【摘要】 目的:比较双源CT前瞻性心电门控大螺距扫描方式与回顾性心电门控小螺距扫描方式的辐射剂量及其电离辐射对人外周血淋巴细胞内DNA的损伤情况,并探索γ-H2AX作为低剂量X线电离辐射损伤生物剂量计的可行性及应用前景。方法:将40例拟行冠状动脉CTA的患者按扫描前的心率分为两组:大螺距组18例,心率<70次/分,螺距3.4,FLASH序列,前瞻性心电门控;小螺距组22例,心率≥70次/分,螺距0.20⁰.33,回顾性心电门控。两组均采用智能CARE-kV结合CARE Dose4D调节技术自动选取最优管电压及管电流。于CT检查前及检查后30min每例患者抽取静脉血4mL,采用γ-H2AX免疫荧光分析法检测淋巴细胞DNA双链断裂（DSBs）情况(γ-H2AX荧光点与淋巴细胞计数的比值,记为R_{焦点/细胞})。采用两组独立样本t检验比较两组间BMI及CT检查前后R_{焦点/细胞}的差异,采用Mann-Whitney U检验比较两组间检查前后R_{焦点/细胞}差值（△R）和辐射剂量指标（CTDIvol、DLP、ED）的差异,采用Spearman等级相关法分析DLP与△R的相关性。结果:两组患者的年龄、性别构成比及体质指数（BMI）的差异无统计学意义（P>0.05）。大螺距组的CTDIvol、DLP和ED值分别为（12.29±1.68）mGy、（100.28±30.60）mGy·cm和（1.41±0.43）mSv,3个指标的均值明显低于小螺距组[分别为（39.11±10.75）mGy、（537.27±152.74）mGy·cm和（7.52±2.14）mSv],组间差异均有统计学意义（P<0.05）]。40例患者CT检查前、后的R_{焦点/细胞}分别为（0.137±0.036）和（0.244±0.072）,CT检查后检查者淋巴细胞内DSBs数量明显增多（t=10.294,P=0.000）。大螺距组和小螺距组的△R分别为（0.058±0.034）和（0.148±0.058）,小螺距组高于大螺距组（U=27.50,P=0.000）。仅小螺距组的DLP与△R之间存在等级线性相关关系（r=0.781,P=0.000）。结论:前瞻性心电门控大螺距FLASH扫描方式的辐射剂量及电离辐射引起的DSBs明显低于回顾性心电门控小螺距扫描方式,而两组图像质量均能满足诊断要求;γ-H2AX监测可较准确地反映低剂量X线辐射损伤,应用前景广。更多还原

【Abstract】 Objective:To compare the radiation dose and in vivo DNA double-strand breaks induced during dual source CT scanning using high-pitch acquisition with prospective ECG-triggering and conventional low-pitch acquisition with retrospective ECG-triggering,and to evaluate the prospect of γ-H2 AX analysis used as a sensitive biologic dosimeter of low-level X-ray radiation.Methods:Forty patients were divided into two groups according to heart rate（HR）before coronary computed tomography angiography（CCTA）:18 cases with low HR [<70 beats per minute（bpm）]in high-pitch group（pitch=3.4）using FLASH sequence and prospective ECG gated technique,and 22 cases with high HR（≥70 bpm）in low-pitch group（pitch=0.20⁰.33）using retrospective ECG-gated technique.CARE kV and CARE Dose4 Dtechnique were used in both groups.Blood samples were obtained before and 30 minutes after CT scanning,and double-strand breaks（DSBs）of DNA in lymphocytes which were stained against the phosphorylated histone variant γ-H2 AX and were visualized using fluorescence microscopy,and the ratio of γ-H2 AX foci and lymphocytes number(R_foci/cell)was calculated.The differences of body mass index（BMI）and R_foci/cell before and after CT scan between the two groups were assessed by two independent samples t test.Difference of R_foci/cell value before and after CT（△R）and radiation dose indexes（CTDIvol,DLP and ED）in the two groups were compared by Mann-Whitney test.Spearman correlation analysis was used for the DLP and △R.Results:The basic characteristics（the composition of age and sex,BMI）of the patients were comparable with no significant difference in the two groups.The CTDIvol,DLP and ED in high-pitch group were（12.29±1.68）mGy,（100.28±30.60）mGy·cm and（1.41±0.43）mSv,which were significantly lower than those in low-pitch group[（39.11±10.75）mGy,（537.27±152.74）mGy·cm and（7.52±2.14）mSv].In all patients,the R_foci/cellbefore and after CT scan was 0.137±0.036 and 0.244±0.072 respectively,and statistical intergroup difference was found（t=10.294,P=0.000）.The R_foci/cellwas lower in high-pitch group（0.058±0.034）than that in low-pitch group（0.148±0.058）with significantly statistical difference（U =27.50,P=0.000）.The increase of γ-H2 AX foci after CT depended linearly on the DLP in low-pitch group（r=0.78,P=0.000）,while no correlation was found in high-pitch group.Conclusion:Spiral CT scanning using high-pitch acquisition and FLASH sequence has significantly lower radiation dose and in vivo DNA double-strand breaks induced than using low-pitch acquisition,while diagnostic image quality was obtained in both groups. γ-H2 AX analysis can be a sensitive biologic dosimeter for evaluating the radiation injury when exposed to low-level radiation.更多还原