不同体位及降低kV对甲状腺CT图像质量的影响

Technique Improvement of Thyroid CT Scan with Different Position and Low kV

目的探讨减轻双上肢置于身体两侧患者甲状腺附近CT图像伪影的扫描技术,并减少辐射剂量。方法将颈部CT检查的患者分为常规组、改进组和低kV组。测量3组患者图像伪影区和非伪影区的肌肉CT值和图像噪声值,并记录患者的剂量长度乘积(DLP),计算平均值和标准差。结果改进组与低kV组的图像质量明显优于常规组(P<0.05)。常规组图像伪影区的肌肉CT值较低,图像噪声变化范围明显增大,噪声平均值明显高于改进组和低kV组,与改进组、低kV组的差异有统计学意义(P<0.05)。低kV组有效剂量明显低于常规组与改进组差异有统计学意义(P<0.05)。结论患者行甲状腺CT扫描,一只手上举,另一只手用力伸向对侧髋关节,使锁骨、肩胛骨及软组织不在同一平面,可明显降低图像伪影及辐射剂量。

Objective To explore a new thyroid CT scanning technique to reduce image artifacts and radiation dose. Methods The patients underwent thyroid CT scan were divided in 3 groups： conventional position group （patients put arms beside their bodies during CT scan）, improved position group （one arm rise upward, another arm reach firmly toward the contralateral hip） and low kV group （the same position as group 2, using 100kV）. CT attenuations, noise of the thyroid with or without artifact of the three groups were measured and analyzed by one way ANOVA test. Results Image qualities of improved position group and low kV group were better than conventional position group （P 〈 0.05 ）. The CT attenuation and noise with artifact were significantly higher in the conventional position group than that in improved position group and low kV group（ P 〈 0. 05 ）. The effective dose of low kV group was significantly lower than that of the conventional and improved position group（P 〈 0.05 ）. Conclusion The image quality can be improved when the patients keep one arm rise upward, another arm reach firmly toward the contralateral hip during CT scan.