膀胱CBCT图像中标记物选取的研究

Marker selection in CBCT image of bladder

目的制定一种可视性量化算法,研究膀胱CBCT图像中不同标记物特性,选取最佳标记物。方法拍摄粘贴于体侧的不同类型及粗细的标记物的CBCT平片,计算不同标记物的信号值、噪音值,进而量化标记物可视性,并获得相应条件下的皮肤剂量。结果所研究的标记物,若其量化值对比度同背景噪音比(CNR)﹥2,该标记物可视性是可以接受的。多数标记物CNR﹥2,但碳标记物和线性螺旋金标记物(0.35 mm×5 mm)在穿越骨组织成像时CNR﹤2;线性螺旋金标记物(5 mm×0.5 mm)的CNR﹥2且射线扰动最小,皮肤剂量可以接受,最适合用来成像。结论线性螺旋金标记物(5 mm×0.5 mm)最适合用来成像,但需完善内植标记物的临床手术。由于条件限制,无法在治疗中实时计算标记物坐标,需提高软硬件水平并研究新的方法。

Objective To develop a visual quantification algorithm and study the different characteristics of markers on CBCT images of bladder and determine the optimal marker. Method CBCT images were obtained with various mark-ers affixed to body with different types and thickness. Calculate the value of signal and noise to quantify the visibility of markers and obtain skin dose under corresponding conditions. Result Marker that had quantitative value CNR （contrast-to-noise ratio） 〉2 was with acceptable visibility. Most markers had CNR 〉 2, but the carbon marker and linear helical gold marker of 0.35 mm × 5 mm were unavailable in lateral imaging through bone tissues for CNR〈2;Linear helical gold marker of 0.5 mm × 5 mm was the most suitable one for imaging as CNR〉2, with least dose perturbation and ac-ceptable skin dose. Conclusion Linear helical gold marker of 0.5 mm × 5 mm is the optimal marker for imaging, though the clinical procedure of markers implantation should be improved. It is impossible to calculate the coordinates of the markers in real time settings for the actual limitations, so the software and hardware conditions should be further im-proved, and new research methods are demanded.