Meryll M. Frost

The Development Of A Digital Video Subtraction System For Intravenous Angiography

A system is under development for a relatively non-invasive technique for the assessment of atherosclerosis. The principle of this method is digital video x-ray subtraction for the visualization of arterial structures after the intravenous injection of contrast media. The prototype unit for the development of video subtraction techniques has been assembled and preliminary testing has started. Re-sults so far in dogs have shown good visualization of the heart, carotid arteries and renal arteries.

A Digital Video Acquisition System For Extraction Of Subvisual Information In Diagnostic Medical Imaging

A system has been developed to allow single frame acquisition of superior quality digitized video images. The system consists of a high-quality x-ray image intensifier coupled to a high-resolution, low-noise video system. The output video signal is fed to a digital memory having 512 x 512 pixels and 8-bit accuracy. The memory output is directly interfaced to a PDP 11/70 image processing facility to allow computer controlled acquisition of video imagery as well as real-time visualization of computer processed images. Computer pro-cessed images are returned to the memory for display. Techniques and examples of processed radiological images will be discussed, and examples shown. Additional digital memories are under construction for 12-bit dynamic range.

Photoelectronic Imaging For Diagnostic Radiology and the Digital Computer

A digital image processing facility is being installed at the University of Arizona to serve the needs of clinical practice and research for improved imaging and diagnosis from radiology. In addition, this facility will support similar needs from other image generating services throughout diagnostic medicine that use ultrasonic devices, gamma cameras, and thermography. Attention is drawn to the structure of this system and its design for dealing with the most severe problems facing diagnostic radiology. These include the input of radiological images to a digital computer, storage, and display. Possible solutions are discussed in terms of utility, performance, economics, and acceptance by the diagnostic radiologist.

Photoelectronic Imaging for Radiology

This paper describes efforts to replace screen-film applications in radiology by an assemblage of x-ray intensifiers, video cameras, displays, and nonfilm storage media, the stimulus for which is twofold: economic and/or improved diagnostic performance. It is quite surprising to find that considerable financial benefit can occur by replacing film with a host of photoelectronic and electronic devices. This is due largely to the cost of a sheet of film being associated with each exposure, whereas photoelectronic devices provide one or thousands of exposures at essentially the same cost. It is not surprising to find, however, that the video output from a photoelectronic system can be readily digitized and made available for the benefits of image processing. This leads to rapid and convenient image acquisition and processing. The radiologist then has the benefit of an interactive display and can diagnose in a manner similar to that managed with the CT scanner. Heretofore, practice required reading out the film-based radiograph with a microdensitometer, followed by digitizing, processing, and producing processed radiographs. This technique is expensive and cumbersome. It was unable to stimulate the radiologist into being a routine user of processed radiographs. This paper examines the x-ray photon diagnostic image for its pertinent characteristics. It follows a review of current image acquisition components, i.e., screens, intensifiers, video tubes, and coupling optics. The purpose is to demonstrate an ability to acquire and transmit diagnostic x-ray images without significant degradation.

Development Of A Digital Video Subtraction System For Intravenous Angiography

This paper represents the third presentation to the SPIE that has dealt with our research activities in photoelectronic radiology and intravenous angiography. The earlier papers have been published in Volumes 1271 and 1642 of the Proceedings, and cover the evolution of the technical facilities and associated radiographic images obtained with dogs. We have now reached a level of competence suitable for the examination of patients, and we present examples of the images obtained to date. Although the research activity reported here began with the task of non-invasive imaging of arteries for the early detection of atherosclerosis, it is becoming increasingly clear that the method is applicable to all areas of the body to which angiography is being currently applied. Furthermore, with the advantages of this technique, new applications are being developed. Thus, we are now beginning examination of animals and patients to determine the utility of intravenous (non-invasive) angiography for examination of the head, coronary arteries, heart, lungs, kidneys, and extremities, and look forward with considerable optimism to the results.

Digital Acquisition System For Photo-Electronic Radiology-A Performance Overview

A digital video acquisition system has been built and is being expanded to evaluate the feasibility of photoelectronic radiology. The system uses specially designed photo-electronic imaging devices to eliminate the use of film as the primary recording medium for radiography. The initial studies using this system have been directed toward intravenous angiography by subtraction techniques. A system performance overview and clinical examples are presented.

High-Resolution Low-Light-Level Video Systems For Diagnostic Radiology

A high-resolution low-light-level (LLL) video system for use in diagnostic radiology is described. Experimental data are presented that clearly reveal the need for a single-stage LLL intensifier.

Image Tubes and Detective Quantum Efficiency

Publisher Summary This chapter discusses about the image tubes and detective quantum efficiency (DQE). DQE is normally used as a single valued estimate of a photosensors performance evaluated at zero frequency. DQE can be expressed as a function of the modulation transfer function (MTF) of a device, quantum efficiency of its photosensor, and of a degradation factor which exists when performance is reduced by noise other than photoelectron noise. The dependence on MTF is important because it permits expression of spatial frequency dependence in an absolute manner, simplifies obtaining a measure of performance of the system, and avoids difficulties which arise when working solely with the MTF. DQE is clearly revealed to give the effective efficiency of a device, when operating in a noisy condition. At high signal levels, DQE improves to a value equal to the photosensors quantum efficiency. DQE can be expressed as a function dependent on spatial frequency. Effective efficiency of a device can be expressed as a function of spatial frequency, and in effect provides an absolute measure of MTF. This chapter elaborates relationship between DQE and the MTF. Concepts of the effective spatial frequency bandwidth are explained. A discussion on passive optics is also presented in this chapter.

Computer-Controlled Video Subtraction Procedures For Radiology

Over the past five years, our group at the Arizona Health Sciences Center has been developing a system for photoelectronic radiology. One of the projects in which we are involved is intravenous angiography, which Dr. Paul Capp reported on in Session 2 of Recent and Future Developments in Medical Imaging II. The purpose of this paper is to show some of the procedures of manipulation and measurements that have been developed to obtain better subtracted images.

Digital Method To Evaluate The Noise Of X-Ray Image Intensifiers

A novel method has been developed to evaluate the noise of x-ray image intensifiers. Fast electronics and a fast photomultiplier tube (PMT) are optically coupled to the output of an x-ray image intensifier. The light emission induced in the intensifier by the absorption of x-ray photons is measured by counting single PMT photoelectrons. The fluctuation in the number of counted PMT photoelectrons per absorbed monochromatic x-ray photon is a measure of the noise of the x-ray image intensifier. It is characterized by an efficiency factor called DQEscin whose values have been obtained from PMT count distributions for five x-ray energies. Experimental results reveal that the output signal-to-noise ratio of the x-ray image intensifier under study is reduced by no more than 10% as expected from the efficiency factor DQEscin.