脊柱椎弓根螺钉内固定术后行多层螺旋CT扫描时减少伪影及放射剂量的参数优化研究

Optimization of parameters for reducing artifact and radiation dose in multi-detector computer tomography after pedicle screw internal fixation

目的评价多层螺旋CT检查时管电压和管电流与金属伪影程度之间的关系,探索适当的方案以减少金属伪影和辐射剂量。方法将4枚椎弓根螺钉植入人体腰椎L4、L5标本内制成的椎弓根螺钉内固定模型用丝线悬吊固定于伪影评价专用水模中央。对其使用不同扫描参数(主要是管电压及管电流)条件下的多层螺旋CT扫描,并测量椎弓根螺钉前端的放射状伪影长度以评价其伪影程度,记录辐射剂量。结果多层螺旋CT管电流的变化并没有明显影响金属伪影,但管电压的变化对伪影程度有较大影响,随着管电压的增大(100～140kV),伪影程度明显减小(P<0.05)。辐射剂量随着管电流及管电压的升高而升高。结论在其他扫描参数不变,能同时减少伪影和辐射剂量的方案是:高管电压(一般为140kV)并保持不变,而管电流则使用低于250～270mA常规使用值的电流。

Objective To assess the correlation between the metal artifact degrees with the tube voltage（in peak kilovolts,kV） and tube current（in milliamperes,mA） in multidetector computed tomography（MDCT）,so as to search for proper strategies to reduce metal artifact and the radiation dose.Methods Four lumbar pedicle screws were implanted in the human L4,L5 specimens to establish the pedicle screw fixation model,and the models were hung on the appropriative water mode to assess the artifacts with silk thread.Different scanning parameters（Hnly tube tension,tube current） were used for scanning.The lengths of the artifacts emanating from the anterior tips of the screw were used to evaluate the degree of artifact.Results The tube current change did not significantly affect the metal artifacts（P0.05）,but the tube voltage had significant impact on the metal artifacts;the degree of artifacts decreased remarkably with the increase of the tube voltage（100-140 kV,P0.05）.Radiation dose rose with tube current and tube voltage increase.Conclusion Simultaneous reduction of the artifact and radiation dose can be achieved with high tube voltages（usually 140 kV） and tube currents should be lower than the generally used values of 250-270 mA.