低辐射剂量与低对比剂剂量在肥胖患者冠状动脉CT血管成像中的应用研究

Feasibility of low radiation dose and low contrast dose for coronary CT angiography in obese patients

目的探讨降低辐射剂量和对比剂用量的双低技术在I级肥胖患者冠状动脉CT血管成像(CCTA)中的可行性。方法前瞻性收集2022年8月至2023年3月于北京大学第三医院放射科行冠状动脉CTA检查的57例肥胖受检者(体重:85~119kg且体质量指数BMI:30~38kg/m^(2)),分为对照组20例和试验组37例,分别采用常规剂量和低剂量方案。对照组和试验组CCTA的管电压、碘对比剂的碘流率(IDR)分别为:120kVp、2.2gI/s与100kVp、1.5gI/s。对照组与试验组使用原始数据分别重建为混合迭代4级与8级的图像,其余扫描和重建参数均一致。测量并比较主动脉根部、左前降支(LAD)近段及右冠状动脉(RCA)远段管腔的CT值及噪声,计算左前降支及右冠状动脉的信噪比(SNR)和对比噪声比(CNR),并采用4分法对冠状动脉18节段的图像质量进行主观评价。记录并比较两组受检者的有效辐射剂量E和碘对比剂用量。采用独立样本t检验、Mann-WhitneyU检验或x²检验分析以上指标组间差异的统计学意义。结果对照组和试验组受检者BMI分别为31.89(30.77,33.81)和31.22(30.46,32.83)kg/m^(2),差异无统计学意义(P>0.05)。两组CCTA图像在主动脉根部、左前降支近段及右冠状动脉远段管腔的CT值及噪声值,左前降支近段及右冠状动脉远段管腔的SNR和CNR值,差异均无统计学意义(均P>0.05)。两组图像冠状动脉各节段主观评分值均分都≥3分,符合诊断标准,两组间的主观图像质量整体评分差异无统计学意义(P>0.05)。对照组和试验组受检者CCTA检查的有效剂量E分别为7.58与4.49mSv(Z=-5.46,P<0.05),对比剂用量分别为66与45ml,试验组受检者辐射剂量和对比剂用量分别较对照组降低41%和32%。结论在I级肥胖患者群体中,使用低管电压(100kVp)和低碘流率(1.5gl/s)进行CCTA检查是可行的,能够在不影响图像质量的情况下降低辐射剂量和碘对比剂用量。

Objective To evaluate the feasibility of low radiation dose and low contrast dosage in coronary CT angiography(CCTA)of class I obese patients.Methods This prospective study enrolled 57 patients(male/female,50/7,age,25-77 years)with body mass index(BMI)of 30-38 kg/m ^(2) and body weight of 85-119 kg scheduled for CCTA from August 2022 to March 2023 in our hospital.The patients were divided into two groups:control group(group A,n=20)and low⁃dose group(group B,n=37).Group A employed a standard⁃dose protocol:tube voltage 120 kVp and IDR 2.2 g I/s,while group B were scanned using the low⁃dose protocol:tube voltage 100 kVp and IDR 1.5 g I/s.Images in Group A and Group B were reconstructed with hybrid iterative reconstruction(HIR)at strength 4 and 8,respectively.Other scanning and reconstruction parameters were the same in two groups.Methods The image quality was assessed by measuring the CT values and noise in the aortic root,left anterior descending artery and right coronary artery,and the signal⁃to⁃noise ratio(SNR)and contrast⁃to⁃noise ratio(CNR)were calculated.Subjective image quality was evaluated for vessels according to the 18⁃segment classification system using a 4⁃point scale(1.poor,4.excellent).The effective dose E and contrast dosage were compared.Statistical analysis was performed using independent samples t⁃test,Mann⁃Whitney U test or χ^(2) test.Results The BMI of groups A and B were 31.89(30.77,33.81)and 31.22(30.46,32.83)kg/m^(2),respectively(P>0.05).No statistically significant differences in CT values,noise,SNR,CNR were noticed between the two groups(all P>0.05).The mean subjective score of all coronary artery segments in the two groups were not less than 3,meeting the requirement of clinical diagnosis.There was no statistically significant difference in the overall subjective image quality between the two groups(P>0.05).The radiation dose E in groups A and B were 758 and 449 mSv,respectively(Z=-5.46,P<0.05).The contrast dosage in groups A and B were 66 and 45 ml,respectively.The radiation dose E and contrast dosage in group B were 41%and 32%lower than that in group A,respectively.Conclusions For class I obese patients,it was feasible to use a low tube voltage(100 kVp)and low IDR(1.5 gI/s)protocol in CCTA.Radiation dose and contrast dosage can be reduced reasonably without compromising the CCTA image quality.