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Biomedical subjects

C E Cann

Publications and source records attributed to C E Cann.

At least 73 records · Page 4Linked to original sources
PubMed1982

Computed tomography of orbital tumors in the dog.

Computed tomography (CT) was used to investigate orbital tumors in 3 dogs. Tumors were clearly defined on transverse CT scans by their inherent density and gross distortion of normal orbital anatomy. Dorsal images synthesized from the original transverse scans were also used to visualize size and extent of tumors. Use of an iodinated contrast medium did not appear to improve localization of tumors in the orbit but was useful for identification of tumor extension into the calvaria. It was concluded that CT offered advantages over existing methods of radiographic diagnosis of orbital tumors and exophthalmos.

Animals↗
PubMed1982

High-resolution computed tomography for the comparative study of fossil and extant bone.

Special methods have been developed to use computed tomography (CT) for 3-dimensional imaging of both fossil and extant bones. Most commercial CT scanners cannot display the internal structure of fossils because the very high density is beyond the upper limits of the normal CT number scale (Hounsfield scale) of the scanners. X-ray projections from CT scans of fossils were modified by scaling the data to provide an expanded CT number scale, allowing the internal structure of highly fossilized objects to be visualized. These images were compared with state-of-the-art, high-resolution CT images of extant bone. Special image reformatting software was used to provide qualitative and quantitative 3-dimensional imaging. The recent rapid advances in CT technology have made this imaging modality the procedure of choice in much of diagnostic radiology. Use of this tool in paleoanthropology has been limited in the past by restricted access to scanners. However, new developments in CT will make this technique available to many researchers in the near future.

Animals↗
PubMed1982

CT densitometry of pulmonary nodules: a phantom study.

Density determinations by computed tomography (CT) have been used to distinguish benign from malignant pulmonary nodules. Unfortunately, clinical scanning of pulmonary nodules frequently yields artifactually low CT numbers because of partial volume artifacts from the surrounding aerated lung. In order to determine the best performance that can be expected from a CT scanner in providing CT numbers for pulmonary nodules free of partial volume artifacts, we scanned a phantom containing plastic spheres surrounded by air to simulate nodules in aerated lung. The relations among size of the sphere, slice thickness (collimation), and centering of the CT slice critically affected the number of accurate voxel values. A simple computer model accurately duplicated the experimental findings. These data enable us to define the basic geometric requirements for accurate CT densitometry of pulmonary nodules.

Densitometry↗
PubMed1982

Quantitative evaluation of the canine brain using computed tomography.

Methods have been developed for the quantitative evaluation of the canine brain using computed tomography (CT). Sixteen studies in 10 adult Beagle dogs were used to define the precision for densitometry and dynamic studies in the normal canine brain. For various regions of the brain, intraanimal and interanimal variability was determined for normal tissue CT number, contrast enhancement, and parameters relating to blood flow and blood volume. High precision was obtained for densitometry both within and among animals when evaluated over a 9 month period. Both intra- and interanimal variability in dynamic measurements was relatively large between studies, but hemispheric comparisons within a given study and between studies showed high precision. These methods can be used to evaluate morphologic and physiologic changes in the canine brain following radiation or other cytotoxic treatments.

Animals↗
PubMed1982

Pelvimetry by digital radiography: a low-dose examination.

Digital radiographs obtained with a CT scanner were evaluated as an alternative to conventional pelvimetry. Dosimetry studies demonstrated an absorbed radiation dose of 22 mrad for each digital radiograph, approximately 3% of the dose for comparable standard radiographs. Distance measurements were accurately made on digital radiographs and axial CT sections by cursor placement and a computer program with no needs to correct for magnification. Clinical studies of 10 patients confirmed that pelvimetry using digital radiographs is an accurate, simple, and extremely low-dose procedure which could replace the conventional method.

Breech Presentation↗
PubMed1982

Radiation effects in the canine brain evaluated by quantitative computed tomography.

Quantitative computed tomography (QCT) and histopathology were used to assess the effects of large single doses of x irradiation on the normal canine brain. Measurable changes demonstrated by QCT included increased contrast enhancement and enlargement of the lateral ventricles, which were observed prior to any clinical signs. The results suggest that QCT methods are effective in the noninvasive evaluation of radiation-induced brain injury.

Animals↗
PubMed1982

Computed tomographic scanning in children: II. An updated comparison of radiation dose and resolving power of commercial scanners.

Surface and internal radiation doses for abdominal CT of children were determined using child-sized phantoms and seven commercial models of CT body scanners. High contrast resolving power and low contrast discrimination for each scanner were determined simultaneously with radiation dose measurements and the results were compared with those from a similar study conducted in 1977 with earlier CT models. The average circumferential surface doses for simulated pediatric CT body examinations were 31% lower in this study compared to 1977 results, with a mean of 1.5 rad (0.015 Gy) vs. 2.2 rad (0.022 Gy) respectively. At the same time, resolving power for high (12%) contrast improved by 31% to a mean of 1.38 mm from 2.00 mm. All scanners in the present study could resolve low contrast differences of 1/4% for a 5 mm object.

Child↗
PubMed1982

Dynamic CT scanning of spinal column trauma.

Dynamic sequential computed tomographic scanning with automatic table incrementation uses low milliampere-second technique to eliminate tube cooling delays between scanning slices and, thus, markedly shortens examination times. A total of 25 patients with spinal column trauma involving 28 levels were studied with dynamic scans and retrospectively reviewed. Dynamic studies were considerably faster than conventional spine examinations and yielded reliable diagnoses. Bone disruption and subluxation was accurately evaluated, and the use of intrathecal metrizamide in low doses allowed direct visualization of spinal cord or radicular compromise. Multiplanar image reformation was aided by the dynamic incrementation technique, since motion between slices (and the resulting misregistration artifact on image reformation) was minimized. A phantom was devised to test spatial resolution of computed tomography for objects 1--3 mm in size and disclosed minimal differences for dynamic and conventional computed tomographic techniques in resolving medium-to-high--contrast objects.

Adult↗
PubMed1982

Quantitative computed tomography of vertebral spongiosa: a sensitive method for detecting early bone loss after oophorectomy.

We assessed serially the bone mineral loss in 37 premenopausal women for 24 months after oophorectomy and determined the dose-response for conjugated estrogen therapy in preventing this loss. Spinal cancellous bone was measured by quantitative computed tomography and measurement of appendicular cortical bone by radial photon absorptiometry and metacarpal radiogrammetry. For the placebo and low-dose treatment groups, the mean annual bone mineral losses were 7% to 9% from the vertebral spongiosum and 1% to 3% from the peripheral cortex. The correlation between axial and appendicular loss was weak (r = 0.581), precluding a reliable estimate of spinal loss from peripheral measurements. For the maximal-dose group (0.6 mg/d), the mean annual bone mineral losses were less than 0.5% from the axial and appendicular sites, and were not significant. The results indicate that spinal quantitative computed tomography provides a highly sensitive measurement of bone mineral loss after oophorectomy, that bone mineral loss is five- to sevenfold greater from the spinal spongiosum than from the appendicular cortex, and that conjugated estrogen in doses of less than 0.6 mg/d are inadequate to prevent the vertebral mineral loss.

Adult↗
PubMed1981

Volumetric CT analysis of hepatic tumors.

Current methods of measuring hepatic volume and the percent of hepatic parenchyma replaced by tumor are crude, yet clinical decisions are often based on these imprecise measurements. We describe a new computed tomographic (CT) assisted volume calculatory program to accurately assess hepatic volume and a new computer program to discriminate tumor from normal liver and thus provide tumor volume measurements. The potential usefulness of these techniques is illustrated by an analysis of pre- and post-therapy CT scans and calculation of changes in hepatic volume and in the volume of hepatic tumor. Analysis revealed small changes in liver volume could be accompanied by substantial changes in tumor volume and vice versa. We conclude (a) quantitative CT techniques allow for rapid, reproducible measurements of liver and tumor volume, and (b) small changes in organ volume may be accompanied by substantial changes in tumor volume.

Humans↗
PubMed1981

Detection of bone-marrow metastases using quantitative computed tomography.

A method is described for using quantitative computed tomography (CT) to detect subtle skeletal metastases not readily identified or precisely located by conventional methods. Four patients with intramedullary metastases are presented along with data from 13 control subjects. The results indicate that CT may demonstrate intramedullary changes that occur in skeletal metastases and that cannot be detected by other techniques. A difference in medullary CT number greater than 20 HU between limbs is abnormal. This asymmetry, however, is not specific for metastatic disease, and clinical judgment must be exercised in interpreting this finding.

Adenocarcinoma↗
PubMed1981

Low-dose CT scanning for quantitative spinal mineral analysis.

The effect of x-ray exposure on the precision of quantitative CT bone mineral measurements was determined using excised vertebrae and phantoms. Specimens were scanned at 80 kVp with exposures ranging from 23 to 380 mAs using the UCSF/GE research scanner, a modified GE CT/T 7800. Dose was measured using thermoluminescent dosimeters. A patient exposure of 100 mrem (10(-3) Sv) was judged adequate to provide useful quantitative vertebral mineral measurements with this scanner.

Humans↗
PubMed1981

Dynamic computed tomography of the brain: techniques, data analysis, and applications.

Rapid sequence computed tomography (CT) scanning has many potential applications in studying intracranial physiologic events. However, visual inspection of these rapid sequence scans fails to extract the large amount of information inherent in the digital data. The concept of corrected mean transit time applied to rapid sequence scans after intravenous bolus injection of contrast material provides quantitative data on relative hemispheric flow. Use of histogram-based areas of interest permits accurate and reproducible identification of anatomic structures including arteries and gray and white matter. Gamma variate curve fit techniques reduce statistical noise. The concept of transit time can be expanded to the creation of functional CT images.

Blood Flow Velocity↗
PubMed1981

Computerized tomography of brain tumors of the rostral and middle fossas in the dog.

Computerized tomography (CT) was used to assess spontaneously occurring brain tumors of the rostral and middle fossas in the dog. Six dogs were used to illustrate the efficacy of CT as a noninvasive diagnostic procedure. Tumors were characterized on CT scans by density changes, presence of edema or calcification, displacement of normal anatomic landmarks, and contrast enhancement after injection of an iodinated contrast material. In terms of CT appearance, there were a number of morphologic similarities between human and canine brain tumors.

Animals↗
PubMed1980

Spinal mineral loss in oophorectomized women. Determination by quantitative computed tomography.

Computed tomography (CT) provides precise anatomic localization coupled with quantitative x-ray attenuation information that can be used to determine bone mineral content. A precise and sensitive method for vertebral mineral measurement by CT is described and illustrated with results from an ongoing study of mineral loss in oophorectomized women. Spinal mineral loss measured by quantitative CT is compared with peripheral loss determined by photon absorptiometry and radiogrammetry. Vertebral cancellous bone loss was significant for the group as a whole at 12 months, while mean peripheral measurements showed no change. In two subjects in whom mineral change was significant at both sites, spinal loss was approximately five times greater than peripheral loss.

Adult↗