單光子放射顯微系統之校正與螺旋重建;System Calibration and Helical Reconstruction of Single Photon Emission Microscope

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题名:	單光子放射顯微系統之校正與螺旋重建;System Calibration and Helical Reconstruction of Single Photon Emission Microscope
作者:	邑瑪儒;Revilla, Enette Mae C.
贡献者:	光電科學與工程學系
关键词:	單光子放射顯微鏡(SPEM);幾何校正;成像模型;螺旋;Single photon emission microscope (SPEM);Geometric calibration;Imaging model;Helical
日期:	2018-08-10
上传时间:	2018-08-31 11:54:42 (UTC+8)
出版者:	國立中央大學
摘要:	本論文以單光子放射顯微鏡(SPEM)作為影像擷取系統，進行此系統的幾何校正方法及螺旋掃描重建演算法的開發。SPEM 為單光子放射電腦斷層掃描儀(SPECT)的分支，其系統設計包含了七針孔準直儀、碘化銫閃爍晶石、光影像縮倍管(DM tube)與電子增益電荷耦合元件 (EMCCD)，目的在獲取高空間解析度之投影及斷層掃描重建影像。在斷層掃描系統中，為了獲得好的重建影像，最重要的關鍵是建立精確的影像系統矩陣，即 H 矩陣。我們利用系統的幾何校正與成像模型來建立 H 矩陣。為了取得七針孔 SPEM 系統的幾何架構，我們將 99mTc 注入三點射源假體作 64 個投影影像，用來估計系統的幾何參數，包括針孔位置、旋轉軸(AOR)的參數、以及相機與位移平台間的線性和旋轉位移。而格點掃描實驗用來將量測的點響應函數 (PRFs)轉成二維高斯參數，並利用 PRFs 建立成像模型，包含通量與寬度模型。而藉由幾何參數與成像模型可以建立出完整的 H 矩陣。另一方面，為了改善圓形軌跡重建時的軸向模糊，並增加取樣完整性及解析度，實驗中以旋轉平台及線性位移平台同時動作來達成螺旋掃描軌跡，並重新設計 H 矩陣的排列方式，搭配最大可能性之期望值最大化演算法來進行影像重建。 ;The single photon emission microscope (SPEM) is an instrument which is developed in order to acquire high spatial resolution single photon emission computer tomography (SPECT) projection images which are necessary for tomographic reconstruction. The SPEM system consists of a thallium-doped cesium iodide [CsI(Tl)] columnar scintillator, a 7-pinhole collimator, a demagnifying tube (DM Tube) and an electron-multiplying charge-coupling device (EMCCD). For any imaging system, it is crucial to have an accurate imaging system matrix, called H matrix, in order to obtain high spatial resolution image reconstructions. In order to generate the H matrix, geometric calibration and the established imaging model are used. In order to get the geometry of the 7-pinhole SPEM system, a three-point phantom filled with 99mTc pertechnetate liquid solution is rotated in order to acquire 64 projections. The geometry of the camera, including the pinhole positions, the parameters of the axis of rotation and the linear and rotary shifts are estimated by getting the centroids of the projections. The grid-scan experiment is used to parameterize the measured point response functions (PRFs) into 2D Gaussians. These PRFs is used to create the imaging model which consists of flux and width models. By having the geometric parameters and the established imaging model, the complete H matrix can be built. In this paper, a helical reconstruction algorithm is developed in order to lessen axial blurring brought by circular-orbit reconstructions and thus, improve sampling and increase resolution. The helical orbit is vii accomplished through the combination of circular motion and linear motion of the imaged object along the axis of rotation (AOR). The projection images of the three-point phantom and resolution phantom are reconstructed with the H matrix of the designed system. The image reconstruction software tool is based on the maximum likelihood algorithm and its ordered-subset version. Correction of the designed H matrix is being explored in order to produce better reconstruction images.
显示于类别:	[Graduate Institute of Optics and Photonics] Electronic Thesis & Dissertation

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