迭代重建算法在80kV低剂量儿童脊柱CT的应用

The application of iterative reconstruction algorithm in80kV low dose spine CT:apediatric intra-patient study

目的:评价基于模型的迭代重建算法(MBIR)及自适应迭代重建算法(ASIR)是否可以在80kV低剂量儿童脊柱CT扫描中获得符合诊断标准的图像,以减少放射线对患儿的损伤。方法:连续选取36例因脊柱病变需要复查脊柱CT的患儿行80kV,50mA低剂量扫描作为观察组,将所得的原始数据分别重建为0.625mm的MBIR图像、ASIR图像、FBP图像。所有患儿治疗前的脊柱CT检查为对照组,扫描管电压120kV,余扫描参数不变,图像重建为0.625mm的FBP图像。四组图像质量主观评价由2名医师分别采用1～4分制(3分合格,4分最好)评价图像主观噪声及椎体结构显示能力;图像质量客观评价为测量L1椎体以及同层面背侧肌肉的CT值及噪声值,并计算椎体的SNR及CNR。同时并记录两次检查剂量报告表中的CT容积剂量指数(CTDIvol)、剂量长度乘积(DLP)。结果:图像的主观评分结果显示:对照组图像以及观察组的MBIR图像可以满足诊断要求;客观噪声结果:观察组MBIR、ASIR、FBP以及对照组FBP图像分别为17.35±2.70、50.89±4.24、76.68±7.11、28.49±3.25,信噪比分别为5.75±1.05、2.74±0.41、1.90±0.28、4.19±0.43;对比噪声比分别为8.14±0.91、2.74±0.38、1.892±0.33、4.46±0.86;观察组放射剂量CTDIvol、DLP分别为(0.77±0.02)mGy,(51.28±11.67)mGy·cm,较对照组分别降低65.47%,64.76%。结论:应用80kV低剂量儿童脊柱CT结合MBIR可以得到满足诊断要求的图像,达到减少患儿放射损伤的目的。

Objective:To explore whether iterative reconstruction algorithm based on model-based iterative reconstruction(MBIR)and adaptive iterative reconstruction algorithm(ASIR)the image can meet the diagnostic ceriteria,using 80kV for spine CT scan in children.Methods:36 cases who need towice spine CT scan in a short-term were enrolled.The second CT scan was set with 80kV and 20mAs as study group.The raw data were reconstructed base on three algorithm by setting slice thickness as 0.625mm,generating MBIR image,50%ASIR image and FBP image.The first spine CT scan was set with 120kV tube voltage and 20mAs tube current,and other parameters the same as the second scan.The raw data were reconstructed to FBP image with the 0.625mm thickness.Image quality of four groups were evaluated by 2 radiologists using a 4 point scale(3 is qualified,4 is the best),display ability of vertebral structure and image noise were evaluated;objective image quality measured the CT values and deviation of the L 1 vertebral body and muscle at the same slice,then calculate the signal-to-noise ratio(SNR)and contrast-to-noise ratio(CNR)of the vertebral body.The CT dose volume index(CTDIvol)and dose length product(DLP)were recorded at the same time in the two exam dose report.Results:The subjective score of MBIR image in study group and control group can meet the diagnostic criteria;objective noise of MBIR,ASIR,FBP in study group and FBP image in control group were 17.35±2.70、50.89±4.24、76.68±7.11、28.49±3.25 respectively,the SNR was 5.75±1.05、2.74±0.41、1.90±0.28、4.19±0.43;the CNR were 8.14±0.91、2.74±0.38、1.892±0.33、4.46±0.86;study group CTDIvol,DLP were(0.77±0.02)mSv,(51.28±11.67)mSv·cm,66.52%and 65.30%lower than control group.Conclusion:The application of MBIR and ASIR can be applied to 80kV low dose children spine CT,MBIR image quality is the best.