低剂量CT扫描用于胸部肿瘤粒子植入的可行性研究

目的 探讨在粒子植入过程中降低扫描条件进行手术的可行性。方法 使用GE Lightspeed RT大孔径CT，分别使用120、100和80 kV，初始毫安数为150 mA，以20 mA的间隔递减至10 mA的扫描条件组合对GEMS模体和包含不同密度组织替代物的062 M模体进行扫描。对扫描剂量进行记录，测量图像感兴趣区的CT值、噪声值，计算信噪比（SNR）值和对比噪声比（CNR）值，评估图像质量，优化出较为适合的扫描条件。结果 随着管电压和管电流的降低，图像的信噪比降低。除120 kV，150~70 mA及100 kV，150~90 mA，其余条件下图像的SNR与标准图像差异有统计学意义（t=-12.710~3.717，P<0.05）。随着管电压和管电流的降低，对比度差异较小的相邻组织的对比噪声比显著降低，当对比噪声比降到2以下时，图像质量过低无法评估。降低管电压和管电流对CT图像的高对比分辨力影响不大。结论 综合实验结果，使用管电压100 kV，管电流70 mA的扫描条件进行扫描时，其图像质量接近标准参数扫描图像。在粒子植入过程中，除第1次扫描外使用标准胸部扫描条件外，其余在反复扫描同一区域时可降低条件至100 kV，70 mA进行扫描，可使患者每次扫描接受的辐射剂量大幅下降。

The feasibility study of low-dose CT scanning in chest tumor with 125I radioactive seed implantation

Objective To investigate the feasibility of reducing CT scanning dose in the process of ¹²⁵I radioactive seed implantation. Methods GEMS phantom and 062 M phantom were scanned using GE Lightspeed RT large hole CT with 120 kV, 100 kV and 80 kV separately, and 150-10 mA (20 mA decreased progressively). The scanning dose, CT value and noise of the region of interest were recorded and the image quality was evaluated. Image signal-to-noise ratio (SNR) and contrast to noise ratio (CNR) values were calculated. Results With the decreasing of tube voltage and current, the SNR values were reduced accorgingly. The values had significant difference with those of standard images except the images acquired with 120 kV, 150-70 mA and 100 kV, 150-90 mA (t=-9.294-3.717, P<0.05). With the decreasing of the tube voltage and current, the CNR decreased significantly. The image quality was too low to evaluate while CNR lower than 2. The high contrast resolution of the CT images were not affected obviously with the tube voltage and current lowering. Conclusions In the process of ¹²⁵I radioactive seed implantation, it is feasible to choose lower tube voltage and tube current(100 kV, 70 mA) to scan the same area repeatedly except for the first scan with standard chest scanning parameters. The patient radiation dose has fallen dramatically.