低管电压结合迭代重建技术在不同BMI患者的头颈部CT血管成像中的应用研究

Study of the Low Tube Voltage Coupling with Iterative Reconstruction Technique in Craniocervical CT Angiography of Patients with Different Body Mass Index(BMI)

目的:探讨在头颈部CT血管成像(CTA)中,以患者体重指数(BMI)为基础的低剂量扫描方案实施前后对图像质量及辐射剂量的影响。方法:连续选取拟行头颈CTA检查患者186例,按检查先后分为,A组:采用管电压120 k V,滤波反投影法(FBP)重建;B组:采用管电压100k V,自适应性迭代重建(ASi R)。A、B组根据患者的BMI进一步分组,A1组和B1组:BMI<24kg/m2;A2组和B2组:24kg/m2≤BMI<28kg/m2;A3组和B3组:BMI≥28kg/m2。对各组的辐射剂量、客观图像质量评价采用两独立样本t检验。由两名有经验的放射科医师对两组图像质量进行主观评价,并对两名医师的阅片结果进行Kappa检验。结果:B1组、B2组及B3组的CT容积剂量指数(CTDIvol)较A1组、A2组及A3组分别下降29.29%、32.70%及40.24%(均P<0.05);B1组、B2组及B3组的剂量长度乘积(DLP)较A1组、A2组及A3组分别下降32.44%、35.10%和40.98%(均P<0.05)。头部,颈部以及胸廓入口处的血管CT值B组各分组较A组对应组均增高,图像噪声均减低,信噪比(SNR)和对比噪声比(CNR)均增高,差异均有统计学意义(均P<0.05)。B组各分组的主观评分较A组对应组均高(均P<0.05),B1组、B2组及B3组图像质量的一致性(Kappa值=0.634,0.644,0.628,均P<0.05)分别高于A1组、A2组及A3组(Kappa值=0.476,0.566,0.595,均P<0.05)。结论:不同BMI患者行头颈CTA检查,采用100k V管电压结合ASi R迭代重建扫描方案,可以降低辐射剂量(尤其是肥胖患者),并且可获得满意的图像质量。

Purpose： To assess the influence on image quality and radiation dose of low-dose craniocervical computer tomography angiography（CTA） using adaptive statistical iterative reconstruction（ASi R） in patients with different BMI. Methods： One hundred and eighty-six patients who were referred to undergo craniocervical CTA were selected and randomly divided into two groups：A [120 k V,filtered back projection（FBP） ] and B（100 k V,ASi R）. Group A and B were further divided into three subgroups： Group A1 and B1 were with BMI 〈24kg/m2, Group A2 and B2 were with 24kg/m2≤BMI〈28kg/m2, and Group A3 and B3 were with BMI≥28 kg/m2. Radiation dose, objective image quality between group A and B were statistically analyzed by independent samples t test. The scores of image quality were obtained by two radiologists. The inter-radiologist agreement of image quality was performed by kappa test. Results： Compared with group A1, A2 and A3, CT dose index volume（CTDIvol） in group B1, B2 and B3 were decreased by 29.29%, 32.70% and 40.24%, respectively（P〈0.05）, and 32.44%, 35.10% and 40.98% for dose length product（DLP）, respectively（P〈0.05）. For head, neck as well as the entrance of thorax, images in group B were with higher CT values（P〈0.05）, lower image noise（P〈0.05）, higher signal to noise ratio（SNR）（P〈0.05） and contrast to noise ratio（CNR）（P〈0.05） than that in group A. The subjective evaluation of images in group B was greater than group A（P〈0.05）. Consistency result of image quality in group B1, B2, and B3（kappa value=0.634, 0.644, 0.628, P〈0.05） was superior to that in group A1, A2 and A3（Kappa value=0.476, 0.566, 0.595, P〈0.05）, respectively. Conclusions： For patients with different BMI, image quality of craniocervical CTA using ASi R could still meet the diagnosis requirements, and radiation dose of obesity patients can be obviously decreased..