本文選題：血管內(nèi)超聲 + 運(yùn)動(dòng)補(bǔ)償　； 參考：《華中科技大學(xué)》2014年博士論文

【摘要】：腹主動(dòng)脈瘤是最常見(jiàn)的動(dòng)脈瘤之一,是一種嚴(yán)重威脅人類生命的大血管疾病。覆膜支架腔內(nèi)隔絕術(shù)是目前治療常規(guī)型腹主動(dòng)脈瘤的最佳選擇。然而,由于特殊型腹主動(dòng)脈瘤不滿足安置覆膜支架的臨床要求,常規(guī)的覆膜支架腔內(nèi)隔絕術(shù)會(huì)封閉重要器官的血管入口,最終導(dǎo)致重要器官的衰竭。而定做帶有分支的支架則有價(jià)格貴、定做周期長(zhǎng)以及臨床操作難度大等問(wèn)題。因此,本文首先提出了利用血管內(nèi)超聲(Intravascular Ultrasound:IVUS)精確定位被覆膜支架覆蓋的重要?jiǎng)用}分支入口,然后再使用激光進(jìn)行開(kāi)窗以解決重要分支動(dòng)脈被覆膜支架阻隔的問(wèn)題。 然而,在IVUS成像過(guò)程中,由于心臟搏動(dòng)以及導(dǎo)管的旋轉(zhuǎn),IVUS序列圖像往往存在運(yùn)動(dòng)偽影,直接影響到醫(yī)生對(duì)于血管分支入口直徑測(cè)量,對(duì)分支血管入口的判斷產(chǎn)生不利影響,給醫(yī)生采用激光介入治療帶來(lái)困難。另外,運(yùn)動(dòng)偽影也會(huì)直接影響到血管內(nèi)斑塊的測(cè)量以及三維顯示效果。IVUS序列圖像的運(yùn)動(dòng)補(bǔ)償技術(shù)旨在解決IVUS序列圖像中的運(yùn)動(dòng)偽影,為醫(yī)生提供更加精確的血管內(nèi)三維結(jié)構(gòu)信息,有助于醫(yī)生準(zhǔn)確無(wú)誤地判斷分支血管入口。此外,運(yùn)動(dòng)補(bǔ)償技術(shù)還可以為斑塊以及血管彈性測(cè)量提供精確的信息。因此,運(yùn)動(dòng)補(bǔ)償技術(shù)不但是本論文迫切需要解決的技術(shù)難題,而且具有廣泛的臨床應(yīng)用價(jià)值。 目前,IVUS序列圖像運(yùn)動(dòng)補(bǔ)償方法主要是基于門控、動(dòng)力學(xué)建模、模板匹配或者光流等。其中,門控法在一個(gè)心動(dòng)周期只能采集一幅圖像；動(dòng)力學(xué)建模無(wú)法提供精確的旋轉(zhuǎn)角估計(jì)結(jié)果；模板匹配會(huì)受到圖像灰度變化的影響；而光流法需要IVUS序列圖像滿足血管中心不發(fā)生位移的條件。因此在實(shí)際應(yīng)用中,四種方法的結(jié)果并不理想。本文針對(duì)IVUS運(yùn)動(dòng)補(bǔ)償技術(shù)的難點(diǎn),結(jié)合醫(yī)生的臨床需求,研究基于非局部均值的IVUS序列圖像運(yùn)動(dòng)補(bǔ)償方法,具體研究?jī)?nèi)容如下： 首先研究了基于非局部均值的IVUS圖像降噪技術(shù)：針對(duì)IVUS圖像中斑點(diǎn)噪聲特性,提出了一種基于權(quán)重更新的非局部均值去斑點(diǎn)噪聲方法。方法針對(duì)當(dāng)前應(yīng)用廣泛的圖像斑點(diǎn)噪聲模型,采用貝葉斯理論,推導(dǎo)出一種適合于斑點(diǎn)噪聲的權(quán)值計(jì)算公式,并利用主成分分析方法(Principal Component Analysis:PCA)將其投影至PCA子空間并迭代更新權(quán)值,迭代過(guò)程可自動(dòng)終止。該方法能夠顯著地去除IVUS斑點(diǎn)噪聲,提高了圖像的對(duì)比度。 其次研究了基于非局部均值的IVUS序列圖像粗運(yùn)動(dòng)補(bǔ)償技術(shù)：通過(guò)對(duì)IVUS導(dǎo)管運(yùn)動(dòng)的建模,將其分為由于導(dǎo)管旋轉(zhuǎn)而導(dǎo)致的旋轉(zhuǎn)運(yùn)動(dòng)以及由于血流脈搏而導(dǎo)致的導(dǎo)管相對(duì)圖像中心的偏移,并且結(jié)合了中膜的橢圓特性,提出了一種基于中膜檢測(cè)的粗運(yùn)動(dòng)補(bǔ)償方法。該方法通過(guò)一種非局部SUSAN邊緣檢測(cè)算子以及對(duì)感興趣區(qū)域的控制點(diǎn)進(jìn)行橢圓擬合來(lái)確定中膜的位置,進(jìn)而利用前后幀中膜的擬合參數(shù)來(lái)對(duì)平移和旋轉(zhuǎn)參數(shù)初始值進(jìn)行估計(jì),并對(duì)時(shí)間維的參數(shù)進(jìn)行一維非局部均值獲取最終補(bǔ)償參數(shù),繼而完成運(yùn)動(dòng)補(bǔ)償。該方法簡(jiǎn)單、快速,并且相對(duì)于前人的方法更具有普適性,能夠適應(yīng)不同情況下的IVUS圖像； 最后研究了基于非局部均值的IVUS序列圖像精確運(yùn)動(dòng)補(bǔ)償技術(shù)：針對(duì)粗運(yùn)動(dòng)補(bǔ)償方法對(duì)于旋轉(zhuǎn)參數(shù)提取不夠精確的問(wèn)題,利用基于中膜的粗運(yùn)動(dòng)補(bǔ)償結(jié)果,提出了一種基于非局部光流法的精確運(yùn)動(dòng)補(bǔ)償方法。該方法將非局部的相似度引入到Lucas-Kanade (LK)光流之中,提高了LK光流法的抗噪能力,并且提出了一種的旋轉(zhuǎn)角矢量的計(jì)算方法,最終利用精確旋轉(zhuǎn)參數(shù)在粗補(bǔ)償結(jié)果的基礎(chǔ)上完成整個(gè)補(bǔ)償過(guò)程。該方法成功的解決了IVUS幀間的偏向旋轉(zhuǎn)問(wèn)題,并在補(bǔ)償精度方面大大優(yōu)于傳統(tǒng)方法。
[Abstract]:Abdominal aortic aneurysm is one of the most common aneurysms and is a major vascular disease that seriously threatens human life. Endovascular stent graft exclusion is the best choice for conventional abdominal aortic aneurysm. However, special type of abdominal aortic aneurysm is not satisfied with the requirements for the placement of covered stent. The entrance of the blood vessel of the important organs is closed to the failure of the important organs, and the stent with branches is expensive, the fixed cycle is long and the clinical operation is difficult. Therefore, this paper first proposed the use of intravascular ultrasound (Intravascular Ultrasound:IVUS) to accurately locate the important arterial components covered by the covered stent. The portal was then used to open the window to solve the problem of obstructing important branch arteries.
However, in the process of IVUS imaging, because of the heart beating and the rotation of the catheter, the motion artifact often exists in the IVUS sequence image, which directly affects the doctor's measurement of the diameter of the branch entrance of the blood vessel. It has a negative effect on the judgment of the entrance of the branch vessel, which brings difficulties to the doctors using the laser to mediate the treatment. In addition, the motion artifact will also be directly shadow. The measurement of the intravascular plaque and the three-dimensional display effect.IVUS sequence image motion compensation technique aims to solve the motion artifact in the IVUS sequence image, provide the doctor with more accurate intravascular three-dimensional structure information, and help the doctor to judge the branch blood vessel entrance accurately and unmistakably. In addition, the motion compensation technique can also be used as a patch for the plaque. And the measurement of vascular elasticity provides accurate information. Therefore, motion compensation technology is not only an urgent technical problem to be solved in this paper, but also has a wide range of clinical applications.
At present, the motion compensation methods of IVUS sequence images are mainly based on gate control, dynamic modeling, template matching or optical flow. Among them, the gate control method can only collect one image in one heart cycle; dynamic modeling can not provide accurate results of rotation angle estimation; template matching will be affected by the change of image gray level; and optical flow method needs to be used. The IVUS sequence image satisfies the condition that the blood vessel center is not displaced. Therefore, in practical application, the results of the four methods are not ideal. This paper, aiming at the difficulty of the IVUS motion compensation technology, combines the clinical needs of the doctors, and studies the motion compensation method of the IVUS sequence image based on the non local mean. The specific research contents are as follows:
In this paper, a non local mean based IVUS image denoising technique is first studied. A non local mean speckle reduction noise method based on weight updating is proposed for speckle noise in IVUS images. A Bayesian theory is used to derive a right for speckle noise based on the widely used image speckle noise model. The value calculation formula, and using the principal component analysis method (Principal Component Analysis:PCA), projection into the PCA subspace and iterating the weight value iteratively, the iterative process can automatically terminate. This method can significantly remove the IVUS speckle noise and improve the contrast of the image.
Secondly, the rough motion compensation technique of IVUS sequence image based on the non local mean is studied. By modeling the motion of the IVUS catheter, it is divided into the rotation motion caused by the catheter rotation and the deviation of the relative center of the catheter caused by the blood flow pulse, and a kind of the medium is combined with the elliptical characteristics of the middle film. The method of coarse motion compensation for membrane detection. This method determines the position of the middle film by a non local SUSAN edge detection operator and the ellipse fitting to the control points of the region of interest. Then the initial values of translation and rotation are estimated by using the fitting parameters of the middle and back frames, and the parameters of the time dimension are non local. The method is simple and fast, and it is more universal and adaptable to the IVUS image in different circumstances.
In the end, the accurate motion compensation technology of IVUS sequence image based on non local mean is studied. In view of the problem that the rough motion compensation method is not accurate enough for the rotation parameter extraction, an accurate motion compensation method based on the non local optical flow method is proposed, which is based on the coarse motion compensation of the middle film. It is introduced into the Lucas-Kanade (LK) optical flow to improve the anti noise ability of the LK optical flow method, and a calculation method of the rotation angle vector is proposed. Finally, the whole compensation process is completed on the basis of the coarse compensation results. The method successfully solves the problem of deflection rotation between the IVUS frames, and the compensation precision is also solved. It's much better than the traditional method.
【學(xué)位授予單位】：華中科技大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2014
【分類號(hào)】：R543.16;R445.1

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本文編號(hào)：1995944