多层螺旋CT盆腔扫描重建图像质量与X射线剂量的关系

目的分析扫描参数的设置与图像质量和吸收剂量之间的关系,选择适合于二维和三维重建较高图像质量和较低吸收剂量的扫描方式。方法使用GE L ightspeed U ltra 16层螺旋CT机,对人体盆腔模型进行扫描。扫描条件:120 kV,管电流分别为250 mA或200 mA,螺距分别为1.375或0.985,层厚分别为5 mm或7.5 mm。评价二维和三维图像质量,在辐射剂量观测栏,观测剂量长度乘积(DLP)的变化。选择其中图像质量较好和DLP相对较低的4种扫描方式对患者进行扫描。结果DLP随管电流的增加、螺距的减小而增大,而二维和三维图像质量也随mA的增加、螺距的减小而提高。二维图像选择250 mA、1.375螺距、7.5 mm层厚,图像噪声低,影像细节能清晰显示,且DLP相对较低;三维图像选择200 mA、0.938螺距、7.5 mm层厚,能够满足诊断需要。结论遵循医疗照射的正当性和防护最优化原则,科学地设置管电流、层厚、螺距等扫描参数,一方面能够保证二维和三维图像质量,另一方面又能减少DLP值,减少X射线辐射对盆腔生殖器官的损伤。

Analysis on the relationship between the quality of reconstructed image and the quantity of X-rays after pelvic cavity scanning with multislice CT

Objective To analyze the relationships among scan parameter setting,the quality of image and the quantity of absorption in order to choose the scanning mode which suits for reconstructing images of high quality 2D or 3D and low absorbing quantity.Methods With GE Lightspeed Ultra 16 slice CT,pelvic cavities of human were scanned under the conditions of(120 kV),250 mA or 200 mA,1.375pitch or 0.985 pitch,5 mm or 7.5 mm slice thick respectively.The quality of 2D or 3D images were evaluated and the changes of DLP from the column of the radiation quantity were observed.4 proper scanning modes were chosen to scan the patients,which had a better image quality and a lower DLP.Results When electric current(mA) increased and pitch decreased,DLP got larger and the qualities of 2D and 3D images got higher.2D images under the conditions of 250 mA,1.375 pitch,7.5 mm slice thick had lower image yawp,much clearly shown images and a relatively lower DLP,while 3D images of 200 mA,0.938 pitch,7.6 mm slice thick could meet the need of diagnosis.Conclusion Following the principles of justice to use and optimization to protect medical radiation,setting the scanning parameters such as mA,slice thickness and pitch scientifically can ensure the quality of 2D or 3D pictures,on the other hand they can decrease DLP and the damage of X-rays to genital organs.