S. Nudelman

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.

A study of photoelectronic-digital radiology—Part I: The photoelectronic-digital radiology department

A three-part study presents the concepts, costs, and basic considerations involved in photoelectronic-digital radiology. This new approach to diagnostic radiology eliminates film as the primary image acquisition medium. It provides an attractive opportunity to develop new diagnostic procedures, be cost effective, and improve on diagnostic accuracy. Part I explores the concept as applied to our thirteen-room radiology department. Part II deals with cost effectiveness, and Part III is concerned with engineering of photoelectronic-digital radiology systems. Part I identifies five organizational units requiring individual attention. They are: 1) examination rooms and their analog image acquisition devices, 2) a computer facility incorporating digital image acquistion, processing, and archival storage, 3) a reading room, 4) offices and clinics, and 5) a possible control center. Features desired for each units components are identified and discussed. Areas of strength and weakness, as well as those attractive for new activity in research and development, are delineated.

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.

A study of photoelectronic-digital radiology—Part III: Image acquisition components and system design

Photoelectronic image acquisition components (X-ray sensors, optics, and video tubes) are examined for their ability to reproduce the X-ray image obtained in diagnostic radiology. Essential characteristics in terms of efficiency, signal, noise, dynamic range, contrast resolution, spatial resolution, and speed are examined for components and systems suited to clinical procedures. Analysis for performance is managed on the basis of calculations using photons, flux, and flux rate with their counterparts in electron numbers for charge distribution and current flow. This avoids the difficulty of working with mixed units. Static imaging for the chest, abdomen, and bone as well as dynamic imaging using intravenous angiography are discussed for their individual requirements.

Measurement Of The X-Ray-Induced Light Photons Emitted From Radiographic CaW04 Intensifying Screens

For calcium tungstate intensifying screens employed in film-screen imaging systems, Coltman found that approximately 1000 light photons of average energy 2.7 eV were produced for each 50 keV x-ray absorbed. Of this number, he found that only about 55% are emitted from the output side of a 109 mg/cm2 screen. We have developed a method based on counting single photons to determine this number for various thicknesses of calcium tungstate screens. Monoenergetic x rays in the energy range from 17-69 keV produce upon absorption, a shower of individual photon pulses which are detected by a low noise photomultiplier. After amplification and discrimination against the noise background of the phototube, the resultant pulses are counted in a 70 MHz scaler or a 150 MHz counter. The detection system has a pulse resolving time of less than 15 ns. The data are then corrected for the quantum efficiency of the detector and normalized to the number of absorbed x rays which is determined in a separate experiment. For calcium tungstate screens with thicknesses of 30, 50, 86, and 123 mg/cm2, the average numbers of light photons emitted per absorbed x ray are measured for 8 x-ray energies between 17- and 69-keV. The values for 50 keV are less than the values found by Coltman. Studies of the causes of this discrepancy are in progress.

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.