[en] Iodine-containing compounds are used as contrast agents in obtaining X-ray images of blood vessels for medical diagnosis. If the X-ray contrast produced by iodine can be enhanced sufficiently relative to that produced by the intervening body tissues, it becomes possible to obtain images of arteries by introducing the contrast agent into the venous circulation rather than through an arterial catheter directly into the vessel under examination. An imaging system that shows promise of accomplishing this goal for examination of the coronary arteries has been developed for operation in an X-ray beam at the Stanford Synchrotron Radiation Laboratory. Iodine-selective contrast enhancement is achieved by logarithmic subtraction of two images of the same field. One of these images is formed by monochromatic X-rays of energy just above the characteristic iodine K-absorption edge at 33.17 keV, the other by X-rays of energy just below the edge. The computer-controlled imaging system acquires digitized images line by line while scanning the subject through a stationary X-ray beam of linear profile. At present, only synchrotron radiation can provide monochromatic X-ray beams of intensity sufficient to image the small and rapidly moving coronary arteries

[en] X-ray computed tomography (CT) is a widely used method of obtaining cross-sectional views of objects. The high intensity, natural collimation, monochromaticity and energy tunability of synchrotron x-ray sources could potentially be used to provide CT images of improved quality. The advantages of these systems would be that images could be produced more rapidly with better spatial resolution and reduced beam artifacts. In addition, images, in some cases, could be acquired with elemental sensitivity. As a demonstration of the capability of such a system, CT images were obtained of four slices of an excised pig heart in which the arteries and the cardiac chambers were filled with an iodinated medium. Images were taken with incident x-rays tuned successively to energies just above and below the iodine K edge. Iodine specific images were obtained by logarithmically subtracting the low energy image data from the high energy data and then reconstructing the image. CT imaging using synchrotron radiation may become a convenient and non-destructive method of imaging samples difficult to study by other methods

[en] A rotating slit system has been designed and tested which can effectively translate a fan-shaped X-ray beam at the same average speed and in the same direction of travel as a patient moving continuously during a line-scan dual-energy medical imaging procedure. The slit has been shown to eliminate the artifacts due to bone in logarithmically subtracted images obtained with monochromatic X-ray beams derived from synchrotron radiation, where one beam is just above and the other just below the K-edge of iodine. Images of iodine-containing phantoms and in vivo canine images after intravenous iodine injection show vessel detail without artifacts due to bone. Corresponding images taken without the rotating slit have severe artifacts

[en] Two 30 cm diameter steel drums with four facets rotating at 1800 RPM have produced high-quality digital-subtraction radiographs by alternately blocking and transmitting dual-energy synchrotron X-ray beams. An eight times faster system with 16.5 cm diameter ten-faceted tin-plated aluminum drums rotating at 5760 RPM is presently under construction

[en] X-ray computed tomography (CT) is a widely used method of obtaining cross sectional views of objects. The high intensity, natural collimation, monochromaticity and energy tunability of synchrotron X-ray sources could potentially be used to provide CT images of improved quality. The advantages of these systems would be that images could be produced more rapidly with better spatial resolution and reduced beam artifacts. In addition images, in some cases, could be acquired with elemental sensitivity. As a demonstration of the capability of such a system. CT images were obtained of four slices of an excised pig heart, in which the arteries and cardiac chambers were filled with an iodinated medium. Images were taken with incident X-rays tuned successively to energies just above and below the iodine K edge. Iodine specific images were obtained by logarithmically subtracting the low energy image data from the high energy data and then reconstructing the image. CT imaging using synchrotron radiation may become a convenient and non-destructive method of imaging samples difficult to study by other methods. (orig.)

[en] The intensity and tunability of synchrotron X-ray beams are highly suited to the non-invasive detection of iodine by K-edge digital subtraction angiography. An imaging system developed for in vivo canine studies is described. Considerations relating to an expanded system for human subject studies are discussed

[en] A program is underway at the Stanford Synchrotron Radiation Laboratory to evaluate a minimally invasive method of visualizing the coronary arteries in man using synchrotron radiation. The design of an X-ray imaging system to accomodate a newly-available X-ray beam 12.3 cm in width is described. The system performance as revealed with test images of phantoms and excised hearts is indicated, and the system components to be tested before clinical studies can begin are identified. (orig.)

[en] A safe and sensitive method of visualizing the coronary arteries is needed. The presently available method of visualization is highly invasive and carries too high a risk and cost. The intensity and tunability of synchrotron X-ray beams provides a new source of X-rays highly suited to the in vivo detection of iodinated contrast agents. The method offers the prospect of non-invasive visualization of the arteries by peripheral venous injection of contrast agent. The studies already conducted and those in preparation for human subjects are reviewed. (orig.)

[en] This study is related to an evaluation of synchrotron radiation for the non-invasive assessment of coronary artery disease in humans. In vivo canine studies are reported for an imaging system developed for use with synchrotron X-ray beams. The probable configuration of an expanded system for pilot human subject studies is described. (orig.)

[en] Synchrotron radiation has been employed to image coronary arteries using a venous injection of contrast agent rather than the more dangerous arterial injection that is currently required. This method uses a pair of monochromatized X-ray fan beams of slightly different energies that intersect at the patient. A pair of images is acquired in a line scanning mode. The contrast agent is iodine-based. At the iodine K edge the absorption cross section jumps by a factor of more than six. Since the energy of one beam is just below the iodine absorption edge and the energy of the other is just above this edge, the logarithmic subtraction of these two images results in an image with excellent sensitivity to the contrast agent and minimal sensitivity to tissue and bone. A prototype system has been developed to test this concept. Improvements in many parts of the system during the past two years have led to the excellent imaging of dog coronary circulation and to the initial studies of human subjects. The basic components of the system will be discussed first and then improvements that have been made recently will be presented. Images of both dogs and humans that have been taken with the upgraded system are presented and planned enhancements are discussed. (orig.)