為了提高重建影像的品質，本論文利用單光子放射顯微鏡系統(SPEM)作為影像擷取系統，此系統為一種高空間解析度的單光子放射電腦斷層掃描系統(SPECT)，當中包括針孔式準直儀、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)。 在影像重建的過程中，最重要的一步為建立影像系統矩陣(H矩陣)，而為了獲得良好的系統矩陣，本論文利用系統幾何校正(System Geometric Calibration)與成像模型建立(Imaging Model Construction)來得到SPEM的影像系統矩陣。在幾何校正實驗中，利用三個點射源作各角度之投影影像，利用影像之投影重心找出在偵測器座標系中針孔及旋轉軸所在位置，並藉由針孔及旋轉軸所在位置與格點掃描實驗之實驗結果建立成像模型，此成像模型包含通量模型與寬度模型，最後利用此成像模型便可得到視域空間中的影像系統矩陣。 在影像重建實驗中以Tc-99m藥劑注入假體中，以SPEM擷取各角度之投影影像，並將影像系統矩陣與投影影像代入序列子集期望值最大化演算法(OSEM)中，最後重建出三維物體影像。 ;This study utilizes a single photon emission microscope (SPEM), which is a high spatial resolution version of single photon emission computed tomography (SPECT) system, to acquire projection images for tomographic reconstructions. The imaging system consists of a 7-pinhole collimator, a thallium activated cesium iodide [CsI(Tl)] columnar scintillator, a de-magnifier tube (DM-tube) and an electron multiplying charge-coupled device (EMCCD). To obtain high quality images, an accurate imaging system matrix, also called H matrix, is indispensable in the image reconstruction process. Two procedures are implemented to build the H matrix of SPEM, including the system geometric calibration and imaging model construction. A three-point phantom filled with Tc-99m pertechnetate solution is rotated to acquire 64 projections. The projection centroids are utilized to estimate the geometric parameters of SPEM, such as the axis of rotation (AOR) and pinhole positions. A grid-scan experiment with a single point source is performed to provide point response functions for constructing the imaging model, including the flux and width models. A complete H matrix is then generated according to the geometric parameters and imaging models. Projections of the three-point phantom and resolution phantom are acquired to evaluate the system performance. The reconstructed images demonstrate the feasibility of the system calibration procedures. Renovations of the instrument shielding is in progress to allow proper object positioning and achieving full resolution capability of SPEM.
