【摘要】：計(jì)算機(jī)斷層成像技術(shù)(Computed Tomography,CT)，利用測(cè)量不同視角下X射線通過(guò)被成像物體的衰減值，重建物體內(nèi)部二維或三維結(jié)構(gòu)圖像。它能夠以無(wú)損、精確、直觀的方式表現(xiàn)物體的內(nèi)部結(jié)構(gòu)信息，現(xiàn)已在工業(yè)檢測(cè)、醫(yī)學(xué)診斷等領(lǐng)域得到了廣泛的應(yīng)用，是最佳的現(xiàn)代無(wú)損檢測(cè)技術(shù)之一。在眾多掃描方式中，圓軌跡錐形束掃描，由于其機(jī)械結(jié)構(gòu)簡(jiǎn)單，具有X射線利用率高、掃描速度快、水平分辨率和軸向分辨率一致等優(yōu)點(diǎn)，是目前最為流行的CT掃描結(jié)構(gòu)之一。 本文介紹了一種偏置探測(cè)器CT系統(tǒng)，，與傳統(tǒng)的錐形束圓軌跡掃描方式不同，通過(guò)將面陣探測(cè)器水平平移，半覆蓋掃描將視場(chǎng)區(qū)域擴(kuò)大了近一倍。不僅未增加機(jī)械復(fù)雜度，還大大減少了重建對(duì)象受輻射的劑量。 針對(duì)這種特殊的掃描結(jié)構(gòu)，本文從CT基礎(chǔ)理論和重建基礎(chǔ)算法出發(fā)，對(duì)插值重排偏置重建算法、預(yù)加權(quán)偏置重建算法進(jìn)行了詳細(xì)的分析以及嚴(yán)格的數(shù)學(xué)推導(dǎo)。比較了兩者在偏置重建時(shí)的不同特點(diǎn)，插值重排偏置重建計(jì)算復(fù)雜度高，對(duì)于傾斜非中心平面的插值重排會(huì)導(dǎo)致空間分辨率的損失，使圖像質(zhì)量下降。預(yù)加權(quán)偏置重建充分利用了數(shù)據(jù)的冗余特性，在濾波之前對(duì)投影數(shù)據(jù)進(jìn)行了加權(quán)，避免了計(jì)算復(fù)雜度的增加。此外，本文分別對(duì)兩者進(jìn)行了GPU加速，改善了算法性能，使其更有實(shí)際應(yīng)用價(jià)值。最后從扇形束二維重建和錐形束三維重建兩方面出發(fā)，分別設(shè)計(jì)了仿真實(shí)驗(yàn)和實(shí)際系統(tǒng)實(shí)驗(yàn)對(duì)上述各方法的可靠性以及準(zhǔn)確性進(jìn)行了驗(yàn)證。
[Abstract]:Computed Tomography CT (Computed Tomography CT) is used to reconstruct 2D or 3D structure images of objects by measuring the attenuation value of X-ray through the object under different angles of view. It has been widely used in the field of industrial detection, medical diagnosis and so on. It is one of the best modern nondestructive testing techniques. Among the many scanning methods, circular track conical beam scanning is one of the most popular CT scanning structures because of its simple mechanical structure, high X-ray utilization rate, fast scanning speed and uniform horizontal and axial resolution. In this paper, a bias detector CT system is introduced, which is different from the traditional conical beam circle path scanning method. By translating the plane array detector horizontally, the semi-coverage scan expands the field of view nearly twice. Not only does the mechanical complexity not increase, but also greatly reduce the radiation dose of the reconstructed object. In view of this special scanning structure, the interpolation rearrangement bias reconstruction algorithm and the preweighted offset reconstruction algorithm are analyzed in detail and the strict mathematical derivation is given based on the basic theory of CT and the basic reconstruction algorithm. The difference between them in bias reconstruction is compared. The computational complexity of interpolation rearrangement is high. The interpolation rearrangement of tilted non-central plane will result in the loss of spatial resolution and decrease the image quality. Pre-weighted bias reconstruction takes full advantage of the redundancy of the data and weights the projected data before filtering to avoid the increase of computational complexity. In addition, this paper accelerates the two algorithms by GPU, which improves the performance of the algorithm and makes it more practical. Finally, the reliability and accuracy of the above methods are verified by simulation experiments and practical system experiments from two aspects of sector beam 2D reconstruction and conical beam 3D reconstruction.
【學(xué)位授予單位】：西安電子科技大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2014
【分類(lèi)號(hào)】：TP391.41;R814

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