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Three medical application beamlines of the SPring-8 are planned to be installed. The first beamline is a beamline from a bending magnet. The remaining two beamlines are from insertion devices. Medical application user group of SPring-8 recommends that those beamlines should be from a wiggler and undulator. Our proposal is as follows: the first goal of the beamline is to develop a coronary cineangiographic system. Single-energy X-ray exposure with energy above K-edge of iodine (contrast medium) is proposed to reduce exposure dose. X-ray with this energy produces cineangiogram with high contrast. To reduce, furthermore, exposure dose to the patient, 37 keV monochromatic X-ray has been proposed, even though its image contrast might slightly deteriorate. A multipole wiggler should be installed in the medical beamline, mainly because we use nonsymmetric monochromator to obtain wide exposure field. Another beamline should be from an undulator. The first application of this beamline is a divergent and monochromatic X-ray source which is necessary for taking diagnostic images of human subjects. The X-ray source will be generated by fluorescent X-ray. Another application of this beamline will be development of diagnostic imaging system using a expanded X-ray by multi-layer and super mirror. Diagnostic imaging systems to be developed using both beamlines will be: 1. Monochromatic coronary angiography, 2. Monochromatic X-ray CT, based on transmitted, Compton scatter, Thomson scatter, fluorescent, and energy subtraction, 3. Microangiography, 4. Tumor detection imaging, 5. Phase-contrast X-ray imaging whose sensitivity is much higher than that of the absorption-contrast imaging, and so on.

Our initial studies in animal experiments using K-edge energy subtraction transvenous coronary angiography at the Photon Factory were undertaken using an iodine filter for energy switching combined with an X-ray image intensifier. In vivo subtracted images of coronary arteries in dogs were obtained in the form of motion pictures. However, the image quality was not good for medical examinations because the contrast material was highly diluted. A new image detector with a fluorescent-screen lens-coupling approach has been developed to take high quality images. By using the new detector in place of the X-ray image intensifier, image quality has markedly increased in coronary angiography.

In this review article, the medical applications of synchrotron radiation in Japan are briefly described, principally on angiography and monochromatic x-ray CT, covering the past, present, and near future. † The history of our medical application began in 1983, when a diagnostic group was formed in Tsukuba. In 1985, the first video image of the cardiovascular system in a cat was successfully taken with K-edge subtraction. Based on the experiences with cats, studies on dogs and goats were carried out, and later human studies were performed in 1996.

We describe a new attenuation correction method for fluorescent x-ray computed tomography (FXCT) applied to image nonradioactive contrast materials in vivo. The principle of the FXCT imaging is that of computed tomography of the first generation. In order to detect smaller iodine concentrations, attenuation correction is needed, because we can not observe net fluorescent x-rays radiating from contrast materials without attenuation within an object. We present a correction method based on the measurement process. The derivative equation system is solved by the least squares method using the singular value decomposition. The attenuation correction method is applied to the projections obtained from the experiment using the synchrotron radiation to confirm its effectiveness.

Two-dimensional synchrotron radiation (SR) coronary arteriography (CAG) with aortographic contrast injection was considered theoretically and animal experiments were performed to examine its diagnostic ability. This system consisted of a silicon monocrystal, fluorescent plate, avalanche-type pickup tube camera, and image acquisition system. The experiment was performed at synchrotron sources in the Photon Factory in Tsukuba. The x-ray energy was adjusted to just above the iodine K-edge.

Interferometric phase-contrast X-ray imaging is experimentally proved to be sensitive to biological soft-tissue features without the need for staining. Radiographic and tomographic applications of this method are attractive from a diagnostic point of view. In this paper, we have presented the principle of phase-contrast X-ray computed tomography and observation results of human soft tissues. We have shown that the structures of soft structures, such as cancer, are clearly revealed. The good image quality motivated us to study the feasibility of the technique for medical applications. An important technical aim is to make an interferometer having large observation area. A two-crystal X-ray interferometer is a candidate as a device for that purpose. We expect that phase-contrast mammography might be possible with such an interferometer.

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.

For the early detection of hepatocellular carcinoma (HCC), the effectiveness of ultrasonography (US) has been widely accepted in Japan. However, US examination of the entire liver is occasionally impossible because of intervening bones, air in the gut or lung, or dense fatty tissue, especially in patients with a small cirrhotic liver. In such patients, computed tomography (CT) has begun to play an increasingly important role in detecting HCC as a complementary imaging method for US. CT is also very useful in differentiating various space-occupying lesions of the liver [1,2], evaluating the location and extension of these lesions, and determining the viability of neoplasms treated by transcatheter arterial embolization (TAE), percutaneous ethanol injection therapy, or chemotherapy. Another advantage of CT is its objectiveness in visualizing the relation between the lesions and the surrounding tissues. For these reasons and because of widespread availability of CT machines in Japan, CT is now performed in almost all patients with HCC and is making a major contribution to the treatment of HCC.

Magnetic resonance imaging (MRI) appeared for use in diagnostic radiology in the early 1980s. This method of diagnostic imaging is characterized by excellent contrast resolution and free direction as well as no exposure to radiation. The intensities of organs and tumors reflect multiple factors, such as proton density, longitudinal relaxation time (Tl), and transverse relaxation time (T2). The weights of these factors are changed by pulse sequences and their timing parameters, whereas X-CT and radionuclide imaging are determined by only one factor. In addition, there are many pulse sequences that can be used in MRI, such as a set of radiofrequency pulses, gradient pulses and time intervals between pulses. However, the standard technique used is spin echo imaging because of the high signal to noise ratio.

Computed tomography (CT) and magnetic resonance imaging (MRI) are useful in the diagnosis of portal hypertension, not only in the demonstration of collaterals but also in the evaluation of the underlying disease and its treatment (e. g., patency of portocaval shunt). Both procedures can examine any parts of the body with minimum interference from body conditions (gas, bone, and/or fat) as long as the patient is cooperative during the examination.

The image obtained by X-ray computed tomography (CT) is a computer-assisted reconstruction of averaged X-ray attenuation in the individual pixel of the matrix. Therefore, CT reflects essentially the same information as the conventional X-ray photograph. The advantage and characteristics of CT are seen in better contrast resolution in a true tomogram. With the conventional film-screen system, a normal organ and its neoplasm show a similar X-ray attenu-ation and cannot be distinguished without the aid of contrast material. CT is capable of distin-guishing a 0.5% difference in contrast expressed in Hounsfield units or numbers (which are set at 0 for water and —1000 for air), whereas the conventional film-screen system can barely distinguish ascites from the liver (about 6% contrast).