Masami Ando

Beamline for a Soft X-Ray Undulator at the Photon Factory

Present status of a beamline for a 60 period permanent magnet soft x-ray undulator inserted in the 2.5-GeV Photon Factory storage ring is described in detail. Two soft x-ray monochromators and a soft x-ray microscope installed in the beamline are also described. Design concepts of these instruments are presented and some remarks are made on their installations.

Medical activities of synchrotron radiation in Japan — Intravenous coronary cineangiography —

A method of examination less invasive and more convenient than conventional coronary angiography has been sought. We have developed intravenous coronary cineangiography (cine-IVCAG) by using a two-dimensional X-ray beam from synchrotron radiation (SR). We investigated its use to visualize the coronary arteries in dogs and a goat and then used it clinically. SR, which has high intensity radiation, was reflected asymmetrically with a silicon crystal to produce an intense, wide and monochromatic (33.3 or 37 KeV) X-ray beam. The subjects received an intravenous injection of contrast agent into the central veins, then the irradiation by the two-dimensional X-ray beam was performed. Images were acquired with an image intensifier and were taken with a CCD camera for 4 msec periods at 33 msec intervals (30 images/sec), which were recorded with a digital fluorography system. The cine-IVCAG was obtained in the dogs and a goat and was shown to be able to visualize even an intentionally created coronary stenosis about 1 mm in length. Furthermore, the cine-IVCAG permitted clear visualization of the coronary arteries and enabled evaluation of coronary artery lesions in the patients with coronary artery disease. Therefore, the cine-IVCAG can be conveniently used for the evaluation of coronary arteries and may be clinically used for screening and follow-up of coronary artery disease.

Development of the photon-counting 256ch CdTe line detector

We have developed a photon-counting 256ch CdTe line detector system for a monochromatic x-ray CT system using fluorescent x-rays generated by synchrotron radiation. The size of each detector element is 1.98 mm(w) X 1.98 mm(h) X 0.5 mm(t). Each element has two discriminators (an upper and a lower discriminator) and two 16-bit counters (an upper and a lower counter). Each discriminator rejects pulses having a pulse height lower than the chosen voltage limits. All pulses in between the upper and lower voltage limits were obtained by subtracting the upper counter value from the lower counter value. By changing the voltage limits, we can obtain an incident x-ray energy spectrum. Several energy spectra for the fluorescent x-ray and standard (gamma) -ray sources were measured by using this detector. The detector showed a sufficient energy resolution, and has been found to be suitable as a detector of monochromatic x-ray CT.

Specific Element Imaging by Monochromatic X-ray CT Using Synchrotron Radiation

We have developed a high energy, high resolution monochromatic x-ray CT system using Synchrotron Radiation. At the present stage, we have achieved the production of monochromatic x-rays up to 75 keV and succeeded in taking the CT images of materials up to 50 keV with large absorption coefficients that are difficult to image by conventional methods. We have produced three-dimensional CT images of a sintered iron ore specimen with a pixel size of about 7 µ m with a slice thickness of 20 µ m. The three-dimensionally reconstructed images of the sintered iron ore provide such information on the inside of sinter that is not obtainable by conventional surface observation alone. To evaluate the contrast resolution using the K-edge subtraction method we have investigated iodine and gadolinium solutions from the subtraction CT images. These results showed that the SR-CT system can quantitatively and nondestructively measure the trace distribution of a given element in the object by selecting the monochromatic x-rays corresponding to the K-edge energy of the element. The developed SR-CT will become a powerful tool to evaluate a wide variety of materials, including in vivo tissues and ferrous materials.

Soft X-ray Microscope with Free-standing Zone Plates

High resolution soft x-ray microscopes have been demonstrated by using zone plate optics (Schmahl, 1983; Kirz and Rarback, 1985). Zone plates can be fabricated by the laser holographic lithography or the electron beam lithography. The latter method is generally used because a wide variety of zone plate specifications can be achieved. The collection efficiency of the zone plate depends on its structure. It is usual that the zone plate is supported by a thin substrate. The absorptivity of the substrate material cannot be negligible in the ultra soft x-ray region.