多层螺旋CT胸部扫描技术与图像噪声及病变检出相关性研究

发布时间：2018-08-03 21:37

【摘要】：目的：探讨胸部CT扫描参数变化与不同组织噪声的相关性及图像质量影响的规律。方法：应用GE BrightSpeed16层CT机以管电压120kV，管电流300mA，螺距0.938为标准，每次扫描改变一种扫描参数，其它扫描参数不变，以不同管电压（80、100、120、140kV）、管电流（80、100、120、180、240、300mA）及螺距（0.562、0.938、1.375、1.75）扫描仿真胸部体模，测量、记录体模不同组织噪声值（CT值标准差，SD），并进行统计学分析。结果：肺组织不同管电压组（80、100、120、140kV）的噪声比较差异无统计学意义（F=0.966,P＞0.05），而胸壁软组织、脊柱旁软组织及主动脉噪声80kV组与常规管电压120kV组比较差异有统计学意义，P＜0.05。肺组织、脊柱旁软组织及主动脉噪声不同管电流组（80、100、120、180、240、300mA）差异均有统计学意义（肺组织F=3.28，P＜0.05、脊柱旁软组织F=11.89，P＜0.05及主动脉F=196.67，P＜0.05）；肺、胸壁软组织、脊柱旁软组织及主动脉噪声80mA组与常规管电流300mA组比较差异有统计学意义，P＜ 0.05；脊柱旁软组织噪声80mA组与常规管电流300mA组比较差异有统计学意义，P＜0.05。肺、胸壁软组织、脊柱旁软组织不同螺距组（0.562、0.938、1.35及1.75）噪声差异无统计学意义（肺组织F=0.23,P＞0.05；胸壁软组织F=1.53,P＞0.05；脊柱旁软组织F=2.27,P＞0.05）；主动脉噪声不同螺距组比较差异有统计学意义（F=9.68,P＜0.05）。结论：降低管电压、管电流，增加螺距时，不同组织噪声逐渐增高，但肺组织的噪声增加不明显，胸部低剂量扫描时能够在保证肺组织图像噪声变化不大的同时降低辐射剂量。目的：分析胸部低剂量CT图像噪声分布特点并优化低剂量扫描参数。方法结果结论方法：利用图像空间噪声添加软件计算中国人仿真胸部体模CT图像（6组不同噪声指数）噪声值，分析预设噪声指数与模拟噪声值差异性。采用图像空间噪声添加软件对20例志愿者在常规参数下扫描获得的原始图像（美国GE公司Brightspeed16排螺旋CT）进行噪声添加，，模拟出10、30、50、80、100、120、150、180及240mA9组胸部低剂量图像，记录每幅图像模拟噪声值，并对不同毫安组模拟噪声值进行统计学分析。结果：图像噪声添加法计算的模拟噪声值与预设噪声指数差异无统计学意义（P0.05）；胸部低剂量扫描时图像模拟噪声值随着管电流降低不断增加，当管电流在10~50mA时噪声降低显著，80~300mA时噪声值降低幅度变缓。80mA组与120mA组之间图像噪声差异无统计学意义（P0.05）。结论：图像空间噪声添加软件可应用于胸部低剂量CT图像噪声的评价研究。胸部低剂量CT检查时采用管电流80~120mA时能够保证图像噪声无明显变化的同时又可以降低辐射剂量。目的：利用置入肺结节和热释光剂量计(thermoluminescentdosimeters， TLD)的胸部体模，测量数字断层融合(digitaltomosynthesis， DTS)技术及多层CT(multi-slice computertomography， MSCT)胸部扫描时不同组织器官的吸收剂量，评价种方法对肺结节的检出率及辐射剂量水平。方法：采用DTS及MSCT分别扫描共置入45个模拟结节及TLD的胸部体模，记录并储存图像，测量胸部主要组织器官的吸收剂量并计算有效剂量。由3名放射诊断医师分别进行阅片并记录结节部位、大小及密度。采用Fisher确切概率法检验与X2检验，比较DTS与MSCT扫描对模拟结节检出率的差别；两种检查方法器官吸收剂量的比较采用配对t检验。结果：DTS与MSCT对肺结节检出率为66.7%(30/45)和91.1%(41/45)，两者差异有统计学意义（X2=8.073，P＜0.05)；对-650HU磨玻璃结节检出率为93.3%和73.3%，两者差异无统计学意义，(P＞0.05)；DTS对-800HU磨玻璃结节及直径小于8mm磨玻璃结节检出率为5/15(33.3%)和2/12(16.7%),MSCT检出率为12/15(80%)和8/12(66.7%)。胸部DTS检查各主要组织器官吸收剂量明显低于MSCT,两者差异有统计学意义(肺t=19.69，P＜0.05；胸椎t=30.01，P＜0.05；心脏t=16.33，P＜0.05；肝脏t=5.06，P＜0.05；、乳腺t=9.43，P＜0.05；甲状腺t=8.05，P＜0.05)；DTS与MSCT胸部扫描的有效剂量分别为0.65mSv、7.71mSv。结论：DTS对于-650HU磨玻璃结节检出率与MSCT相近，DTS对极低密度(-800HU)磨玻璃结节及直径小于8mm磨玻璃结节检出率低。肺胸部结节检查时，DTS有效剂量低于MSCT，约为MSCT辐射剂量的8.41%。
[Abstract]:Objective: To investigate the correlation between the changes of the parameters of the chest CT scan and the noise of different tissues and the law of the influence of the image quality. Methods: using the GE BrightSpeed16 layer CT machine, the tube voltage 120kV, the tube current 300mA, the pitch 0.938 are the standard, and the scanning parameters are changed each time, the other scanning parameters are constant, and the different tube voltage (80100120140kV), Tube current (80100120180240300mA) and pitch (0.562,0.938,1.375,1.75) scanning simulation of chest body model, measurement, recording different tissue noise values (CT standard deviation, SD), and statistical analysis. Results: different tube voltage group (80100120140kV) of lung tissue (80100120140kV) has no statistically significant difference (F=0.966, P > 0.05), but the chest wall The difference between the soft tissue, the para spinal soft tissue and the aortic noise 80kV group was statistically significant compared with the conventional tube voltage 120kV group. The differences in P < 0.05. lung tissue, the paravertebral soft tissue and the aortic noise different tube current group (80100120180240300mA) were statistically significant (F= 3.28 in the lung tissue, P < 0.05, F=11.89 of the paravertebral soft tissue, P < 0.05). The aorta was F=196.67, P < 0.05); the lung, the soft tissue of the chest wall, the soft tissue of the spinal column and the 80mA group of the aortic noise were significantly different from that of the conventional tube current 300mA group, P
0.05, there were significant differences in the noise between the 80mA group and the routine tube current 300mA group. There was no significant difference between the P < 0.05. lung, the chest wall soft tissue and the different pitch groups (0.562,0.938,1.35 and 1.75) of the para soft tissue (0.562,0.938,1.35 and 1.75) (P > 0.05; the chest wall soft tissue F=1.53, P > 0.05; F=2.27, P in the para spinal soft tissue. > 0.05) and there was a significant difference between the different spiral distance groups of the aorta (F=9.68, P < 0.05). Conclusion: the noise of different tissues increases gradually when the tube voltage, the tube current and the pitch are increased, but the increase of the noise of the lung tissue is not obvious, and the low dose scanning of the chest can reduce the change of the image noise of the lung tissue at the same time. Shoot dose.
Objective: to analyze the noise distribution characteristics of low dose chest CT images and optimize the low dose scanning parameters. Method results: using image spatial noise adding software to calculate the noise values of Chinese human simulated chest CT images (6 groups of different noise indices), and analyze the difference between the preset noise index and the simulated noise value. Noise addition software was used to add noise to the original images (GE Brightspeed16 row spiral CT) of 20 volunteers, to simulate the low dose chest images of 10,30,50,80100120150180 and 240mA9 groups, to record the noise values of each image, and to make statistical analysis of the simulated noise values of the different MS group. Results: there is no significant difference between the simulated noise value calculated by the image noise addition method and the presupposed noise index (P0.05). The noise value of the image in the low dose chest increases with the decrease of the tube current, and the noise decreases significantly when the tube current is at 10~50mA. The reduction of noise value at 80~300mA slows down the map between the.80mA group and the 120mA group. There is no statistical significance (P0.05). Conclusion: the image spatial noise adding software can be applied to the evaluation of low dose CT image noise in the chest. When the chest low dose CT examination is used, the use of the tube current can ensure that the image noise has no obvious change while reducing the radiation dose.
Objective: to measure the absorbable dose of different tissues and organs in the chest scan of multi-layer CT (multi-slice computertomography, MSCT), and to evaluate the detection rate of the pulmonary nodules by using the digitaltomosynthesis (digitaltomosynthesis, DTS) technique and the chest scanning of the thermoluminescentdosimeters (TLD). Method: DTS and MSCT were used to scan and store 45 mock nodules and TLD models of chest body, recorded and stored images, measured the absorption dose of the main tissues and organs of the chest and calculated the effective dose. 3 radiologists performed the film and recorded the location, size and density of the nodules. The exact probability of Fisher was used. The difference between DTS and MSCT scan on the detection rate of simulated nodules was compared with the X2 test. The comparison of the two methods of organ absorption was compared with the paired t test. Results: the detection rate of DTS and MSCT for pulmonary nodules was 66.7% (30/45) and 91.1% (41/45), and the difference was statistically significant (X2=8.073, P < 0.05), and the detection of -650HU glass nodules was detected. The rate was 93.3% and 73.3%, the difference was not statistically significant (P > 0.05); the detection rate of DTS for -800HU grinding glass nodules and the diameter less than 8mm grinding glass nodules was 5/15 (33.3%) and 2/12 (16.7%), MSCT detection rate was 12/15 (80%) and 8/12 (66.7%). Chest DTS examination of the main tissues and organs absorption dose was significantly lower than MSCT, the difference was statistically significant ( Lung t=19.69, P < 0.05; thoracic vertebra t=30.01, P < 0.05; heart t=16.33, P < 0.05; liver t=5.06, P < 0.05; breast t=9.43, P < 0.05; t=8.05 thyroid gland, P < 0.05). The detection rate of ground-glass nodules and ground-glass nodules less than 8 mm in diameter was low. The effective dose of DTS was lower than that of MSCT, which was about 8.41% of the radiation dose of MSCT.
【学位授予单位】：重庆医科大学
【学位级别】：硕士
【学位授予年份】：2012
【分类号】：R816.4

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