M. P. Capp

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.

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.

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.

X-Ray Image Intensifier Video System For Diagnostic Radiology: Part 1, Design Characteristics

This paper describes considerations that are important for the successful application of x-ray image intensifier video systems to diagnostic radiology. Particular attention is given to spatial resolution amd maximum signal-to-noise ratio.

Psychophysical Evaluation Of The Spatial And Contrast Resolution Necessary For A Picture Archiving And Communication System: Works In Progress

The Radiology Department of the University of Arizona Health Sciences Center is involved in a five year project to develop a prototype for a Totally Digital Radiology Department (TDRD). One prerequisite for such a department is that the system must allow the radiologist to perform at the same level as with the existing film-based system. The amount of spatial and contrast resolution required to equal the diagnostic information in films will impact directly on the capabilities of the equipment needed to image, transmit, display, and store such images. This is a crucial question that must be addressed because of its diagnostic import and due to its engineering implications.

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.

High Speed Fiber Optic Link For Diagnostic Radiology

Photoelectronic-digital radiology has become a means for image acquisition at the University of Arizona. Large amounts of high speed image data are generated routinely from rooms remotely located from the computer/display facility. As an alternative to coaxial cables, a realtime digital video fiber optic link was developed. This paper will discuss some design considerations. It points out advantages and disadvantages of fiber optics. Some system and network applications are discussed.

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.

Psychophysical Evaluation Correlated With System Measures: Part 2

Psychophysical contrast and resolution responses obtained from r.diologists in two experimental studies are compared with similar data from previous work by the authors. Five observers participated in two experiments that were designed to compare the effectiveness of two video systems (a standard system set at 525 scan lines and a high-resolution system set at 1023 scan lines) for displaying nodules of different size and contrast. We co elude, based on the results of all studies, that video systems exist that have a sufficient contrast transfer to allow detection accuracy similar to that achieved with film.