X-ray dark-field and bright-field imaging in the Laue geometry has been successfully demonstrated. Using a Bragg-case asymmetric monochromator that produces an X-ray beam with a 0.3 mrad divergence incident onto an object and a Laue geometry analyzer that can simultaneously provide dark-field imaging (DFI) and bright-field imaging (BFI). The DFI has only an X-ray refraction component on the object without illumination, while the BFI has reasonable illumination. This was achieved by a 1.075 mm thick silicon analyzer with 4, 4, 0 diffraction at 35 keV X-ray photon energy. An image of an insect embedded in polymethylmethacrylate, which can not be visualized by absorption, has been obtained.

An analysis of three-dimensional movement of the mitral valve annulus (MVA) may address the question of geometrical change after mitral valve repair to preserve mitral annular function. Conventionally, annular contraction has been studied for this purpose. We investigated this geometrical change occurring in the anterior half of the MVA and discuss its clinical significance. Three-dimensional images of the MVA during systole were reconstructed from magnetic resonance images of eight normal subjects. The posterior half of the MVA exhibited translational motion. We assume that this portion, exhibiting translational motion as well as contraction, purely follows the motion of the left ventricular contraction. Compensating for the discrepancy between the motion of the aortic root and that of the posterior half of the MVA, the anterior half exhibited a flexible change in shape during systole, thus maintaining a sufficient left ventricular outflow tract (LVOT). The increase in the extent of displacement of the anterior MVA from the posterior half of the MVA during systole, which was 3.6 +/- 1.0 mm (mean +/- SD), indicates the annular flexibility. The preservation of annular flexibility may prevent LVOT obstruction. Further geometrical analysis of patients after mitral repair will clarify annular function as presented in this article.

The development of an artificial graft requires formulation of biomechanical design criteria. The compliance of artifical grafts, based on the intraluminal pressure-internal diameter (Pi-Di) relationship, was measured by a novel method using a digital X-ray imaging system coupled with an edge detection algorithm and a pressure transducer. The Pi-Di values were obtained from digital angiographic images under continuous inflation of a canine femoral artery anastomosed with an expanded poly(tetrafluoroethylene) (ePTFE) vascular graft as a model vessel with a pressurized contrast medium. The Di at Pi using an NIH Image software specially programmed for the entropy filter method, which enables the detection of the edge of the vessel phantoms of the images, was determined. The Pi-Di relationships showed a "J-shape" curve for the artery, a steeper line with a very low pressure-dependent distensibility for the ePTFE graft, and an intermediate curve for the anastomosis protion. The two indices for the vessel compliance, the stiffness parameter (beta value) and the diameter compliance (Cd), both of which were calculated from the Pi-Di relationships, were 10.6 and 6.8%/mmHg x 10(-2) for the artery, 164 and 0.51%/mmHg x 10(-2) for the ePTFE, and 14.4 and 5.5%/mmHg x 10(-2) for the anastomosis portion, respectively. This method can measure compliance at any portions of the sampling vessel in a single experiment on a real-time basis with very high accuracy, compared with conventional methods, and even in cases of intimal thickening and/or connective tissues-adhered vessels, and may serve to provide information on compliant design criteria of artificial and tissue-engineered graft.

In Japan, various medical applications of synchrotron X-ray imaging, such as angiography, monochromatic X-ray computed tomography (CT), radiography and radiation therapy, are being developed. In particular, coronary arteriography (CAG) is quite an important clinical application of synchrotron radiation. Using a two-dimensional imaging method, the ®rst human intravenous CAG was carried out at KEK in May 1996; however, further improvements of image quality are required in clinical practice. On the other hand, two-dimensional aortographic CAG revealed canine coronary arteries as clearly as those on selective CAG, and coronary arteries less than 0.2 mm in diameter. Among applications of synchrotron radiation to X-ray CT, phase-contrast X-ray CT and¯uorescent X-ray CT are expected to be very interesting future applications of synchrotron radiation. For actual clinical applications of synchrotron radiation, a medical beamline and a laboratory are now being constructed at SPring-8 in Harima.

A three-dimensional model was constructed from helical CT images for abdominal aortic aneurysm (AAA) and thoracic aortic aneurysm (TAA). A stent-graft was designed and positioned endoluminally on the computer. One hundred and nine stent-grafts for 101 patients were designed by this method and deployed well in all patients. The design time was reduced from 4 to 0.5 hr.