William H. Kennedy

Regional pulmonary ventilation measurements by xenon enhanced dynamic computed tomography: an update.

New developments in computed tomographic technology permit rapid, serial images that may yield information concerning tracer kinetics through a large tissue volume. One possible application of these developments is the derivation of local lung ventilation by observing the temporal changes of stable xenon concentrations. Preliminary results from six multilevel ventilation studies in dogs demonstrate that the lung may be repeatedly imaged during reproducible phases of respiration even when interscan table incrementation is employed to survey a number of tissue segments and breathing is permitted between scans. In addition, subanesthetic xenon concentrations provide adequate enhancement for possible quantification.

Xenon enhanced dynamic computed tomography: multilevel cerebral blood flow studies.

Xenon enhanced computed tomography with a fast scanning mode and interscan table incrementation was used to derive local cerebral blood flow in a nonhuman primate 19 days following infarction. The in vivo autoradiographic methodology was used to derive blood flow in normal and diseased tissue at four different brain levels (slices) during a single inhalation study.

Computer Electronic Radiography For Early Detection Of Vascular Disease

A computerized electronic radiography system is being developed for early non-invasive detection, characterization and quantification of atherosclerotic lesions. The method uses a conventional x-ray source combined with a solid state detector system which is coupled to a digital computer for processing and display of the radiographic information. The computer stores and optimizes the image for improved interpretation of the image detail. The computer assisted image enhancement, vessel localization and pattern analysis is an integral part of the instrumentation system. The system has been evaluated in preliminary studies to determine contrast sensitivity, radiation exposure, resolution and diagnostic quality. Even at this early developmental stage of this technique, very low contrasts have been visualized. The arterial images obtained with intravenous injections in dogs have demonstrated the potential of this method for the non-invasive detection and quantification of atherosclerotic disease.

X-Ray Imaging With Two-Dimensional Charge-Coupled Device (CCD) Arrays

Two basic approaches to digital radiography have been thoroughly investigated in the last decade. In one, the traditional video chain is modified, and the output of the camera is digitized and analyzed by a computer to produce an image of the area of the body being examined. The other approach uses a linear detector array to generate a sequential series of line images as the array is scanned across the area being observed; the line images are then combined by a computer to form a two-dimensional image. We are investigating the characteristics of a third method, a prototype digital radiography system in which two-dimensional diode arrays (CCD) are fiberoptically coupled directly to either a scintillating fiberoptic plate or to a fluorescent screen. In this paper we describe the- concepts and design configuration of this approach, as well as preliminary results from several phantom studies. Our results indicate that high resolution, high signal-to-noise ratio imaging can be attained with this method.

Errors associated with single-scan determinations of regional cerebral blood flow by xenon enhanced CT.

Possible errors in the determination of xenon concentrations in arterial blood, and uncertainties in CT tissue enhancements during inhalation of xenon-oxygen mixtures, are used to assess errors in the determination of regional cerebral blood flow by the in vivo autoradiographic (single-scan) technique. The results of this study indicate that errors associated with the determination of xenon concentrations in arterial blood decrease rapidly as the time of scanning after the initiation of xenon inhalation is increased. Analysis of errors caused by statistical uncertainties in image enhancement indicate that time of scanning is optimal between 1.5 and 2.5 min for determination of fast flow, while errors in single-flow determinations gradually decrease as the time of scanning increases.

Computed Tomography X-Ray Scanning NDE of Graphite/Epoxy Coupons

Exploratory tests of computed tomography (CT) x-ray scanning of damaged Gr/E coupons demonstrate the potential utility of this NDE method for Gr/E structures. The resulting images are presented with dye penetrant enhanced film radiographs and photographs.

Digital Radiography of the Chest by Self-Scanning Linear Diode Arrays

Diode array digital radiography DADR is a method of radiographic imaging that combines the advantages of computer technology with self-scanning linear diode arrays. These digital images are superior to those obtained by film in recording and displaying information in the lightest and the darkest areas of the film, resulting in a balanced image of the entire thorax without compromising detail, and at reduced radiation dose. This is a direct result of the wide dynamic range, high contrast sensitivity, fiber optic coupling, small diode size, short exposure time, and rejection of scattered x-rays of the system coupled with digital post-processing enhancement of the image displayed at 1024 X 1024 pixels.

Fiber Optically Coupled Diode Array Digital Radiography System

A new type of digital radiography system of very high contrast sensitivity and spatial resolution is described which is based on the use of six linear arrays of self-scanning diodes fiber-optically coupled to a phosphor screen. The high detail of the system results from the fact that 6144 discrete diodes, 1024 per array, scan a field of view of 6 inches wide. A contrast sensitivity five times greater than film is achieved due to the high dynamic range of the diodes combined with the scatter rejection associated with the slit geometry. The entrance radiation exposure per image is 100 mR but could be reduced well below that in the future. Initial clinical experience has demonstrated the advantage of being able to display a single image over a wide range of window levels and window widths at the same time having a high contrast sensitivity in both the dark and light areas of the image. The complete digital radiograph is taken in a second, however the motion unsharpness is held to a minimum by virtue of an effective exposure time of 8 milliseconds. Applications to digital chest radiography and digital intravenous subtraction angiography in over 30 patients have shown the clinical value of this new form of radiography.

Preliminary Clinical Studies Using A Self Scanning Lineak Diode Array To Obtain 1024 X 1024 Digital Radiographs

A digital radiography system using self scanning linear diode arrays is being developed for improved diagnosis at reduced radiation dose. Our technique is based on the use of solid state sensors with 1024 diodes per inch and with very high dynamic range. The slit geometry of our method results in image improvement and dose reduction by efficiently rejecting scattered x-rays in the patient. In our present configuration the images have a field of view of six inches by six inches or 6 inches by 12 inches and are digitized to 1024 x 1024 pixels with 12 bits. This digital system differs from the conventional digital radiography in that no image intensifier TV fluoroscopy chain is required. Preliminary clinical studies have demonstrated the high detail of our system at low radiation levels. In dog studies the system has clearly visualized very small coronary arteries following aortic root injection of contrast material. Even with intravenous injections some of the coronary arteries could be seen.

Improved Diagnostic Radiography and Reduced Radiation Exposure Using a 1024 × 1024 Pixels Linear Diode Array Imaging System

Publisher Summary A new type of digital radiography system is developed based on a series of self-scanning linear photodiode arrays. The system has the ability to detect contrast approximately five times smaller than film at a spatial resolution compared to standard film-screen systems. The system is sufficiently versatile to permit serial digital subtraction angiography as well as planar low-contrast images of very wide dynamic range. In early clinical studies, it was found that the images can be displayed over a broad range of window levels and window widths, depicting detail both in the lightest and darkest areas and bringing out features that cannot be seen on a single standard film. In effect, it is possible to achieve wide latitude while retaining high-contrast sensitivity in all parts of the image. The initial clinical experience indicates that the self-scanning diode array system allows achieving an electronic form of radiography that has the potential for replacing X-ray film in most clinical applications.