No abstract available

[en] Large-format digital x-ray imaging systems, based on storage phosphors, have been developed for use in radiology. They are also useful as two-dimensional dosimeters for use in analyzing x-radiation fields. The parameters of the system's signal transfer function, printed out together with the image, provide a precise relation between pixel values and exposure x. This presentation addresses such performance characteristics as linearity of response, linearity with respect to exposure time, energy dependence, spatial nonuniformity, signal decay as a function of time after exposure, accuracy, and precision

[en] This paper describes research to define the needed spatial resolution for maintaining diagnostic accuracy in digital systems. Posteroanterior images from 30 normal and 30 abnormal studies of patients with various stages of interstitial disease were digitized at 51 p/mm with 12 bits of gray level and then processed in a computer to reduce spatial resolution from 5.0 to 2.5, 1.875, and in 1.25 Ip/mm. A Kodak laser writer using a LUT devised to ensure the copies had equal densities to those measured from the original images was used to write the images back to film. These film images were then shown to radiologists (one resolution level per radiologist). They were asked to give their diagnosis and certainty for each image (receiver operating characteristic [ROC] paradigm) and also to rate each image on overall spatial and contrast resolution as well as the visibility of seven diagnostically important structures

[en] Radiology is vital to the life-saving efforts of surgeons and other physicians, but precious time can be lost generating the images and transferring them to and from the operating room. Furthermore, hospitals are straining under the task of storing and managing the deluge of diagnostic films produced every year. A 300-bed hospital generates about 1 gigabyte (8 x 10⁹ bits) of picture information every day and is legally bound to hold it for three to seven years--30 years in the case of silicosis or black lung disease, illnesses that may have relevance to future lawsuits. Consequently, hospital warehouses are filling with x-ray film and written reports that are important for analysis of patient histories, for comparison between patients, and for analyzing the progress of disease. Yet only a fraction of the information's potential is being used because access is so complicated. What is more, films are easily lost, erasing valuable medical histories

[en] The point spread function (PSF) is used to characterize imaging systems. The PSF is usually not measured directly but rather the line spread function (LSF) is measured by scanning across the image of an input slit. One of the well known LSF-PSF conversion formulas is then applied. These formulas make the assumption that the length of the input-slit image is great compared to the PSF extent. This assumption is unfortunately unwarranted for one of the most important medical image devices: the x-ray image intensifier. The large extent image intensifier's PSF and the limited size of the intensifier's isoplanatic patches combine to make consideration of the finite length of the input slit important. Formulas for calculating the PSF from a measurement of the finite-length line spread function (FLSF) have been developed for the case of a rotationally symmetric PSF. In this presentation the authors generalize the conversion formulas to cover non-symmetric PSF's

[en] An extension to the contrast-enhancement algorithm Adaptive Histogram Equalization (AHE) has been developed at our institution for use on digital chest images. Our algorithm, Artifact-Suppressed Adaptive Histogram Equalization (ASAHE), has been targeted for ultimate use on high-resolution radiological workstations. Recent modifications to the algorithm suggested that it would make nodules more easily detectable than the standard processing available with the computed radiography system at our disposal. The authors designed and carried out a carefully controlled observer experiment, detailed in this article, that used phantoms and simulated nodules to verify our hypothesis. This paper reports that the results showed that the ASAHE algorithm did produce a significant improvement in nodule detection

[en] With the constant increase in available computational power per dollar, we have reached a point where very complex processing images is feasible. An area where such processing has proved to be useful is image enhancement. The authors describe a much more computationally intensive algorithm which enhances line-like structures such as vessels. The property of line-likeness is quantified using a path optimization technique known as dynamic programming. The algorithm examines the neighborhood of each point in the picture to determine whether the neighborhood exhibits line-likeness. They concentrate their discussion on the principle of operation of this algorithm. They also briefly describe the intended application of this algorithm to a new high resolution imaging system being developed in the Department of Radiology

[en] This paper describes a high resolution x-ray imaging device, which is under development at the University of Arizona. It is sponsored by NIH for application in coronary angiography, but has also application in other x-ray imaging fields requiring high spatial resolution, such as mammography and nondestructive testing. It consists of a 6 in. diameter external modular sensor, coupled fiber optically to the input of a 6 in. proximity focussed image intensifier. The intensifier's output is coupled via 6 fiber optic tapers to 6 CCD's for readout. The tapers are joined at the large end to form a 6 in. by 6 in. coplanar fiber optic taper assembly. The electronics are designed to from a composite image out of the 6 individual images provided by the 6 CCD's and display the image in full resolution (1152 x 1152) on a high resolution physicians review console. The paper discusses the design considerations, the features, the major problems and some preliminary results

[en] This paper describes a new method to determine the lower limit of patient exposure: By placing several imaging plates of a computed radiography system (CR) into the same cassette, several images of the same patient can be obtained at different exposure levels (determined by the x- ray transmission of the various imaging plates. Initial experiments indicate that exposure reduction of between 50 and 75% might be acceptable. CR provides a powerful tool to study the subject of exposure reduction

[en] A high-speed fiberoptic communications network for use in a picture archiving and communication system was constructed. The network, which is presently under test, includes a 32-port fiberoptic star coupler of novel design capable of transmitting images over kilometer distances without significant losses, network interface units (NIU) with 10-megabit/second control channels and 140-megabit/second image transmission channels, ACR/NEMA interfaces connecting imaging equipment (IE) to the NIUs, and interface translation units integrated into the IEs. The imaging equipment items presently connected to the network are a high-performance viewing console and an experimental multitaper CCD-based image intensifier unit