Development of phase contrast x-ray imaging system

相衬X射线成像是利用折射率的差异产生的，其灵敏度是传统方法的1000倍左右，在揭示软组织内部结构方面具有巨大的潜力。与正常肝组织相比，人类癌细胞如结肠癌、肝细胞癌和乳腺癌具有低折射率ddelta。脂肪组织的ddelta非常低，低于水。在这些病理标本中，纤维化组织具有相对高的ddelta。然而，在目前的相衬X射线成像中，由于X射线干涉仪的尺寸小，对象的视图尺寸被限制在5 mm x 5 mm。为了增加对大样品成像的视场，从直径10厘米的高度完美的单晶硅锭中切割出三倍劳厄情况的大X射线干涉仪。在这种非分离型大型干涉仪中，获得了30 mm x 25 mm的预期视场。该干涉仪的可见度足以获得相位衬度X射线成像，并获得了良好的投影图像质量。使用相位衬度X射线成像，可以区分生物样品的内部结构，而无需造影剂。此外，不同组织间的ddelta变化差异明显。随着世界上最大的干涉仪的研制，我们可以获得大物体（约30 mm）的相衬X射线成像。

Phase-contrast x-ray imaging generated by the differences in refractive indices has great potential to reveal the structures inside soft tissues because about 1000 times higher sensitivity is obtained with this method compared to the conventional method depending on the differences of x-ray absorption.Then the development of phase-contrast x-ray imaging system has performed to understand what was revealed in the human pathological specimens. Human cancer cells such as colon cancer, hepatocellular carcinoma and breast cancer had low refractive index ddelta compared to normal liver tissue. Fat tissue had very low ddelta less than that of water. Fibrotic tissues had relatively high ddelta in these pathological specimens. Necrosis had high ddelta.However in the present phase-contrast x-ray imaging, the view size of the object was limited to 5 mm x 5 mm due to the small size of the x-ray interferometer. To increase the field of view to image large samples, the triple Laue-case large x-ray interferometer was cut out of a 10-cm in diameter highly perfect single-crystal silicon ingot. In this non-separated type of large interferometer, the expected field of view with 30 mm x 25 mm was obtained. Visibility of this interferometer was sufficient to obtain the phase-contrast x-ray imaging and excellent quality of projection image was obtained.Using the phase-contrast x-ray imaging, the inner structures of biological specimens can differentiated without an contrast agents. In addition, the ddelta changes among tissues were differentiated clearly. As the largest interferometer in the world was manufactured, we can obtain the phase-contrast x-ray imaging of large object (about 30 mm).