K-edge Digital Subtraction Angiography Research Articles

Dual energy CT at the synchrotron: A piglet model for neurovascular research

Background Although the quality of imaging techniques available for neurovascular angiography in the hospital environment has significantly improved over the last decades, the equipment used for clinical work is not always suited for neurovascular research in animal models. We have previously investigated the suitability of synchrotron-based K-edge digital subtraction angiography (KEDSA) after intravenous injection of iodinated contrast agent for neurovascular angiography in radiography mode in both rabbit and pig models. We now have used the KEDSA technique for the acquisition of three-dimensional images and dual energy CT. Materials and methods All experiments were conducted at the biomedical beamline ID 17 of the European Synchrotron Radiation Facility (ESRF). A solid state germanium (Ge) detector was used for the acquisition of image pairs at 33.0 and 33.3 keV. Three-dimensional images were reconstructed from an image series containing 60 single images taken throughout a full rotation of 360°. CT images were reconstructed from two half-acquisitions with 720 projections each. Results The small detector field of view was a limiting factor in our experiments. Nevertheless, we were able to show that dual energy CT using the KEDSA technique available at ID 17 is suitable for neurovascular research in animal models.

Beam loading compensation for acceleration of multi-bunch electron beam train

The laser undulator compact X-ray source (LUCX) is a test bench used with the compact, high-brightness X-ray generator at KEK (High Energy Accelerator Research Organization). Our group is conducting experiments with LUCX to demonstrate the possibility of K-edge digital subtraction angiography, based on Compton scattering. One of the challenging problems is to generate high-brightness multi-bunch electron beams to compensate for the energy difference arising from the beam loading effect. In this paper we calculate the transient beam loading voltage and energy gain from the RF field in the gun and accelerating tube for a multi-bunch train. To do so we consider the process by which the RF field builds up in the gun and accelerating tube, and the special shape of the RF pulse. We generate and accelerate 100 bunches with a 50 nC electron bunch train, effectively compensating for the beam loading effect by adjusting the injection timing. Using a beam position monitor (BPM) and optical transition radiation (OTR) system, we measure the electron beam energy bunch by bunch. The average energy of a 100-bunch train is 40.5 MeV and the maximum energy difference from bunch to bunch is 0.26 MeV.

Synchrotron-based intravenous cerebral angiography in a small animal model

K-edge digital subtraction angiography (KEDSA), a recently developed synchrotron-based technique, utilizes monochromatic radiation and allows acquisition of high-quality angiography images after intravenous administration of contrast agent. We tested KEDSA for its suitability for intravenous cerebral angiography in an animal model. Adult male New Zealand rabbits were subjected to either angiography with conventional x-ray equipment or synchrotron-based intravenous KEDSA, using an iodine-based contrast agent. Angiography with conventional x-ray equipment after intra-arterial administration of contrast agent demonstrated the major intracranial vessels but no smaller branches. KEDSA was able to visualize the major intracranial vessels as well as smaller branches in both radiography mode (planar images) and tomography mode. Visualization was achieved with as little as 0.5 ml kg−1 of iodinated contrast material. We were able to obtain excellent visualization of the cerebral vasculature in an animal model using intravenous injection of contrast material, using synchrotron-based KEDSA.

Performance of the K-edge digital subtraction angiography imaging system at the European synchrotron radiation facility

In this work we have characterised the K-edge digital subtraction angiography imaging system at the European Synchrotron Radiation Facility (ESRF, Grenoble, France). With this technique, after the minimally invasive intravenous injection of a contrast agent (iodine), two images are recorded simultaneously using monochromatic beams with energies bracketing the iodine K-edge. The image receptor consists of a two-line 432-pixel germanium detector. The logarithmic subtraction of the image set produced results in an iodine-enhanced image, where vessels are clearly visualised and contrast agent concentration can be precisely quantified. We have studied the imaging system in terms of the modulation transfer function, which was measured at the patient position, the 2-D normalised noise power spectrum, calculated for both raw and processed data, and the frequency-dependent detective quantum efficiency, which was calculated directly for final images. In addition, images of cylindrical phantoms with different concentrations of iodine, were also acquired.

The potential for neurovascular intravenous angiography using K-edge digital subtraction angiography

Background: Catheterization of small-caliber blood vessels in the central nervous system can be extremely challenging. Alternatively, intravenous (i.v.) administration of contrast agent is minimally invasive and therefore carries a much lower risk for the patient. With conventional X-ray equipment, volumes of contrast agent that could be safely administered to the patient do not allow acquisition of high-quality images after i.v. injection, because the contrast bolus is extremely diluted by passage through the heart. However, synchrotron-based digital K-edge subtraction angiography does allow acquisition of high-quality images after i.v. administration of relatively small doses of contrast agent. Materials and methods: Eight adult male New Zealand rabbits were used for our experiments. Animals were submitted to both angiography with conventional X-ray equipment and synchrotron-based digital subtraction angiography. Results: With conventional X-ray equipment, no contrast was seen in either cerebral or spinal blood vessels after i.v. injection of iodinated contrast agent. However, using K-edge digital subtraction angiography, as little as 1 ml iodinated contrast agent, when administered as i.v. bolus, yielded images of small-caliber blood vessels in the central nervous system (both brain and spinal cord). Conclusions: If it would be possible to image blood vessels of the same diameter in the central nervous system of human patients, the synchrotron-based technique could yield high-quality images at a significantly lower risk for the patient than conventional X-ray imaging. Images could be acquired where catheterization of feeding blood vessels has proven impossible.

Pulsed X-Ray Source for Non-Invasive Digital Subtraction Angiography

In recent years synchrotron radiation from electron storage rings has been found to be a highly effective source for iodine K-edge Digital Subtraction Angiography (DSA). The intense radiation available at 33 keV photon energy used in DSA provides maximum sensitivity to intraarterial iodine and essentally eliminates contrast due to nonvascular body structures. Arteries can be visualized with high resolution in spite of their constant motion. So far, high energy storage rings are required to produce hard X-rays at 33 keV in sufficient intensity. For a dedicated source a lower energy and therefore smaller storage ring at reduced cost would be desirable. In this paper the potential and limitations of low energy storage rings as dedicated radiation sources for DSA are discussed. With high field pulsed magnets in a 1.2 to 1.5 GeV storage ring of about 10 m diameter the required photon intensity can be provided for DSA. Several photon beam lines can be installed at such a ring and of the order of 10,000 patients per year and beam line could be screened.

Evaluation of Synchrotron X-Rays for Digital Subtraction Coronary Angiography

The intensity and tunability of synchrotron X-ray beams are highly suited to the non-invasive detection of iodine by K-edge digital subtraction angiography. An imnaging system developed for in vivo canine studies is described. Considerations relating to an expanded system for human subject studies are discussed.

The application of synchrotron radiation to non-invasive angiography

Synchrotron radiation provides a new source of X-rays highly-suited to iodine K-edge Digital Subtraction Angiography (DSA). The use of such beams provides maximum sensitivity to intra-arterial iodine and virtually eliminates image contrast due to non-vascular body structures. The intensity of the beams permits short exposure times and allows images to be recorded, in line-scan fashion, in sharp focus despite arterial motions. The sensitivity of this method offers the prospect of visualizing arteries, and in particular the coronary arteries, by peripheral venous injection. The principles of DSA have been demonstrated using phantoms and excised animal hearts, and in vivo studies in animals have begun. The instrumentation developed for this purpose and the results obtained to date are summarized.

Implementation of Digital Subtraction Angiography with a Synchrotron X-Ray Beam

The intense synchrotron radiation produced by wiggler magnets at electron storage rings provides a new source of x-rays highly suited to iodine K-edge digital subtraction angiography. The monochromaticity and tunability provide maximum sensitivity to intraarterial iodine and virtually eliminate contrast due to soft tissue and bone. Visualization of arteries, in particular the coronary arteries, by peripheral venous injection is possible. A system design, based on tests already performed, is presented.