电子计算机断层扫描系统球管焦斑与扫描中心平面校准的设计及验证

本文开发设计了一种电子计算机断层扫描(CT)系统球管焦斑与扫描中心平面校准的方法。该方法是把球管分别旋转到0°和180°位置,首先让CT系统在冷态下分别静态扫描一次自制的具有对称窗口A、B的金属校准工具;然后对扫描的原始数据进行去噪、均值、归一化处理后,利用球管焦斑、准直器中心和校准工具的几何关系,计算球管焦斑到扫描中心平面的校准距离。为验证该方法的实用性和有效性,本文采用该方法对16排CT系统(Brivo CT385, GE,中国)的球管焦斑进行校准,校准结果用即显胶片扫描方式进行验证,结果显示球管焦斑与扫面中心平面距离误差为0.02 mm,处于焦斑校准误差范围±0.1 mm之内。通过本文研究结果表明,作为一种简单、低成本的设计,该方法可以实现球管焦斑与扫描中心平面的快速校准。

Design and validation of calibration between tube focus spot and center plane of rotation in computed tomography system

This study proposed a method to calibrate tube focus spot and the center plane of rotation in computed tomography system. In the method, the tube was rotated to 0° and 180° respectively, and then one metal jig with symmetric windows A and B was scanned at each position under the tube cool and static condition. According to the geometry of tube focus spot, aperture center of the collimator and jig, the distance between tube focus spot and the center plane of rotation were calculated with the X ray transmittance data after denoising, mean value and normalization. To verify the practicability and validity of the method, the tube focus spot in a 16 slices CT system (Brivo CT385, GE, China) was calibrated, and the result after calibration was validated by scanning a polaroid film. The validation result showed that the deviation between tube focal spot and center plane of rotation was 0.02 mm and was in the error range within ±0.1 mm. The results of this study showed that, as a simple and low-cost design, the method could be used for fast calibration between tube focus spot and the center plane of rotation.