不同扫描参数对宽体探测器CT散射线的影响研究  

Effect of different scanning parameters on scattered radiation from wide-detector CT

作　　者：郭森林[1] 任悦[1] 牛延涛[1] Guo Senlin;Ren Yue;Niu Yantao(Beijing Tongren Hospital,Capital Medical University,Belting 100730,China)

机构地区：[1]首都医科大学附属北京同仁医院放射科,北京100730

出　　处：《中华放射医学与防护杂志》2019年第1期22-25,共4页Chinese Journal of Radiological Medicine and Protection

基　　金：北京市卫生系统高层次卫生技术人才培养计划(20143019);北京市医院管理局临床医学发展专项经费(ZYLX201704).

摘　　要：目的探讨宽体探测器CT在使用不同扫描模式、不同探测器宽度时在z轴方向上散射线的分布特点。方法使用美国GE Revolution 16 cm宽体探测器CT,在机架扫描孔洞中心轴(z轴)上,以一定间隔布放热释光剂量计(TLD),分别在逐层扫描模式下使用4、8、16cm和螺旋扫描模式下4、8cm探测器宽度,对CT标准剂量模体进行扫描,扫描条件:管电压为120kV,有效管电流为200mAs,扫描长度为16cm,螺旋扫描时螺距分别为0.984∶1、0.516∶1。所有扫描重复4次,曝光后将所有TLD测量值除以4,并对数据进行统计学分析。结果z轴方向上,人体头侧散射线剂量值均高于人体足侧(Z=-2.366、-2.197、-2.366、-2.371、-2.028、-2.236、-2.028,P<0.05)。逐层扫描时,不同探测器宽度的散射线分布差异有统计学意义(χ^2=28.000,P<0.05),均为探测器4cm时最大,16cm时最小,最大差值为67.5μGy。螺旋扫描时,不同探测器宽度的散射线分布差异有统计学意义(Z=-3.233、-2.982,P<0.05),均为探测器8cm时最大,4cm时最小,其中螺距0.516∶1时最大差值为97.67μGy。螺旋扫描相同探测器宽度及有效管电流条件下,螺距为0.516∶1时高于螺距为0.984∶1的散射线,差异有统计学意义(Z=-3.296、-3.296,P<0.05),其中探测器宽度为8cm时最大差值为49.95μGy。结论宽体探测器CT不同探测器宽度的选择,可显著影响辐射场的分布和辐射值,应根据具体的临床需求选择合理的探测器宽度和相关参数,从而降低受检者、近台操作医务人员以及陪护人员的辐射剂量。Objective To explore the distribution characteristics on z-axis of scattered radiation from a wide-detector CT with different scan modes and detector widths. Methods The CT standard-dose phantom was scanned using a 16 cm wide detector Revolution CT. Thermoluminescent dosimeters (TLDs) were placed on the central axis (z-axis) of the scan hole at given intervals. As scan modes, both axial scan mode (using detector with width in 4, 8 or 16 cm) and the helical scan mode (using detector with width in 4 and 8 cm) are used. The scan parameters were as follows: tube voltage 120 kV;effective tube current 200 mAs;scan length 16 cm;pitch (for helical scan): 0.984∶1 and 0.516∶1, and all scans were repeated for 4 times. All TLDs were measured, after exposure, and divided by four for further analysis. Results The scattered radiation on z-axis was higher at the direction of human head than at the direction of human foot (Z=-2.366, -2.197, -2.366, -2.371, -2.028, -2.236, -2.028, P<0.05). Under the axial scan, the difference in distribution of scattered radiation with different detector widths was statistically significant. The maximum increase for detector width of 4 cm and 16 cm was 67.5 μGy(χ^2=28.000, P<0.05). Under the helical scan, the difference in distribution of scattered radiation with different detector widths was statistically significant (Z=-3.233, -2.982, P<0.05). The largest distribution of scattered radiation was found when the detector width was 8 cm and the smallest at the detector width is 4 cm. The maximum increase for detector width of 8 and 4 cm was 97.67 μGy at a pitch of 0.516∶1. Furthermore, when the detector width and effective mAs were the same, the scattered radiation at a pitch of 0.516∶1 was greater than that at a pitch of 0.984∶1, with the statistically significant difference(Z=-3.296, -3.296, P<0.05). The maximum increase was 49.95 μGy when the detector width was 8 cm. Conclusions In a 16 cm wide-detector CT, the selection of different detector widths can significantly influence the d

关 键 词：宽体探测器CT 探测器宽度 散射线 

分 类 号：R814.2[医药卫生—影像医学与核医学]