颈部低剂量CT检查实验及临床应用

Experimental study of low-dose cervical CT scan and its clinical application

目的评价山羊及人体颈部多层螺旋CT的辐射剂量和图像质量,探寻颈部多层螺旋CT的最佳低剂量扫描条件。方法通过CT机的辐射剂量预测软件并结合文献,选取10组低剂量扫描条件(140kV-50mA、140kV-30mA、120kV-100mA、120kV-50mA、120kV-30mA、90kV-200 mA、90kV-150mA、90kV-100mA、90kV-50mA、90kV-30mA)。扫描3只山羊的颈部,采用双盲法对CT图像质量(骨质)进行评分,筛选满足诊断要求的扫描条件。另将180例颈椎CT检查的患者随机分成9组,每组20例,用动物实验筛选出的条件进行扫描,对软组织和骨质CT图像质量进行评分。结果 CT辐射剂量与管电压、管电流变化呈线性正相关;CT辐射剂量变化的斜率随管电压或管电流的增大而增大。除90kV-30mA以外,其他9组扫描条件的骨质图像均能满足诊断要求。人体检查时扫描剂量高者图像质量评分高,各组图像的骨质评分均高于软组织评分。120kV-100mA、90kV-200mA组软组织图像质量良好、骨质图像质量优;140kV-50mA、140kV-30mA、120kV-50mA、90kV-150 mA、90kV-100mA组软组织图像基本不影响诊断,骨质图像质量良好;120kV-30mA、90kV-50mA组软组织图像影响诊断,骨质图像基本不影响诊断。结论采用低管电压、相对略高的管电流,能获得满足诊断要求的图像,且辐射剂量更低。颈部CT检查时,满足诊断要求的软组织扫描条件为90kV-100mA,若仅需观察颈部的骨质情况,可选用更低的扫描条件90kV-50mA。

Objective To access the optimal scan conditions of low- dose multi- slice CT on cervical region. Methods In the first step, 10 groups of low- dose scan conditions （140kV- 50mA, 140kV- 30mA, 120kV- 100mA, 120kV- 50mA, 120kV- 30mA, 90kV- 200mA, 90kV- 150mA, 90kV- 100mA, 90kV- 50mA , 90kV- 30mA） were selected according to the software prediction of CT radiation dose combined with the literature reports. In the second step, the necks of 3 goats were scanned with the conditions above. The quality of images was independently scored by two senior radiologists with double blind method and 9 groups of scan conditions （except 90kV- 30mA） met the requirement of diagnosis were selected. In the third step, 180 patients undergoing cervi-cal CT scan were randomly divided into 9 groups with 20 cases in each, patients were scanned with the conditions selected in animal experiments. And the quality of images was scored and anylyzed by SPSS 16.0 software. Results The CT radiation dose demonstrated a positive linear correlation with the change of tube voltage and current. The variety slope of CT radiation dose in-creased with the increasing of tube voltage or the current. The animal experiments demonstrated that 9 groups of conditions al met the requirement of diagnosis except 90kV- 30mA. The human cervical CT scan demonstrated that high radiation dose had a high score and bone scores were higher than soft tissue. 120kV- 100mA and 90kV- 200mA obtained good soft tissue images and excel ent bone images; 140kV- 50mA, 140kV- 30mA, 120kV- 50mA, 90kV- 150mA and 90kV- 100mA obtained good bone im-ages, and the diagnosis was not influenced by the soft tissue images. 120kV- 30mA and 90kV- 50mA obtained the soft tissue im-ages influencing the diagnosis and the bone images not influencing the diagnosis. Conclusion The images meeting the require-ment of diagnosis can be obtained by adopting low tube voltage and relative high tube current with lower radiation dose. In cervi-cal CT scan, 90kV- 100mA is the scan condition for soft tissue and 90KV- 50mA can be selected to observe the bone only.