Double beam bent Laue monochromator for coronary angiography

High photon fluxes are crucial in dichromatic digital subtraction angiography with line scan systems to allow for adequate image quality. To obtain images wide enough and with sufficient vertical resolution, each of the two beams used has to be at least 100 mm wide but not more than 0.5 mm high at the patient’s heart with the beam energies bracketing the iodine‐K edge at 33.17 keV. A new monochromator in Laue transmission geometry has been developed, successfully tested at beamline ID11 of the European Synchrotron Radiation Facility (ESRF) and is now in use at the angiography wiggler beamline W2 at HASYLAB. The monochromator consists of two almost identical goniometer heads which are independently controlled. Within each head a bent silicon single crystal extracts a quasimonochromatic beam and focuses it vertically to the patient thus also increasing intensity compared to an unbent crystal. With a storage ring current of 50 mA the new monochromator provides 0.8×10¹¹ photons/mm²/s in front of the patient which is an increase by a factor of 6 compared to the formerly used Bragg design with Ge crystals. Also, it is remarkably more stable against variations of the input power load.