【摘要】：計算機斷層成像技術(Computed Tomography,CT)，利用測量不同視角下X射線通過被成像物體的衰減值，重建物體內部二維或三維結構圖像。它能夠以無損、精確、直觀的方式表現物體的內部結構信息，現已在工業(yè)檢測、醫(yī)學診斷等領域得到了廣泛的應用，是最佳的現代無損檢測技術之一。在眾多掃描方式中，圓軌跡錐形束掃描，由于其機械結構簡單，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，是目前最為流行的CT掃描結構之一。 本文介紹了一種偏置探測器CT系統(tǒng)，，與傳統(tǒng)的錐形束圓軌跡掃描方式不同，通過將面陣探測器水平平移，半覆蓋掃描將視場區(qū)域擴大了近一倍。不僅未增加機械復雜度，還大大減少了重建對象受輻射的劑量。 針對這種特殊的掃描結構，本文從CT基礎理論和重建基礎算法出發(fā)，對插值重排偏置重建算法、預加權偏置重建算法進行了詳細的分析以及嚴格的數學推導。比較了兩者在偏置重建時的不同特點，插值重排偏置重建計算復雜度高，對于傾斜非中心平面的插值重排會導致空間分辨率的損失，使圖像質量下降。預加權偏置重建充分利用了數據的冗余特性，在濾波之前對投影數據進行了加權，避免了計算復雜度的增加。此外，本文分別對兩者進行了GPU加速，改善了算法性能，使其更有實際應用價值。最后從扇形束二維重建和錐形束三維重建兩方面出發(fā)，分別設計了仿真實驗和實際系統(tǒng)實驗對上述各方法的可靠性以及準確性進行了驗證。
[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.
【學位授予單位】：西安電子科技大學
【學位級別】：碩士
【學位授予年份】：2014
【分類號】：TP391.41;R814

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