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Results for “computed tomography”

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PubMed1999

New low-contrast resolution phantoms for computed tomography.

Computed tomography (CT) has been established as a major imaging modality in diagnostic radiology. Accordingly, acceptance testing and quality control of CT scanners is of great importance. While most procedures and phantoms for testing are widely accepted, there is still discussion and uncertainty about low-contrast (LC) sensitivity. In our opinion this unsatisfactory situation is caused at least in part by the lack of suitable phantoms for LC resolution measurements. We investigated the commonly used phantoms for LC detectability, the Catphan, and for LC resolution, the ATS phantom. While the Catphan showed stable object contrasts, the ATS phantom's measured contrast exhibited a strong dependence on temperature and x-ray quality. Based on newly developed polyurethane resin materials, we designed and tested a LC resolution phantom with several different contrast steps. The object contrasts showed no dependence on temperature and beam quality. The new LC resolution phantom proved to be very suitable for measuring a scanner's low-contrast sensitivity in the image plane, one of the most important image quality parameters. To assess LC resolution in three dimensions we designed an additional phantom with rows of spherical objects. A first prototype was evaluated in a multicenter study. The setup proved to be very helpful to quantify the in-plane and axial LC sensitivity of spiral CT scan modes.

Image Enhancement↗

PubMed2004

Interpretation of mandibular condyle fractures using 2D- and 3D-computed tomography.

Computed tomography (CT) has been increasingly used in the examination of patients with craniofacial trauma. This technique is useful in the examination of the temporomandibular joint and allows the diagnosis of fractures of the mandibular condyle. Aiming to verify whether the three-dimensional reconstructed images from CT (3D-CT) produce more effective visual information than the two-dimensional (2D-CT) ones, we evaluated 2D-CT and 3D-CT examinations of 18 patients with mandibular condyle fractures. We observed that 2D-CT and 3D-CT reconstructed images produced similar information for the diagnosis of fractures of the mandibular condyle, although the 3D-CT allowed a better visualization of the position and displacement of bone fragments, as well as the comminution of fractures. These results, together with the possibility of refining and manipulating perspectives in 3D images, reinforce the importance of its use in the surgical planning and evaluation of treatment. We concluded that 3D-CT presented supplementary information for a more effective diagnosis of mandibular condyle fractures.

Computer Graphics↗

PubMed1990

[A comparison of conventional tomography and computed tomography in cases of diseases of the sacroiliac joint].

16 patients with diseases of the sacroiliac joints were examined both with computer tomography and with conventional tomography. Both techniques were characterized by a high sensitivity. Computer tomography was superior in exactly delineating the extent of the pathologic changes. In conventional tomography the joint surface was more blurred, erosions were larger, and signs of ankylosis were more expanded, so that the joints seemed to be more altered in 8 cases than demonstrated by computer tomography. Very accurate changes like subchondral cysts were recognized only in the computer tomograms. In all cases in which anteroposterior radiographs revealed no clear result, the authors recommend to additionally employ computer tomography.

Adult↗

PubMed2005

Lung cancer screening with low-dose spiral computed tomography.

Computed tomography (CT) has been compared to plain radiographs and bronchial washings as a screening tool for lung cancer. In comparison with other screening modalities, CT allows detection of lung lesions at an earlier cancer stage. Technologic improvements have decreased imaging costs, thus making chest CT a more feasible option as a screening tool in the community hospital. In this study, smokers over the age of 45 years with a greater than 20 pack-year smoking history were referred for screening chest CT. Noncalcified nodules larger than 10 mm underwent CT-guided biopsy, and smaller nodules underwent follow-up CT in 3 months. Currently, patients have been followed for 4 years. The prevalence, stage, and histology of lung cancer were compared to study results from academic centers. Eighty-seven patients underwent screening chest CT. The study population was 51 per cent male with a mean age of 64 +/- 9 years. Four (3 female and 1 male) patients were biopsied and found to have lung cancer giving a prevalence of 5 per cent. Stage IA disease was found in three patients and stage IIIA disease was found in one patient. Adenocarcinoma was present in two patients, adeno-squamous carcinoma in one patient, and squamous cell carcinoma in one patient. The stage and histology of lung carcinomas in this study were comparable to studies performed at larger institutions. However, the disease prevalence was almost double the highest prevalence found in other studies. This discrepancy could be related to study size, as the patient populations were similar. Clearly, screening chest CT in the community setting is equally efficacious in the diagnosis of lung cancer at earlier stages. Following these patients beyond the 5-year mark will give some insight on the effect of screening chest CT on the mortality of lung cancer.

Age Distribution↗

PubMed1992

Historical experiments predating commercially available computed tomography.

Computed tomography (CT) was a revolution in radiology. Commercially available CT scanners appeared in 1972, a joint effort between the EMI Company, Atkinson Morley's Hospital, London and the Department of Health and Social Security (DHSS). The name of Sir Godfrey Hounsfield will always be associated with these developments. Like most developments in science the breakthrough came by standing on the shoulders of giants and many experiments can, with the curious wisdom of hindsight, be considered precursors to CT. Gabriel Frank's patent in 1940 showed apparatus for back-projection CT and Takahashi developed equipment in the 1940s for reconstructing from a sinogram; in both cases using an optical "computer". A medical CT scanner was reportedly constructed in 1957 in Kiev. Transmission CT was performed by Kuhl in 1965. Cormack built an experimental scanner in 1963. Oldendorf identified what was needed for successful CT as early as 1960. Throughout the 1960s a host of independent workers were busy on the mathematical problems of reconstructing from projections with both medical scanning and non-medical applications in mind. Experiments in early emission tomography influenced the development of CT. With imagination one can even see how close "classical" tomography, as started even before 1920, came to the realization of CT. The pioneering British radiographer Watson stands out from a galaxy of inventors. The lecture at Radiology and Oncology '91 in Brighton was a thumbnail sketch of the origins of radiological CT. A fuller story is told elsewhere (Webb, 1990).

History, 20th Century↗

PubMed2001

Radiographic evaluation of cervical spine trauma. Plain radiography and conventional tomography versus computed tomography.

Different imaging modalities are available for the diagnosis of cervical spine injuries. There is a controversial discussion about whether plain radiography (PR), conventional tomography (CTO) or computed tomography (CT) should primarily be used. PR and CTO are more often available and less costly than CT. Especially in second-care hospitals, CT is not always available. The diagnostic work-up in these centres has to rely on conventional techniques. The aim of this study was to define the role of PR supplemented by CTO in the diagnosis of cervical spine trauma in comparison to CT. Twenty-five patients were identified who underwent plain radiography (PR), conventional tomography (CTO) and computed tomography (CT) for the diagnosis of a cervical fracture. In 19 patients a fracture of the cervical spine was identified. All images were reviewed by two independent observers to estimate the interobserver variability. The highest detection rate was achieved by CT (18/18 fractures detected for observer 1/2), followed by CTO (16/16 fractures) and then PR (15/14 fractures). When the detection rates of PR and CTO are combined, 18 fractures were detected by each of the observers. The results were analysed for the dens and the rest of the cervical spine independently. For PR and CTO the detection rates were lower for fractures of the dens than for the rest of the cervical spine. We conclude that the combination of PR and CTO accurately detects fractures of the cervical spine compared with CT. If a fracture of the dens is suspected, the patients should be referred to CT due to its superior accuracy in this region.

Adolescent↗

PubMed1980

Brain maturation followed by computed tomography.

Computed tomography scans of normal infants were analyzed by computer methods to determine the average brain tissue density during development. A 20% increase was found from term to 20 weeks of age (29 to 35 Hounsfield units); then no further significant change was found over the next 60 weeks. The increase in density parallels the known increase in dry weight of the tissue, but calculations indicate that biochemical changes, such as the accumulation of lipids, are also important.

Age Factors↗

PubMed2003

A pointwise limit theorem for filtered backprojection in computed tomography.

Computed tomography (CT) is one of the most important areas in the modern science and technology. The most popular approach for image reconstruction is filtered backprojection. It is essential to understand the limit behavior of the filtered backprojection algorithms. The classic results on the limit of image reconstruction are typically done in the norm sense. In this paper, we use the method of limited bandwidth to handle filtered backprojection-based image reconstruction when the spectrum of an underlying image is not absolutely integrable. Our main contribution is, assuming the method of limited bandwidth, to prove a pointwise limit theorem for a class of functions practically relevant and quite general. Further work is underway to extend the theory and explore its practical applications.

Algorithms↗

PubMed1988

Cerebral infarctions studied by [123I]iodoamphetamine. Clinical aspects of the findings on single photon emission computed tomography and transmission computed tomography.

We have used single photon emission computed tomography (SPECT) and the radioisotope [123I]-iodoamphetamine to study 16 patients with cortical and central cerebral infarctions. In 12 cases SPECT, in addition to changes at the site of infarction, showed areas of deficient uptake in other regions of the brain. Diaschisis as well as infarctions, not detected on the transmission computed tomography scanning, seem to explain these findings.

Aged↗

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↗

PubMed1983

Recognition of metastatic bone disease in cancer of the breast by computed tomography.

Computed tomography has been used to evaluate the significance of positive bone scans in 44 patients with carcinoma of the breast. Of patients with apparently early cancer of the breast who had a positive bone scan 76% were found to have benign joint disease, while 33% of patients who developed a positive bone scan after mastectomy also had benign disease on CT scan. Seventy five per cent of patients with apparently early disease but a positive bone scan who were shown to have metastases died within 30 months. All the patients have been followed for 5 years and only one false positive CT scan was reported.

Bone Neoplasms↗

PubMed1994

3-D reconstruction of an ancient Egyptian mummy using X-ray computer tomography.

Computer tomography has been used to image and reconstruct in 3-D an Egyptian mummy from the collection of the British Museum. This study of Tjentmutengebtiu, a priestess from the 22nd dynasty (945-715 BC) revealed invaluable information of a scientific, Egyptological and palaeopathological nature without mutilation and destruction of the painted cartonnage case or linen wrappings. Precise details on the removal of the brain through the nasal cavity and the viscera from the abdominal cavity were obtained. The nature and composition of the false eyes were investigated. The detailed analysis of the teeth provided a much closer approximation of age at death. The identification of materials used for the various amulets including that of the figures placed in the viscera was graphically demonstrated using this technique.

Humans↗

PubMed1985

Comparison of body composition in middle-aged and elderly males using computed tomography.

Computed tomography (CT) scans were taken of 21 middle-aged men (mean age 46.3 years) and 20 older men (mean age 69.4 years) to measure differences in body composition with age. Overall, the older men weighed 8.2 kg less than the middle-aged men, and this difference was primarily the result of their having less lean tissue. Although fat mass (by whole body potassium counting) was only slightly less in older men, there were distributional differences in fat between the age groups. Total abdomen adipose tissue area (from CT) was similar in both groups, although the subcutaneous portion of the abdomen adipose tissue was less in the older men, and they had correspondingly more adipose tissue within the abdominal cavity. Muscle areas of the leg and arm were significantly less in the older men, as were all lean tissues of the abdomen and chest. When these data were corrected for differences in body weight with age, the results were still significant, suggesting a centripetalization and internalization of fat with age. Causes of this apparent fat redistribution and decrease of lean tissue with age were not revealed by this study and are presently unknown.

Adipose Tissue↗

PubMed1986

Quantitative analysis of the cervical spinal canal by computed tomography.

Computed tomography measurements of the AP diameter, width, and cross-sectional area of the bony cervical canal were derived from cervical spine examinations of fifty-two normal adults. These quantitative parameters were then used to evaluate 80 patients with various cervical abnormalities to determine the clinical usefulness of the measurements. With the exception of spinal stenosis, quantitative cervical canal analysis was found to be of limited usefulness since normal measurements frequently occurred in the presence of significant cervical pathology.

Adolescent↗

PubMed1992

Patterns of lesions of corpus callosum in inner cerebral trauma visualized by computed tomography.

Computed tomographic analysis of lesions of the corpus callosum in 13 patients with "inner cerebral trauma" showed significant congruence of linear translation of acceleration and the topographic distribution of such lesions. This congruence permits computed tomography to be used to reconstruct the course of linear translation and the site of the main blow, which can be important for forensic use. The findings of even a small lesion in the corpus callosum indicates the need for further investigation of other structures which are usually involved in inner cerebral trauma, such as the hippocampus and brain stem.

Adolescent↗

PubMed1984

Importance of the falciform ligament, ligamentum teres and splenic hilus in the spread of malignancy as demonstrated by computed tomography.

Computed tomographic detection of significantly large (greater than 1.5 cm) transcoelomic secondary malignant serosal deposits is discussed. Attention is drawn to the importance of the falciform ligament, ligamentum teres, and splenic hilus as sites of secondary deposits. An anatomical explanation is presented for the detection of these findings on computed tomography.

Abdomen↗

PubMed1983

Orbital histiocytosis on computed tomography.

Computed tomography (CT) findings in two patients with orbital histiocytosis are described. The main features are (a) replacement of bone by soft tissue, which has an absorption value of approximately 40 Hounsfield units (HU) and is not contrast-medium enhanced; (b) bone expansion at the rim of the lesion; (c) a large intraosseous component and a small extraosseous part; and (d) absence of calcification or periosteal reaction.

Adult↗

PubMed1984

Hemochromatosis simulating hepatoma by computed tomography.

Computed tomography of the liver in hemochromatosis characteristically demonstrates diffusely increased attenuation. We report a patient with this disorder who presented with such a finding over the right lobe of the liver and a benign, large lower density area occupying the other lobe, closely simulating malignancy. Biopsies of the liver showed prominent fibrosis of the left lobe as compared with the right lobe, which probably accounts for the attenuation difference.

Adult↗