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

Intravenous coronary angiography with synchrotron radiation

Worldwide several systems for Digital Subtraction Angiography in energy subtraction mode (dichromography) with synchrotron radiation are developed. Two of the systems–the system NIKOS in the Hamburger Synchrotronstrahlungslabor HASYLAB in Hamburg and the system in Brookhaven–allow investigations of patients.The aim of the work is to visualize coronary arteries down to 1 mm diameter with an iodine mass density of 1 mg/cm2, thus allowing non-invasive investigations by intravenous application of the contrast medium. The two images for subtraction are simultaneously 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-monochromatic beams with a bandwidth of 180 eV out of the white synchrotron radiation beam.In a safety system three independent very fast beam shutters 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 moves the patient with up to 50 cm/s through the two monochromatic beams.As a detector a two-line ionization chamber with a spatial resolution 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 photons is 85%.The computer system is used for control of the system, data acquisition, image processing and presentation.Since 1990 thirty patients were studied with the system NIKOS. In all cases follow-up investigations after interventions like bypass surgery, angioplasty or rotablation were performed. Intravenous angiograms from investigations with version III of the system are presented

Coronary angiography with synchrotron radiation

Worldwide several systems for Digital Subtraction Angiography in energy subtraction mode (dichromography) are developed. One of the systems which allows investigations of patients - the system NIKOS in the Hamburger Synchrotronstrahlungslabor HASYLAB at DESY is described. The system consists out of six main parts : The 20 pole wiggler HARWI in the beamline W2 of the storage ring DORIS, the two beam monochromator for the two 12.5 cm wide monochromatic X-ray beams, the safety system, the fast scanning device, the fast low-noise two-line ionization chamber and the computer system. Since 1990 patients were investigated with the system NIKOS. Aim of the work is to visualize coronary arteries down to 1 mm diameter with an iodine mass density of 1 mg/cm2, thus allowing non-invasive investigations by intravenous application of the contrast medium. The two images for subtraction are simultaneously taken with photon energies just below and above the iodine K-edge (33.17 keV) in a line scan mode. Intravenous angiograms from investigations with version III of the system NIKOS are presented and the next steps for getting an increased image quality are described

A dual line multicell ionization chamber for transvenous coronary angiography with synchrotron radiation

A position sensitive one‐dimensional x‐ray detector with a large dynamic range (≳214:1) for high photon fluxes with fast image recording sequence (300 ms per frame) has been developed for transvenous coronary angiography with synchrotron radiation. A position resolution of 1 LP/mm and a detection quantum efficiency (DQE) of at least 58% (for 11 000 photons per pixel) has been achieved for 33 keV photons in a Xe‐CO2 gas mixture at 20 bars. The use of Kr‐CO2 as conversion gas provides a better contrast of the weak iodine signal than Xe‐CO2 or Si, respectively, for a fraction of 2% of the second harmonics of the synchrotron beam used

The concept of spatial frequency depending DQE and its application to a comparison of two detectors used in transvenous coronary angiography

A comparison of two different multi-channel line detectors utilized in transvenous coronary angiography was performed. An Li+ drifted silicon strip detector (SSD) was tested at the SMERF facility X17B2 at the National Synchrotron Light Source (NSLS). An ionization chamber (IC) was tested at the W2 beamline at HASYLAB. Both detectors were operated in the charge-integrating mode. The main purpose was to measure and compare the Modulation Transfer Function (MTF(f)), Noise Power Spectrum (NPS(f)), Detective Quantum Efficiency (DQE(f)) in terms of spatial frequencies and the dynamic range of both detector systems. It turned out that the IC is superior to the SSD in time resolution and dynamic range at a single gain setting and has a slight advantage in the transmission of high spatial frequencies. Although for high photon flux the DQE values of the IC exceed those of the SSD, it is the reverse for low photon flux caused by a higher noise floor of the read-out electronics. This makes the SSD superior to the IC since the incident flux is limited by the tolerable entry dose to the patients. For the comparison other criteria like price, reliability, maintenance, etc., are not taken into consideration