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At least 19 recordsLinked to original sources
PubMed1992

Absorbed doses and energy imparted from tomography for dental implant installation. Spiral tomography using the Scanora technique compared with hypocycloidal tomography.

Tomography is sometimes needed to obtain information on the amount of bone available in the maxilla and in the posterior parts of the mandible prior to implant surgery. Both conventional and computed tomography can be employed. Recently a new imaging device, the Scanora, has been introduced which can be used for spiral tomography. The aim of this study was to compare absorbed doses and energy imparted from this new unit with those from conventional hypocycloidal tomography using the Philips Universal Polytome. A multi-film cassette with five pairs of calcium tungstate screens was used in the latter while a single film technique was used with the Scanora. The absorbed dose measurements were made on an anthropomorphic phantom. Most absorbed doses were found to be below 0.2 mGy except those to the major salivary glands. The absorbed doses with the Scanora were higher than with the Polytome. The beam direction and shorter focus-object distance in the Scanora influenced the absorbed dose distribution. The energy imparted was found to be low for both techniques, 1.8-1.9 mJ with the Scanora for both jaws, and for hypocycloidal tomography 0.78 mJ in the maxilla and 1.3 mJ in the mandible.

Absorption↗
PubMed1988

[Conventional tomography, computerized tomography and proton spin tomography in lung disorders].

In addition to conventional tomography, CT and MRI have been introduced into clinical pulmonary radiology in recent years. Involving little or no ionizing radiation, these two digital imaging methods offer well-defined sections that can be post-processed to analyze different anatomical compartments. MRI of the lung currently faces technical problems, in particular motion artifacts and low proton density, and is more expensive. Thus, it is still reserved for selected problems, e.g. lesion characterization or vascular pathology. CT has replaced conventional tomography for many indications. The performance of these imaging methods in clinical problem situations, such as obstruction of the central bronchial tree, solitary pulmonary nodules, metastases, larger focal lesions, or diffuse disease, is discussed. A rational approach to percutaneous lung biopsy is suggested.

Biopsy↗
PubMed1992

Identification of recurrent ischemia after coronary artery bypass surgery: a comparison of positron emission tomography and single photon emission computed tomography.

Current techniques for the detection of recurrent coronary stenoses following bypass grafting have shown disappointing diagnostic accuracy. This study used the same dipyridamole-handgrip stress to compare the accuracy of rubidium-82 positron emission tomography and thallium-201 single photon emission computed tomography, in 50 consecutive post-bypass patients undergoing coronary arteriography at a mean interval of 6.5 years after surgery. Significant stenoses in native coronary vessels (greater than 50% diameter) or grafts (greater than 70% diameter) were defined by quantitative angiography. Forty-six patients had recurrent or residual stenoses, 43 (93%) had a perfusion defect identified by positron emission tomography, and 35 (76%) were identified by single photon emission computed tomography (P = 0.04). Fourteen of the 17 patients (82%) without previous Q-wave myocardial infarction were identified by positron emission tomography; 10 of the 17 (59%) were detected by single photon emission computed tomography (P = NS). Stress-induced perfusion defects were demonstrated by positron emission tomography in 19 patients; of this group, thallium imaging identified reversible defects in 11, showed no perfusion defect in 1, and portrayed a persistent defect in 7 patients. Significant graft disease was present in 33 patients; perfusion defects were identified by positron emission tomography in 30 (91%), and by single photon emission computed tomography in 24 (73%, P = NS). Four patients were fully revascularized, without significant recurrent coronary disease; normal perfusion was present in 3 (75%) by positron emission tomography, and 4 (100%) by single photon emission computed tomography.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

[The significance of computed tomography in ophthalmologic diagnosis. I: The place of computed tomography, indications, study technics, anatomic representation, computed tomography of eyeball and orbital injuries].

CT is recognized today as method of choice for examining pathological conditions of eyeball and orbit. Several techniques of CT examination are needed to attain the most accurate and detailed information about orbital and eyeball lesions. The exact knowledge of the normal anatomic CT feature of orbital structures is necessary. In traumatic lesions of the globe and the orbit foreign bodies, haematomas and fractures of the orbital walls can be proved and localized and traumatic sequelae can be diagnosed.

Eye Foreign Bodies↗
PubMed1984

Magnetic resonance imaging of the chest: a diagnostic comparison with computed tomography and hilar tomography.

Computed tomography (with and without contrast enhancement) provides excellent diagnostic accuracy for the evaluation of the chest. Oblique (55 degrees) and anteroposterior hilar tomography is accurate for the evaluation of hilar nodes and masses. Magnetic resonance techniques provide excellent differentiation of vascular and nonvascular structures and therefore should be useful in the hilum and mediastinum. Magnetic resonance imaging was used in 55 patients with known pathologic conditions in the mediastinum, hilum, and lungs to determine the accuracy and efficacy of this technique compared with computed and hilar tomography. The pathologic conditions included primary and metastatic neoplasms, benign masses, vascular abnormalities, and pulmonary nodules and infiltrates. Spatial resolution with magnetic resonance imaging is less than with computed tomography with our instrument (0.15 T resistive magnet). However, in the hilum and mediastinum, magnetic resonance imaging provided diagnostic information equal to that of computed tomography with contrast in 90% of patients. Vascular and nonvascular structures were more easily differentiated than with hilar tomography. Computed tomography was far superior in the evaluation of multiple pulmonary nodules. Lesions of the chest wall were better seen with magnetic resonance imaging because of the improved soft tissue contrast.

Adolescent↗
PubMed1984

Computed tomography of the sacroiliac joints: comparison with complex-motion tomography.

Forty-seven patients with sacroiliac joint abnormalities were examined with computed tomography and conventional complex-motion tomography. Twenty-nine patients had spondyloarthritis. Of the 29, complex-motion tomography detected bone erosions in 16 patients, whereas computed tomography revealed erosions in nine. Computed tomography was more sensitive in detection of joint narrowing, joint widening, osteosclerosis, and intraarticular bony ankylosis. In the remaining 13 patients, computed tomography was the modality of choice in detection of paraarticular soft tissue pathology, such as abscess or tumor, and in detection of the lesions involving the sacral canal and neural foramina.

Adult↗
PubMedDate not supplied

Relative properties of tomography, K-edge imaging, and K-edge tomography.

The properties of tomography, K-edge imaging, and K-edge tomography are discussed in relation to the imaging of small concentrations of elements such as iodine and xenon and are compared by means of phantom images. It is demonstrated that the complementary selectivities provided by depth and energy subtraction are combined in K-edge tomography. Using a three-spectrum subtraction technique, the iodine difference signal predicted by computer calculations is on the order of 8000 times that of an equal concentration fo bone. The corresponding ratio in tomography without energy subtraction is 20:1. It is argued that K-edge tomography can successfully eliminate artifacts due to tissue inhomogeneities which presently enable 0.6% variations in tissue attenuation to mimic minimum detectable iodine signals in conventional computed tomography. Various instrumentation possibilities and energy subtraction techniques are discussed.

Models, Structural↗
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↗
PubMed1986

Reconsideration of conventional tomography versus computerized tomography in the evaluation of lung metastases.

Several published reports compare linear chest tomography to computerized chest tomography regarding the detection of lung metastases in adults. As linear tomography does not result in a sectional image, a study comparing multidirectional tomography to computed tomography in the chest was carried out. Equal sensitivity and specificity of these two modalities is shown by reviewing 28 cases who had known extrathoracic malignancies prospectively. The currently prevailing impression that computerized tomography is superior in the detection of lung metastases is thus not justified.

Adolescent↗
PubMed1978

Comparison of whole lung tomography and computed tomography for detecting pulmonary nodules.

Detecting pulmonary metastasis is important when planning surgical therapy, radiotherapy, or chemotherapy in patients with known malignancy. A series of 91 patients was studied by both whole lung tomography and computed tomography (CT) of the lungs. More pulmonary nodules were detected with CT than with whole lung tomography in 32 (35%) of the patients. Of the 91 patients in the study, 31 had resection of some or all of the pulmonary nodules. In 27 patients, the nodules were primary or metastatic malignant lesions. Bilateral pulmonary nodules were detected with CT in 13 patients when whole lung tomography had demonstrated nodules in only one lung. CT has replaced whole lung tomography as the method preferred by the authors for detecting pulmonary nodules in selected patients at risk to develop pulmonary metastasis.

Adolescent↗
PubMed1982

Diagnosis of vertebral fractures. A comparison of conventional radiography, conventional tomography, and computed axial tomography.

Thirty patients with acute thoracic, lumbar, or thoracolumbar fractures, dislocations, or fracture-dislocations were evaluated with standard radiographs, conventional polytomography, and computerized axial tomography. The resulting ninety studies were coded, randomized, and independently interpreted by three radiologists. The diagnostic accuracy of the interpretations based on the computerized tomography scans combined with standard radiographs equaled that of the interpretations based on just the tomograms in the evaluation of fractures of posterior elements. In addition, computerized tomography was superior to the other methods in demonstrating impingement on the neural canal as well as injuries to other organ systems. Also, when compared with conventional polytomography, computerized tomography could be completed with less risk to the patient (no changes in position and ten times less radiation). We concluded that computerized tomography should replace conventional polytomography as the initial study to augment standard radiographs in the assessment of thoracic and lumbar fractures. Conventional polytomography should be reserved for patients in whom precise evaluation of the pars interarticularis is deemed necessary.

Adolescent↗
PubMed1991

[Current role of conventional tomography in the staging of pulmonary neoplasms. Reflections based on the comparison of tomography-magnetic resonance in 81 cases].

The preoperative conventional tomographic and Magnetic Resonance images were reviewed of 81 patients affected with bronchogenic carcinoma; all patients underwent surgery 1986 to 1988. Radiological findings were compared with surgical and pathological results to evaluate the actual role of conventional tomography in the staging of bronchogenic carcinoma. MR Imaging proved to be more useful in the evaluation of mediastinal and hilar lymph nodes. As for mediastinal node status, conventional tomography had 23.5% sensitivity, 90.6% specificity, and 76.5% overall accuracy; MR Imaging had 82.3% sensitivity, 84.4% specificity, and 84% overall accuracy. As for hilar adenopathies, tomographic sensitivity, specificity and overall accuracy were 53.3%, 72.5%, and 65.4% versus 50%, 82.3% and 70.4% with MR Imaging. Tomography was slightly superior in identifying the primary tumor (97.5% versus 92.6% for MR), as well as in the demonstration of central bronchial involvement (100% for conventional tomography versus 50% for MR Imaging). Conventional tomography is useful as a complementary technique to MR Imaging in the preoperative staging of bronchogenic carcinoma when information on central bronchial involvement is needed.

Carcinoma↗
PubMed1985

[Imaging of the heart using nuclear magnetic resonance tomography. I: Tomography].

Magnetic resonance (MR) is a new concept in the diagnostics of the cardiovascular system. The basic principle of MR is nuclear magnetism. MR tomography is based on induction and spatial encoding of a nuclear magnetic resonance signal. Due to the high tissue concentration and MR sensitivity, medical MR imaging chiefly uses protons of water, 1H. MR tomography of protons presents highly contrasted images of soft tissue organs with spatial resolution in millimeters. Parametric analysis of the MR signal enables quantitative assessments of physico-chemical tissue properties, blood flow and perfusion. The method is noninvasive and without serious biological side effects. Ionising radiation or traditional contrast agents are not utilized. Using conventional ECG synchronized MR tomography the cardiac and great vessels anatomy are superbly resolved, exceptions being the resolution of coronary vasculature and cardiac valve apparatus. The excellent spatial resolution and flexible spatial image orientation are important advantages of quantitative assessment of cardiac function by MR imaging. Preliminary studies demonstrated clinical utility of tomographic assessments of T1 and T2 relaxation parameters as well as phase angle analysis for definition of myocardial ischemia, blood flow rates and wall motion dynamics. The first comparative studies between imaging modalities in diagnostics of specific cardiac disorders point to a superior anatomic resolution of the heart and vascular morphology by MR tomography. The utilization of MR tomography in cardiovascular medicine is new and it would be premature to assign a definite value to this costly technique in clinical evaluations of patients with heart disease. However, there is unequivocal evidence that MR technology will play a decisive role in cardiology in the future, and MR imaging already represents significant progress in the evaluation of patients with cardiac disease.

Aortic Diseases↗
PubMed1991

Computed tomography, magnetic resonance imaging and positron emission tomography with [18F]fluorodeoxyglucose in multiple system atrophy and pure autonomic failure.

We studied 45 patients who had autonomic failure with computed tomography, magnetic resonance imaging and positron emission tomography with [18F]fluorodeoxyglucose to characterize the neuroimaging features of multiple system atrophy and pure autonomic failure and determine the utility of these techniques in distinguishing multiple system atrophy from pure autonomic failure. There were 30 patients with multiple system atrophy and 15 with pure autonomic failure. In the multiple system atrophy group, eight patients had mainly cerebellar signs, seven extrapyramidal and 15 had combinations of cerebellar and extrapyramidal signs. Cerebellar atrophy on computerized tomography and magnetic resonance imaging, signal hypointensity in the posterolateral putamen on magnetic resonance imaging and a generalized reduction in glucose utilization rate with positron emission tomography with [18F]fluorodeoxyglucose, were the main findings and were seen only in the patients with multiple system atrophy. Decreased glucose utilization (hypometabolism) was most prominent in the cerebellum, brainstem, striatum and frontal and motor cortices. These results indicate clear differences, using neuroimaging studies, between multiple system atrophy and pure autonomic failure.

Atrophy↗
PubMed1989

[Radiation dosage and clinical value of conventional tomography and high resolution computerized tomography of the nose and ear].

Hypocycloidal (frontal and temporal) tomography of the base of the skull is compared with high resolution computed tomography (HR-CT) with respect to dose and clinical usefulness. In most cases HR-CT is indicated because of its better density resolution in comparison with conventional hypocycloidal tomography. As the X-ray beam is directed at the slice plane the dosage is noticeably less than when using conventional tomography. Slice thickness depends on the required geometric resolution. This is an additional factor in radiation protection.

Ear↗
PubMed1985

Low-dose transaxial tomography. An alternative to computed tomography for the evaluation of anteversion of the femur during childhood.

Low-dose transaxial tomography is a technique that can produce cross-sectional images of the hips and femurs in children to permit calculation of the angle of femoral anteversion. Transaxial tomography was compared with computed tomography in terms of measured radiation dose and image quality. Transaxial tomography was found to require at least 90% less radiation dose, and the images were judged to be acceptable for the determination of anteversion.

Child↗
PubMed1978

[The efficiency of computer-tomography and conventional tomography of processes of the skull and of the skullbase (author's transl)].

In 12 patients with tumorous or chronic-inflammatory diseases of the skull and the skullbase the results of conventional and computer-tomography were compared with the operative findings. The computer-tomography of the most important regions is demonstrated by individual examples. The preliminary results indicate, that computer-tomography is reliable in evaluation of the extend of pathological processes. Therefor follow-up data after treatment were obtained by computer-tomography only.

Carcinoma↗