比较以自适应性统计迭代重建技术和滤过反投影重建的低剂量腹部CT的图像质量

目的比较应用自适应性统计迭代重建技术(ASIR)和滤过反投影(FBP)两种重建技术获得不同低剂量腹部CT扫描图像的质量及对病变的优化显示。方法选取22例临床诊断肝脏占位而接受腹部增强扫描的患者,在常规动脉期扫描后门静脉期分别以150mAs和100mAs对病变中心上下10cm范围进行连续扫描,分别用FBP及3个水平(30%、50%、70%)的ASIR重建图像,测量并比较图像噪声及容积CT剂量指数(CIDIvol),并对所得图像进行图像质量评分。结果与FBP相比,ASIR可降低图像噪声,减少伪影,增加诊断信心度(P<0.001)。采用150mAs及100mAs扫描时,30%ASIR和50%ASIR图像的诊断信心度评分较好,CIDIvol分别为12.74mGy、8.59mGy,均低于常规扫描剂量(P<0.05)。150mAs时,与FBP比较,30%ASIR、50%ASIR和70%ASIR重建图像中,肝实质、背景肌肉及门静脉的平均噪声均有所降低,分别为(18.74%、30.39%、41.49%)、(18.73%、30.67%、41.85%)、(22.66%、37.14%、43.61%);100mAs时,则分别降低(20.37%、32.22%、43.32%)、(18.63%、30.48%、41.57%)和(21.39%、35.09%、45.72%)。100mAs-30%ASIR图像噪声与150mAs-FBP图像噪声差异无统计学意义(P>0.05),而扫描剂量降低32.96%。结论采用ASIR重建算法可有效提高图像质量,降低腹部CT扫描辐射剂量。

Image quality of low-dose abdominal CT: Comparison between adaptive statistical iterative reconstruction and filtered back projection reconstruction

Objective To compare image quality and lesion conspicuity on low-dose abdominal CT images reconstructed with adaptive statistical iterative reconstruction (ASIR) and filtered back projection (FBP) techniques. Methods Twenty-two patients with clinically diagnosed liver lesions underwent contrast-enhanced abdominal multiphase CT examination. Images were acquired with different tube current-time products (150 mAs, 100 mAs) and encompassed liver lesions over 10 cm scan length. Images were reconstructed separately with FBP and three levels of ASIR (30%, 50% and 70%). The volume CT dose index (CTDIvol), image noise, and image quality scores were compared. Results Compared with FBP, ASIR reconstruction technique greatly reduced image noise, improved image quality and diagnostic confidence (all P<0.001). The diagnostic confidence was better when images were reconstructed with 30%ASIR at 150 mAs and 50%ASIR at 100 mAs, respectively, while CTDIvol value was 12.74 mGy and 8.54 mGy, respectively, lower than that of routine image (P<0.05). Compared with FBP, the average noise reduction for liver, background muscle and portal vein at 150 mAs with 30%ASIR, 50%ASIR and 70%ASIR were (18.74%, 30.39%, 41.49%), (18.73%, 30.67%, 41.85%) and (22.66%, 37.14%, 43.61%), at 100 mAs were (20.37%, 32.22%, 43.32%), (18.63%, 30.48%, 41.57%) and (21.39%, 35.09%, 45.72%), respectively. The noise of the images had no difference between 30%ASIR at 100 mAs and FBP at 150 mAs (P>0.05), but CTDIvol reduced by 32.96%. Conclusion ASIR has the potential to improve image quality at lower radiation dose.