Ultrasonic Renal-Stone Tracking with Mesh Regularization

體外震波碎石技術和腎結石的震波聚焦能力有很大的關係。為了達到移動物體、目標的自動聚焦，必須能夠做到及時追蹤。一種具有網格式的區塊比對計算程序能夠適當的用在超音波影像的腎結石追蹤。雖有需要同時追蹤多個目摽，但是對於解決腎結石追蹤的目標物消失和影像的強度衰退，網格的追蹤計算程序能夠發揮一個制約調整的功能。 將人體軟組織視為一個彈性體，以彈簧模型來分析其應力、應變、變形能量與位移間的關係。藉由最佳化參數設計，定義區塊比對的位移初始值，最小化因位移向量造成的匹配誤差能量和變形能量的 函數，求解出網格節點的位移向量最佳值。其中，變形能量裡的剛性矩陣由有限元素法求解出。 而為了簡化剛性矩陣的計算量，我們選擇規則四邊形元素作為網格模型，以期達到及時追蹤的效果。經由最佳化參數設計的結果，改善了因區塊比對錯誤所造成的誤判率，避免碎石機對人體腎臟過多的傷害。The efficacy of Extracorporeal Shock Wave Lithotripsy (ESWL) depends greatly on the capability to focus shock waves on renal stone. To achieve automatic focusing on moving target, the target must be under tracking. A mesh-based block matching algorithm is proposed for renal stone tracking using ultrasound image sequence. Since multiple targets are tracked together, the mesh-based tracking algorithm can provide a function of contextual regularization for solving the target missing and image degradation problems in renal stone tracking. Recorded ultrasound images of kidney during ESWL treatment are modified for demonstrating the capability of this algorithm. We regard the soft tissue of the body as elastic in order to analyze the relationship of stress, strain, deformable energy and displacement. On the basis of the optimal design, we also define the initial displacement of block-matching to minimum the function of matching error energy and the deformable energy by displacement vector to solve the optimal value of displacement of mesh grid nodes. Therein, we figure out the stiffness matrix of deformable energy by finite element method. In order to simplify the calculation, we choose a regular quadrilateral element as the mesh model to achieve the tracking of real time. According to the optimal design, we amend the performance of block-matching to avoid the damage of renal caused by stone breakers.目錄……………………………………………………………………………….. …i 圖目錄………………………………………………………………………………...iii 表目錄………………………………………………………………………………...iv 摘要……………………………………………………………………………………v Abstract.........................................................................................................................vi 第一章 前言 1.1 前言..............................................................................................................1 1.2 震波碎石治療的發展................................................................................2 1.3 研究目的.....................................................................................................3 1.4 研究動機.....................................................................................................3 1.5 體外震波碎石機原理簡介........................................................................4 1.6 超音波原理簡介.........................................................................................7 1.7 腎結石超音波影像之特徵.......................................................................9 1.8 腎結石之運動模式....................................................................................9 第二章 網格式影像追蹤 2.1 區塊比對...................................................................................................12 2.2 斑點追蹤的新方法..................................................................................13 2.3 可適應性變形網格..................................................................................14 2.3.1 網格節點的運動模式.............................................................................15 2.3.2 網格的目的..............................................................................................15 2.4 特徵擷取...................................................................................................16 2.5 彈簧模型...................................................................................................16 2.5.1 彈簧特性..................................................................................................17 2.6 變形，位移，位移向量，可變形能量................................................17 2.7 影像力..........................................................................................................18 2.8 變形能量.....................................................................................................19 2.9 有限元素法.................................................................................................19 2.9.1 剛性矩陣.....................................................................................................21 2.9.2 有限元素三角形與四邊形模型..............................................................21 第三章 網格計算程序 3.1 區塊比對計算程序..................................................................................23 3.2 初始值.......................................................................................................23 3.3 剛性矩陣計算程序..................................................................................24 3.4 最佳化參數設計.......................................................................................25 3.5 網格式制約...............................................................................................27 3.6 制約（Regularization）..............................................................................27 3.7 網格式計算程序......................................................................................29 第四章 模擬結果 4.1 實驗測試...................................................................................................30 4.2 模擬結果...................................................................................................32 4.3 結論............................................................................................................34 第五章 未來工作....................................................................................................35 參考文獻..............................................................................................................................36 圖目錄 圖1.1聚焦方式示意圖........................................................................................................5 圖1.2電磁式震波產生器示意圖.......................................................................................6 圖1.3信號與影像處理系統圖............................................................................................8 圖1.4超音波影像所見之腎結石.......................................................................................9 圖1.5結石位置與時間關係圖..........................................................................................10 圖2.1區塊比對示意圖 ..................................................................................................13 圖2.2 超音波腎臟影像....................................................................................................15 圖2.3網格式的超音波影像..............................................................................................15 圖2.4 有限元素分割示意圖............................................................................................20 圖3.1剛性矩陣計算程序..................................................................................................24 圖3.2 網格制約示意圖....................................................................................................28 圖3.3未受制約前的位移向量.........................................................................................28 圖3.4受制約後的位移向量..............................................................................................29 圖4.1 The image blocks used for displacement estimation, the block size is 11 by 11 pixels....................................................................................................................................30 圖4.2 The mesh model used for displacement regularization........................................30 圖4.3 The x-trajectory of renal stone using simple block matching..............................31 圖 4.4 The x-trajectory of renal stone using mesh regularization.................................31 圖.4.5 The y-trajectory of renal stone using simple block matching. ...........................32 圖4.6 The y-trajectory of renal stone using mesh regularization. ................................32 圖.4.7 The observed displacement with artificial interference from frame-300 to 500. ......................................................................................................................................33 圖4.8 The regularized displacement with ....................................................33 圖4.9 The mesh regularized y-trajectory of renal stone with .........................34 圖.4.10 The mesh regularized y-trajectory of renal stone with ......................34 表目錄 表1.1腎臟運動之量測結果.............................................................................................1