128层双源CT冠脉成像X线剂量评估

Evaluating radiation dose of 128-slice dual-source computed tomographic coronary angiography with different electrocardiogram pulsing models

目的评价第2代双源CT冠脉成像的3种不同心电采集模式的人体X线吸收剂量及临床运用价值。方法收集2010年4至5月间因胸痛来同济大学附属东方医院就诊并进行CT冠脉成像的253例患者进行扫描剂量评价，CT扫描仪为128层双源CT扫描机，所有患者扫描前均未使用药物控制心率，根据患者心率将患者分成3组进行扫描：A组：心率≤75次／min，节律规整，采用flash扫描（前瞻性心电门控螺旋扫描）；B组：采用sequence模式（自适应性前瞻性心电门控序列扫描）扫描，心率范围〉75次／min，节律规整（早搏〈5次／min）；C组：采用routine模式（回顾性心电编辑螺旋扫描）扫描，心率〉75次／min，且心律不齐，早搏≥5次／min。结果253例冠脉成像中31例因呼吸运动造成图像错层，不能进行诊断，判定为成像失败，能够达到诊断标准冠脉图像共222例，其中A组83例，扫描时实际心率范围：53～81次／min，平均有效吸收X线剂量（ED）为（0．602±0．363）mSv；B组63例，扫描时实际心率范围72—118次／min，节律规整，ED为（1．253±0．804）mSv；C组76例，扫描时实际心率范围34～154次／min，均为节律不齐，ED为（9．039±5．657）mSv。A、B、C三组间差异有统计学意义（P〈0．01）。结论前瞻性心电门控螺旋扫描在低心率患者可以减少X线吸收剂量至亚mSv；前瞻性心电门控序列扫描可减少高心率患者的X线吸收剂量；心律不齐、房颤患者亦可以获得满意的冠脉图像质量。

Objective To determine the effects of heart rate frequency （HRF） and heart rate variability （HRV） on radiation exposure and image quality in a large cohort of patients undergoing DSCT （dual-source computed tomograph ） coronary angiography with three different electrocardiogram （ECG） pulsing models, to prospectively investigate CT image quality parameters by using different protocols and to calculate the radiation dose estimates for noninvasive coronary angiography performed by DSCT. Methods Over a 1-month period, 253 consecutive patients were recruited and categorized into 3 groups： Group A：low HRF （ ≤75 beats/min） with normal-minor heart rate variability （HRV） （mean interbeat difference （IBD）, 0- 3）, coronary CT angiography proceeding with prospective ECG-triggered flash spiral scan; Group B： intermediate-high HRF （ 〉 75 beats/min） with normal-minor HRV （ IBD, 0-4）, with prospective ECG- triggered sequence scan; Group C： intermediate-high HRF （ 〉 75 beats/min） with moderate-severe HRV （IBD≥5） with retrospective ECG-gated spiral scan. Results CT coronary angiography yielded excellent image quality in 87.7% of patients （222/253）. No significant differences were found among three groups with different HRF and HRV in image quality and diagnostic performance. Radiation exposure was significantly higher in patients With low versus high HRF and in patients with severe versus normal HRV. Significant difference （P 〈 0. 001 ） was found among the effective doses of group A （ mean ±standard deviation,0. 602 ±0. 363 mSv ）, group B （1. 253±0. 804 mSv） and group C （9. 039±5. 657 mSv）. Conclusion The higher temporal resolution of dual-source spiral CT coronary angiography performed with adaptive ECG pulsing results in preserved diagnostic image quality and performance independent of HRF or HRV at the cost of limited dose reduction in arrhythmic patients.