锥形束CT应用于寰枢椎成像的低剂量研究

Low-dose study of cone-beam CT applied to atlantoaxial spine imaging

目的 :探讨锥形束计算机X线体层摄影(Cone beam computed tomography,CBCT)应用于寰枢椎成像的低剂量检查实现方法。方法:使用CBCT对头颈部体模进行扫描,选择3D牙齿成像的齿列扫描程序,扫描容积大小设置为Φ70 mm×50 mm,以5种体型模式、3种分辨率模式、2种剂量模式共30种曝光条件对体模进行扫描。以单因素方差分析比较3组不同分辨率影像的检查剂量和主、客观图像质量。结果:(1)检查剂量:常规剂量模式的剂量面积乘积(Dose-area product,DAP)值高于超低剂量模式;不同体型之间的DAP值无统计学差异;不同分辨率之间的DAP值有统计学差异(P<0.05),两两比较150μm分辨率组的DAP值与200μm分辨率组无差别,均高于400μm分辨率组;(2)成像质量客观评价:常规剂量模式的对比度分辨率(CNR)值高于超低剂量模式,超低剂量模式的噪声高于常规剂量模式;不同体型、不同分辨率之间的噪声和CNR值均无统计学差异;(3)成像质量主观评价:不同体型之间的主观图像质量评分均有统计学差异;不同剂量模式、不同分辨率之间的总体图像质量、对比度、清晰度以及噪声评分均有统计学差异(P<0.05),不同剂量模式、不同分辨率之间的伪影评分均无统计学差异。结论:使用齿列程序进行寰枢椎成像,最佳扫描序列为低剂量模式200μm分辨率下的S体型,以可接受的噪声水平实现了影像质量与检查剂量的平衡。

Objective: To investigate the application of low-dose cone beam computed tomography(CBCT) in atlantoaxial imaging. Methods: The CBCT was used to scan the head and neck body model, selecting the dentition scanning program for3D dental imaging, setting the scan volume size to Φ 70 mm ×50 mm, with 5 body modes, 3 resolution modes, and 2 dose modes for a total of 30 exposure conditions. A one-way ANOVA was performed to compare noise, examination dose and sub-jective and objective image quality in the 3 groups of images with different resolutions. Results:(1)Dose comparing: Dose-area product(DAP) values were higher in the conventional dose mode than in the ultra-low dose mode. No statistical difference in DAP values was found between body types. The DAP values were statistically different among resolutions(P<0.05), with no difference between the 150 μm and the 200 μm resolution group in a two-by-two comparison, both higher than the 400 μm resolution group.(2)Objective evaluation of image quality: Contrast-to-noise ratio(CNR) values were higher in the conventional dose mode than in the ultra-low dose mode, and noise was higher in the ultra-low dose mode than in the conventional dose mode. There were no significant differences in noise and CNR values among different body types and resolutions.(3)Subjective evaluation of imaging quality: subjective image quality scores were statistically different between body types, overall image quality, contrast, sharpness, and noise scores were statistically different between dose modes and resolutions( P<0.05), and there was no statistical difference in pseudo-imaging scores between dose modes and resolutions. Conclusion: Atlantoaxial imaging using the dentate procedure, with the optimal scan sequence being S-body at 200 μm resolution in low dose mode, achieves a balance between image quality and examination dose with acceptable noise levels.