基于70 kV管电压的双源CT“双低”冠状动脉检查应用于腹型肥胖患者的可行性

Feasibility of 70 kV tube voltage-based dual-source CT coronary imaging with "double low" protocol applied to patients with abdominal obesity

目的 探讨基于70kV管电压的双源CT“双低”冠状动脉检查应用于高体质指数及超高体质指数腹型肥胖患者的可行性。方法 纳入120例需行冠状动脉CT血管造影(CTA)的腹型肥胖患者,包括高体质指数患者(26kg/m^2<体质指数≤28kg/m^2)及超高体质指数(体质指数>28kg/m^2)患者各60例。前者随机分为双低A组及常规a组各30例,后者随机分为双低B组及常规b组各30例。双低A组、双低B组均采用对比剂碘克沙醇(碘浓度270mg/mL),CTA管电压为70kV,采用基于原始数据迭代重建算法;常规a组、常规b组均采用对比剂碘普罗胺(碘浓度370mg/mL),CTA管电压为120kV,采用滤波反投影重建算法。4组的对比剂用量均为1mL/kg,注射速率为5mL/s,均使用自适应前瞻性心电门控序列扫描技术。对4组进行图像质量主观及客观评价,并评估辐射剂量及碘摄入量。结果 双低A组、双低B组的管电流分别高于常规a组、常规b组(均P<0.05),而容积剂量指数、剂量长度乘积、有效辐射剂量、体型依赖的有效辐射剂量及总碘量分别低于常规a组、常规b组(均P<0.05)。双低A组的冠状动脉图像质量主观评分以及冠状动脉分支的CT值、信噪比、对比信噪比(CNR)与常规a组比较,差异均无统计学意义(均P>0.05),但双低A组各冠状动脉分支的图像优良指数(FOM)均高于常规a组(均P<0.05)。双低B组的CT值、信噪比、CNR、FOM以及主观图像质量评分均低于常规b组(均P<0.05)。结论 对于高体质指数的腹型肥胖患者,行“双低”冠状动脉CTA检查时,将管电压进一步减少到70kV是可行的,其在不降低图像质量的前提下,能够大幅度减低辐射剂量和碘摄入量。而对于超高体质指数的腹型肥胖患者,同等条件下70kV的管电压不能满足日常诊断需求。

Objective To explore the feasibility of 70 kV tube voltage-based dual-source CT coronary imaging with "double low" protocol applied to abdominal obesity patients with high or very high body mass index(BMI). Methods A total of 120 abdominal obesity patients requiring coronary CT angiography(CTA) were enrolled,including 60 high BMI(26 kg/m^2<BMI≤28 kg/m^2) cases and 60 very high BMI(BMI>28 kg/m^2) cases.The former cases were randomly divided into double low group A( n =30) and routine group a( n =30),and the latter cases were randomly divided into double low group B( n =30) and routine group b( n =30).The double low group A and the double low group B underwent CTA with contrast agent,iodixanol(iodine concentration,270 mg/mL), 70 kV tube voltage,and algorithm of sinogram affirmed iterative reconstruction;the routine group a and the routine group b underwent CTA with contrast agent,iodixanol (iodine concentration,370 mg/mL), 120 kV tube voltage,and algorithm of filtered back-projection reconstruction.In the four groups,the dose of contrast agent was 1 mL/kg and the injection velocity was 5 mL/s,and scanning was performed with self-adapted and prospective step-and-shot electrocardiography-triggering technique.Image quality was subjectively and objectively assessed in the four groups,and radiation dose and iodine intake were also evaluated . Results The tube current of the double low group A/B was higher than that of the routine group a/b(all P <0.05),however,the double low group A/B obtained lower volume-dose index,dose-length product,effective radiation dose,size-dependent effective radiation dose and total iodine intake compared to the routine group a/b(all P <0.05).There were no statistically significant differences in subjective score for coronary image quality,CT value,signal to noise ratio(SNR) or contrast noise ratio(CNR) of coronary branches between the double low group A and the routine group a(all P >0.05),but the double low group A had higher figure of merit(FOM) of each coronary branch compared to the routine group a(all P <0.05). The CT value,SNR,CNR,FOM and subjective score for image quality in the double low group B were lower than those in the routine group b(all P <0.05). Conclusion For abdominal obesity patients with high BMI,it is feasible to decrease tube voltage further to 70 kV in coronary CTA with "double low" protocol, which can dramatically reduce radiation dose and iodine intake without sacrificing image quality.Whereas for abdominal obesity patients with very high BMI, 70 kV tube voltage can′t meet the demand of daily diagnosis in the same condition.