自由呼吸对提高冠状动脉CT图像强化效果及均一性的研究
Improving the degree and uniformity of enhancement in coronary CT angiography with free breathing

摘要：目的 比较屏气与自由呼吸在不控制心率的情况下对冠状动脉图像强化效果及均一性的影响。方法 2017年3月-7月期间，在我院256排Revolution CT行冠状动脉CT检查的60例患者随机纳入本研究。60例患者随机分为两组，A组：屏气组(30例，检查过程中嘱患者吸气后屏气)；B组(30例，检查过程中嘱患者平静呼吸)。两组患者扫描方案及对比剂注射方案均一致。比较两组图像的CT值、强化变化率、信噪比、对比噪声比、主观得分(1～5分，1分差，不能诊断，5分优)及两组患者扫描前后心率变化差异。结果 自由呼吸组的CT值[(405.10±58.20)Hu]及强化均一性(14.37%)均优于屏气组[(337.60±72.70)Hu，21.53%]，差异有统计学意义(P<0.01)。两组冠脉节段平均得分分别为4.49±0.41、4.33±0.36，两组患者扫描前后的心率分别是(1.74±1.86)次/min、(1.30±1.25)次/min，两组比较均无统计学差异。结论 自由呼吸可提高图像的强化效果及强化均一性，且可得到与屏气条件下同样质量的图像。
ABSTRACT: Objective To explore the feasibility of improving the degree and uniformity of contrast enhancement in coronary CT angiography (CCTA) with free breathing and uncontrolled heart rates. Methods We recruited 60 patients with suspected coronary heart disease who received CCTA scanning with 256-row Revolution CT scanner at our hospital between March and July 2017. They were randomly divided into Group A (n=30) during breath holding and Group B (n=30) during free breathing. Similar scanning and contrast injection protocols were used in both groups and no heart rate control was made before examination in either group. CT value, standard deviation (SD), signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) in the aortic sinus (AS) were calculated. Image quality of each coronary artery segment was evaluated using a 5-point grading scale (1: non-diagnostic, 5: excellent) by two experienced radiologists. Results The mean enhancement in vessels was significantly higher in Group A [(405.10±58.20)Hu] than in Group B [(337.60±72.70)Hu] (P<0.05). The fluctuation rate for the enhancement was lower in Group B (14.37%) than in Group A (21.53%). The subjective image quality score for coronary artery images was 4.49±0.41 (Group A) and 4.33±0.36 (Group B) with no difference. The mean difference in heart rate before and during scanning was 1.74±1.86 counts per minute in Group A and 1.30±1.25 counts per minute in Group B with no difference. Conclusion Free-breathing CCTA is feasible using 256-row, 16 cm detector CT scanner without heart rate control to provide high image quality with improved degree and uniformity in contrast enhancement