冻土CT图像中环形伪影和射线束硬化伪影的成因及校正方法

Ring artifact and beam hardening artifact in CT image of frozen soil:causes and correction methods

冻土CT图像中不可避免地会出现环形伪影和射线束硬化伪影。为解决这些问题,分析了两类伪影的特征和形成机理,提出了降低伪影的硬件优化方案。首先,通过改变X射线管电压,以此改变X射线光通量来降低冻土CT图像的环形伪影。其次,利用不同厚度的滤过材料,将X射线中的低能射线预先过滤,使得穿过冻土试样的X射线能谱范围变窄,以此来降低射线束硬化伪影对试样的影响。对比分析结果表明:将扫描电压提高到120kV既能有效降低同类型冻土试样CT图像中的环形伪影,又能保证图像的质量;选用材质为2A12、厚度为18mm的航空铝材,在扫描电压为120kV、扫描电流为230mA的条件下可以有效抑制射线束硬化所造成的伪影。

Ring artifacts and beam hardening artifacts are unavoidable in CT image of frozen soil.In order to remove the two kinds of artifacts,in this paper the characteristics and formation mechanisms of the two kinds of artifacts are analyzed and a hardware optimization solution for reducing artifacts is proposed.Firstly,the ring artifacts are reduced by increasing the X-ray luminous flux to change the X-ray energy spectrum.Secondly,the low energy rays in X-rays are pre-filtered by the filter materials of different thickness,so that the X-ray energy spectrum range across the frozen soil specimen is narrowed to correct the beam hardening artifacts.The test results show that increasing the scanning voltage to 120 kV can not only effectively reduce the ring artifacts in CT images of frozen soil,but also ensure the quality of the images.At the same time,the aluminum material of 2A12 with 18 mm thickness can effectively correct the artifacts caused by the beam hardening under the scanning voltage of 120 kV and scanning current of 230 mA.