【作者】 吴吉丽；

【导师】 李健丁；

【作者基本信息】 山西医科大学 ， 影像医学与核医学， 2008， 硕士

【摘要】 目的:探讨64层螺旋CT低剂量仿真结肠镜在理想状态下,不同剂量扫描对不同大小的猪结肠模拟息肉的检出率,并评价二维、三维重建及二维和三维联合观察对模拟息肉检出的敏感性。方法:猪结肠15段,每段25cm,彻底清洁后,每段制作6枚息肉样模型,3-4.9mm、5-9.9mm、10-15mm的模拟息肉各两枚,用空气扩张,并浸入水中,采集50mA、20mA、12mA的影像,CT剂量加权指数(CTDIw)分别为3.83mGy、1.53mGy、0.93mGy,采用轴位像+MPR图像、CTC、2D+3D观察病变,采用成组设计多个样本比较的秩和检验和多个样本两两比较的秩和检验评价图像质量。不同剂量各种后处理方法对模拟息肉的检出率及不同后处理方法三种剂量对模拟息肉的检出率,进行多个相关样本的卡方检验。结果:1.不同剂量采集的1mm显示层厚的轴位像及MPR影像质量存在统计学意义,而CTC影像质量差异无统计学意义。2.不同管电流50mA、20mA、12mA其CT仿真结肠镜成像对≥10mm模拟息肉检出率均为100%,对5-9.9mm模拟息肉检出率分别为96.7%、96.7%、93.3%,对<5mm模拟息肉检出率为86.7%、83.3%、80%,不同剂量对同组模拟息肉的检出率无统计学意义。不同管电流50mA、20mA、12mA其轴位+MPR成像对≥10mm模拟息肉检出率均为100%,对5-9.9mm模拟息肉检出率分别为93.3%、66.7%、60%,对<5mm模拟息肉检出率为70%、50%、36.7%,不同剂量对≥10mm组模拟息肉的检出率无统计学意义,对5-9.9mm组,<5mm组模拟息肉均存在统计学意义。不同管电流50mA、20mA、12mA其2D+3D联合观察对≥10mm模拟息肉检出率均为100%,对5-9.9mm模拟息肉检出率分别为96.7%、96.7%、93.3%,对<5mm模拟息肉检出率为86.7%、83.3%、80%。随着管电流由50mA减低致20mA、12mA CTDIw(mGy)分别减少60.1%、75.7%。3.使用50mA管电流采集图像,轴位+MPR、CTC、2D+3D不同观察方法对≥10mm息肉检出率均为100%,对5-9.9mm息肉检出率分别为93.3%、96.7%、96.7%,对<5mm息肉检出率为70%、86.7%、90%,使用20mA、12mA管电流采集图像也显示2D+3D观察方法对不同大小的息肉检出率最高,CTC次之,轴位+MPR对于小息肉的检出率下降。结论:1.在模拟的理想状态下64层螺旋CT12mA低剂量仿真结肠镜对模拟息肉的检出有较高的敏感性,对模拟息肉的显示没有明显影响,而X线辐射剂量较50mA剂量减少了约4/5。2.各种不同观察方法中,二维和三维图像联合观察可提高息肉检出率,CTC检出率略低,轴位+MPR对于小息肉的检出率明显下降。低剂量仿真结肠镜将为结肠病变普查提供广阔前景。更多还原

【Abstract】 Objective: The objective of this experimental study was to study the ability of CT virtual colonography by 64 multislice spiral CT using low X-ray dose scanning technique in the diction of polyps under ideal imaging conditions. The different dose scanning to the different size’s pig colon simulation polyp’s detection rate, and appraises two dimensional, the three dimensional reconstruction and two dimensional and the three dimensional union observation to simulates the sensitivity which the polyp picks out.Methods: fifteen segments of 25cm-long porcine colon were explanted and thoroughly cleaned. 6 stimulated polyps(2 lesions,2-4.9mm; 2 lesions,5-9.9mm; 2 lesions,10-15mm)were placed in every segment of 25cm-long thoroughly cleaned porcine colon that was distended with air and submerged in a water phantom.15 segments were scanned with 64 detector-row MSCT scanner using 50mA、20mA、12mA parameters, and the same time tracked record the CT dose index(CTDIw) 3.83mGy、1.53mGy、0.93mGy respectively. The data were reviewed using axial+MPR、CTC、combined 2D/3D approach. Statistically, Adopted a number of design group Samples of the rank and number of samples tested and compared the February 2 rank and test evaluation of image quality. After dealing with different doses of various methods to simulate the polyp detection rate and after the treatment of three different doses of simulated polyps detection rate, the number of card-related samples to test.Results:1.There were statistical differences in image quality between the axial images with 1mm slice thickness and MPR acquired by using different X-ray dose techniques. There were no statistical differences in image quality the images of CTC acquired by using various X-ray dose acquisition techniques respectively.2.The detection rates of 50mA、20mA、12mA CTC images for stimulated polyps with different dimensions were as follows:100% for the ones with diameters of≥10mm,with all three dose,96.7%、96.7%、93.3% for the ones of 5-9.9mm in diameter and 86.7%、83.3%、80% for those of <5mm in diameter by using 50mA、20mA、12mA.There was no statistical differences in detection rates to stimulated polyps in same group with different X-ray dose. Different from the current 50mA、20mA、12mA its axial + MPR imaging≥10mm stimulated polyp detection rate was 100 percent, the simulation of 5-9.9mm polyp detection rate was 93.3%、66.7%、60%, to the <5mm simulation polyp detection rate is 70%、50%、36.7%, different doses of≥10mm group simulated polyps detection rate was not significant, 5-9.9 mm group, <5mm group simulated polyps there are significant. Different tube electric current 50mA, 20mA, 12mA its 2D+3D union observation to≥10mm the simulation polyp detection rate is 100%, to the 5-9.9mm simulation polyp detection rate respectively is 96.7%、96.7%、93.3%, to the <5mm simulation polyp detection rate is 86.7%、83.3%、80%. With tube current declining, comparing to 50mA, the CTDIw(mGy) of 20mA、12mA was decreased by 60.1%、75.7%.3. Using the 50mA tube electric current gather the image, axial +MPR, CTC, the 2D+3D different observation method for≥10mm the polyp detection rate is 100%, to the 5-9.9mm polyp detection rate respectively is 93.3%、96.7%、96.7%, <5mm polyp detection rate of 70%、86.7%、90%, 2D+3D observation methods were the most sensitive technique for showing polyps of different size, while CTC was in the second place. MPR is less sensitive for demonstrating polyps with less than 5mm in diameter.conclusion:1.Under ideal imaging conditions, sensitivity was higher for detecting polyps using 64 detector-row MSCT colonography scan technology with 12mA low X-ray dose, to simulated polyps showed no obvious effects, and X-ray radiation dose than 50mA dose decreased by about 4/5.2. Various methods of observation, two dimensional and the three dimensional image union observation may raise the polyp detection rate, the CTC detection rate is slightly low, axial + MPR small polyp detection rate decreased significantly. Low-dose simulation colonoscopy for colon lesions census provided broad prospects.更多还原