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Biomedical subjects

C E Cann

Publications and source records attributed to C E Cann.

At least 19 recordsLinked to original sources
PubMed1992

Description of a prototype emission-transmission computed tomography imaging system.

We have developed a prototype imaging system that can perform simultaneous x-ray transmission CT and SPECT phantom studies. This system employs a 23-element high-purity-germanium detector array. The detector array is coupled to a collimator with septa angled toward the focal spot of an x-ray tube. During image acquisition, the x-ray fan beam and the detector array move synchronously along an arc pivoted at the x-ray source. Multiple projections are obtained by rotating the object, which is mounted at the center of rotation of the system. The detector array and electronics can count up to 10(6) cps/element with sufficient energy-resolution to discriminate between x-rays at 100-120 kVp and gamma rays from 99mTc. We have used this device to acquire x-ray CT and SPECT images of a three-dimensional Hoffman brain phantom. The emission and transmission images may be superimposed in order to localize the emission image on the transmission map.

Algorithms↗
PubMed1991

Effect of bone distribution on vertebral strength: assessment with patient-specific nonlinear finite element analysis.

Three-dimensional quantitative computed tomographic (QCT) studies of the lumbar spine were extended with finite element analysis (FEA) to include bone distribution in assessment of vertebral body strength. Fifty-nine FEA models were created from data from 43 patients, 28 with no evidence of osteoporosis and 15 with previous vertebral fractures. Simulated loads were applied to the vertebral models to estimate vertebral strength. Yield strength in the models from patients with osteoporosis was 0.22-1.05 MPa (average, 0.57 MPa +/- 0.26 [mean +/- standard deviation]), compared with 0.80-2.79 MPa (1.46 +/- 0.52, P less than .001) in patients with normal bone. Yield strength of vertebrae in patients with osteoporosis uniformly fell below approximately 1.0 MPa, with minimal overlap between patients with osteoporosis and those with normal bone compared with the overlap in bone mineral content and trabecular mineral density. Reproducibility of the FEA technique was 12.1% in a subgroup of patients with normal bone. A constant relationship between cortical and trabecular contributions was observed in patients with osteoporosis but not in control patients.

Adult↗
PubMed1991

Carcinoma of the uterus: use of gadopentetate dimeglumine in MR imaging.

This prospective study assessed the role of gadopentetate dimeglumine-enhanced magnetic resonance imaging in the detection and staging of carcinomas of the endometrium and cervix. Surgical-pathologic findings were used as the standard of reference. In the evaluation of endometrial carcinoma, contrast-enhanced imaging improved tumor detection and differentiation between viable tumor and retained debris. Use of contrast material significantly improved the staging accuracy. The ability to assess the depth of myometrial invasion was also improved. In the evaluation of cervical carcinoma, assessment of tumor location and size did not improve following contrast enhancement. Use of gadopentetate dimeglumine resulted in overestimation of stromal, parametrial, vaginal, and/or bladder wall invasion in eight patients. However, evaluation of intratumoral architecture and large lesions was easier with contrast-enhanced imaging. When only stage II and higher disease was analyzed, use of contrast material improved the evaluation of disease extent. The authors conclude that gadolinium enhancement adds to the accuracy of evaluation of endometrial carcinoma but is useful in only advanced cases of cervical carcinoma.

Adenocarcinoma↗
PubMed1991

Measurement of regional cerebral blood flow using ultrafast computed tomography. Theoretical aspects.

Theoretical and practical limitations have prevented the measurement of regional cerebral blood flow using dynamic x-ray computed tomography. Development of the ultrafast computed tomography scanner has made it possible to overcome the practical limitations and measure changes in contrast concentration in the brain with excellent time and spatial resolution. By applying modifications of indicator dilution theory, we have derived a method to use these changes in contrast concentration determined using ultrafast computed tomography to measure the fractional vascular volume, mean transit time of blood, and blood flow within specific regions of the brain in a relatively simple and practical manner. This method could theoretically be used in the evaluation of physiological and pathophysiological alterations in cerebral blood flow.

Animals↗
PubMed1991

Measurement of regional cerebral blood flow in the dog using ultrafast computed tomography. Experimental validation.

The applicability, feasibility, reproducibility, and accuracy of the method of measuring regional cerebral blood flow using ultrafast computed tomography were evaluated in 25 dogs under varying physiological and pathophysiological conditions. Regional cerebral blood flow values were 75.6 +/- 29.4 ml/100 g/min (mean +/- standard deviation) for the hemisphere, 68.4 +/- 28.2 ml/100 g/min for the basal ganglia, 41.2 +/- 15.0 ml/100 g/min for the internal capsule, and 80.8 +/- 37.2 ml/100 g/min for the neocortex. Measurements made 10 minutes apart were significantly (p less than 0.05) correlated. Simultaneous measurements of regional cerebral blood flow by the microsphere and ultrafast computed tomography methods showed a significant (p less than 0.05) correlation for the hemisphere (r = 0.95), basal ganglia (r = 0.95), and neocortex (r = 0.94) but not for the internal capsule (r = 0.51). Microsphere and ultrafast computed tomography regional cerebral blood flow values were also in agreement in radiation-damaged brain with appreciable blood-brain barrier breakdown, and the two methods demonstrated similar responsiveness of regional cerebral blood flow to alterations in arterial carbon dioxide tension. The accuracy and sensitivity of the ultrafast computed tomography technique suggests that it affords a useful new tool for studying normal and abnormal regional cerebral blood flow.

Animals↗
PubMed1990

Long-term effects of tissue expansion on cranial and skeletal bone development in neonatal miniature swine: clinical findings and histomorphometric correlates.

Progressive tissue expansion induces significant gross, histologic, and bony changes in skulls and long bones of neonatal miniature swine. These bony changes consist of erosion underlying tissue expanders, with bony lipping and bone deposition at the periphery of the expander. Cranial suture lines underneath expanders appear effaced and convoluted. Serial CT scans reveal decreased bone thickness and volume (p less than 0.02) but identical bone density (p = 0.60) beneath expanders. Increased bone volume and thickness occur at the periphery of expanders (p less than 0.02). Bone density (CT number) is unaffected by tissue expansion in both cranial and long bones. These findings have histomorphometric correlates: Osteoclastic bone resorption occurs underneath expanders with periosteal reaction at the periphery of expanders. Cranial sutures are similarly affected, but no cranial synostosis results. No changes to the inner table of the skull or stigmata of increased intracranial pressure were observed either in CT scans or in behavioral changes in long-term animals. The pathophysiology of bony changes is a remodeling effect, not one of simple pressure deformation. Increased bone resorption and complete inhibition of bone formation occur until the pressure is removed. Cranial bone is significantly more affected than long bone. After removal of the expanders, reparative bone remodeling begins within 5 days and nearly complete healing of the cranial defects occurs within 2 months (p less than 0.02). No plagiocephaly results despite early coronal suture changes. On the basis of this study, we conclude that tissue expansion causes significant but reversible effects, readily monitored by high-resolution CT scans, on neonatal and infant cranial and long bones.

Animals↗
PubMed1990

Cervical incompetence: preliminary evaluation with MR imaging.

The ability of magnetic resonance (MR) imaging to demonstrate cervical incompetence in nonpregnant women was investigated in a prospective study of 41 volunteers referred in random order. These included 20 patients with normal cervices, 11 with cervical incompetence of traumatic or congenital origin, and 10 with clinically small cervices due to in utero diethylstilbestrol (DES) exposure. On MR images of the normal patients, cervical length was 33.0 mm +/- 1.0 (mean +/- standard error of the mean) and the width of the internal cervical os was 3.3 mm +/- 0.1. In patients with cervical incompetence, the cervical length did not significantly differ from those in the normal group. However, the internal cervical os was significantly wider (4.5 mm +/- 0.3, P less than .001), and localized irregularity of the endocervical canal was demonstrated in two patients. The MR appearance of the cervical stroma varied from normal, uniformly low signal intensity (n = 4) to uniformly (n = 3) or partially (n = 4) medium-to-high signal intensity on T2-weighted images. In the patients with in utero DES exposure, the mean length of the cervical canal (22.9 mm +/- 1.7) was significantly shorter than that of the normal group. The width of the internal cervical os and the MR signal intensity of the cervical stroma were normal. In summary, MR findings of a cervical length shorter than 3.1 mm (95% confidence limit), an internal cervical os wider than 4.2 mm (95% confidence limit), or abnormal signal intensity in the cervical stroma are highly suggestive of incompetent cervix and should assist in planning further therapeutic decisions.

Cervix Uteri↗
PubMed1989

Effects of simulated weightlessness on rat osteocalcin and bone calcium.

Some of the musculoskeletal changes that occur in growing rats during spaceflight are simulated by a model that selectively unloads the hindlimbs while maintaining normal weight bearing on the forelimbs. Using this model we studied the response of mineral and the mineral-binding protein osteocalcin (OC) in the third lumbar vertebra (L3) and the femoral midshaft to periods of unweighting from 2 to 28 days. Serum OC decreased by 25%, consistent with a decreased rate of bone growth, during the first week of suspension and returned toward control values after 15 days. The L3 and femur weighed 20% less than control bones after 10-28 days. OC content of L3 and femur diaphysis were lower after 7 days of suspension and returned to normal levels at 28 days, whereas Ca content rose slightly at 5 days then decreased sharply. OC:Ca ratio was also affected. The data suggest that unweighting affects formation and deposition of OC and Ca differently depending on bone location and duration of unweighting. Both serum and bone OC are highly sensitive indicators of disruption of osteoblast activity by altered skeletal loading.

Animals↗
PubMed1988

Peak trabecular vertebral density: a comparison of adolescent and adult females.

To determine when spinal bone density reaches its peak, the trabecular vertebral density was assessed, via quantitative computed tomography, among females from two age groups: (1) adolescents (aged 14-19 years; N = 24); and (2) young adults (aged 25-35 years; n =24). The adolescent girls had a higher mean trabecular vertebral density (P less than 0.01), suggesting that spinal density reaches its peak around the time of cessation of longitudinal growth and epiphyseal closure.

Adolescent↗
PubMed1988

Radiation dose response of normal brain.

Dose response relationships were determined after hemibrain x-irradiation of normal beagle dogs. Radiation doses of 11.5, 13.5, 14.3, and 17 Gy were delivered in a single dose and results were compared to previous studies using doses of 15 and 30 Gy. Brain injury was quantified using computed tomography (CT), with serial studies obtained monthly up to 1 year following irradiation. Quantitative endpoints included low density volume and contrast enhancement. Doses above 14.3 Gy resulted in high lethality 5-8 months following irradiation, and an LD50 of 14.9 Gy was calculated. At these lethal doses, low density volume representing edema, demyelination, and necrosis had a similar response with an ED50 of 14.6 Gy. Radiation-induced decreases in white matter density appeared 5-6 months after sublethal doses (less than or equal to 14.3 Gy) and the volume of tissue characterized by this low density increased with time and dose. This sublethal low density change had an ED50 of 12.8 Gy, and may reflect a loss or generalized atrophy of glial cells and/or myelin. These results show that: (a) the dose response curves obtained after hemibrain x-irradiation are extremely steep; and (b) at least two processes may be involved in the development of late radiation damage, one that is rapid upon onset (a "delayed acute" reaction) and the other which is a slower and more degenerative process.

Animals↗
PubMed1988

Craniomandibular bone density in the primate as assessed by computed tomography.

Ten normal rhesus monkeys, five juvenile and five adult animals, were analyzed for symmetry in bone density across the cranioskeleton with computed tomography (CT). Fifty contiguous axial CT scans were done using 1.5-mm thick scans between the lower mandibular border and inferior orbital ridge, and 3-mm thick scans from the inferior orbital ridge to the rostral level of insertion of the temporalis muscle. Eleven regions comprising areas of the lower mandibular border, lower ramus, upper ramus with condyle, the coronoid process, the zygomatic arch, and cranial bone were analyzed for symmetry using small regions of interest. Only one region, the condyle, demonstrated a statistically significant difference between the two sides with all other measured sites demonstrating the same bone mineral density bilaterally. Large area analysis of five regions--the lower mandibular border, upper ramus with condyle, the coronoid process, the zygomatic arch, and upper cranium--demonstrated no significant difference in the distribution of CT numbers. This analysis of bilateral distribution of bone density in the primate craniofacial skeleton demonstrates a basic symmetry that can be used to study altered patterns of neuromuscular function and their effects on bone density.

Aging↗
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↗