Transvenous coronary angiography in humans using synchrotron radiation.

Abstract

The risks and costs of the present method of visualizing the coronary arteries have limited the use of coronary angiography in long-term serial studies needed to establish the natural history of coronary atherosclerosis and its response to interventions. A less invasive method, in which the contrast agent is administered intravenously, has been developed using synchrotron radiation as the illuminating source. The present report describes the initial results in human subjects. The findings indicate that transvenous coronary angiograms can be acquired in this manner. Further refmements in the x-ray imaging system are expected to result in increased x-ray fluence and improved image quality.Coronary artery disease is the leading cause of death in the United States (1). Although a number of factors that increase the risk of the development of the disorder are known, the natural history of the underlying atherosclerotic process and its response to preventive measures have been difficult to assess (2). Large-scale studies have been conducted on the effects of efforts to reduce the severity of predisposing factors (3, 4). The ambiguity of the results may be due in part to the use of such end points as definite coronary artery disease death or nonfatal myocardial infarction rather than the direct evaluation ofthe status of the coronary arteries (4). Serial studies of the coronary circulation, as determined by angiography, have been done; but the risks of the procedure limited the number of subjects and the number of examinations (5). A less-invasive imaging system, suitable for longterm sequential studies, is needed (6).The hazards of coronary angiography are principally the result of the arterial catheterization procedure and the injection of undiluted contrast agent directly into the orifice of the coronary arteries. This approach is necessary because of the low sensitivity of conventional x-ray imaging systems to iodine-containing contrast agents. This problem stems from the limitations of the x-ray tube, which emits radiation into a cone of large solid angle and over a broad energy spectrum. Intravenous injections, far safer than intraarterial injections, can be used by employing synchrotron radiation (emitted from an electron storage ring) as the x-ray source. The Lorentz transformation that determines the angular distribution of synchrotron radiation creates the opportunity (7): the extreme collimation of the radiation into a forward-directed cone of very small solid angle allows for monochromatization by Bragg diffraction and results in the exceedingly high brightness needed for brief, motion-freezing exposure times. METHODS AND PATIENTSThe transvenous angiographic method is based on the principle of iodine dichromography (8). Two monochromatic x-ray beams closely bracket the k-edge of iodine, 33,170 electron volts or 33.17 keV. The logarithmic subtraction of the images produced by these beams results in an image that enhances signals arising from attenuation by iodine and suppresses signals arising from a...

Synchrotron Radiation Imaging for Advancing Our Understanding of Cardiovascular Function

“…The first approach, K-edge subtraction angiography, produces images of a large sample area at 2 different energies simultaneously, just above and below the K-edge energy, with narrowly separated strip or line detectors. 1 Subtracting the low-energy image from the high-energy image produces an image that emphasizes X-ray absorption by the iodine contrast agent in the blood. In this approach, high-resolution imaging is compromised for the rapid imaging of a large area (essential for large animal or patient imaging).…”

“…1 The small X-ray source size of SR is inherently suited to dynamic small-area imaging applications, such as absorption microangiography and phase-contrast imaging, and even diffraction studies. All of these techniques are now being applied to cardiovascular biology and, in particular, to smallanimal studies.…”

Design study of compact Laser-Electron X-ray Generator for material and life sciences applications

“…It was suggested that the high power of a synchrotron beam allows for the improvement in image quality by digitally subtracting images obtained on two sides of absorption K-edge of iodine contrast agent [26]. This substantially reduces the concentration of the contrast agent and gives possibility to inject it intravenously (noninvasively).…”

Synchrotron Radiation Applications in Medical Research

“…The concept of synchrotron based coronary angiography was first developed at Stanford University and the early human studies were done at the Stanford Synchrotron Radiation Laboratory [38,39]. In 1989 the project moved to the NSLS where the hardware was installed in the SMEW medical research facility [25, 40, 411.…”

“…Both differences in the x-ray optics and the types of detectors appear among the experimental groups depending upon the needs of the technology. The pioneering work in angiography in Russia at the Institute of Nuclear Physics [36,37] and the programs at the NSLS [38][39][40][41] and HASYLAB [42-441, as well as the planned work at the ESRF [19,45], move the patient through a stationary one-dimensional fan beam. Fig.…”