不同管电流对正常颅脑CT灌注参数和辐射剂量的影响

Influence of Tube Current on CT Perfusion and Radiation Dose of Normal Head

目的分析管电流与正常颅脑各灌注参数及图像质量之间的关系,探讨低电流颅脑CT灌注扫描的可行性。资料与方法 2010年7月至2011年5月所有拟行颅脑CT灌注检查的受检者,按管电流随机分为A组(常规剂量组)(200 mA),B组(150 mA),C组(120 mA),D组(100 mA)不同管电流进行扫描,每组筛选10例无颅脑疾病者进行研究。在额叶、颞叶及小脑白质对称各选取3个感兴趣区,分别测量脑血流量(CBF)、脑血容量(CBV)、平均通过时间(MTT)和达峰时间(TTP),噪声(SD)及辐射剂量(E),计算对比度噪声比(CNR)、变异系数(CV)及信噪比(SNR),并对各参数进行统计学分析,记录各组辐射剂量。结果各兴趣区各项灌注参数在4组间比较差异无统计学意义。在4组间两两比较结果显示,A组与D组额叶、颞叶、小脑CBF及额叶、颞叶CBV组间两两比较差异有统计学意义,A组与C组颞叶CBF及额叶CBV组间两两比较差异有统计学意义,A组与B组各项灌注参数组间两两比较差异无统计学意义。各组客观图像质量指标在4组间比较差异显著,而在4组间两两比较结果显示A组与B组CNR差异无统计学意义。随着电流的降低,CV、SD有升高趋势,SNR有降低趋势。A～D组的吸收剂量分别为2.39 mSv、1.79 mSv、1.43 mSv、1.2 mSv。结论以150 mA的低管电流行颅脑CT灌注扫描对灌注参数和图像质量无明显影响,与常规剂量组对比辐射剂量降低25%,可用于低剂量颅脑CT灌注扫描。

Objective To verified the relationship between tube current,normal head perfusion parameters and image quality,and to assess the feasibility of CT perfusion with low tube current.Materials and Methods Between Jul 2010 and May 2011,all patients who performed CT perfusion of head were randomly divided into four groups with different tube currents applied,including group A（200 mA）（conventional dose group）,group B（150 mA）,group C（120 mA） and group D（100 mA）.Ten normal cases in each group were selected to analyse.Region of interest（ROI） with 50mm2 in the white matter of frontal lobe,temporal lobe and cerebellum were drew and the parameters in ROI,including cerebral blood flow（CBF）,cerebral blood volume（CBV）,mean transit time（MTT） and time to peak（TTP）,noise（Standard Deviation,SD）,radiation dose（E） were measured.Contrast signal to noise ratio（CNR）,coefficient of variation（CV）,signal to noise ratio（SNR） were calculated.Quantitative analysis was performed.Results There were no significant differences of perfusion parameters acquired between 4 groups.Slight differences of CBF in frontal lobe,temporal lobe and cerebellum,CBV in frontal lobe,temporal lobe were existed between A and D groups.There were also slight differences existed of CBF in temporal lobe,CBV in frontal lobe between A and C groups.Between group A and B,parameters have no significant difference.The image quality were great different between 4 groups,there was a tendency for CV,SD to increase and SNR to decrease with decreasing tube current,but no difference of CNR between group A and B.The effective dosage of group A to group B were 2.39 mSv,1.79 mSv,1.43 mSv,1.2 mSv,respectively.Conclusion There was no significant influence on the CT perfusion parameters and image quality using 150mA tube current,and the radiation dose could be reduced by 25% when compared with that of conventional group and could be used for low dose CT perfusion of head.