INTRAVENOUS CORONARY ANGIOGRAPHY WITH SYNCHROTRON-RADIATION

Worldwide several systems for Digital Subtraction Angiography in energ y subtraction mode (dichromography) with synchrotron radiation are dev eloped. Two of the systems-the system NIKOS in the Hamburger Synchrotr onstrahlungslabor HASYLAB in Hamburg and the system in Brookhaven-allo w investigations of patients. The aim of the work is to visualize coro nary arteries down to 1 mm diameter with an iodine mass density of 1 m g/cm(2), thus allowing non-invasive investigations by intravenous appl ication of the contrast medium. The two images for subtraction are sim ultaneously taken with photon energies just below and above the iodine K-edge (33.17 keV) in a line scan mode. In principle the system NIKOS consists of six main parts: A 20-pole wiggler with a total length of 2.4 m and a field of 1.26 T is installed in the storage ring DORIS at DESY in Hamburg. In a two beam monochromator two bent perfect Si(111) crystals in Laue geometry are used for filtering the quasi-monochromat ic beams with a bandwidth of 180 eV our of the white synchrotron radia tion beam. In a safety system three independent very fast beam shutter s are installed which close within less than 10 ms at any malfunction of the system. Because the line scan mode is used a scanning device mo ves the patient with up to 50 cm/s through the two monochromatic beams . As a detector a two-line ionization chamber with a spatial resolutio n of 0.4 mm is installed. The chamber has a dynamic range of 39,000:1 and reads a line within 0.73 ms. The quantum efficiency for 33 keV pho tons is 85%. The computer system is used for control of the system, da ta acquisition, image processing and presentation. Since 1990 thirty p atients were studied with the system NIKOS. In all cases follow-up inv estigations after interventions like bypass surgery, angioplasty or ro tablation were performed. Intravenous angiograms from investigations w ith version III of the system are presented.