应用迭代重建技术的低剂量增强CT评估肝脏肿瘤的可行性

Feasibility of iterative reconstruction technique for reducing body radiation dose with enhanced CT of liver tumors

目的评价采用iDOSE迭代重建技术低剂量增强CT评估肝脏肿瘤的可行性。方法选择临床拟诊肝脏肿瘤患者48例进行常规剂量及低剂量门脉期肝脏增强CT扫描,常规剂量扫描采用滤波反投影（FBP）重建生成图像（A组）,低剂量扫描分别采用FBP（B组）及iDOSE重建生成图像（C组）,计算噪声（Noise）及CNR;按1~4分评价诊断信息（肿瘤边缘锐利度、肿瘤与正常肝脏组织对比度、图像主观噪声、图像总体质量）,并对3组结果进行比较。结果低剂量扫描序列有效剂量（ED）较常规剂量平均降低49.71%。C组图像噪声较A、B两组降低（NoiseC=12.79±2.53,NoiseA=14.27±3.44,NoiseB=19.04±4.03;P均〈0.001）,CNR升高（CNRC=3.52±1.87,CNRA=2.61±1.77,CNRB=2.56±1.37;P均〈0.001）。C组图像各项诊断信息评分与A组无差异（P〉0.05）。结论应用iDOSE迭代重建技术可在扫描剂量减半的情况下获得满足诊断要求的肝脏增强CT图像。

Objective To evaluate the feasibility of iDOSE iterative reconstruction technique for reducing body radiation dose at enhanced CT of liver tumors.Methods Forty-eight patients with known or suspected liver tumors underwent hepatic enhanced 256 slice CT scan.Routine and low dose CT scans were acquired sequentially during the hepatic portal venous phase after contrast injection.Routine dose data were reconstructed using filltered back projection（FBP,group A）,low dose acquisition with FBP（group B） and iDOSE iterative reconstruction algorithm（group C）.Quantitative noise and CNR measurements were performed.Sharpness of tumors,contrast between tumors and normal liver tissue and image quality were graded（scale： 1—4） and compared among 3 groups.Results Low dose acquisitions were obtained with average 49.71% dose reduction.Group C had the lowest image noise（NoiseC=12.79±2.53,NoiseA=14.27±3.44,NoiseB=19.04±4.03;both P0.001） and the highest CNR（CNRC=3.52±1.87,CNRA=2.61±1.77,CNRB=2.56±1.37;both P0.001）.Group C obtained identical observer image quality scores as group A（P0.05）.Conclusion The iDOSE iterative reconstruction technique enables 50% radiation dose reduction in CT imaging of liver tumors,while maintains the diagnostic quality of routine dose CT.