The device could identify veins that were invisible to the naked eye and too shallow for ultrasound detection. The V-V-P may help find feeder veins and may also help various types of vein treatments.

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...

A computed tomography imaging technique called variable resolution x-ray (VRX) detection provides detector resolution ranging from that of clinical body scanning to that of microscopy (1 cy/mm to 100 cy/mm). The VRX detection technique is based on a new principle denoted as "projective compression" that allows the detector resolution element to scale proportionally to the image field size. Two classes of VRX detector geometry are considered. Theoretical aspects related to x-ray physics and data sampling are presented. Measured resolution parameters (line-spread function and modulation-transfer function) are presented and discussed. A VRX image that resolves a pair of 50 micron tungsten hairs spaced 30 microns apart is shown.

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The Synchrotron Medical Research Facility (SMERF) at the National Synchrotron Light Source has been completed and is operational for human coronary angiography experiments. The imaging system and hardware have been brought to SMERF from the Stanford Synchrotron Radiation Laboratory where prior studies were carried out. SMERF consists of a suite of rooms at the end of the high-field superconducting wiggler X17 beam line and is classified as an Ambulatory Health Care Facility. Since October of 1990 the coronary arteries of five patients have been imaged. Continuously improving image quality has shown that a large part of both the right coronary artery and the left anterior descending coronary artery can be imaged following a venous injection of contrast agent.