Riederer S J, Mistretta C A
Med Phys. 1977 Nov-Dec;4(6):474-81. doi: 10.1118/1.594357.
Iodine is commonly used as a contrast material in computerized x-ray tomography. In some cases the determination of the iodine distribution in the image may be prevented by the presence of bone or tissue variations within the tomographic slice. This paper describes a method for quantitative selective imaging of the iodine concentration in the slice. The method employs scans using three heavily filtered x-ray beams, two having mean energies which straddle the iodine K edge (33 keV) and another at a slightly higher energy. The results are independent of tissue and bone over a broad range of projection path lengths. It is shown that, for separation of iodine from one other material, a two-beam K-edge approach requires less integral dose than a two-beam technique at conventional CT energies for slice diameters up to 30 cm. For selective iodine imaging in the presence of more than one other material, the three-spectrum K-edge technique is a necessity. Exposure requirements and beam-hardening corrections are discussed in detail and a computer-simulated CT image generated by the proposed scheme is presented.
碘通常用作计算机X射线断层扫描中的造影剂。在某些情况下，断层切片内骨骼或组织差异的存在可能会妨碍对图像中碘分布的测定。本文描述了一种对切片中碘浓度进行定量选择性成像的方法。该方法采用使用三束经过大量过滤的X射线束进行扫描，其中两束的平均能量跨越碘的K边（33keV），另一束能量稍高。在很宽的投影路径长度范围内，结果与组织和骨骼无关。结果表明，对于从另一种材料中分离碘，对于直径达30cm的切片，在传统CT能量下，双束K边方法比双束技术所需的积分剂量更少。对于在存在不止一种其他材料的情况下进行选择性碘成像，三谱K边技术是必需的。详细讨论了曝光要求和束硬化校正，并给出了由所提出方案生成的计算机模拟CT图像。
