H.J. Gordon

Bronchial imaging in humans using xenon K-edge dichromography

Abstract This report describes the initial use of K-edge xenon dichromography for imaging the bronchial tree in humans. The subjects inhale an anatomic dead-space volume of a mixture of 80% xenon and 20% oxygen, following which a dichromographic line-scan image is recorded using two monochromatic synchrotron radiation beams closely bracketing the k-edge of xenon (34.56 keV). Images of airways, from main-stem bronchi to fourth-order branches, are recorded with a pixel resolution of 0.5×0.5 mm. The scanning rate is 12 cm/s, the line exposure time is 4 ms, the skin dose to the exposed area (125 mm × 150 mm) is

Synchrotron radiation coronary angiography with a dual-beam, dual-detector imaging system

Abstract This is a study of the use of a dual-beam, dual-detector synchrotron radiation system for transvenous coronary angiography in a human subject. This system eliminates the need for rapid beam switching, increases X-ray fluence by a factor of about 2.5, and makes it possible to record high- and low-energy images simultaneously, thus excluding artifacts arising from time subtraction. Besides coronary angiography, it may be possible to image the vertebral-basilar arterial circulation with this system.

Transvenous coronary angiography using synchrotron radiation

X-ray-based angiography continues to be the standard method of assessing the severity and the extent of coronary atherosclerosis. The relative insensitivity of conventional X-ray imaging systems to iodine-containing contrast agents necessitates that the images be acquired with essentially undiluted contrast agent in the lumen of the vessels being studied. This, in turn, requires arterial catheterization and the insertion of the catheter tip in or near the ostia of the vessels and the direct injection of the contrast agent. The health risks and monetary costs of the procedure have limited its use to circumstances in which there is a high probability of the presence of severe disease. Despite these problems, coronary angiography has been employed in serial studies to evaluate the effects of drug therapy and diet on coronary atherosclerosis (1).

Coronary angiography using synchrotron radiation (invited)

Imaging of coronary arteries using a venous instead of an arterial injection of contrast agent could provide a much safer method to diagnose heart disease. The tunability, intensity, and collimation of synchrotron radiation x‐ray beams makes possible imaging systems with greatly improved imaging sensitivity. A pair of fan x‐ray beams, a movable patient chair, and a multielement x‐ray detector are used to acquire a pair of x‐ray images above and below the iodine K edge. The logarithmic subtraction of these two images produces an image with excellent sensitivity to contrast agent and minimal sensitivity to bone and tissue. High‐quality images from a dog and preliminary images from five humans have been obtained. Improvements are being made to the system to increase the effective radiation flux and to measure the position of both x‐ray beams.

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

Abstract 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.

Coronary steal caused by a coronary artery fistula

C ORONARY ARTERY fistulae, anomalous connections between the coronary arteries and a cardiac chamber or the venous circulation, are the most common hemodynamically significant coronary congenital anomalies,’ found in up to 0.2% of the adult population.’ Many patients with coronary fistulae remain asymptomatic, but others present with angina or myocardial infarction due, in part, to a “coronary steal.” Definitive treatment of symptomatic coronary fistulae usually requires cardiac surgery, often with cardiopulmonary bypass (CPB). Although this problem is likely to be encountered by the practicing cardiovascular anesthesiologist, the principles of anesthetic management have not been previously published. A case concerning a congenital fistula between the left main coronary artery (LMCA) and the pulmonary artery (PA) in an adult patient who presented with unstable angina is presented. The pertinent literature is reviewed, and the implications for the anesthesiologist are examined.

Transvenous coronary angiography in dogs using synchrotron radiation

SummaryThe application of coronary angiography is limited because it requires arterial invasion and the direct injection of contrast agent into the coronary arteries. A prototype system has been developed which achieves sufficient sensitivity to the iodinated contrast agent to allow the visualization of coronary arteries in dogs after its intravenous injection. The system uses two fan beams of x-rays from an electron storage ring and a 300 element linear silicon detector. Two interlaced images, spaced at 150 eV above and below the K absorption edge of iodine (33.2 keV), are acquired and the logarithmic subtraction of these two images produces an image which has maximal sensitivity to iodine and minimal sensitivity to soft tissue and bone. This approach appears suitable for studies on human subjects.

Effects of spatial resolution and spectral purity on transvenous coronary angiography images

Measurements have been made on the National Synchrotron Light Source Coronary Angiography X17B2 beamline under ideal and real imaging conditions to investigate the optimal imaging conditions for spatial resolution and spectral purity.

A 1200 ELEMENT DETECTOR SYSTEM FOR SYNCHROTRON-BASED CORONARY ANGIOGRAPHY

Abstract A 1200 channel Si(Li) detector system has been developed for transvenous coronary angiography experiments using synchrotron radiation. It is part of the synchrotron medical imaging facility at the National Synchrotron Light Source. The detector is made from a single crystal of lithium-drifted silicon with an active area 150 mm long × 11 mm high × 5 mm thick. The elements are arranged in two parallel rows of 600 elements with a center-to-center spacing of 0.25 mm. All 1200 elements are read out simultaneously every 4 ms. An Intel 80486 based computer with a high speed digital signal processing interface is used to control the beamline hardware and to acquire a series of images. The signal-to-noise, linearity and resolution of the system have been measured. Human images have been taken with this system.

Imaging of coronary arteries using synchrotron radiation

Abstract Currently the imaging of coronary arteries is dangerous since it requires that a catheter be inserted into a peripheral artery and threaded up to the heart so that contrast agent can be injected directly into the artery being imaged. Using synchrotron radiation it may be possible to use a much safer venous injection of a contrast agent and still have sufficient image contrast to visualize the coronary arteries. A pair of monochromatized X-ray beams are used which have energies that bracket the iodine K absorption edge where the iodine absorption cross section jumps by a factor of six. Therefore, the logarithmic difference image has excellent sensitivity to contrast agent and minimal sensitivity to tissue and bone. Images have been taken of both dogs and humans. Improvements are being made to the imaging system which will substantially improve the image quality.