Search PubMed⌕ Search

Biomedical subjects

G Revesz

Publications and source records attributed to G Revesz.

At least 19 recordsLinked to original sources
PubMed1990

Teaching effectiveness in the radiology residency: a method of evaluation by residents.

Feedback from the residents can provide a valuable means to acknowledge good teaching by the faculty and a strong stimulus to improve weak teaching performances. As there were no published reports that describe a quantitative and systematic method to achieve this type of evaluation in the radiology residency, we developed a questionnaire of 62 elements that asked each resident to rate each member of the faculty and also to rate the program overall. Residents supplied a scaled response to each question using a rigid protocol that maintained anonymity. Several computer programs were written to process the large volume of data. Statistical evaluation of the data demonstrated that the method is capable of reproducing the residents' assessments with a high degree of accuracy and consistency.

Internship and Residency↗
PubMed1989

The effect of magnetic resonance imaging on metal spine implants.

In Part 1 of this study, the forces and torques exerted on metallic spine implants by a 0.3-T magnetic field were evaluated using a cantilever system sensitive to forces as low as 250 mg and torques as low as 4 g/cm. Results indicated that the 0.3-T magnification field did not cause forces or torques that could be measured within this range. It is concluded that patients with spine implants may safely undergo magnetic resonance scanning. In Part 2, the magnetic resonance scans from 33 patients (61 studies) then were reviewed to determine which, if any, parameters could be adjusted to minimize artifact. Magnetic power, slice thickness, plane of scan, and pulse sequence were considered. Plane of scan was found to be the most significant parameter in achieving useful studies, with the sagittal plane being the preferred orientation. Scans of patients who had posterior wiring were more likely to be useful, while scans of patients with spinal rods usually showed a large amount of artifact.

Humans↗
PubMed1987

Proximal femoral focal deficiency: radiologic analysis of 49 cases.

Proximal femoral focal deficiency, an uncommon congenital anomaly, necessitates early radiologic classification for surgical planning and treatment. Objective radiographic criteria, including femoral length index, acetabular depth index, acetabular angle index, and shape of the proximal femur were determined in 49 patients before cartilaginous ossification of the femoral capital epiphysis; final classification was based on follow-up radiographs or findings at arthrography or surgery. These parameters were analyzed to determine the accuracy and contributions of each in classification. Correct classification into one of three groups was possible in 86% of cases with use of three of the parameters: femoral length index, acetabular depth index, and shape of the proximal femur. The acetabular angle was found to contribute insignificantly to classification. Magnetic resonance imaging, used in only one case, depicted the nonossified cartilaginous femoral capital epiphysis, thus obviating the need for invasive diagnostic procedures and facilitating early classification.

Acetabulum↗
PubMed1987

Osteochondritis dissecans: analysis of mechanical stability with radiography, scintigraphy, and MR imaging.

Twenty-one joints with stable (n = 9) or loose (n = 12) osteochondritis dissecans (OCD) lesions were examined in 15 subjects with plain radiography, three-phase bone scintigraphy, and magnetic resonance (MR) imaging. The lesion size and the thickness of the sclerotic margin as measured on plain radiographs were good parameters for predicting loosening. However, bone scintigraphy was more sensitive and specific in determining the mechanical stability of OCD lesions. MR imaging permitted direct visualization of loosening and fragment displacement; the latter permits differentiation of in situ loosening from a grossly unstable lesion. The noninvasive nature of bone scintigraphy and MR imaging makes them potentially preferable diagnostic modalities to arthrography for evaluating the mechanical status of OCD lesions.

Adolescent↗
PubMed1985

The effect on medical metal implants by magnetic fields of magnetic resonance imaging.

Forces and torques, due to a 0.3 Tesla magnetic field were evaluated on ten hip prostheses and ten hemostat clips. Measurements were performed with an instrument utilizing the movement of a laser beam caused by the deflection of a cantilever. The results indicate effects, if any, to be smaller than the instrument's sensitivity which, at its highest, was 7 mg of force and 125 mg.cm of torque.

Alloys↗
PubMed1985

Conspicuity and uncertainty in the radiographic detection of lesions.

Conspicuity refers to how well a given feature stands out from surrounding structures. While this concept is being used increasingly as a qualitative descriptor, attempts to express it in quantitative form have not been entirely successful. It is necessary to quantitate detectability and also to ascertain that the detected feature is indeed the one being sought. The author has introduced the concept of uncertainty, a quantity derived from false-positive rates. Experiments show that the resulting expression of conspicuity correlates well with the probability of detecting lesions on chest radiographs and may also be used to compare imaging techniques so as to determine their relative accuracy.

Absorptiometry, Photon↗
PubMed1982

Digital analysis of chest radiographs in pulmonary vascular congestion.

Twenty-five erect postero-anterior chest radiographs of 7 patients in and out of congestive heart failure, as well as 6 healthy controls, were graded as to severity of pulmonary vascular congestion. These visual gradings were compared with a vascular complexity index (VCI) computed after digitization of each radiograph. Good correlation was found between visual grading and the VCI (R = 0.77) and for assessing changes in a given patient (R = 0.95). In parallel animal experiments, correlation between the VCI and left-ventricular end-diastolic pressure (LVEDP) was also evaluated. Hypervolemia was induced in 5 dogs by infusion of dextran. LVEDP was measured in each catheterized erect animal and radiographs taken before and after infusion. Correlation between the VCI and LVEDP during infusion was good (R = 0.99).

Animals↗
PubMed1981

Measuring pulmonary vascular congestion with quantitative radiographic indexes from digitized images.

Experiments were conducted with the aim of deriving quantitative indexes from radiographs that describe the status of the pulmonary vasculature under hypervolemic doncitions. Hypervolemia was induced in four baboons by the infusion of dextran solution. Left ventricular pressures were monitored in the erect animals during the infusion and radiographs were obtained. The radiographs subsequently were digitized with a scanning laser-densitometer and a PDP 11/40 minicomputer. An index was derived (the vascular complexity index, Cx), which combined the mean density difference between upper and lower lung zones (indicative of incipient pulmonary edema) and the ratio of density variations in the upper versus lower zones (indicative of redistribution of blood flow). The data indicate a good correlation between left ventricular and diastolic pressure and Cx during the infusion in each animal.

Animals↗
PubMed1977

Psychophysical studies of detection errors in chest radiology.

In 62 of 124 cases analyzed, there occurred a failure to detect a pulmonary nodule which was retrospectively noted only after detection at a subsequent examination. The characteristics of the lesions and their surrounds were measured, and a computer analysis used, to identify that combination of parameters (the conspicuity, K) which was best capable of separating the group into populations of missed and detected lesions.

Diagnostic Errors↗
PubMed1976

Lesion conspicuity, structured noise, and film reader error.

The concept of conspicuity is introduced in an attempt to objectively quantitate radiographic observational error. Defined as a ratio between lesion contrast and surround complexity, the measure correlates well with the probability of detecting faint nodular lesions in chest radiographs. The concept helps in understanding why abnormalities are missed by radiologists. It is also used to explain why image-processing techniques advocated in the past did not yield improvements in diagnostic accuracy and to outline directions for the future. Preliminary results are presented which show that photographic subtraction can increase the conspicuity of simulated early lung lesions and improve their detection.

Absorptiometry, Photon↗
PubMed1975

Breast thermography as a screening technique. An evaluation of performance data.

The concepts of relative operating characteristics (ROC-curves) and detectability index (d') are introduced for the purpose of evaluating performance in breast thermography. In assessing published information on the subject we have found that much of it is anecdotal and lacks sufficient data to determine performance. We have also found that for those published findings which had sufficient data it was possible to reconcile conflicting conclusions as to the efficacy of thermography, and that performance could be quantitated with the use of the detectability index. Conclusions for optimizing available clinical thermographic techniques are given together with ways for future improvement.

Breast Neoplasms↗