应用MBIR优化低剂量儿童鼻窦CT图像质量的可行性

Feasibility study of using MBIR to optimize the image quality of low dose paranasal sinus CT of pediatric patients

目的探讨应用基于模型的迭代重建算法(MBIR)技术降低儿童鼻窦CT扫描方案的辐射剂量,保护眼球健康。方法选取18例(年龄4～11岁,中位年龄8岁)经低剂量扫描(电压80kV,电流80mA,转速0.8s,Pitch1.375)肿瘤患儿的鼻窦CT检查,所得到的原始数据重建为0.625mm的MBIR图像,作为观察组;该组患儿1～3月前使用常规扫描方法(120kV,ATCM自动设置管电流,NI=14,转速0.8s,Pitch1.375)得到的鼻窦ASIR30%重建CT图像作为对照组,比较两组图像的主观、客观图像质量。图像主观质量由两位医师应用4分制(3分满足诊断,4分最好)评价,内容包括主观噪声,鼻窦复合体的显示能力,鼻窦骨壁的显示能力,软组织的清晰程度;客观噪声测量左侧眼球玻璃体,蝶骨体部以及同层面左侧咬肌的CT值及标准差,计算信噪比及对比噪声比;并记录CT剂量指数(CTDIvol)及剂量长度乘积(DLP),最后计算有效放射剂量。结果主观评分结果两组图像均可满足诊断要求;观察组骨组织的CT值、SNR、CNR较对照组明显增高24.70%、78.57%、123.61%,噪声值较对照组降低23.52%。放射剂量观察组CTDIvol较对照组降低64.95%,DLP降低68.78%,ED降低65.03%。结论利用MBIR算法可以大幅度降低儿童鼻窦CT的放射剂量,达到保护眼球的目的。

Objective To explore the feasibility on reduction in radiation dose of CT scanning program in children with sinuses by use of the model-based iterative reconstruction (MBIR) image so as to protect the eye health. Methods 18 children with tumor, aged from 4 to 11 years old, with a median age of 8 years, who underwent the repeated paranasal CT exam in a short-term, were enrolled in this work. The children subjected to routine scan used low dose protocol (voltage 80 kV, current 80 mA, speed 0.8 s, Pitch 1.375) were taken as a study group. The raw data were reconstructed to the 0.625 mm MBIR image. All of the children, who were previously adopted the routine dose protocol CT, were taken as a control group. The subjective image quality in tow groups was evaluated by two physicians using a 4-point scale (3 was qualified and 4 was the best), which involved whole image quality, display ability of vertebral structure, display ability of bone and soft tissues. The objective image quality was involve in the measurement of CT values and deviation of left eye vitreous body, sphenoid body and left masseter muscle at the same level, and then, the signal-to-noise ratio and contrast to noise ratio were calculated. The CT dose index (CTDIvol) and dose length product (DLP) were recorded and, finally, the effective radiation dose was calculated. Results The subjective score of 2 groups can meet the diagnostic requirements;The CT value, SNR and CNR of study group were increased by 24.70%, 78.57%, 123.61%, respectively, and image noise was decreased by 23.52%. The CTDIvol was decreased by 64.95%, DLP was decreased by 68.78%, and ED was decreased by 65.03% compared to the control group. Conclusion The application of MBIR can be applied to low dose children paranasal CT, thereby achieving the purpose of protecting the eye.