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At least 19 recordsLinked to original sources

PubMed1997

Medical applications of synchrotron radiation x-rays.

The use of synchrotron radiation is not widespread in the field of medicine and in fact few health-care professionals have even heard of it. It is the purpose of this article to explain what it is and to give some examples of how it can contribute to medical science. X-rays have been used for diagnostic medical imaging for more than 100 years and, whilst new techniques such as computed tomography have been developed, the means of producing x-rays has altered little during that time. Synchrotron radiation sources provide multiple, extremely intense and tuneable beams of photons over a huge range of energies from infrared through to hard x-rays. Their advent has revolutionized many experimental techniques and synchrotron radiation is being applied across many fields from imaging to molecular dynamics. It has spawned several methods for studying live and wet tissue samples, yielding information on both structure and composition on all length scales down to atomic resolution. Such techniques have played a crucial role in the development of molecular biology and the solution of protein structures. The application of synchrotron radiation in the field of radiography is now expanding and it is clear that very substantial improvements in image quality and patient dose can be realized. Following an overview of the production and properties of synchrotron radiation, some of the ways in which this remarkable tool has already been exploited for medical research are reviewed and some potential clinical opportunities highlighted.

Animals↗

PubMed1996

Intravenous coronary angiography with dichromography using synchrotron radiation.

Dichromography represents a digital subtraction angiography mode based on energy substraction which allows imaging of fast moving subjects like the heart. For logarithmic subtraction 2 images with X-rays just below and above the iodine K-edge (33.17 keV) are simultaneously obtained in a line scan mode. Monochromatic X-rays of sufficient intensity to visualize coronary arteries of 1 mm diameter with extremely low iodine concentrations (1 mg/cm2) after venous injection is only provided by synchrotron radiation. The system NIKOS (non-invasive coronary arteriography with synchrotron radiation) at the Deutsches Elektronen Synchrotron (DESY) consists of 6 components: a wiggler, a monochromator, a safety system, a scanning device, a detector and a computer system. After experimental studies in dogs patients are imaged since 1990. Initial results demonstrate feasibility and safety of synchrotron radiation coronary angiography. Large scale studies are designed to further evaluate sensitivity and specificity. When compact synchrotron radiation sources become available, this technique could be used for follow-up studies and for evaluation of certain high coronary risk populations.

Angiography, Digital Subtraction↗

PubMed1991

Synchrotron-produced ultrasoft X-rays: a tool for testing biophysical models of radiation action.

Ultrasoft X-rays are useful for mechanistic studies of ionizing radiation damage in living cells due to the localized nature of their energy depositions. To date radiobiology experiments in this energy region have relied on characteristic X-rays (mainly Alk and Ck) from X-ray tubes. However, limitations in the photon intensity and the available energies from X-ray tube sources prevent a definitive characterization of the relationship between photon energy and biological damage. Synchrotron radiation has the potential to avoid these limitations, since it produces X-rays with high intensity over a continuous spectrum. We have established a synchrotron-based system for radiation biology studies using the ES-0 exposure station of the Center for X-ray Lithography at the University of Wisconsin Synchrotron Radiation Center storage ring, Aladdin. A characterization of the system including spectral and intensity properties of the photon beam is presented. The first mammalian cell survival curve for synchrotron-produced ultrasoft X-rays was generated and is presented. Cell survival curves of C3H/10T 1/2 cells using synchrotron radiation of 1.48 keV agree with previous data using Alk X-rays (1.49 keV). An RBE of 1.47 +/- 0.30 at the 10% survival level was measured with reference to 250 kVp X-rays.

Animals↗

PubMed1997

Time-resolved synchrotron X-ray "footprinting", a new approach to the study of nucleic acid structure and function: application to protein-DNA interactions and RNA folding.

Hydroxyl radicals (.OH) can cleave the phosphodiester backbone of nucleic acids and are valuable reagents in the study of nucleic acid structure and protein-nucleic acid interactions. Irradiation of solutions by high flux "white light" X-ray beams based on bending magnet beamlines at the National Synchrotron Light Source (NSLS) yields sufficient concentrations of .OH so that quantitative nuclease protection ("footprinting") studies of DNA and RNA can be conducted with a duration of exposure in the range of 50 to 100 ms. The sensitivity of DNA and RNA to X-ray mediated .OH cleavage is equivalent. Both nucleic acids are completely protected from synchrotron X-ray induced cleavage by the presence of thiourea in the sample solution, demonstrating that cleavage is suppressed by a free radical scavenger. The utility of this time-dependent approach to footprinting is demonstrated with a synchrotron X-ray footprint of a protein-DNA complex and by a time-resolved footprinting analysis of the Mg(2+)-dependent folding of the Tetrahymena thermophilia L-21 ScaI ribozyme RNA. Equilibrium titrations reveal differences among the ribozyme domains in the cooperativity of Mg(2+)-dependent .OH protection. RNA .OH protection progress curves were obtained for several regions of the ribozyme over timescales of 30 seconds to several minutes. Progress curves ranging from > or = 3.5 to 0.4 min-1 were obtained for the P4-P6 and P5 sub-domains and the P3-P7 domain, respectively. The .OH protection progress curves have been correlated with the available biochemical, structural and modeling data to generate a model of the ribozyme folding pathway. Rate differences observed for specific regions within domains provide evidence for steps in the folding pathway not previously observed. Synchrotron X-ray footprinting is a new approach of general applicability for the study of time-resolved structural changes of nucleic acid conformation and protein-nucleic acid complexes.

Animals↗

PubMed1998

A microangiographic technique using synchrotron radiation to visualize dermal circulation in vivo.

Conventional angiography cannot resolve dermal small vessels with a diameter of 200 microm or less. In vitro microangiography is currently characterized by better spatial resolution than conventional angiography but does not allow visualization of the blood stream in dermal vessels in vivo. In this study, we introduce a novel synchrotron radiation microangiographic system for visualizing the structure of and blood flow in dermal microvessels in vivo repeatedly. We used monochromatic synchrotron radiation with an energy just above the k-edge of iodine (33.3 keV) as an x-ray and a high-definition television camera system with a high-sensitivity image pick-up tube for detection. The 33.3-keV monochromatic synchrotron radiation allows detection of a small amount of iodine, and the high-definition television camera system can resolve small vessels with high-spatial resolution and no loss of sensitivity. We performed synchrotron radiation angiography of superficial inferior epigastric arteries and their branches in nine rats, and of the caudal artery in 14 rats, and compared angiographic images taken by the current system with those taken by a conventional angiographic system in seven rats. With this new microangiographic technique, we could visualize small dermal vessels with a diameter as low as 50 microm. In addition, repeated angiograms at baseline and under increasing body temperature could be obtained. This new microangiographic approach is expected to be very useful for the assessment of dermal circulation in patients.

Angiography↗

PubMed1992

[Synchrotron radiation: a new source in x-ray mammography].

This work was aimed at evaluating the image quality obtainable in X-ray mammography using synchrotron radiation monochromatic lines. After a short review of the current mammographic techniques, the main features of synchroton radiation in the X-ray field are analyzed, especially of that emitted by the Adone storage ring. Its features are then compared with the radiation emitted by a Coolidge tube. The experimental unit used in this study, including beamline, monochromator and mammograph, is then described together with the experimental method for carrying out a series of experiments in the mammographic field employing both monochromatic lines (E = 17 keV) and white radiation from conventional sources. The first series of experiments is described, which employed standard phantoms: the dependence of resolution and contrast on both wavelength and thickness of breast specimens is reported. Several mammograms of neoplastic breast specimens were obtained after mastectomy: they were acquired using both synchrotron monochromatic lines and radiation emitted by a conventional tube and employing the same acquisition system. The comparison of the two series of images shows that synchrotron radiation can demonstrate a high number of anatomopathologic details with high definition, contrast and resolution which cannot be obtained by means of a conventional source. Our results appear very promising and suggest synchrotron radiation as the major tool in the early diagnosis of neoplastic breast lesions.

Breast Neoplasms↗

PubMed1997

The synchrotron beam, a new dimension for contrast media research?

Synchrotron sources can provide intense, collimated and tunable X-ray beams suitable for medical imaging and research, allowing the use of monochromatic X-rays for human examinations. At the European Synchrotron Radiation Facility (ESRF), a beam line dedicated to medical research is under commissioning. Two imaging programs are being developed, for coronary angiography and cerebral CT. The new monochromatic imaging systems should improve image contrast and provide better image quantification. The properties of synchrotron radiation are described, as well as the instrumentation of the medical beam line and its 2 imaging programs. The new possibilities offered by synchrotron radiation for contrast media research are discussed, the improvement on concentration measurement precision achievable is underlined.

Academies and Institutes↗

PubMed1988

X-ray fluorescence with synchrotron radiation.

The use of synchrotron radiation for X-ray fluorescence has several advantages over the use of other conventional X-ray sources. The principles of synchrotron radiation and methods for applying synchrotron radiation to the X-ray fluorescence measurements of trace elements are discussed. The Brookhaven National Laboratory X-ray microprobe, facilities dedicated to X-ray fluorescence, and related analytical techniques are discussed. Some examples of trace element analyses in biological materials with synchrotron radiation are presented.

Electron Probe Microanalysis↗

PubMed1990

New trend of cardiac imaging--intravenous coronary arteriography by synchrotron radiation.

Synchrotron radiation is a broadspectrum intense X-ray beam. Selected X-ray wavelength was obtained by Bragg reflex. That is a monochromatic beam, which has a high spatial resolution, and has a K-edge discontinuity in attenuation coefficient, which, by energy subtraction, contributes to improve time resolution. An attempt to apply this method to intravenous coronary arteriography was performed in 7 anesthetized dogs. The beam was obtained by synchrotron radiation from accumulation ring, was reflected by silicon crystal, and was detected by 7 inch image intensifier system. Two-dimensional real time images were recorded on video tape. Phantom experiment was also performed. In dogs, coronary arteries were clearly distinguished by synchrotron radiation, especially at real time by video system. Phantom experiment suggested that coronary arteries could be visualized even over the visualized left ventricle. In conclusion, synchrotron radiation using two-dimensional real time images is expected to be useful in intravenous coronary arteriography in man.

Animals↗

PubMed1994

Synchrotron X-ray studies of lipids and membranes: a critique.

This review gives a description of techniques, suitable for the study of lipid dispersions and unorientated membranes, that are available at synchrotron facilities to determine either the kinetics of transitional phenomena in the time after a temperature or pressure jump is initiated, or the phases present while a sample undergoes a phase transition. Included in this description is information about synchrotron X-ray sources, sample holders and temperature controllers, detection systems, as well as data reduction. Examples involving lipid dispersions are provided to illustrate the application of these methods using synchrotron radiation.

Kinetics↗

PubMed1998

Following the folding of RNA with time-resolved synchrotron X-ray footprinting.

The rapid mixing synchrotron X-ray footprinting technique described in this article allows nucleic acid folding and ligand binding reactions to be followed on a millisecond time resolution with single nucleotide resolution. In principle, the change in .OH protection of every nucleotide in a nucleic acid hundreds of nucleotides long can be monitored separately. In addition, a wide range of solution conditions are compatible with the radiolytic generation of .OH. These characteristics of synchrotron X-ray footprinting create opportunities for conducting thermodynamic and kinetic studies of nucleic acids that are both comprehensive and detailed. Kinetic footprinting studies of a number of systems have been initiated by the Center for Synchrotron Biosciences using this technique.

Flow Injection Analysis↗

PubMed1995

High-resolution macromolecular structure determination using CCD detectors and synchrotron radiation.

BACKGROUND: Synchrotron radiation sources have made impressive contributions to macromolecular crystallography. The delay in development of appropriate X-ray detectors has, however, been a significant limitation to their efficient use. New technologies, based on charge-coupled devices (CCDs), provide capabilities for faster, more accurate, automated data collection. RESULTS: A CCD-based X-ray detector has been developed for use in macromolecular crystallography and has been in operation for about one and a half years at the Cornell High Energy Synchrotron Source. It has been used for a variety of crystallographic projects, including a number of high-resolution structural studies. The statistical quality of the data, the detector's ease and efficiency of use, and the growing number of structural results illustrate the practical utility of this new detector system. CONCLUSIONS: The new detector has enhanced capabilities for measuring diffraction patterns from crystals of macromolecules, especially at high resolution, when the X-ray intensities are weak. The survey of results described here ranges from virus crystallography to weakly diffracting small-molecule structure determination and demonstrates the potential of CCD detectors when combined with synchrotron radiation sources.

Amino Acid Sequence↗

PubMed1999

Polymorph determination for the GP IIb/IIIa antagonist, roxifiban, using a combination of electron diffraction and synchrotron X-ray powder diffraction techniques.

Unit cell parameters of two polymorphs of roxifiban have been determined by a combination of transmission electron microscopy (TEM) single-crystal and synchrotron X-ray powder diffraction techniques. While it was difficult to differentiate the two forms by their standard X-ray diffraction patterns, the high-resolution synchrotron patterns clearly showed striking differences. Unit cells for the two forms required the use of cell parameters derived from TEM diffraction patterns. The two unit cells are, not surprisingly, very similar except for a doubling of one of the axes for form II. The combined use of TEM and synchrotron patterns appears to be a good general approach for characterizing complex (low-symmetry, large unit cell) polymorphs.

Amidines↗

PubMed1996

High-resolution confocal microscopy using synchrotron radiation.

A confocal scanning light microscope coupled to the Daresbury Synchrotron Radiation Source is described. The broad spectrum of synchrotron radiation and the application of achromatic quartz/CaF2 optics allows for confocal imaging over the wavelength range 200-700 nm. This includes UV light, which is particularly suitable for high-resolution imaging. The results of test measurements using 290-nm light indicate that a lateral resolution better than 100 nm is obtained. An additional advantage of the white synchrotron radiation is that the excitation wavelength can be chosen to match the absorption band of any fluorescent dye. The availability of UV light for confocal microscopy enables studies of naturally occurring fluorophores. The potential applications of the microscope are illustrated by the real-time imaging of hormone traffic using the naturally occurring oestrogen coumestrol. (The IUPAC name for coumestrol is 3,9-dihydroxy-6H-benzofurol[3,2-c][1]benzo-pyran-6-one (Chem. Abstr. Reg. No. 479-13-0). The trivial name will be used throughout this paper.

Animals↗

PubMed1998

Integrated software for a macromolecular crystallography synchrotron beamline.

A package of software has been produced for the operation of the synchrotron beamline X12-C at the National Synchrotron Light Source at Brookhaven National Laboratory. Years of observing common user mistakes has enabled the production of software that reduces user errors significantly. Users of the beamline communicate with all the experimental apparatus, including both the data-collection equipment and the beamline components, including the monochromator, through an easy-to-use graphical user interface (GUI). Important features of the system are (1) its modularity, so that different underlying programs or different apparatus can be incorporated easily; (2) its ease of use, minimizing both user errors and training effort; and (3) that most of the experimental operations and parameters are logged automatically, again minimizing errors and facilitating more-or-less automatic reduction of the data. Features of the software are useful enough to have been incorporated into operations at other synchrotron beamlines.

Crystallography, X-Ray↗

PubMed1996

Small-vessel radiography in situ with monochromatic synchrotron radiation.

PURPOSE: To evaluate the usefulness of a radiographic system with monochromatic synchrotron radiation to depict small vessels and peripheral secretory ducts. MATERIALS AND METHODS: Radiography of various organs was tested in 14 anesthetized dogs and pancreatography was performed in an excised human pancreas by using the following system: monochromatic synchrotron radiation with an energy level just above the k absorption edge of iodine as an x-ray source and a high-definition TV system with a high-light-sensitivity image pick-up tube camera coupled with a fluorescent screen as a detector. RESULTS: This system allowed depiction of small vessels (diameter < 50-100 microns) of the heart (penetrating transmural artery), brain (perforating arteries that arise directly in the circle of Willis), and intestinal organs (vasa recta and their submucosal communications) and of small branches (down to the fifth order) of the pancreatic duct. CONCLUSION: The synchrotron radiation system may be useful for evaluating microcirculatory disorders and early-stage malignant tumors in various human organs.

Adult↗

PubMed1998

Ultraspatially-resolved synchrotron infrared microspectroscopy of plant tissue in situ.

Routine use of 6 microm or 12 microm apertures with synchrotron microspectroscopy provide good spectra without excessive co-addition of scans. 100% mapping by stepping in pixel sized increments reveals chemical heterogeneity within cellular dimensions. The brightness of the synchrotron source and the absence of thermal noise compared to a conventional thermal (globar) source yields favorable signal-to-noise operation. The nondivergent characteristics of the source result in minimal loss of radiation at the aperture, hence, spatial resolution approaches the diffraction limit. Details of cellular dimensions are then localized within any maps produced and individual spectra obtained from adjacent pixels clearly shows the striking difference in chemistry even within a microscopic vicinity. In this report the mapping of plant tissue with the synchrotron is contrasted to previous lower spatial resolution mapping experiments done with the globar on similar materials using interpolation between separated sampling spots and larger apertures.

Absorption↗

PubMed1991

Trace element determinations using a 15-keV synchrotron X-ray microprobe.

At the Synchrotron Radiation Source (SRS), Daresbury, U.K., a synchrotron microprobe was constructed, in order to create an instrument capable of analyzing at the ppm or in favorite cases sub-ppm level with a lateral resolution of 10 x 15 microns2. In order to span a wide range of elements to be analyzed, a beam energy of 15 keV was chosen. Focusing and monochromation of the white beam was done in one single step with a high-precision ellipsoidally concave curved Si(111) crystal. Sufficient flux of X-rays in a narrow energy band is available in the spot to measure trace elements at the femtogram level. Measurements on standard materials, reference standard materials, and biological samples showed the lower relative minimum detection limits and higher sensitivity for the higher Z-elements obtainable with micro-SXRF (synchrotron X-ray fluorescence) as compared with microtechniques using ion accelerators. Moreover, the much lower energy deposited in the specimen represents a major argument to prefer X-rays to ions for the analysis of radiation-sensitive samples.

Animals↗