低管电压联合迭代重建算法对胸部CT血管造影图像质量及辐射剂量的影响

目的 探讨低管电压联合迭代重建算法对胸部CT血管造影成像图像质量及辐射剂量的影响.方法 利用ATOM 701-D型成年男性仿真人胸部模型,配置碘水混合对比剂注入输液管后置入胸部模拟胸部血管.采用320排容积CT以80、100和120 kV分别联合自适应迭代降剂量技术(AIDR 3D)迭代重建4个等级(关闭、轻、标准、强)共12种方案按管电流等其他参数不变进行胸部扫描,记录辐射剂量.获得横断面输液管CT值及噪声水平、纵隔区软组织CT值、信噪比(SNR)和对比噪声比(CNR).比较不同管电压扫描及不同迭代算法水平重建对图像质量的影响.结果 容积CT剂量指数(CTDI_vol)、剂量长度乘积(DLP)及有效剂量(E)在120 kV时为12.50 mGy、453.50 mGy ·cm、6.35 mSv;在100 kV时为7.60 mGy、276.50 mGy ·cm、3.87 mSv;在80 kV时为3.80 mGy、138.70 mGy ·cm、1.94 mSv.随着管电压的降低,辐射剂量显著降低.不同管电压时,输液管CT值、噪声标准差(SD)、SNR、CNR差异均具有统计学意义(F=1 029.24、8.56、3.44、4.09,P<0.05).按不同重建算法,输液管SD、SNR、CNR差异均具有统计学意义(F=33.99、54.80、54.72,P<0.05),但对输液管CT值没有显著影响(P>0.05).管电压或重建算法对纵隔区软组织CT值的影响差异均无统计学意义(P>0.05).结论 80 kV管电压扫描联合标准水平的迭代重建算法方案可降低有效剂量,并获得较高质量的胸部血管图像.

Influence of low tube voltage in combination with simultaneous iterative reconstruction algorithm on image quality and radiation dose in thoracic CT angiography:a chest phantom study

Objective To study the effect of low-tube voltage combined with the iterative algorithm(IR) on image quality and radiation dose in thoracic CT angiography. Methods A simulated blood vessel of chest was constructed using an ATOM 701-D adult male chest phantom and iodine-water mixture contrast medium. A 320-row volume CT was used to scan the chest at tube voltages of 80, 100 and 120 kV in combination with off, mild, standard and strong IR levels (12 protocols in total), respectively. Tube currents and other parameters were not changed during scanning. The radiation doses were recorded. CT value of the transverse infusion tube and its corresponding noise, CT value of mediastinal soft tissues, signal-to-noise ratio(SNR) and contrast-to-noise ratio (CNR) were obtained. Influence of different tube voltages and simultaneous iterative reconstruction levels on image quality was investigated. Results The CTDI_vol, DLP and E were 12.50 mGy, 453 mGy ·cm, and 6.35 mSv, at 120 kV; 7.60 mGy, 276.50 mGy ·cm and 3.87 mSv at 100 kV; 3.80 mGy, 138.70 mGy ·cm and 1.94 mSv at 80 kV, respectively. Radiation dose significantly decreased as the tube voltage decreased. The tube voltage had significant influence on the CT values and its standard deviation(SD), SNR and CNR(F=1 029.24,8.56,3.44,4.09,P<0.05).The reconstruction algorithms had great influence on the SD, SNR and CNR as well(F=33.99,54.80,54.72,P<0.05), while no significant influence on CT values (P>0.05). There were no significant differences between the influences of tube voltages and reconstruction algorithms on the CT values of mediastinal soft tissues (P>0.05).Conclusions Using a protocol of 80 kV with a standard IR algorithm could result in reduction of the effective dose and high-quality thoracic CT angiogram.