John H. Feist

University of Pittsburgh, Pittsburgh, PA, United States

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Publications (10)12.35 Total impact

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    ABSTRACT: In order to subjectively determine acceptable dose levels for portable CR, two blind experiments were performed while maintaining conventional screen-film radiography as a reference quality. In the first experiment, a team of two technologists and two radiologists were trained to expose and to quality-assure portable CR images obtained with standard screens at conventional exposures (400 speed). After providing them with a new set of cassettes and informing them that these were 'better and faster,: they were allowed to practice clinically, using the system for bedside AP chest radiography. After four weeks, exposure factors used in those cases were reviewed, and the experiment was repeated with two different teams and two CR systems. In the second experiment, portable CR was used for a large number of cases. The number of radiologists who complained about CR image quality was monitored for cased were alternating technologies (CR and conventional) were used and routinely viewed side by side. during a two-month period, radiation dose gradually increased to a level where radiologists' complaints were significantly reduced. In both experiments, exposure levels gradually migrated to and stabilized at 40-60% higher levels than that routinely used with conventional 400-speed film screen techniques. The perceived need for high exposure ratios between Cr and conventional radiography was related to body size. When the reference quality 'gold standard' remains unchanged, Cr requires higher exposures to yield acceptable image quality, particularly in large patients.
    Proc SPIE 04/1995;
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    ABSTRACT: Forced-choice just noticeable difference (JND) studies are extremely sensitive to image quality variations that are below the threshold at which the differences are apparent to or definable by the observer. Paired comparisons of 4K and 2K laser-printed posteroanterior chest images consistently demonstrated that although images are viewed as comparable by radiologists, when forced to choose the better ("sharper") image, they actually select the higher-resolution images in 83% of the paired observations. We conclude that small differences in image quality may be detectable even in image sets which are considered to be comparable by subjective assessments.
    Journal of Digital Imaging 06/1994; 7(2):77-8. · 1.10 Impact Factor
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    ABSTRACT: The purpose of this study was to compare observer performance in interpreting high-quality, digitally acquired computed radiographs of the chest displayed on either laser-printed radiographs or a workstation with observer performance in interpreting conventional chest radiographs. We performed a receiver-operating-characteristic study in which the presence or absence of five abnormalities was determined by nine experienced radiologists on 310 posteroanterior radiographs of the chest displayed in three forms: conventional radiographs, laser-printed films of digital radiographs, and digital radiographs on a high-resolution workstation. The results of our study suggest that observer performance with laser-printed films of digital radiographs obtained with high-resolution (4K x 5K), high-contrast sensitivity (12 bits) and appropriate exposure is comparable to observer performance with conventional radiographs. Observer performance with digital radiographs displayed on the workstation was found to be significantly lower for abnormalities that contained high-frequency and low-contrast information (e.g., interstitial disease and pneumothorax). Computed radiography technology can produce image quality that is adequate for interpreting posteroanterior radiographs of the chest. Observer performance is not as good when radiographs displayed on workstations are used to diagnose specific abnormalities.
    American Journal of Roentgenology 04/1994; 162(3):575-81. · 2.90 Impact Factor
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    ABSTRACT: In a series of large ROC studies, the authors analyzed the time radiologists took to diagnose PA chest images as a function of observer performance indices (Az), display environments, and difficulty of cases. Board-certified radiologists interpreted at least 600 images each for the presence or absence of one or more of the following abnormalities: interstitial disease, nodule, and pneumothorax. Results indicated that there exists a large inter- reader variability in the time required to diagnose PA chest images. There is no correlation between a reader's specific median reading time and his/her performance. Time generally increases as the number of abnormalities on a single image increases and for cases with subtle abnormalities. Results also indicated that, in general, the longer the time for interpretation of a specific case (within reader), the further the observer's confidence ratings were from the truth. These findings were found to hold true regardless of the display mode. These results may have implications with regards to the appropriate methodology that should be used for imaging systems evaluations and for measurements of productivity for radiologists.
    Proc SPIE 07/1991;
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    ABSTRACT: In an ongoing, multi-reader, multi-project program dealing with the interpretation of radiological images, we have examined several issues of methodology which have not as yet been addressed that may impact on the determination of reader performance as measured by receiver operating characteristic (ROC) analysis. Among these are issues associated with the training of observers prior to such studies. We employed three types of observer training that we found to be necessary for the successful performance of such studies: 1) a general instructional session for observers on the study protocol and system operation; 2) practice with an interactive computerized feedback teaching file that demonstrates the imaging systems and familiarized readers with an idea of the types of cases that were used in the study along with their correct diagnoses; and 3) training sessions in which readers were taught the manner in which to distribute answer ratings over an ordinal confidence scale. The possible effect of such types of training on the performance and results of ROC studies should be carefully considered prior to their commencement.
    Proc SPIE 08/1990;
  • Proc SPIE 08/1990;
  • W F Good, D Gur, W H Straub, J H Feist
    Investigative Radiology 12/1989; 24(11):932-3. · 5.46 Impact Factor
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    ABSTRACT: We compared storage phosphor images with high-quality conventional film-screen images by evaluating physicians' perceptions of image quality and their levels of confidence in making diagnostic interpretations. Eight physicians each examined 11 posteroanterior storage phosphor chest images (obtained with an experimental high-resolution storage phosphor system) side by side with conventional film images of the same patients. The storage phosphor images were obtained only minutes after the conventional radiographs were obtained. Storage phosphor images were digitally printed onto films in two different formats: a full-size (12 X 14 in. [30.5 X 35.6 cm]) and a half-size format of four computer-processed, minified images (6 X 7 in. [15.2 X 17.8 cm] each). Most of the responses rated the quality and resolution/sharpness of conventional images, as well as their ability to display the complete lung field, as either "excellent" or "good"; however, the storage phosphor images received significantly better ratings (p less than .05). Computer-processed minified versions of the storage phosphor images also received better ratings than did the conventional images. When the physicians were asked to rate their confidence level in making diagnoses with each of the two techniques, in 74 of 88 cases they indicated that their level of confidence would be at least as high when using the storage phosphor images as when using the conventional images.
    American Journal of Roentgenology 06/1988; 150(5):1011-4. · 2.90 Impact Factor
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    ABSTRACT: A digital radiography system using self scanning linear diode arrays is being developed for improved diagnosis at reduced radiation dose. Our technique is based on the use of solid state sensors with 1024 diodes per inch and with very high dynamic range. The slit geometry of our method results in image improvement and dose reduction by efficiently rejecting scattered x-rays in the patient. In our present configuration the images have a field of view of six inches by six inches or 6 inches by 12 inches and are digitized to 1024 x 1024 pixels with 12 bits. This digital system differs from the conventional digital radiography in that no image intensifier TV fluoroscopy chain is required. Preliminary clinical studies have demonstrated the high detail of our system at low radiation levels. In dog studies the system has clearly visualized very small coronary arteries following aortic root injection of contrast material. Even with intravenous injections some of the coronary arteries could be seen.
    Medical Imaging and Instrumentation '84; 08/1984
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    ABSTRACT: Initial results for a new technique of imaging the small and rapidly moving coronary arteries using linear arrays of self-scanning diodes coupled directly to a computer are described. The technique involves a thin, fanshaped x-ray beam and a phosphor screen fiber-optically coupled to a set of light sensitive self-scanning linear diode arrays that are scanned across the heart to give a scatter-free, high detail digital image. Coronary arteries have been imaged successfully in the rapidly moving heart of 23 kg dogs using both aortic root and intravenous injections. In the aortic root injection, coronary arteries as small as 0.3 mm have been imaged. This is the first step in the development of a noninvasive, low-dose technique for the early detection and quantification of atherosclerotic disease in human coronary arteries presently going on in our laboratory.
    01/1983;