D. Chapman

First operation of the medical research facility at the NSLS for coronary angiography

The Synchrotron Medical Research Facility (SMERF) at the National Synchrotron Light Source has been completed and is operational for human coronary angiography experiments. The imaging system and hardware have been brought to SMERF from the Stanford Synchrotron Radiation Laboratory where prior studies were carried out. SMERF consists of a suite of rooms at the end of the high‐field superconducting wiggler X17 beam line and is classified as an Ambulatory Health Care Facility. Since October of 1990 the coronary arteries of five patients have been imaged. Continuously improving image quality has shown that a large part of both the right coronary artery and the left anterior descending coronary artery can be imaged following a venous injection of contrast agent.

A single crystal bent Laue monochromator for coronary angiography

Abstract A new monochromator has been developed for the human coronary angiography project at the National Synchrotron Light Source. It is a single bent crystal of silicon in the Laue transmission geometry. The design, testing and use of this monochromator in a human imaging procedure will be discussed.

Cryogenic cooling of monochromators

In this paper, we report on the design and x‐ray diffraction properties of cryocooled silicon single crystals exposed to the following wiggler beams: power density: 150 W/mm2, total power: 75 W and power density: 0.5 W/mm2, total power: 100 W. First, thermomechanical and engineering aspects of low‐temperature crystal cooling are discussed, leading to two basic cooling geometries: internal cooling and side cooling. Experimental tests of both these cooling schemes at NSLS on beam lines X25 and X17 are then described and discussed. Finally, engineering problems related to the integration of cryogenic cooling on ESRF beam lines are presented.

The superconducting wiggler beamport at the National Synchrotron Light Source

Abstract A beamport is currently being instrumented to utilize high energy synchrotron radiation from the superconducting wiggler magnet on the X-ray ring at the National Synchrotron Light Source. Two independent programs are being developed to run in tandem, nonconcurrently, on the central beamline: material sciences on X17B1 and medical research/angiography on X17B2. A high pressure research program will run independently on a side station. X17C. Considerations in the design of the beamline include handling severe power loading, radiation shielding protection and beam energy filtering.

PHOTON: A program for synchrotron radiation dose calculations

Abstract A computer program, PHOTON, has been developed to calculate radiation levels associated with a general synchrotron beamline arrangement. PHOTON calculates the transmitted and scattered spectra as the synchrotron beam passes through sequential filters. The Compton component of this scattered radiation can then be passed through a series of materials composing a shielding wall. This radiation can then be used to calculate a dose in a medium outside of the shielding wall. Program input is such that the sequence of operations is easily followed and modified for any beamline configuration. Measurements have been performed by Brauer on existing NSLS beamlines in various geometries. Good agreement between calculated and measured dose values was found in all cases. This agreement implies that results obtained for shielding of sources containing a wide range of energies, such as that of the NSLS High Field Superconducting Wiggler, are correct.

Performance evaluation of a bent Laue monochromator

Abstract A prototype focusing Laue geometry dual-energy monochromator, designed fro human coronary angiography, has been tested at the National Synchrotron Light Source. The monochromatic photon beams from (111) reflections from two cylindrically bent [100] wafers of silicon were adjusted such that the energy of one of the beams was just above the K edge of iodine and the other beams energy was just below the edge. Focusing of the beams by the bent crystals was measured with photographic film. An incident beam 4 mm high was focused to a line less than 0.3 mm high at a distance of 3 m. The monochromatic flux was determined by measuring the integrated intensities of a standard Mo powder sample and was excellent agreement with the theoretical estimates. The reflectivity of the crystals was enhanced due to bending by an order of magnitude over the dynamical value.

Multiple energy computed tomography (MECT) at the NSLS: Status report

Status of the synchrotron‐based computed tomography system, called multiple energy computed tomography (MECT), is described. MECT, that uses monochromatic beams from the X17 superconducting wiggler beam line at the National Synchrotron Light Source, will be used for imaging the human head and neck. An earlier prototype MECT produced images of phantoms and living rodents. This report summarizes the studies with the prototype, and describes the design, construction, and test results of the clinical MECT system components.

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.

Monochromator harmonic content measurements and calculations at energies above 20 keV

Measurements of the harmonic content from single‐ and double‐crystal silicon monochromators have been made in the 20‐ to 100‐keV range at the X17 superconducting wiggler beam line at the NSLS. These measurements are compared with calculations which estimate the monochromatic beam harmonic content and the detection system efficiency with good agreement. At high photon energies (≳20 keV), the scattering of x rays from an amorphous scatterer is dominated by the inelastic Compton process. At large scattering angles this will completely overwhelm the more forward directed elastic scattering. The Compton x‐ray energy shift is large enough to make the distinction between elastic and Compton scattering unambiguous when a spectrum is acquired with a solid‐state detector. This shift, which is energy dependent, allows the measurement of the relative harmonic intensity in a way that is not affected by pulse pileup in the detector and electronics. The present measurements were done to assess the level of harmonic cont...