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Biomedical subjects

C E Cann

Publications and source records attributed to C E Cann.

At least 37 records · Page 2Linked to original sources
PubMed1988

Brisk walking does not stop bone loss in postmenopausal women.

The rate of loss of spinal trabecular mineral density (TMD) in postmenopausal women, 49-64 years, was measured during a 52 week walking program. The 8 women who walked were 5.6 +/- 4.4 years past menopause (mean +/- SD) compared to 6.5 +/- 5.1 for 9 nonwalkers. Walkers participated in a progressive walking program for 15-40 min at a heart rate of between 60-85% of maximal age adjusted heart rate, 3 days per week for 52 weeks. Spinal trabecular mineral density was measured using quantitative computed tomography at entry, 6 and 12 months. Pre-exercise heart rate in the walkers decreased 7.8 +/- 1.7 beats per min (mean +/- SEM) (p less than 0.01) from week 0 to week 52, while post-exercise heart rate did not change. Initial spinal mineral density in the walkers was 114 +/- 18 mg/cm3 (mean +/- SD) and 98 +/- 19 mg/cm3 in the controls (NS). Bone loss was 5.6 +/- 1.4% (mean +/- SEM) in the walkers and 4.0 +/- 1.2% in the controls; both of these losses were significantly different from zero (p less than 0.005, p less than 0.01, respectively), but they were not different from each other. Our study shows that a moderate brisk walking program of one year duration does not prevent the loss of spinal bone density in early-postmenopausal women.

Body Weight↗
PubMed1988

Quantitative CT for determination of bone mineral density: a review.

One of the major uses of quantitative computed tomography (CT) has been the measurement of bone mineral density (BMD) at various skeletal sites. The published literature on this subject from 1974 to the present is extensive. Because many investigators and clinicians are just now starting to explore the utility of this technique, the author reviewed this literature to provide both the historic perspective and current status of BMD measurement with CT. The physical and physiologic bases of the method, accuracy, reproducibility, radiation dose, and clinical utility are all discussed.

Bone and Bones↗
PubMed1988

Circulating osteocalcin in rats is inversely responsive to changes in corticosterone.

Decreased bone formation in rats during spaceflight may be attributable to corticosteroid excess induced by environmental factors other than weightlessness that are associated with spaceflight experiments. To determine whether decreased osteocalcin, which may reflect altered bone formation rate, could be associated with corticosteroid excess, we measured serum osteocalcin in rats after injection of corticosterone or in response to various environmental stimuli. Exogenous steroid elicited a time- and dose-related decrease in serum osteocalcin, which was significant within 1 h of administration and maximally 25% below controls 1.5 h after injection of 3.3 mg corticosterone/kg body wt, the highest dose we tested. Adrenalectomy resulted in a 38% increase in osteocalcin. Exposure to environmental stressors lasting from 1.5 h to 3 wk also resulted in decreased osteocalcin levels, which showed a strong negative correlation (P less than 0.001) with serum corticosterone levels and adrenal mass after 1-3 wk of chronic cold exposure. Changes in serum osteocalcin were maximally about +/- 40% after 3 wk of chronic exposure to steroid excess or depletion. The response of osteocalcin to the well-defined adrenal hormone system implies an important role for corticosteroids in the control of serum osteocalcin.

Adrenal Glands↗
PubMed1988

CT densitometry of pulmonary nodules in a frozen human thorax.

The influence of (1) calcium concentration, (2) exposure technique, (3) reconstruction algorithm, (4) nodule size, and (5) nodule location on the CT attenuation values (CT density) of pulmonary nodules was examined in a frozen human thorax. Nodules with calcium concentrations of 0-310 mg/ml and diameters of either 0.95 or 1.59 cm were inserted into a frozen, unembalmed human thorax. The nodules were placed either at the lung apex or 4 cm below the tracheal carina. Each nodule was scanned on a GE CT 9800 scanner; five different exposure techniques were used. The slice thickness was uniformly 1.5 mm. As expected, increasing the kilovoltage caused a significant decrease in CT nodule density in all nodules with calcium concentrations greater than 80 mg/ml. The inverse relationship between kilovoltage and nodule density was exaggerated with increasing calcium concentration. A high-resolution (bone) algorithm gave a significantly higher CT number than did a smoothed (standard) algorithm, regardless of nodule size and location, but this difference could be attributed almost entirely to the edge-enhancement effect of the bone algorithm. The CT density of the larger nodules was significantly higher than that of the smaller nodules at calcium concentrations greater than 65 mg/ml for both standard and bone algorithms. Densities were significantly higher in the mid lung than in the apex with a standard algorithm, but this was not the case with a bone algorithm. The GE CT 9800 scanner had a linear response between CT density and increasing calcium concentration within the confines of a human thorax. A high-resolution (bone) reconstruction algorithm has higher spatial resolution but does show an edge-enhancing effect not found with the smoothed algorithm. Two major variables in CT densitometry for pulmonary nodules are the kilo electron voltage of the X-ray beam and the reconstruction algorithm used; these two parameters should be standardized, with a high kilovoltage and high-resolution algorithm favored on the GE CT 9800 scanner.

Absorptiometry, Photon↗
PubMed1987

Quantitative CT applications: comparison of current scanners.

Quantitative computed tomography (QCT) has been used with variable success to measure the density of lung nodules, bone, and kidney stones and to determine volumes of tumor. Commercially available CT scanners vary in their ability to quantify high-atomic-number (high-Z) and low-Z components accurately and reproducibly. Sixteen models of CT scanners from eight manufacturers were compared as to their capability for QCT. Field uniformity was determined in phantoms simulating the human torso. For high-Z (250 HU) materials, the difference in CT numbers from the center to a radial distance of 13 cm ranged from 1 to 50 HU (mean, 15 HU); for water, the range was 0-15 HU. Accuracy of computed radiographic localizer systems ranged from +/- 0.5 to +/- 2.0 mm without gantry angulation and up to +/- 4 mm with an angled gantry. A variety of artifacts also reduced QCT accuracy and reproducibility. Thus, not all CT scanners are equally suited to QCT, and results on one machine may not be comparable to those of another unless correction factors are used.

Tomography, X-Ray Computed↗
PubMed1987

Pseudarthrosis following lumbar fusion: detection by direct coronal CT scanning.

Twenty patients with fusions of the lumbar spine (seven with pseudarthrosis, 11 with solid bony fusions, and two with fusions that appeared solid but assessment was complicated by the presence of surgical hardware) underwent computed tomographic (CT) scanning in the supine position in the axial plane and, employing a specially designed seat, in the coronal plane. Three-millimeter contiguous sections were acquired. The direct coronal images were compared with those reformated from the axial images. The higher-resolution direct coronal images facilitated the diagnosis of pseudarthrosis and increased confidence in interpretation of normal studies. Direct coronal imaging is easy to perform and in many cases requires fewer scans and less radiation than reformations. Because it provides more useful diagnostic information, direct coronal imaging should replace current methods for evaluating fusions of the lumbar spine.

Adult↗
PubMed1987

Fragility and composition of growing rat bone after one week in spaceflight.

To gain some insight into the early effects of spaceflight on skeletal metabolism, we quantified the major chemical constituents and a noncollagenous protein, osteocalcin, in the third-lumbar vertebrae and humeri from 8-wk-old rats that were part of the 7-day NASA Spacelab 3 flight experiments. The ratio of calcium to hydroxyproline in the humeral diaphysis increased from 8.5 in preflight to 9.8 in ground simulation control and only to 8.9 in flight bones. There was no demonstrable change in the fraction of nonmineralized collagen. Osteocalcin content was reduced in the humerus and vertebra. Reduced accumulation of mineral and osteocalcin with no associated decrease in collagen in flight animals suggests that both mineralization and collagen metabolism are impaired in growing animals during spaceflight within a few days after launch. Strength tests of the humeri of flight rats showed substantial deficits that appeared to be related, not only to the reduced bone mass, but also to the composition and quality of new bone formed.

Animals↗
PubMed1987

Postmenopausal bone loss is prevented by treatment with low-dosage estrogen with calcium.

Bone mass was measured prospectively in 73 women during the period immediately after menopause. By comparing the rates of loss at three skeletal sites, we assessed the protective effects of calcium supplements given alone or combined with low-dosage estrogen therapy. After 2 years of follow-up, spinal trabecular mineral content, measured by quantitative computed tomography, decreased by a mean of 9.0% (p = 0.002 compared with baseline) in untreated women and a mean of 10.5% (p = 0.0001) in women given calcium supplements alone. By contrast, women given conjugated estrogens, 0.3 mg/d, with calcium supplements showed an insignificant increase of 2.3%. Significant losses of a lesser magnitude were seen in the appendicular cortical skeleton of women not receiving therapy and in those receiving calcium alone, but no significant changes were observed in women receiving estrogen with calcium.

Bone and Bones↗
PubMed1986

Contrast enhancement of brain tumors and irradiated normal brain: a comparison of iohexol and iothalamate.

The nonionic contrast agent iohexol was compared with the ionic agent iothalamate for contrast enhancement of brain tumors and radiation brain damage in dogs. Tissue enhancement during infusion of contrast and 5, 10, 15 and 30 min later was measured using quantitative computed tomography. Blood iodine was measured using x-ray fluorescence. Peak contrast enhancement occurred during infusion in tumors and after 5 min in irradiated normal brain for both contrast agents. Absolute uptake of contrast in each lesion was the same for both agents when normalized to total grams of iodine administered. Blood iodine levels were slightly but not significantly higher using iohexol. The reduced osmotic load and similar contrast enhancement of lesions suggest that the nonionic contrast medium iohexol may be a useful agent for routine CT of the brain.

Animals↗
PubMed1986

Direct coronal and direct sagittal CT of abdomen and pelvis: an approach to staging malignancies.

Direct coronal and sagittal CT images are of high quality and are applicable to a majority of patients in daily practice. Because of the fact that transverse scans alone can be misleading, direct CT images in two or more different planes greatly enhance one's capability to stage neoplasms that are complex and extensive. The integrity of the margins of an organ, in the presence of tumor, is best determined by coronal or sagittal scanning. Lesions of the adrenal and kidney and retroperitoneal processes with possible extension into liver or other adjacent organs can be evaluated best using the combination of transverse and coronal or sagittal scans of the upper abdomen. Depending on the origin of pelvic lesions, the radiologist must consider in every individual case the performance of either direct coronal or sagittal sections or both. This judgment is based on the findings on the transverse scans, understanding of anatomic relationships of the pelvic viscera and knowledge of staging systems and their implications with respect to therapeutic decisions. In such a tailored approach, multiplanar CT facilitates improved presurgical evaluation. In some cases, the true extent of the lesion can only be seen in the coronal or sagittal planes. A potential new role for direct multiplanar CT is that it may be used as a sort of "gold standard" for the analysis of multiplanar ultrasound and MRI studies.

Abdominal Neoplasms↗
PubMed1986

Normal brain iodine-125 radiation damage: effect of dose and irradiated volume in a canine model.

High-activity iodine-125 sources in plastic catheters were surgically placed in the cerebral white matter of healthy beagle dogs and later removed. Reference doses, calculated at a point 0.75 mm from the source, ranged from 10 to 40 Gy. Necrosis, vascular-related damage, and edema were quantified by computed tomography. Volumetric analyses were used to derive the relationship of dose and dose rate to necrosis and contrast enhancement. The extent of necrosis was related to irradiated volume; a minimum effective dose averaging 180-200 Gy was required to induce this type of damage. Contrast enhancement was less dependent on irradiated volume or total dose. The extent of radiation-induced edema was directly related to the volumes of necrosis plus contrast enhancement. Noninvasive serial studies in a well-characterized in vivo model can address specific clinically related questions on damage to normal tissue after interstitial irradiation.

Animals↗
PubMed1985

Quantitative computed tomography for prediction of vertebral fracture risk.

Vertebral trabecular mineral content and peripheral cortical bone mineral were measured in 94 female and 44 male osteoporotic patients and compared to vertebral mineral values obtained for 323 control subjects in a cross-sectional study. The rate of change of spinal trabecular mineral with age (measured by quantitative computed tomography) in control females averaged 1.2% per year from age 20 to 80, with an accelerated loss demonstrated at the menopause. Trabecular bone mass in male controls declined an average 0.72% per year. Female osteoporotics had a mean decrement of 48 mg cm-3 (39%) compared to age-matched controls, whereas males were decreased 66 mg cm-3 (50%). Radial cortical bone was correlated with spinal mineral in osteoporotics for both males (r = 0.48) and females (r = 0.62). Vertebral compression fractures or wedging was generally absent in patients with vertebral mineral values above 110 mg cm-3, whereas almost all patients with values below 65 mg cm-3 had fractures. Quantitative computed tomography for measurement of vertebral trabecular bone mineral density is useful for defining those patients in whom the risk of vertebral fracture is increased.

Adult↗
PubMed1985

CT measurement of the diameter of spinal and other bony canals: effects of section angle and thickness.

The effects of section angle and thickness on the measurement of spinal canal diameter by computed tomography (CT) were tested. A phantom of three spinal canals was constructed of three Lucite rods of different diameters, each covered with 1.8-mm-thick Teflon. A second phantom was constructed of two Lucite rods of the same diameter covered with 1.8- and 8.8-mm-thick Teflon, respectively. CT sections 10, 5, and 1.5 mm thick were obtained at various angles relative to the transverse plane of each canal. Anteroposterior diameters were measured at bone window settings using a standard software package and a method that uses a CT-number profile. Results show that sections obtained at an angle to the transverse plane of the canal do not always overestimate its diameter, as previously suggested, but can make it appear artifactually stenotic. The effect is from volume averaging and is most marked when thick, severely angled sections are used.

Humans↗
PubMed1985

Metrizamide CT myelography in cervical myelopathy and radiculopathy: correlation with conventional myelography and surgical findings.

Conventional myelography, metrizamide computed tomographic (CT) myelography, and surgical findings were correlated in 30 patients with cervical radiculopathy and/or myelopathy. In 60% of patients, metrizamide CT myelography provided significant additional information including better characterization of the abnormality, lateralization if the conventional myelogram was indeterminate, more definitive demonstration of cord atrophy, foraminal narrowing not appreciated on myelography, and demonstration of abnormalities distal to a myelographic block. In no case was a myelographic abnormality not detected on metrizamide CT myelography. In patients with cervical myelopathy, a cross-sectional diameter of the cord equaling less than 50% of the subarachnoid space is predictive of poor patient response to surgical intervention.

Adult↗
PubMed1985

Long-term estrogen replacement therapy prevents bone loss and fractures.

Although several case-control studies have shown an inverse association between postmenopausal estrogen use and fractures, quantitation of fracture incidence has been lacking. To quantify the degree to which estrogen replacement therapy prevents postmenopausal osteoporosis, a retrospective study was done comparing the occurrence of fractures in 245 long-term estrogen users and 245 case-matched controls, followed for an average of 17.6 years. Quantitative bone mineral assessments were obtained from 18 women using estrogen replacement therapy and their controls (average age, 73 years). Osteoporotic fracture incidence in estrogen users was 50% as great as in the controls (p less than 0.01). Estrogen users showed significantly greater bone mineral: 54.2% greater spinal mineral (p less than 0.0002), 19.4% greater forearm mineral (p less than 0.0005), and 15.6% greater metacarpal cortical thickness (p less than 0.005). Long-term estrogen replacement therapy confers significant protection against bone loss and fracture.

Bone Resorption↗