低管电压联合迭代模型重建技术在肝脏CT增强扫描中的可行性研究

目的 探讨低管电压联合迭代模型重建(IMR)技术在肝脏CT增强扫描中的可行性。方法 60例患者按随机数字表法分为A组和B组,每组30例。扫描方案A组动脉期100 kV,门静脉期120 kV,B组动脉期120 kV,门静脉期100 kV。各组管电流均固定为250 mAs。A组动脉期和B组门静脉期采用IMR,A组门静脉期和B组动脉期采用滤波反投影(FBP)重建,得到4组图像,包括A1组(动脉期,100 kV,IMR),B1组(动脉期,120 kV,FBP),A2组(门静脉期,120 kV,FBP)以及B2组(门静脉期,100 kV,IMR)。分别比较A1组和B1组,A2组和B2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、图像失真及诊断信心度),并计算有效剂量。结果 有效剂量A1组较B1组、B2组较A2组明显下降(t=11.05、11.64, P<0.01)。低对比分辨力、病灶边缘锐利度A1优于B1组、 B2优于A2组(Z=6.391、3.200、6.559、3.409, P<0.01),图像失真和诊断信心差异无统计学意义(P>0.05)。图像噪声A1组低于B1组,B2组低于A2组(t=12.889、15.163, P<0.01),SNR和CNR A1组高于B1组,B2组高于A2组(t=15.458、1.325、15.308、3.136, P<0.01)。结论 与常规管电压FBP重建相比,低管电压联合IMR重建可显著降低肝脏增强CT的辐射剂量,并提高其图像质量。

Feasibility study of contrast-enhanced hepatic CT with low tube voltage using iterative model reconstruction technique

Objective To investigate the feasibility of contrast-enhanced CT with low tube voltage using iterative model reconstruction(IMR) technique. Methods Sixty patients were randomly assigned into 2 groups (group A and group B, 30 each) according to random number table. All patients underwent contrast-enhanced hepatic CT. Group A was scanned with 100 kV at arterial phase(AP) and 120 kV at portal vein phase (PVP), while group B was scanned with 120 kV at AP and 100 kV at PVP. All protocols were performed at the same tube current of 250 mAs. Raw data were reconstructed with IMR for AP images in group A and PVP images in group B; and reconstructed with FBP for AP images in group B and PVP images in group A. Images of 4 different groups were obtained: A1(AP,100 kV,IMR), B1(AP,120 kV,FBP), A2(PVP,120 kV,FBP) and B2(PVP,100 kV,IMR). Subjective evaluation indexes for image quality including low-contrast detectability, lesion edge sharpness, image distortion and diagnostic confidence. Objective evaluation indexes included CT attenuation of hepatic parenchyma, image noise, SNR and CNR, which were assessed and compared between groups A1 and B1, groups A2 and B2. Effective radiation doses were calculated. Results Effective dose in group A1 was reduced 35.1% compared to B1 (t=11.05, P<0.01), while a reduction of 37.7% in group B2 compared to A2 (t=11.64,P<0.01). Subjective image quality score of low-contrast detectability and lesion edge sharpness were significantly higher in group A1 compared to B1 (Z=6.391, 3.200, P<0.01), as well as in group B2 compared to A2(Z=6.559, 3.409, P<0.01). No differences were found in image distortion and diagnostic confidence between groups A1 and B1, groups A2 and B2, respectively (P>0.05). Significantly lower image noise and higher SNR/CNR were found in group A1 compared to group B1(t=12.889, 15.458, 1.325, P<0.01), as well as in group B2 compared to group A2(t=15.163, 15.308, 3.136, P<0.01). Conclusions Significant radiation dose reduction and image quality improvement in contrast-enhanced hepatic CT can be reached by using low tube voltage protocol combining with IMR technique.