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Biomedical subjects

C H Chesnut

Publications and source records attributed to C H Chesnut.

At least 55 records · Page 3Linked to original sources
PubMed1992

A comparison of two dual-energy X-ray absorptiometry systems for spinal bone mineral measurement.

Two dual-energy X-ray absorptiometry (DEXA) systems--the Hologic QDR-1000 and the Norland XR-26 bone densitometers--were evaluated in terms of precision, accuracy, linearity of response, X-ray exposure, and correlation of in vivo spinal measurements. In vitro precision and accuracy studies were performed using the Hologic anthropomorphic spine phantom; linearity of response was determined with increasing thicknesses of aluminum slabs and concentrations of Tums E-X in a constant-level water bath. Both systems were comparable in precision, achieving coefficients of variation (CVs) of less than 1% in bone mineral content (BMC, g), bone area (cm2), and bone mineral density (BMD, g/cm2). Both were accurate in their determination of BMC, bone area, and BMD with reference to the Hologic spine phantom. Both systems also showed good BMC and BMD linearity of response. Measured X-ray skin surface exposures for the Hologic and the Norland systems were 3.11 and 3.02 mR, respectively. In vivo spinal measurements (n = 65) on the systems were highly correlated (BMC: r = 0.993, SEE = 1.770 g; area: r = 0.984, SEE = 1.713 cm2; BMD: r = 0.990, SEE = 0.028 g/cm2). In conclusion, both systems are comparable in terms of precision, accuracy, linearity of response, and exposure efficiency.

Absorptiometry, Photon↗
PubMed1991

In vitro comparability of dual energy X-ray absorptiometry (DEXA) bone densitometers.

Six Hologic QDR-1000 DEXA bone densitometers at different centers across the USA were compared to determine the intermachine variability. Nine scans in succession were acquired on each machine using a single anthropomorphic lumbar spine phantom (manufactured by Hologic). Values for BMC, area, and BMD were recorded for each measurement. Means, standard deviations (SD), and coefficients of variation (CV) were calculated for each machine. All the CVs (BMC, area, BMD) were less than 1% (range 0.3%-0.6%). The CV of the means at the six sites were 0.4%, 0.6%, and 0.5% for BMC, area, and BMD, respectively. Although several significant differences for BMC, area, and BMD were noted by ANOVA between machines at different sites, the difference between the highest and lowest means of the individual machines was only 1.1%, 1.31%, and 1.07% for BMC, area, and BMD. The small variations between the DEXA systems are encouraging for researchers involved in multicenter trials in which data are pooled.

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

Bone density changes during pregnancy and lactation in active women: a longitudinal study.

Six healthy active women, aged 28-34, had bone mineral density (BMD) measured (DPA & SPA) at seven sites prior to pregnancy, within 6 weeks of parturition, and after 6 months of lactation. Twenty-five nonpregnant women of the same age, height, weight, activity level and calcium intake were tested during the same period. Average calcium intake during pregnancy was 1526 mg/day; during lactation, 1622 mg/day. The nonpregnant women averaged 1756 mg/day. BMD decreased in the femoral neck (P less than or equal to 0.05) and radial shaft (P less than or equal to 0.05) during pregnancy but increased in the tibia (P less than or equal to 0.05). A 3.3% decrease in lumbar BMD during pregnancy returned to pre-pregnancy values during lactation. Bone loss at the femoral neck continued during lactation (P less than or equal to 0.05). Changes in BMD during pregnancy and lactation may represent changes in mechanical stress as a result of weight gain, changes in posture and/or activity, or some other factor specific to this population of active women.

Absorptiometry, Photon↗
PubMed1991

Exacerbation of rheumatoid arthritis by sodium fluoride treatment of osteoporosis.

Recent studies have suggested that sodium fluoride therapy may be an effective treatment for vertebral osteoporosis. Unfortunately, the high frequency of side effects may limit the use of this treatment modality. This report documents the repeated exacerbation of rheumatoid arthritis on three occasions after the initiation of sodium fluoride therapy. This apparent complication of sodium fluoride treatment may be mediated by stimulation of leukocyte production of reactive oxygen species and other mediators of the acute inflammatory response. We suggest that sodium fluoride should be used cautiously in patients with rheumatoid arthritis.

Aged↗
PubMed1990

Menstrual history as a determinant of current bone density in young athletes.

The relationship of prior menstrual irregularities and current menstrual status to the bone density of 97 young athletes was determined at seven sites using single- and dual-photon absorptiometry. Menstrual patterns were ranked on a scale of 1 to 9 in terms of their potential adverse affect on bone. Only vertebral density was significantly related to menstrual patterns (r = -.43). Women who had always had regular cycles had higher lumbar densities (1.27 g/cm2) than those with a history of oligomenorrhea/amenorrhea interspersed with regular periods (1.18 g/cm2). The lumbar density of both groups exceeded that of women who had never had regular cycles (1.05 g/cm2). Body weight became more important as a predictor variable as the severity of menstrual irregularities increased. The combination of menstrual pattern and body weight predicted 43% of the total variation in lumbar density. These data suggest that extended periods of oligomenorrhea/amenorrhea may have a residual effect on lumbar bone density.

Adolescent↗
PubMed1990

Relationships between mandibular and skeletal bone in a population of normal women.

In this study, we measured mandibular bone mass and density and cortical thickness at gonion in 50 normal women between the ages of 20 and 90. The subjects showed neither radiographic nor metabolic evidence of osteoporosis. Comparisons (by age) were made between mandibular measurements. Mandibular measurements were also compared with measurements of bone mass in the spine and the wrist. Mandibular bone mass was not significantly affected with age but mandibular bone mass was significantly correlated with skeletal bone mass. Cortical thickness at gonion decreased with age.

Absorptiometry, Photon↗
PubMed1990

Factors that influence peak bone mass formation: a study of calcium balance and the inheritance of bone mass in adolescent females.

We suggested that calcium may be an important determinant of peak bone mass. For further elucidation, calcium balances in adolescent females with different calcium intakes (270-1637 mg/d), and a 2-y intervention study of calcium supplementation were performed. Hereditary influences on bone status were also evaluated by comparing subjects' and parents' bone mass. The main determinant of calcium balance was calcium intake; net calcium absorption increased with intake and urinary calcium did not change. Adolescent females retained 200-500 mg Ca/d, suggesting that inadequate calcium intake may translate into inadequate calcium retention and a reduction in peak bone mass. There was a more pronounced increase in bone mass over time in the calcium-supplemented group (1640 mg Ca/d) than in the control group (750 mg Ca/d), but the differences between bone mass measurements were not statistically significant, possibly because of a type II error. By the age of 16 y daughters had accumulated 90-97% of the bone mass of their premenopausal mothers.

Adolescent↗
PubMed1989

Osteoporotic bone fragility. Detection by ultrasound transmission velocity.

We evaluated ultrasound transmission velocity at the patella as an indicator of osteoporotic fragility in 293 nonobese women. Osteoporosis was defined by atraumatic vertebral compression deformity. Ultrasound velocity averaged 1954 +/- 71 (+/- SD) m/s in premenopausal normal women and declined significantly with age after menopause, largely independently of age-related loss of spine bone mass. Postmenopausal osteoporotic women had lower velocities than normal women (-76 m/s). After allowing for slight differences in age between the groups, the difference (-54 m/s) was still significant. Women with velocities below 1825 m/s were about six times more likely to have one or more fractures than women with velocities about that level. By sensitivity-specificity analysis, ultrasound velocity discriminated between normal and osteoporotic women as well as direct measurement of spine bone mass. Ultrasound velocity measures both bone mass and a component of bone fragility distinct from decreased mass; it is a potentially valuable new tool for evaluating women for osteoporotic fragility.

Adult↗
PubMed1989

Calcitriol treatment is not effective in postmenopausal osteoporosis.

STUDY OBJECTIVE: To determine if calcitriol is an effective treatment in postmenopausal osteoporosis. DESIGN: Double-blind, randomized clinical trial of 2 years' duration. SETTING: University medical center with patients recruited by media announcements. PATIENTS: Eighty-six postmenopausal women with vertebral compression fractures. INTERVENTIONS: Patients were treated with calcitriol or placebo. Mean dose was 0.43 micrograms/d. Dietary calcium was 1000 mg/d (24.9 mmol/d). The medication dose and dietary calcium were adjusted for hypercalciuria or hypercalcemia. MEASUREMENTS AND MAIN RESULTS: No significant differences between placebo and control groups were seen in the percent change in total body calcium (0.4% +/- 1.0 compared with 0.0% +/- 0.9), single photon absorptiometry (-0.5% +/- 1.2 compared with -3.1% +/- 0.9) or dual photon absorptiometry (0.0% +/- 1.7 compared with -1.0% +/- 2.2). New fractures were seen in 16% of the placebo group and 26% of the calcitriol groups, so the difference in percent fractures was 10% (95% CI, -5.7% to 25.7%). Bone biopsies did not show changes in either group. The calcitriol group had significantly higher serum and urine calcium values, but renal function was not worse than in the placebo group. CONCLUSIONS: Calcitriol is not an effective treatment for established postmenopausal osteoporosis.

Aged↗
PubMed1989

Relationships between mandibular and skeletal bone in an osteoporotic population.

This study attempted to determine relationships between bone mass in the mandible and skeletal bone mass in a group of 85 postmenopausal women with osteoporosis. Mandibular bone mass was determined by microdensitometry, cortical thickness at the gonion, the height of the alveolar ridge in subjects who were edentulous, and periodontal probings. Skeletal measures were made up of total body calcium, bone mass at the radius, and the two newer bone mass measures of dual photon and computed tomography of the vertebrae. The height of the edentulous ridge correlated with total body calcium and mandibular mass. Most of the edentulous patients had ridges that were extremely resorbed. Mandibular mass correlated with all skeletal measures.

Aged↗
PubMed1988

Mineral loss in the parenteral nutrition patient.

The impact of parenteral nutrition on mineral loss was examined in 11 long-term (10-79 mo) and 6 short-term (1-8 mo) patients. In the long-term patients, there was a significant (p less than or equal to 0.02) urinary loss of calcium and magnesium during infusion compared with periods off infusion. The magnitude of urinary excretion of these minerals was much lower than in previously reported series and in short-term patients. Despite this, in long-term patients the mean bone mass at the spine was lower than normal (p less than 0.001) but mean bone mass at the wrist was not. Current data suggest that hypercalciuria is not a consistent feature of parenteral nutrition. Furthermore, osteopenia is a feature of some long-term parenteral nutrition patients.

Adult↗
PubMed1988

Comparisons among methods of measuring bone mass and relationship to severity of vertebral fractures in osteoporosis.

Several techniques are now available for quantitation of bone mass, including total body calcium by neutron activation analysis (TBC), single and dual photon absorptiometry at the radius and spine, respectively (SPA and DPA), quantitative computed tomography of the spine (QCT), and cancellous bone volume from iliac crest bone biopsies. The aims of this study were to assess the correlation among these techniques and to determine if bone mass correlated with height loss or the severity of vertebral fractures in osteoporotic women. These measurements were performed in the same group of women (n = 122) with postmenopausal osteoporosis. TBC, SPA, DPA, and QCT correlated significantly with each other (r = 0.33-0.76). The correlation between QCT and DPA improved significantly (r = 0.33-0.57; P = 0.02) when integral QCT was used instead of the usual QCT of the central vertebra. The correlation was not improved by expressing DPA in different dimensions, but was improved by including normal women. Multiple linear regression analysis showed that TBC was predicted better using SPA, DPA, and QCT than by any single variable. Cancellous bone volume correlated weakly (r = 0.10-0.26) to the other measurements. Height loss and fracture index correlated significantly with each other (r = 0.66; P less than 0.001), but the correlations with bone mass measurements were weak (r = -0.09 to -0.47). For each patient, a bone mass index was defined using z scores from the SPA, DPA, QCT, and TBC measurements; this index correlated inversely with the fracture index (r = -0.29; P = 0.009). This correlation was not significant when controlled for age. Thus, bone mass measurements correlate moderately well with each other, but poorly with severity of fracture. Other factors in addition to low bone mass may be important in determining whether bone will fracture.

Adult↗
PubMed1987

Ability of four different techniques of measuring bone mass to diagnose vertebral fractures in postmenopausal women.

Since bone mass has been shown to be an important determining factor of fractures in vitro, we undertook a study to evaluate whether bone mass measurements could separate postmenopausal women with vertebral compression fractures from women of a similar age without fractures. We also wanted to see if methods of measuring bone mass at the spine would be more sensitive or specific than methods that measured bone at the wrist or the entire skeleton. The techniques used were: total body calcium by neutron activation analysis (TBC), single photon absorptiometry (SPA), dual photon absorptiometry (DPA), and quantitative computed tomography (QCT). Normal women aged 20-85 were measured, but only those greater than 50 yr were used in the analysis. Mean values for women with fractures were significantly lower than normals (p less than .001): TBC 642 +/- 103 g vs. 764 +/- 114; SPA .658 +/- .134 g/cm vs. .779 +/- .142; DPA 3.75 +/- .82 g/cm vs. 4.37 +/- .86; QCT 59.0 +/- 25.7 mg/cc vs. 92.6 +/- 36.0. However, each of the methods showed considerable overlap between women with and without fractures. At 90% specificity the sensitivities of the tests were: TBC 34%; SPA 29%; DPA 33%; QCT 36%. When values were expressed as the % expected (based on age and height) then the sensitivities were: TBC 52%; SPA 36%; DPA 35%; QCT 44%. Using Bayes' theorem, we constructed curves showing the posttest probability of these tests at a prevalence of 20%. None of these bone mass measuring techniques showed complete separation between normal and osteoporotic women with fractures; about one-half of the women with fractures were below the normal range. The risk of having a fracture increases as bone mass declines, but our data suggest that bone mass is not the only factor leading to vertebral fractures in postmenopausal women.

Adult↗