6.1 結論
我們在模擬的情境下建立了三維的平面波影像，並進行了特徵追蹤與傳統斑 點追蹤分析共六項的比較。首先，我們驗證了平面波影像因空間解析度較雙向聚 焦影像差，使得斑點追蹤正確率下降；另外，我們比較了在影像的直角座標系與 極座標系上進行斑點追蹤的差異，發現在極座標系的追蹤結果誤差較小，但我們 推論兩者座標系追蹤差異的大小會隨著掃描轉換(scan conversion)的精細程度而定。
在特徵追蹤法與傳統斑點追蹤法的比較方面，我們驗證了隨著資料量越大，傳統 斑點追蹤法所需的運算時間呈指數上升，並遠大於特徵斑點所需的時間，不過在 追蹤正確率方面，傳統斑點追蹤法就有顯著的優勢。此外，我們亦進行了物體在 旋轉的運動型態下特徵追蹤法與傳統斑點追蹤法的比較，兩種方法都有不錯的追 蹤正確性，但最好確保探頭掃描的波束夠密能夠包括物體旋轉的角度。另一方面，
我們也探討了不同域值及不同內核大小的設定對特徵斑點篩選及特徵追蹤結果的 影響，我們發現設定越大的閾值或越大的內核範圍，皆會有較高的追蹤正確率，
這主要是由於較大的域值或較大的內核範圍都同樣會讓斑點形態匹配的正確率增 加。
除了進行模擬分析外，我們嘗詴將特徵追蹤法應用於實際臨床資料上，但發 現受限於影像品質較差、相關係數較低以及特徵追蹤法在應變量計算上應用的限 制等等，使得在臨床三維心臟超音波影像上所找到用以運算心肌應變量的特徵斑 點數目極少，無法代表整體心肌形變的狀態。
6.2 未來工作
我們認為在影響特徵追蹤的因素中，影像品質是很重要的關鍵，因此如何在 提高平面波影像的空間解析度的同時，又不會過度犧牲其高度的時間解析度是很 重要的議題，諸如Generalized coherent factor、Coherent Plane Wave Compounding 等方法，都是可以進一步探討的方法。除此之外，鑒於在實際臨床資料心肌應變 量的分析上需先獲得心肌內外膜邊界上斑點的座標位置，因此結合自動邊緣偵測 法來改善心肌應變量估計的效能，勢必是不可或缺的。另一方面，特徵斑點追蹤 法雖然已經能夠大幅降低演算的運算量，但由於所處理的資料為四維的高維度資 料，當所篩選出的特徵斑點數目較多時，仍需要耗費數個小時之久，因此可再進 一步的的結合平行運算技術更精進運算的效能。最後，可嘗詴在形變後的斑點訊 號上採用時間延展法(Temporal stretching)，我們預期能提高形變前後斑點訊號相關 性，達到增進斑點追蹤正確率的目的。
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