubMed1984

Persistence of diminished bone mineral content following renal transplantation in childhood.

Bone mineral content (BMC) was measured in the nondominant arm of 18 children (aged 3 7/12 to 17 1/2 years) for a total 783 months after renal transplantation. Using photon absorptiometry, 89 measurements were made; 17 of the 18 patients had a functioning graft and one patient died. Significant demineralization, a BMC greater than -2 SD below appropriate control volumes, was found in 11 of 18 patients (62%) and 55 of 89 measurements (61%). Bone loss was progressive; among the 16 patients followed for more than 6 months, ten showed a decline of more than 0.5 SD in BMC, five had no change, and only one showed improvement. No relationship was found between BMC and the use of furosemide, type of transplant (15 living, seven cadaver), prior renal disease (six with glomerulonephritis, 11 tubulointerstitial), need for a second graft (five patients), chronic anticonvulsant therapy, or serum calcium and phosphate values. BMC was slightly correlated (P less than .05) with alkaline phosphatase values. BMC was more strongly correlated with serum creatinine (y = -0.48x + 1.25, r = -.042, P less than .001) and prednisone dose (mg/kg/d) (y = -0.65x + 0.481, r = -.543, P less than .001) in an inverse relationship. Patients whose serum creatinine value was less than 1 mg/dL had a BMC of -0.71 +/- 0.34 SD; those with serum creatinine value greater than 2 mg/dL had BMC of -3.32 +/- 0.31 SD, different at P less than .001. Patients receiving daily prednisone therapy had a significantly lower BMC than those receiving alternate-day therapy (-3.11 +/- 1.23 SD v -1.72 +/- 1.29 SD, P less than .005).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1984

Does bone measurement on the radius indicate skeletal status? Concise communication.

Single-photon (I-125) absorptiometry was used to measure bone mineral content (BMC) of the distal third of the radius, and dual-photon absorptiometry (Gd-153) was used to measure total-body bone mineral (TBBM), as well as the BMC of major skeletal regions. Measurements were done in normal females, normal males, osteoporotic females, osteoporotic males, and renal patients. The BMC of the radius predicted TBBM well in normal subjects, but was less satisfactory in the patient groups. The spinal BMC was predicted with even lower accuracy from radius measurement. The error in predicting areal density (bone mass per unit projected skeletal area) of the lumbar and thoracic spine from the radius BMC divided by its width was smaller, but the regressions differed significantly among normals, osteoporotics, and renal patients. There was a preferential spinal osteopenia in the osteoporotic group and in about half of the renal patients. Bone measurements on the radius can indicate overall skeletal status in normal subjects and to a lesser degree in patients, but these radius measurements are inaccurate, even on the average, as an indicator of spinal state.

Adult↗
PubMed1983

Errors in measuring trabecular bone by computed tomography due to marrow and bone composition.

The linear attenuation coefficient (mu in cm-1) of trabecular bone was modeled for different conditions of bone and marrow composition in order to assess their influence on computed tomography (CT) quantitation. A large relative change (10% of TBV at 15% TBV) of bone concentration resulted in small changes of mu: 2.3% at 60 keV, 3.4% at 44 keV, 5.2% at 29 keV. Relative changes of trabecular bone volume (TBV) on the order of 3% could be detected in vivo by CT were it not for errors of relocation and for compositional influences on accuracy. The mu (and density) depended critically not only on amounts of bone substance and marrow but on their compositions. Normal variation in the composition of bone substance produced an uncertainty in mu equivalent to 0.5 to 1% TBV. Increases of yellow marrow produced a decrease of mu which could be mistaken for a decrease of bone concentration. The biological variation (90% confidence limit) of marrow composition gives an uncertainty at 15% TBV of about 2.4% TBV at 60 keV, 1.7% at 44 keV, and 1.3% at 29 keV. These correspond to relative uncertainties of 16, 11, and 9% respectively. These factors help explain the large accuracy errors (30%) observed in all studies of trabecular bone where single-energy CT was used. Marrow composition also can affect precision of bone measurement. Systematic shifts of red and yellow marrow could mask biological changes such as those occurring with aging or treatment.

Adult↗
PubMed1983

An accurate and reproducible absorptiometric technique for determining bone mineral content in newborn infants.

At the Bone Mineral Laboratory of the University of Wisconsin a microcomputer-based digital read-out system was designed specifically for determining bone mineral content (BMC) and bone width (BW) in newborn infants with the following features: (1) high accuracy and precision; (2) high reproducibility in vivo; (3) direct read-out of BMC and BW; (4) automatic data calibration; and (5) use of a low activity [125I] source (less than 50 mCi). BMC and BW were determined on the left radius on a series of 114 newborn infants of all gestational ages and a curve for intrauterine bone mineral content extrapolated from the data. Accuracy of the photon absorptiometric system was assessed by measuring BMC on a series of nine small bone sections (29-212 mg/cm) and confirmed by subsequent ashing of these bone sections (r = 0.99). Short-term precision (weekly, coefficient of variation 1.7%) and long-term precision (monthly, coefficient of variation 2.1%) for measuring BMC were determined by multiple determinations on a four-chambered bone phantom calibrated with the bone sections. Immediate reproducibility (without repositioning the arm) for the 4-6 scans performed for each determination of BMC and BW was good with a mean coefficient of variation of 3.9% for BMC and 3.6% for BW. In 84 infants, repositioning error was determined by repeating the measurement of BMC and BW after repositioning the arm. The correlation coefficients between measurements before and after repositioning the arm were 0.97 for BMC and 0.95 for BW. BMC correlated well with gestational age (r = 0.92), birth weight (r = 0.89) and bone width (r = 0.92). BW also correlated with gestational age (r = 0.84) and birth weight (r = 0.85). A multiple linear regression analysis of BMC versus BW, gestational age, and birth weight was done. The correlation coefficient between the predicted BMC from these variables and measured BMC was 0.95. Photon absorptiometry can be used with high accuracy, precision, and reproducibility in vivo in newborn infants. BMC correlates with gestational age, birth weight, and bone width.

Birth Weight↗
PubMed1983

Interlaboratory variation in a commercial bone mineral analyzer.

Measurements of bone mineral content (BMC) were made in 14 different laboratories in the U.S. and four in Europe using commercially produced instrumentation (Norland Bone Mineral Analyzer) for 125I absorptiometry. A three-chambered standard (dipotassium hydrogen phosphate) was measured in each laboratory following their own calibration. The values of BMC in the middle range (0.6 g/cm) all were adequate (within +/- 2%), but the BMC values were underestimated by 5% or more in five laboratories for the largest chamber and in three laboratories for the smallest chamber. Width values were accurate (+/- 3%) over 0.7-1.6 cm. The effect of underestimating large values in clinical studies is to reduce the difference between normals and abnormals. Calibration error also may be responsible for the variable normal values found in the U.S. and Europe by some users of this instrument.

Bone and Bones↗