头颈部多层螺旋CT低剂量扫描研究

目的评价不同管电流条件下多层螺旋CT头颈部扫描对图像质量及辐射剂量的影响，探讨多层螺旋CT头颈部低剂量扫描应用的可行性及其适宜的低剂量扫描条件。方法随机选取头颈部CT扫描患者140例，男92例，女48例，年龄7岁～78岁，分7组，每组20例，管电流分别为150mA、120mA、90mA、60mA、40mA、30mA、20mA。由2位高年资放射科医生对所有资料进行双盲法评价，应用SPSS 14.0对资料进行统计学处理。结果不同条件下，软组织／病变、骨质、噪声、伪影及MPR备组有差异（P〈0.05）。150mA、120mA、90mA三组图像诸指标无差异（P〉0.05）。60mA～150mA各组对软组织／病变显示均在3分以上。40mA、30mA和20mA组分别有6例（30％）、13例（65％）及20例（100％）软组织／病变显示不佳。30mA～150mA各组对骨质显示较清晰，评分均为3分以上。60mA及以上各组SD值均在5Hu以下，40mA、30mA及20mA组SD值在5Hu以上分别为6例（30％）、20例（100％）、20例（100％）60mA～150mA各组MPR图像评分均在3分以上，40mA、30mk、20mA组MPR图像分别有6例（30％）、9例（45％）、20例（100％）影响诊断。结论头颈部低剂量扫描适宜条件为：软组织60mA，骨质30mA，可明显降低辐射剂量。

The Study of Low Dose Scan with Multislice Helical CT in Head and Neck

Objective To evaluate the effect of tube current on image quality of computed tomography（CT） in the head and neck, to explore the possibility of low dose CT scan in the examination of the head and neck and choose the suitable scan parameters. Methods 140 patients were divided into seven groups randomly（92 male, 48 famale; age range 7-78 years）, 20 cases in each group and underwent CT scan in the head and neck at current of 150mA, 120mA, 90mA, 60mA, 40mA, 30mA and 20mA, respectively. All images were separately evaluated by two experienced radiologists in a blind way. All the data were statistically analyzed with SPSS 14.0. Results There were significant differences in imaging quality for soft tissue/disease, bone structure, image noise, artifact and MPR image at various tube current（P〈0.05）.There were no differences in all aspects at 90 mA, 120 mA and 150 mA（P〉 0.05）. For the soft tissue and disease, all the cases scored more than 3 points from 60 mA to 150mA. 6（30%） cases at 40mA, 13（65%） cases at 30mA and 20（100%） cases at 20mA scored less than 3 points. For the bone structure, all the cases scored more than 3 points from 30mA to 150mA. The SD value of ROI is less than 5Hu when the tube current was larger than 60mA, while SD is more than 5Hu at 40mA （n=6）, 30mA（n=20） and 20mA（n=20）. For MPR, all the cases scored more than 3 points from 60mA to 150mA. 6（30%） cases at 40 mA, 9（45%） cases at 30mA and 20（100%） cases at 20mA scored less than 3 points. Conclusion The suitable parameters of low dose scan are 60mA for the soft tissue and 30mA for bone structure.