HDCT结肠成像对息肉检出有效性实验研究

发布时间：2018-02-27 07:36

本文关键词： 辐射剂量图像处理自适应统计迭代重建技术 CT结肠成像结肠息肉能谱成像双能CT CT结肠成像对比噪声比结肠息肉　出处：《天津医科大学》2012年硕士论文　论文类型：学位论文

【摘要】：第一部分自适应统计迭代重建技术提高低剂量CT结肠成像息肉检出率有效性的体模研究目的：评价应用不同水平白适应统计迭代重建技术(adaptive statistical iterative reconstruction,ASIR)在低剂量CT结肠成像中提高结肠息肉检出率的有效性。材料和方法：在一段离体猪结肠上通过结扎粘膜根部获得20个1-10mm(5mm及以下10个,大于5mm10个)连续排列的模拟息肉,运用宝石高分辨CT (HDCT)在不同剂量条件下(管电压保持120kVp,管电流10、20、30、40、50及100mAs)扫描,然后分别应用6种不同ASIR水平(0、10%、30%、50%、70%及100%)进行图像后重建,最后在工作站上获得CT仿真内窥镜、多平面重建和虚拟分割图像。由两名有经验的放射医师采用盲法对不同采集条件、不同ASIR水平的图像进行客观和主观评价,测量并比较平均噪声、平均信噪比(signal to noise ratio, SNR)、平均对比噪声比(contrast noise ratios, CNR)和息肉检出率。结果：结肠模拟息肉模型研究显示不同管电流-时间下噪声随应用ASIR水平升高而降低,SNR及CNR随应用ASIR水平升高而增高(P0.05)。大于5mm结肠息肉在低剂量扫描时应用ASIR对检出率的提高具有统计学意义(P0.05)；5mm及以下的结肠息肉检出率随着剂量水平的增高而明显提高,但应用高水平ASIR时息肉检出率没有明显的提高(P0.05) 结论：离体模型研究表明在低剂量CT结肠成像中,应用ASIR可以显著降低图像噪声,提高信噪比及对比噪声比；在低剂量时可提高大于5mm结肠息肉的检出率,但不会明显提高5mm及以下结肠息肉的检出率。第二部分能谱CT结肠成像探测结肠小息肉的体模研究目的：评价能谱CT结肠成像提高小于10mm结肠息肉检出率的有效性,并找出显示结肠息肉最佳的单能量图像。材料和方法：两段离体猪结肠通过结扎粘膜根部分别获得连续的模拟息肉,第一段结肠内含有直径1-5mm息肉20枚,第二段结肠含有1-10mm息肉20枚。第一段结肠使用64排单源宝石能谱CT在40-140KeV范围内扫描,提取45、60、75、90、105、120和135keV单能量图像数据,再使用普通64排螺旋CT在同等条件下扫描作为对照；第二段使用64排单源能谱CT结肠在三种固定辐射剂量(17.77mGy、25.53mGy和32.52mGy)下分别进行45、60、75、90、105、120和135keV单能量扫描；在工作站上获得CT仿真内窥镜、多平面重建和虚拟分割图像。由两名有经验的放射医师采用盲法对每组图像进行主观及客观评价,记录并比较每组图像中的息肉检出率以及平均对比噪声比。结果：应用常规64排螺旋CT进行三种后处理图像得到结肠小息肉的平均检出个数为13个(检出率65%),应用能谱CT进行的单能量图像得到的最低检出个数为15个(检出率75%),最高为16个(检出率80%),因此单能量图像可轻度提高结肠小息肉检出率,但有效性尚不具有统计学意义(P0.05)75keV单能量图像显示结肠息肉的对比噪声比最高(P0.05)。结论：能谱CT结肠成像可轻度提高小结肠息肉(≤5mm)的检出率,显示结肠息肉的最佳单能量图像为75keV图像。
[Abstract]:The first part of adaptive statistical iterative reconstruction technique to improve the effectiveness of low dose CT colonic polyp detection rate
Objective: To evaluate the effectiveness of adaptive statistical iterative reconstruction (ASIR) at different levels in low dose CT colon imaging to improve the detection rate of colonic polyps.
Materials and methods: in a porcine colon mucosa obtained by ligation of roots of 20 1-10mm (5mm and below 10, more than 5mm10) simulated polyps in consecutive order, using the gem high resolution CT (HDCT) in different dose condition (tube voltage 120kVp, tube current 10,20,30,40,50 and 100mAs scan). Then, using 6 different levels of ASIR (0,10%, 30%, 50%, 70% and 100%) for image reconstruction, finally get the CT virtual endoscopy in workstation, multiplanar reconstruction and virtual image segmentation. By two experienced radiologists to adopt different acquisition conditions with blind method, objective and subjective evaluation the images of different levels of ASIR were measured and compared the average noise, the average signal-to-noise ratio (signal to noise ratio, SNR), the average contrast to noise ratio (contrast noise ratios, CNR) and polyp detection rate.
Results: the simulation of the model shows that the time of colonic polyps in different tube current noise decreases with the application of elevated levels of ASIR, SNR and CNR increased with the application level of ASIR increased (P0.05). More than 5mm colonic polyp detection rate of ASIR increased with statistical significance in the low dose scan (P0.05); 5mm and below the detection rate of colonic polyps with higher dose levels and significantly improve the detection rate of polyps, no obvious improvement but the application of high level ASIR (P0.05)
Conclusion: in vitro model shows that in the low dose of CT colonography, the application of ASIR can significantly reduce the image noise and improve the signal-to-noise ratio and contrast to noise ratio; at low doses can improve the detection rate of more than 5mm of colonic polyps, but not significantly improve 5mm and colonic polyp detection rate.
Second parts of CT colonography for detecting small colonic polyps
Objective: To evaluate the effectiveness of CT colonic imaging to improve the detection rate of less than 10mm colonic polyps, and to find out the best single energy image of colonic polyps.
Materials and methods: two porcine colon mucosa obtained by ligating the roots of simulated polyps continuous respectively, the first paragraph in the colon with a diameter 1-5mm 20 polyps, second colon containing 1-10mm 20 polyps. The first section of the colon using 64 rows of single source gemstone CT scan in the range of 40-140KeV, 45,60,75,90105120 and 135keV extraction the energy of the image data, and then use the ordinary 64 slice spiral CT in the same condition as the control section second scanning; using 64 rows of single source spectra of CT colon in three fixed dose (17.77mGy, 25.53mGy and 32.52mGy) were conducted under 45,60,75,90105120 and 135keV single energy scan; CT virtual endoscopy in the workstation, and more planar reconstruction and virtual image segmentation. By two experienced radiologists blinded to the subjective and objective evaluation of each image, recorded and compared each image in polyp detection Rate and average ratio of contrast to noise.
Results: the application of conventional 64 slice CT average detection three kinds of postprocessing images of small colon polypus number 13 (detection rate 65%), single energy spectrum CT image application has the lowest detection number is 15 (positive rate 75%), 16 (the highest detection rate of 80% therefore, the single energy image) can improve the detection rate of mild colonic small polyps, but the effectiveness is not statistically significant (P0.05) 75keV single energy image display contrast noise ratio (P0.05) of the highest colonic polyps.
Conclusion: CT imaging can improve the spectrum of colon mild small colon polyps (5mm) detection rate, show the optimal monochromaticenergy image of colonic polyps for 75keV images.

【学位授予单位】：天津医科大学
【学位级别】：硕士
【学位授予年份】：2012
【分类号】：R816.5

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