ASiR-V权重自动控制能谱CT图像质量与辐射剂量的可行性:体模研究

Feasibility of Adjusting the Image Quality and Radiation Dose via Pre-ASiR-V Algorithm of Energy Spectral CT Scan:A Phantom Study

目的分析Revolution CT的剂量控制新功能前置多模型迭代算法(ASiR-V)在CT能谱扫描中图像质量的变化规律及辐射剂量的降低程度,探讨前置ASiR-V的临床应用价值。材料与方法对QSP Phantom体模(试管碘浓度为2.5、5.0、10.0 mg/ml各1支,20.0 mg/ml 3支、未加碘盐、加碘盐及水各1支)进行能谱扫描,预设前置ASiR-V权重(10%、20%、30%、40%、50%)及滤波反投影(FBP)。测量目标试管不同权重图像的CT值、SD值并计算图像的信噪比(SNR)及对比噪声比(CNR),记录每次体模能谱扫描辐射剂量相关参数容积CT剂量指数(CTDIvol)、剂量长度乘积(DLP)、有效剂量(ED),比较各目标试管CT值、SD值、SNR及CNR,分析ED在FBP与不同权重前置ASiR-V的组间差异及随前置ASiR-V的权重变化。结果体模中各目标试管的CT值、SD值、SNR及CNR在不同权重前置ASiR-V的能谱图像中差异均无统计学意义(F=0.251~2.498,均P>0.05);在FBP与不同权重前置ASiR-V能谱图像两两比较中差异均无统计学意义(均P>0.05)。前置ASiR-V迭代水平与ED呈线性负相关,ED的回归方程为Y=−0.35X+2.912(r^(2)=0.984,P<0.05)。能谱图像的管电流随着ASiR-V的迭代强度增加而自动调节减低,前置增加至50%时,毫安秒达到能谱扫描的最低200 mA,ED也随着毫安秒的降低而降至最低。与FBP相比,前置ASiR-V权重10%、20%、30%、40%、50%的ED(mSv)依次降低了8.7%、26.2%、35.1%、43.9%、61.4%。结论Revolution CT的剂量控制新功能前置ASiR-V可在不改变能谱图像质量的情况下,有效降低能谱扫描的检查辐射剂量,可应用于临床各部位检查,尤其适用于辐射敏感器官及儿童。

Purpose To investigate the effects of pre adaptive statistical iterative reconstruction-V algorithm(ASiR-V)on the image quality and radiation dose via spectral CT scanning,and to explore the value of pre-ASiR-V algorithm in clinical application.Materials and Methods A polyethylene cylindrical phantom(QSP Phantom)[containing 9 test tubes with iodine concentrations of 2.5,5.0,10.0 mg/ml each,20.0 mg/ml 3,uniodized salt,iodized salt and water each]was scanned via spectral CT,pre-set ASiR-V level 10%-50%(interval 10%)and filtered back projection(FBP).The CT value and image noise of different level ASiR-V images of the target tube were measured,the signal noise ratio(SNR)and contrast noise rate(CNR)of the images were calculated.The radiation dose related parameters volumetric CT dose index(CTDIvol),dose length product(DLP)and effective dose(ED)were recorded for each body mode energy spectrum scan.The objective indicators(CT value,SD value,SNR and CNR)were analyzed and to analyze the differences between groups in ED at FBP and different weights of antecedent ASiR-V and the changes with the weight of antecedent ASiR-V.Results The differences in CT value,SD value,SNR and CNR of each target tube in the body model were not statistically significant in the energy spectrum images with different weights of the anterior ASiR-V(F=0.251-2.498,all P>0.05);the FBP with different weights were not statistically significant differences in the two-by-two comparison of the energy spectrum images of the anterior ASiR-V(all P>0.05).The pre-ASiR-V iteration level was negatively correlated with ED,and the regression equation of ED was Y=−0.35X+2.912(r^(2)=0.984,P<0.05).The tube current of the energy spectrum image was automatically adjusted to decrease as the intensity of the ASiR-V iteration increased,with the front increasing to 50%when the milliamperes reached a minimum of 200 mA for the energy spectrum scan,and the ED decreased to a minimum as the milliamperes decrease.Compared with FBP scans,ED with ASiR-V level of 10%,20%,30%,40%and 50%decreased by 8.7%,26.2%,35.1%,43.9%and 61.4%,respectively.Conclusion The revolution CT combined with pre-ASiR-V algorithm can effectively reduce the radiation dose without changing the image quality simultaneously.It can be applied to scan all parts of body in clinical practice,especially for radiation-sensitive organs and children.