迭代重建技术在低剂量肾动脉CT血管造影检查中的应用

目的 迭代重建技术（iDose⁴）在低剂量肾动脉CT血管造影检查（CTA）中应用的可行性研究。方法 选取拟行肾动脉CT血管造影检查且体重在60~70 kg的患者90例，按检查先后分为，120 kV，120 mAs组（A组）；120kV，60 mAs组（B组）和100 kV，100 mAs组（C组），每组30例。其中A组采用滤波反投影法（FPB）生成图像，B组与C组采用iDose⁴迭代重建算法生成图像。测量记录各组图像的肾动脉CT值、噪声、信噪比（SNR）及对比噪声比（CNR）。对采集后的图像进行容积再现三维成像（VR）后处理，并按1~5分对VR图像质量进行评定。结果 A组与B组肾动脉CT值、SD值、SNR、CNR及VR图像质量评分差异无统计学意义；C组的SD值与A组、B组相当，而肾动脉CT值、SNR、CNR及VR图像质量评分均明显高于A组和B组，两组差异有统计学意义（t_CT值=-12.326，t_SNR=-7.136，t_CNR=-7.649；Z_VR=-2.690，P_VR <0.05）。 结论 肾动脉CTA运用iDose⁴迭代重建技术，在mAs降低50%的情况下仍能保证图像质量，而在管电压降低到100 kVp，辐射剂量（机器显示）降低50%的情况下，图像质量反而有所提高。

The use of iterative reconstruction technique in low-dose CT angiography of renal artery

Objective To assess the feasibility of computed tomography angiography (CTA) in renal artery using the iterative reconstruction technique(iDose⁴) in Brilliance iCT (Philips Ltd.). Methods 90 patients (body weight 60-70 kg) supposed to undergo renal artery CTA were selected and randomly divided into three groups: A(120 kV, 120 mAs), B(120 kV, 60 mAs) and C(100 kV, 100 mAs). CTA images from Group A were obtained using filtered back projection and those from the rest groups were generated by iDose⁴. Then CT number of renal artery, noise (denoted as standard deviation SD), signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) of images for each group were measured and recorded. Images were post-processed using volume reformation (VR) 3D imaging and image quality were assessed in five-level grade (1-5). Results The five parameters (CT number of renal artery, SD value, SNR, CNR and VR grade) of group A and group B were statistically insignificant (P>0.05). While SD values of group C were comparable to those of group A and B, the rest four parameters of group C were apparently larger, which was statistically significant (t_{CT value}=-12.326,t_SNR=-7.136,t_CNR=-7.649,Z_VR=-2.690,P_VR<0.05).Conclusions Image quality could still fit the diagnosis requirements using iDose⁴ when mAs decreased lower than 50%. The image quality increases when radiation dose is halved at 100 kVp kV.