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目的比较滤波反投影(FBP)、高级迭代重组算法(iDose~4)、模型迭代重组技术(IMR)在胃癌CT增强扫描的图像质量和辐射剂量,评价IMR的临床应用价值。方法 40例患者按随机数表法分为低剂量组(A组)和常规剂量组(B组),每组20例,患者均行上腹部CT平扫和动态增强扫描,将门静脉期扫描数据作为研究对象。为保证图像质量,每组患者扫描时均固定噪声比(DRI),根据辐射剂量和重组算法不同将图像分为6组,包括A1组(120 kV,FBP),A2组(120 kV,iDose~4),A3组(120 kV,IMR),B1组(80 kV,FBP),B2组(80 kV,iDose~4),B3组(80kV,IMR)。分别比较A1、A2、A3组和B1、B2、B3组的图像质量客观评价指标[图像噪声、图像信噪比(SNR)、对比噪声比(CNR)]和主观评价指标(低对比分辨力、病灶边缘锐利度、图像失真和诊断信心度),并计算有效辐射剂量(ED)。结果低剂量组ED较常规剂量组平均降低73.7%。A组IMR重组的图像噪声显著低于FBP重组和iDose~4重组(P<0.01),CNR及SNR显著高于FBP重组和iDose~4重组(P<0.01);B组的客观评价结果同A组。A、B两组IMR重组的低对比分辨力(LCD)、病灶边缘锐利度(LES)、图像失真(ID)和诊断信心度(DC)优于FBP重组和iDose~4重组,其中,A1组和A3组,B1组和B2、B3组的差异有统计学意义(P<0.05)。结论在显示胃癌病灶方面,IMR相比较iDose~4、FBP技术能大幅度降低图像噪声,提高图像质量。
Objective To compare the image quality and radiation dose of FBP, iDose ~ 4 and IMR in gastric cancer and evaluate the clinical value of IMR. Methods Forty patients were divided into low dose group (A group) and conventional dose group (B group) by random number table method. Each group had 20 cases. All patients underwent CT scan of upper abdomen and dynamic enhanced scan. The portal venous scan data As research target. In order to ensure the image quality, each group of patients was fixed with a fixed noise ratio (DRI). The images were divided into 6 groups according to the radiation dose and recombination algorithm, including A1 group (120 kV, FBP), A2 group (120 kV, iDose ~ 4), group A3 (120 kV, IMR), group B1 (80 kV, FBP), group B2 (80 kV, iDose ~ 4) and group B3 (80 kV, IMR). The objective evaluation indexes of image quality (image noise, image SNR, CNR) and subjective evaluation indexes (low contrast and contrast ratio) of A1, A2 and A3 groups and B1, B2 and B3 groups were compared respectively. Lesion edge sharpness, image distortion and diagnostic confidence), and calculate the effective radiation dose (ED). Results The ED of low-dose group decreased by 73.7% on average compared with the conventional dose group. The image noise of group I was significantly lower than that of FBP and iDose ~ 4 (P <0.01), CNR and SNR were significantly higher than those of FBP and iDose ~ 4 (P <0.01) group. The low contrast resolution (LCD), lesion edge sharpness (LES), image distortion (ID) and diagnostic confidence (DC) in group A and B were better than those in FBP and iDose ~ 4, And A3 group, B1 group and B2, B3 group difference was statistically significant (P <0.05). Conclusion Compared with iDose ~ 4 in IMR, the FBP technique can significantly reduce the image noise and improve the image quality.