Conceptual design of an 8 Tesla superconducting wiggler for a dedicated digital subtraction angiography source

摘要

One of the most important techniques used to diagnose heart disease is coronary angiography. Coronary angiography is only used when it is absolutely essential because of the risk of fatalities and other serious complications arising from the insertion of the catheter. The technique also exposes the patients to large amounts of x-rays. Research, begun at SSRL and continued on the X17 beam line at NSLS, demonstrated the feasibility of imaging human coronary arteries following venous injection of the contrast agent. The technique, caged digital subtraction angiography (DSA), uses two monochromatic beams of x-rays, one slightly above and one slightly below the iodine K absorption edge (33.169 KeV) to collect simultaneous images. When the two images are subtracted, the contrast agent, contained primarily in the blood vessels, is revealed and the background that is common to both images is suppressed. The images must be collected during a single heartbeat to avoid blurring from motion of the blood vessels. Conventional x-ray sources are too weak to provide the intense flux that is required in the narrow energy bandwidth of the beams. Only the most powerful synchrotron radiation beams from wiggler magnet sources can provide the intensity required in the short exposure time. Although DSA experiments have shown promise, they have been conducted at large, research synchrotron radiation facilities. A small, dedicated source will be needed before DSA can be used as a standard medical procedure. Such x-ray sources as laser backscattering, Cherenkov radiation, parametric x-radiation, and channeling radiation have been suggested for hospital based DSA sources but none of them appear to produce enough flux to be useful. Barring the discovery of a new source of intense x-rays, only synchrotron radiation seems to meet the requirements for DSA. This report briefly describes the preliminary design of a high field, superconducting wiggler magnet that can be used as a DSA source.