一种用于肺部图像引导放射治疗的双能X射线透视成像方法

A dual-energy X-ray fluoroscopy method for image-guided lung radiotherapy

目的研究一种双能X线透视成像方法,采集呼吸周期高低能X线图像序列,通过改进双能减影算法获取软组织减影图像,以提高在图像引导放射治疗中无标记肺部肿瘤运动跟踪的肿瘤可视度。方法采用具有C臂旋转结构和高低能快速切换采图机制的双能X线透视成像系统,分别在4个投影方向实时采集呼吸周期9或10个时相的高低能图像对序列。通过优化加权对数减影算法,对去除同一时相高低能图像对中的骨骼,得到软组织减影图。双能减影算法采用CNR作为图像质量评价参数,自动获取最佳软组织减影图像。采集和分析20例患者数据,评价软组织减影图像中肿瘤可视度的提高程度。结果分别在0°、45°、90°和135°投影方向采集198、196、198、和198个高低能图像对,肿瘤可视图像分别为198、38、69和49对。所获软组织减影图像中,肿瘤可视图像分别为198、108、149和159幅。结论本研究提出的双能X线透视成像方法可显著提高肺部肿瘤的可视度。

Objective To investigate a dual-energy X-ray fluoroscopy imaging method to acquire a high-and low-energy X-ray image sequence within a breathing cycle,so as to obtain soft tissue image through an improved dual-energy image subtraction algorithm to improve tumor visibility for marker-less lung tumor tracking in image-guided radiotherapy.Methods A dual-energy X-ray fluoroscopy imaging system with a C-arm rotating mechanical structure and a high-low energy fast switching mechanism was designed.A sequence of high-and low-energy X-ray image pairs of 9 or 10 breathing phase within a breathing cycle were acquired from 4 different projection directions.For a high-and low-energy image pair in the same phase,a soft tissue image was obtained by removing the skeleton through an optimized weighted logarithmic subtraction algorithm.The best soft tissue image was automatically determined by using CNR as the image quality evaluation parameter in the subtraction algorithm.Twenty patients with lung tumor were collected,and their data were analyzed to evaluate the improvement of tumor visibility in soft tissue subtraction images.Results In the projection directions of 0°,45°,90°and 135°,198,196,198 and 198 high and low energy image pairs were collected,respectively.The visibility images of tumor were 198,38,69 and 49 pairs,respectively.On soft tissue images after removing skeleton from high and low energy image pairs by automatic subtraction algorithm,the visibility images of tumors were 198,108,149 and 159,respectively.Conclusion The above mentioned dual-energy X-ray fluoroscopy method can be used to acquire real-time high-and low-energy X-ray image sequences of respiratory cycle,therefore obtain soft tissue subtraction images and significantly improve the visibility of lung tumors.