兔颅脑螺旋CT扫描吸收剂量与图像质量的关系

The relationship between image quality and CT dose index in spiral CT for the brain of rabbit

目的:探索螺旋CT在兔颅脑进行低剂量扫描的可能性和合理性,为新生儿颅脑低剂量螺旋CT扫描的临床研究提供实验依据。方法:在水体模的同一层面,用120kV,分别作1.0和1.5两种螺距,3mm层厚的200、110、70mAs扫描。在每幅图像的相同位置测5个兴趣区,作CT值的均匀性和噪声水平比较;选用15只健康成年兔,用扫描参数120kV、3mm层厚、FOV115,1.0和1.5两种螺距在同一范围作200、110、70mAs三种不同剂量的螺旋扫描。由4名CT医生盲法评价兔脑CT图像,按优、良、差三个等级评判每一幅图像。结果:CT图像的均匀性随CT扫描剂量减少而变差,图像噪声水平随CT扫描剂量减少而增高。对螺距1.0,200、110、70mAs及螺距1.5,200、110mAs五组扫描图像质量比较,差异无显著意义(P>0.05)。结论:对兔颅脑进行低剂量螺旋CT扫描,既能保证图像质量,又能降低兔在接受颅脑CT检查时的放射辐射。

Objective：To explore the feasibility and rationality of low-dose spiral CT scan in the examination for the head of rabbit and provide the basis for the low-dose CT scanning in the head of neonate. Methods：The technical parameters were 120 Kv,3 mm slice thickness and every slice was scanned using tube current of 200, 110,70 mAs. Five same regions of interest were measured on every image. The homogeneity and noise level of CT were appraised. The technical parameters were 120 kV,3 mm slice thickness. 200,110,70 mAs were employed in each same slice. CT images were evaluated by four doctors using single-blind method,and 3 degrees including excellent image, good image and bad image. Results.The phantom measurement showed that the lower of CT dose and the lower of homogeneity. The lower of CT dose and the higher of noise level. The image quality had no significant diference between five conditions （pitch 1.0,200, 110,70 mAs; pitch 1.5,200,110 mAs）, （P 〉 0.05 ）. Conclusion： Low-dose spiral scan for examinating the head of rabbit might not only guarantee image quality but also reduce the radiation during CT scan.