低剂量颞骨多层螺旋CT扫描技术的应用研究

Studies on the application of low-dose CT in temporal bone scanning

目的探讨颞骨高分辨率CT扫描时降低扫描mA值对其图像质量的影响及临床应用价值。方法将60例颞骨高分辨率冠状面CT扫描患者根据扫描mA值设置分为100和50组。全部图像行高分辨率骨密度算法重组,并利用多平面重建(MPR)技术重建轴面图像,得到两组不同mA值的直接扫描冠状面图像和与之对应的两组通过重建的轴面图像。分别评价不同扫描mA时直接冠状面及重建轴面图像质量。结果当扫描mA值由100减至50时单次扫描加权CT剂量指数量(CTDIw)值由42·00mGy下降至21·00mGy,下降幅度达50·0%。而直接扫描冠状面图像质量无明显下降(P>0·05);并且颞骨低剂量高分辨率CT能基本达到图像各向同性,经(MPR)重建的轴面图像能较好地显示颞骨细小解剖结构,保证病灶检出率。结论降低扫描mA值和利用MPR重建图像来替代颞骨其他方位的直接扫描都大大减少了患者的辐射剂量,50mA的颞骨CT扫描能够提供较好诊断质量的影像信息。

Objective To investigate the influence of reducing mA on the diagnostic quality of image and the value of clinical application with high resolution CT （HRCT） in temporal bone. Methods Sixty patients performed with temporal bone coronal HRCT scan were randomly assigned into 100 mA group and 50 mA group. The two group images including coronal direct scan images and the corresponding axial images by multi-planar reconstruction（MPR） with different mA were obtained by using bone mineral density algorithm recombination. Evaluation criterion was as followed： clearly demonstrated （2 points）, demonstrated but not visualized （1 points）, or not seen （0 points）. Points were performed according to left and right sides respectively. Results The CTDIw value with single scan of temporal bone HRCT decreased from 42.00 mGy （ 100 mA） to 21.00 mGy （50 mA） and the radiation dose to the temporal bone was reduced by 50% . Meanwhile there was no significant difference of image quality between the two mA in coronal direct scan （ P 〉 0.05）. Furthermore, temporal bone low-dose HRCT could basically reach the isotropy. Axial images by MPR could display the small anatomic structure of temporal bone clearly, which ensured the detectable rate of focus. Conclusions The radiation dose of patients could be obviously decreased by reducing mA and using MPR technology in place of direct scans of temporal bone, Temporal bone HRCT with 50 mA could provide enough image information for the diagnosis.