ISSN:
1089-7623
Source:
AIP Digital Archive
Topics:
Physics
,
Electrical Engineering, Measurement and Control Technology
Notes:
We have been developing a two-dimensional imaging system for K-edge subtraction angiography with a large size monochromatic SR beam by using asymmetrical reflection from a crystal and a two-dimensional detector system [M. Akisada et al., Nucl. Instrum. Methods A 246, 713 (1987); K. Hyodo et al., KEK-Preprint 89–181 (1990)]. Through our preliminary experiments, the advantages in the two-dimensional imaging system with real-time image aquisition were confirmed. However, taking account of a clinical application, it needs a faster energy switching system between above and below the K-edge energy and the incident x-ray intensity onto a patient should be more than 1011 photons mm2/s to attain subtracted images with high S/N ratio. If the dual SR beam produced by an EMPW would be used, we can overcome those problems. The EMPW installed at the accumulation ring (AR) primarily designed to produce elliptically polarized SR also naturally yields dual and very intense linearly polarized SR [S. Yamamoto et al., Phys. Rev. Lett. 62, 2672 (1989)]. Their angle separation is described as Ψ=2×Kx/γ(rad), where Kx=0.834Bxeλu, Bxe is the value of the horizontal magnetic field, λu is the periodicity of the magnet array, and γ is the ratio of the acceleration energy over the rest energy of an electron. In the case of the current device, its maximum separation is about 0.48 mrad.The advantages of use of these beams are as follows: (a) They will cause no resonant vibration of a crystal which deteriorates x-ray energy resolution because only a mechanical switch of the incident x-ray energy is needed in the current imaging system [K. Hyodo et al., KEK-Preprint 89–181 (1990)]. (b) The x-ray intensity is large enough for clinical application. Two asymmetrical cut Si(311) crystals were set to attain each linearly polarized SR beam, which corresponds to the x-ray energy at above and below the K edge, respectively. Both beams were introduced to an II-TV detector system after a vessel phantom filled with iodine concentration of 15% in weight. The spatial and concentration resolution of the x-ray images were evaluated. The possibility of this new imaging method for angiography was successfully demonstrated.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.1142664
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