Biomedical subjects

H L Kundel

Publications and source records attributed to H L Kundel.

9 recordsLinked to original sources

PubMed1979

Images, image quality and observer performance: new horizons in radiology lecture.

Technical and diagnostic image quality are distinguished and the limitations of three methods currently used for assessing diagnostic image quality are discussed. They are evaluations based on individual clinical experience, measurement of diagnostic performance, and physical measurements made on images or imaging systems. Finally, a psychophysical approach to image quality evaluation is presented and its potential value discussed.

Humans↗

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

Peripheral vision, structured noise and film reader error.

The ability of film readers to detect a nodular target abnormality with the peripheral vision was studied using a gray structureless background, chest radiographs with a bilateral pneumothorax and chest radiographs with pulmonary vasculature. Peripheral detection of the nodular abnormality was profoundly decreased by the presence of the normal structures even though the nodule properties such as size and contrast were not different and, in the case of the pneumothorax, the nodules did not overlap normal structures. Structured noise is an important and often neglected variable in studies of visual search, film reader error and image processing in radiology.

Diagnostic Errors↗

PubMed1975

Interpreting chest radiographs without visual search.

Ten radiologists were shown a series of 10 normal and 10 abnormal chest films under two viewing conditions: a 0.2-second flash and unlimited viewing time. The results were compared in terms of verbal content, diagnostic accuracy, and level of confidence. The overall accuracy was surprisingly high (70% true positives) considering that no search was possible. Performance improved as expected with free search (97% true positives). These data support the hypothesis that visual search begins with a global response that establishes content, detects gross deviations from normal, and organizes subsequent foveal checking fixations to conduct a detailed examination of ambiguities. The total search strategy then consists of an ordered sequence of interspersed global and checking fixations.

Cardiomegaly↗

PubMedDate not supplied

The influence of film density on the radiologic detection of lung lesions.

Experiments were conducted on a series of chest radiographs to evaluate the effects of mean film density on reader performance. It was found that the false negative is not measurably affected, in agreement with earlier published data. It was also found, however, that the false positive rate increases with increasing film density. The causes and implications of these results are discussed.

False Negative Reactions↗

PubMedDate not supplied

Visual scanning, pattern recognition and decision-making in pulmonary nodule detection.

Eye movements were recorded while four subjects searched a set of 60 films, 24 normal and 36 abnormal for pulmonary nodules. Error rates, scanning patterns and the dwell time of fixation clusters on normal and nodule-containing areas of the film were studied. Using the assumption that prolonged dwell time indicates intensive processing of visual data, a model was developed for nodule detection that includes four steps: orientation, scanning, pattern recognition and decision-making. False-negative errors were divided into three classes: scanning errors, recognition errors and decision-making errors. Of 20 false-negative errors, 30% were considered scanning, 25% recognition and 45% decision-making.

Decision Making↗

PubMedDate not supplied

Contrast gradient and the detection of lung nodules.

The effects of edge gradient and blur on the detection pulmonary nodules were studied, using a test series of 175 artificial nodules on 30 chest films. The nodules were of homogeneous texture, about 1 cm in diameter and had a mean contrast of .12. Six observers viewed the film set, scoring both location and confidence. The sensitivity or the probability of a true-positive response was linearly related to the blur and a modified ROC analysis resulted in a family of ROC curves with the index of detectability monotonically decreasing with increased blur.

Evaluation Studies as Topic↗

PubMedDate not supplied

A laser scanner for the densitometric analysis of radiographs.

An instrument is described which can scan radiographs and collect densitometric readings for subsequent computer analysis. A laser beam is focused onto the film. Raster scan of the beam is provided by two orthogonal mirror galvanometers. The light, attenuated by the radiograph, is gathered by a lens in such a way that it is directed into a small detector regardless of the scan position. Beam position signals and density readings are stored and analyzed in a minicomputer.

Absorptiometry, Photon↗