The modeling of diagnostic examinations reduces the sample size needed to acquire statistical power. This paper compares the models of ROC analysis, channel models of diagnostic examinations, and uncertainty measures in modeling mammography examinations. The cited models are applied to screening mammography. The result of the use of these models is that less data is required for achieving the chosen levels of statistical power. Thee models are able to manage the large number of variables involved in comparing diagnostic examinations.

A dialup wide-bandwidth digital teleradiology system is discussed. A laser film digitizer and a gray scale display system are used at Irwin and Munson Army Community Hospitals to digitize radiographic films and display digital images. A laser film printer at the University of Kansas Medical Center generates a film hardcopy of the transmitted digital data, and an interactive gray scale display is used to review the digital image data. The communication system consists of dialup switched multiple 56000 b/s digital channels, transmitting digital image data in parallel. Conventional radiographic films, multiformat camera films, and laser printed films from multimodality imaging systems have been successfully digitized, transmitted, and laser film recorded or gray scale displayed. It was found that the system provided clinically acceptable image quality reproductions.>

A prototype Computed Tomography Breast Scanner (CT/M) built by General Electric Medical Systems Divi sion was installed at the University of Kansas Medical Center in October 1976. Over 1,500 patients have now been examined by this CT/M Scanner. During this period of clinical evaluation it was determined that clinical effectiveness could be enhanced by correlating iodine concentration with CT number changes. The comparison of tissue localization of iodinated contrast material is achieved by performing two sets of similar CT/M scans, one pre-contrast study and one post-contrast study. The percent iodinated uptake, as reflected by comparing changes in CT/M numbers, was found to vary for breast lesions. An interactive graphics software system was designed and evaluated as a computer-aided system for detecting distinguishable changes in the present iodinated breast tissue uptake. Multiple CT/M images may be displayed simultaneously. Interactive CTIM image processing includes a Region of Interest selection. Image processing includes estimates of first and second order statistics from selected regions of interest in comparing pre and post contrast CT/M scans.

A computer algorithm is described that extracts the edge information from a digital image of an AP radiograph of the knee. Automated image field partitioning is used as a simplifying first step in the process. Methods that employ a priori knowledge are used to insure simple connected edges.

Feature extraction is one of the more difficult steps in image pattern recognition. Some sources of difficulty are the presence of irrelevant information and the relativity of a feature set to a particular application. Several preprocessing techniques for enhancing selected features and removing irrelevant data are described and compared. The techniques include gray level distribution linearization, digital spatial filtering, contrast enhancement, and image subtraction. Also, several feature extraction techniques are illustrated. The techniques are divided into spatial and Fourier domain operations. The spatial domain operations of directional signatures and contour tracing are first described. Then, the Fourier domain techniques of frequency signatures and template matching are illustrated. Finally, a practical image pattern recognition problem is solved using some of the described techniques.

An approximate method for rapid multiplication or division with relatively simple digital circuitry is described. The algorithm consists of computing approximate binary logarithms, adding or subtracting the logarithms, and computing the approximate anti- logarithm of the resultant. Using a criteria of minimum mean square error, coefficients for the approximations are developed. An error analysis is given for three cases in which the algorithm is useful. Finally, applications to digital filtering computations are considered which illustrate that log-antilog multiplication is not simpler than an array multiplier for computing single products, but is useful for parallel digital filter banks and multiplicative digital filters.

The usual statement of the Gilbert bound is an assertion that at least one member of a given ensemble of codes satisfies a minimum distance criterion. This result is strengthened by showing that for sufficiently large constraint lengths, an arbitrarily large fraction of the ensemble of codes have minimum distance exceeding the usual asymptotic Gilbert bound. New asymptotic bounds are derived for the nonbinary case.