工业CT扫描文物的伪影与校正

工业计算机断层成像(computed tomography,CT)可以无损获得被检器物的结构组成、材质分布和密度变化等内部信息,是文物结构特征和材质分布无损分析的常用方法之一。由于文物的材料种类繁多、厚度不一、器形复杂,其工业CT扫描结果会伴随一定的伪影——伪影会严重降低图像质量,甚至导致无法准确判断文物的内部结构。因此,需要寻找避免或减弱CT伪影的方法。CT成像的伪影源于多种因素:物理因素导致的伪影和CT投影数据采集过程有关；样品因素导致的伪影和样品的摆放、结构和材料有关；CT算法伪影和CT设备所使用的软件及重建算法有关。其中有些伪影可以通过软件校准减少,但在许多情况下,通过样品的合理摆放和选择合适的CT扫描参数是避免CT伪影的最佳手段之一。本文列举CT检测文物中所遇到的一些常见伪影,并解析这类伪影的消除或减弱的方法,以期为今后CT检测文物提供一定的借鉴作用。

Research on the artifacts of industrial CT for cultural relics and their reductions

Industrial computed tomography (CT) can non-destructively analyze the structural composition, material distribution, density variation and other internal information of an object, and is one of the common methods for non-destructive analysis of the structural characteristics and material distribution of cultural relics. Due to the variety of materials, shapes and thicknesses of cultural relics, the scanning results of industrial CT can be accompanied by certain artifacts which will seriously worsen the image quality, and even make it impossible to accurately determine the internal structure of cultural relics. Artifacts in CT imaging originate from various factors:artifacts caused by physical factors are related to the CT projection data acquisition process; artifacts caused by sample factors are related to the placement, structure and material of the sample; artifacts caused by CT reconstruction algorithms are related to the CT equipment scanning method and its algorithms in the software. Some of these artifacts can be reduced by software calibration, but in many cases, proper sample placement and selection of appropriate CT scanning parameters is one of the best ways to reduce CT artifacts.