本文關(guān)鍵詞： 輻射劑量 圖像處理 自適應(yīng)統(tǒng)計迭代重建技術(shù) CT結(jié)腸成像 結(jié)腸息肉 能譜成像 雙能CT CT結(jié)腸成像 對比噪聲比 結(jié)腸息肉　出處：《天津醫(yī)科大學(xué)》2012年碩士論文　論文類型：學(xué)位論文

【摘要】：第一部分自適應(yīng)統(tǒng)計迭代重建技術(shù)提高低劑量CT結(jié)腸成像息肉檢出率有效性的體模研究 目的：評價應(yīng)用不同水平白適應(yīng)統(tǒng)計迭代重建技術(shù)(adaptive statistical iterative reconstruction,ASIR)在低劑量CT結(jié)腸成像中提高結(jié)腸息肉檢出率的有效性。 材料和方法：在一段離體豬結(jié)腸上通過結(jié)扎粘膜根部獲得20個1-10mm(5mm及以下10個,大于5mm10個)連續(xù)排列的模擬息肉,運用寶石高分辨CT (HDCT)在不同劑量條件下(管電壓保持120kVp,管電流10、20、30、40、50及100mAs)掃描,然后分別應(yīng)用6種不同ASIR水平(0、10%、30%、50%、70%及100%)進(jìn)行圖像后重建,最后在工作站上獲得CT仿真內(nèi)窺鏡、多平面重建和虛擬分割圖像。由兩名有經(jīng)驗的放射醫(yī)師采用盲法對不同采集條件、不同ASIR水平的圖像進(jìn)行客觀和主觀評價,測量并比較平均噪聲、平均信噪比(signal to noise ratio, SNR)、平均對比噪聲比(contrast noise ratios, CNR)和息肉檢出率。 結(jié)果：結(jié)腸模擬息肉模型研究顯示不同管電流-時間下噪聲隨應(yīng)用ASIR水平升高而降低,SNR及CNR隨應(yīng)用ASIR水平升高而增高(P0.05)。大于5mm結(jié)腸息肉在低劑量掃描時應(yīng)用ASIR對檢出率的提高具有統(tǒng)計學(xué)意義(P0.05)；5mm及以下的結(jié)腸息肉檢出率隨著劑量水平的增高而明顯提高,但應(yīng)用高水平ASIR時息肉檢出率沒有明顯的提高(P0.05) 結(jié)論：離體模型研究表明在低劑量CT結(jié)腸成像中,應(yīng)用ASIR可以顯著降低圖像噪聲,提高信噪比及對比噪聲比；在低劑量時可提高大于5mm結(jié)腸息肉的檢出率,但不會明顯提高5mm及以下結(jié)腸息肉的檢出率。 第二部分能譜CT結(jié)腸成像探測結(jié)腸小息肉的體模研究 目的：評價能譜CT結(jié)腸成像提高小于10mm結(jié)腸息肉檢出率的有效性,并找出顯示結(jié)腸息肉最佳的單能量圖像。 材料和方法：兩段離體豬結(jié)腸通過結(jié)扎粘膜根部分別獲得連續(xù)的模擬息肉,第一段結(jié)腸內(nèi)含有直徑1-5mm息肉20枚,第二段結(jié)腸含有1-10mm息肉20枚。第一段結(jié)腸使用64排單源寶石能譜CT在40-140KeV范圍內(nèi)掃描,提取45、60、75、90、105、120和135keV單能量圖像數(shù)據(jù),再使用普通64排螺旋CT在同等條件下掃描作為對照；第二段使用64排單源能譜CT結(jié)腸在三種固定輻射劑量(17.77mGy、25.53mGy和32.52mGy)下分別進(jìn)行45、60、75、90、105、120和135keV單能量掃描；在工作站上獲得CT仿真內(nèi)窺鏡、多平面重建和虛擬分割圖像。由兩名有經(jīng)驗的放射醫(yī)師采用盲法對每組圖像進(jìn)行主觀及客觀評價,記錄并比較每組圖像中的息肉檢出率以及平均對比噪聲比。 結(jié)果：應(yīng)用常規(guī)64排螺旋CT進(jìn)行三種后處理圖像得到結(jié)腸小息肉的平均檢出個數(shù)為13個(檢出率65%),應(yīng)用能譜CT進(jìn)行的單能量圖像得到的最低檢出個數(shù)為15個(檢出率75%),最高為16個(檢出率80%),因此單能量圖像可輕度提高結(jié)腸小息肉檢出率,但有效性尚不具有統(tǒng)計學(xué)意義(P0.05)75keV單能量圖像顯示結(jié)腸息肉的對比噪聲比最高(P0.05)。 結(jié)論：能譜CT結(jié)腸成像可輕度提高小結(jié)腸息肉(≤5mm)的檢出率,顯示結(jié)腸息肉的最佳單能量圖像為75keV圖像。
[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.

【學(xué)位授予單位】：天津醫(yī)科大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2012
【分類號】：R816.5

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