摘要
目的：
随着空间和时间分辨率的提高和改善,多层螺旋CT冠状动脉成像(Coronary Angiography, CA)作为无创而实用的检查技术,能够快速而准确地评价冠状动脉狭窄程度和粥样斑块性质,且阴性预测值高,为临床冠心病的诊断提供可靠依据。但随着薄层大容积扫描的广泛使用,使得心脏扫描时因射线剂量的累积而产生了相对较高的总体剂量,大大增加了病人辐射损伤随机效应的危险性。本研究旨在探讨低剂量冠脉成像临床应用的可行性,通过64层螺旋CT冠状动脉成像低剂量与常规剂量扫描的对照研究,比较图像质量、辐射剂量方面的差异,最终确定以图像能满足诊断为前提的最小管电流量,在保证图像质量满足诊断要求的前提下,更大程度地减少受检者的辐射剂量,实现辐射剂量最优化,同时延长CT球管的寿命。
方法：
1.选择性收集临床疑诊冠心病患者60例,随机分为4组,每组15例,各组在年龄、身高、体重及体质量指数方面无显著性差异(P>0.05),进行冠状动脉CT检查(采用心电门控电流调制技术)。
2.第一组为对照组(常规扫描最大电流设定量为700 mA)；另外三组为实验组(低电流量扫描)——最大电流设定量分别为常规扫描的90%(630 mA)、80%(560 mA)、70%(490 mA),其它扫描参数不变。
3.对各组的图像质量评分、CTDI及ED值差异进行统计学分析。对照组与各实验组的图像质量分数、辐射剂量采用单因素方差分析进行比较。
结果：
1.对照组与实验D组(最大电流量为常规设定量的70%)图像质量评分组间比较有显著性差异,而其余两组实验组与对照组图像质量评分组间比较无显著性差异。
2.对照组患者接受X线有效剂量ED为18.27±4.9mSv；低剂量的三个组(630 mAs、560 mAs和490 mAs)与常规剂量组(700 mAs)扫描比较,其X射线辐射量分别降低了8.6%、17.9%、21.2%。
3.常规剂量组与低剂量组之一(490 mAs)的图像质量评分组间比较有显著性差异(P<0.05),而其余两组(其中包括4例扫描时心率超过70 bpm的患者,图像出现有明显血管错层,但不影响对冠状动脉的评价)均能满足临床诊断要求,达到降低辐射剂量的目的。
结论：
适当降低电流量,可获得满足诊断需求的图像,能够对正常体重人群提供低剂量冠状动脉成像检查。本研究认为：560 mAs能够在图像质量达到诊断要求的前提下,对正常体重人群提供冠状动脉成像检查。
Objective:With the enhancement and improvement of the space and time-resolved rate, the technology of multi-slice spire computed tomography coronary angiography can quickly and accurately evaluate the nature of coronary artery stenosis and atherosclerotic plaques, as a kind of non-invasive examination and practical means, it has advantages of high negative predictive value, and for clinical diagnosis of coronary heart disease provides a reliable basis. However, with the thin-layer scanning the widespread use of large volume, it allows for the accumulation of radiation dose produced a relatively high total dose, patients has greatly increased the risk of radiation damage of random effects.To evaluate the impact of ECG mA modulation method of 64-slice spire CT on image quality and X-ray dosage in CT coronary artery imaging, and to explore the best settings of ECG modulated mA.
Methods:
1.60 patients were randomly divided into four groups,15 included in each group. There was no significant difference in terms of age height and weight and body mass index of every group(P>0.05). All of them checked the CT coronary angiography.
2. CT coronary artery images were scanned with tube current modulation by the most tube current of 700 mA,630 mA,560 mA,490 mA, respectively.
3. In all groups, the mean effective dose and image quality were calculated and compared with the method used the single factor analysis of variance.
Results:
1. There were significant differences between image quality by 700 mA and that by 490 mA in CT coronary artery imaging, but there were no significant differences between image quality by 700 mA and that by 630 mA and 560 mA.
2. Mean ED of the most tube current of 700 mA was 18.27±4.9 mSv, the Mean ED of the other three groups decreased by 8.6%、17.9%、21.2%.
3. There were significant differences between image quality by 700 mA and that by 490 mA in image quality score. The other two groups images can meet the requirements of clinical diagnosis, with the purpose of lowering the radiation dose.
Conclusion:Radiation dose can be reduce by controlling the most tube current of CT coronary artery scan with the maintaining the quality of CT image for diagnosis. The investigation testified that the CT coronary artery imaging with 560 mA could meet the requirements of clinical diagnosis in the normal weight group.
引文
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