螺距的选择对老年慢阻肺患者CT成像质量的影响

发布时间：2018-04-28 08:14

本文选题：螺距 + 图像质量　；参考：《山东中医药大学》2013年硕士论文

【摘要】：目的：：探讨不同螺距对老年COPD患者64层胸部CT图像质量的影响。资料与方法：选取2010年8月-2012年5月在本院行64层CT检查的COPD患者。男52例，女48例，年龄65～92岁，平均72.5岁。使用GE Lightspeed sys#vct64层螺旋CT机进行胸部扫描，将患者分为２组：A组（50例）采用螺距0.984，B组（50例）采用螺距1.375,其它扫描参数两组基本一致,管电压120kV，管电流200mA，扫描层厚5mm，准直宽度40mm。扫描范围由肺尖部向下至肺底。图像主观评价方法，3名高年资影像诊断医师，在病史和扫描方式都不知情的情况下进行独立分析图像并对图像质量评级，评分采用3分级法：1分为图像质量为优，图像清晰，各横断面肺野的肺血管、气管及以下分支，显示清晰、锐利；纵隔内组织结构清楚；能分辨细小血管断面(图1)；2分为图像质量为良，欠清晰(不影响诊断)：横断层面出现肺血管、气管及支气管分支边缘模糊，，细小血管断面可见(图2)；3分为图像质量为差，模糊(影响诊断)：连续1～3个横断层面(尤其有病灶层面)出现肺血管、气管走行呈“双管”影或心影、膈肌“双边”影，病灶边缘模糊，细小血管断面显示不清(图3)。图像噪声测量,在降主动脉、背部肌肉，选取位置相同的感兴趣区，以CT值的标准差作为图像噪声。为避免测量误差，降主动脉和背部肌肉水平分别选取三个层测量，图像CT值取其平均值。统计学分析：应用SPSS11.5软件分析，P值＜0.05为差异有统计学意义。结果：100例病例中，A组50例出现呼吸运动伪影17例，伪影发生率为34％，B组出现呼吸运动伪影4例，伪影发生率为8％，伪影发生率较A组减少了26％，2种扫描方法伪影发生率在统计学上具有显著性差异(P0.05)见表1。两组图像主观评分无显著差异，见表2。两组噪声对比无显著差异，见表3。两组扫描时间有明显差异(P0.05)，B组明显短于A组，见表4。结论：老年COPD患者的胸部CT扫描，在管电压（ｋＶ）和管电流（ｍＡ）恒定不变的情况下，应用螺距1.375与螺距0.984比较，减少运动伪影的产生是可行的、有效的，在保证肺组织图像质量的同时，呼吸运动伪影相对减低，可以同时达到降低辐射剂量的目的，减少辐射损伤。
[Abstract]:Objective: to investigate the effect of different pitch on 64 slice CT image quality in elderly patients with COPD. Materials and methods: COPD patients who underwent 64-slice CT from August 2010 to May 2012 were selected. There were 52 males and 48 females, aged 6592 years (mean 72.5 years). The patients were divided into two groups: group A (n = 50) and pitch 0.984B (n = 50). The other scan parameters were basically the same. The voltage of the tube was 120kV, the current of the tube was 200mA, the thickness of scanning slice was 5mm, and the width of collimation was 40mm. The scanning range was from the apex of the lung to the bottom of the lung. The image subjective evaluation method: 3 senior image diagnostics were analyzed independently and rated the image quality without knowing the medical history and the scanning method. The score was divided into three grades: the image quality was the best, the image was clear, and the image was clear. The pulmonary blood vessels, trachea and below branches of the cross section of the lung field are clear and sharp; the structure of the mediastinal tissue is clear; the fine blood vessel section can be distinguished (fig. 1: 2) the quality of the image is good. Unclear (not affecting the diagnosis): pulmonary vessels appeared on the transverse plane, the edges of the trachea and bronchus branches were blurred, and the small blood vessels were visible on the cross-section (fig. 2 / 3), the quality of the images was poor. Fuzzy (influence diagnosis): pulmonary vessels appeared on 1 ~ 3 transected plane (especially with lesion), trachea was "double tube" or cardiac shadow, diaphragm was "bilateral", the edge of lesion was blurred, and the small blood vessel was not clear on section (Fig. 3). Image noise measurement, in descending aorta, back muscles, select the same position of the region of interest, using the standard deviation of CT value as image noise. In order to avoid the measurement error, the descending aorta and back muscle were measured in three layers, and the average value of CT image was calculated. Statistical analysis: SPSS11.5 software was used to analyze P < 0. 05 as the difference was statistically significant. Results among 100 cases, 17 cases of respiratory motion artifacts appeared in group A and 4 cases in group B (group B). The incidence of artifact was 8%. The incidence of artifact was 26% less than that in group A. There was a statistically significant difference in the incidence of artifact between the two methods (P 0.05), as shown in Table 1. There is no significant difference in image subjective scores between the two groups, as shown in Table 2. There is no significant difference in noise between the two groups, as shown in Table 3. There was a significant difference between the two groups in scanning time. Group B was significantly shorter than group A, as shown in Table 4. Conclusion: it is feasible and effective to reduce motion artifacts by using pitch 1.375 and pitch 0.984 in chest CT scan of elderly patients with COPD under the condition of constant tube voltage and tube current. While ensuring the image quality of lung tissue, the respiratory motion artifact is relatively low, which can reduce the radiation dose and reduce the radiation damage at the same time.
【学位授予单位】：山东中医药大学
【学位级别】：硕士
【学位授予年份】：2013
【分类号】：R816.41;R563.9

【参考文献】