睡眠呼吸中止症為一種睡眠過程中咽喉部呼吸道反覆阻塞的呼吸失調疾病，會導致間歇性缺氧及睡眠過程中頻繁的甦醒等。根據許多研究顯示舌根的變形在睡眠呼吸中止症中扮演著重要的角色，且在我們先前的研究中發現舌根最大厚度(TBT)與睡眠呼吸中止症的病患具有相關性，可做為一項指標。然而於先前的研究中，無法提供動態的TBT資訊及舌根變形的狀態。因此本篇研究的目的為發展斑點追蹤演算法，於超音波影像上追蹤舌根動態變化，以利醫生於臨床上評估睡眠呼吸中止症患者(OSA)之舌根動態變化。
在仿體驗證的實驗中，本研究所發展的基於光流法之斑點追蹤演算法與常用於追蹤組織位移的板塊匹配法於超音波標準仿體及模擬仿體中比較。結果顯示，於仿體中無論是絕對誤差或是誤差率之比較，本研究所發展之演算法均展現較高的正確率。
最後於本研究的人體實驗中，受測者均被要求實行倒氣測試(Mueller Maneuver)，此動作可使得舌根暫時性的塌陷進而造成咽喉部呼吸道阻塞，藉此模擬睡眠時之舌根動態。過程中動態B-mode影像之擷取皆利用3.5MHz超音波陣列式探頭，超音波探頭緊貼於脖子部位的頦下皮膚，區域約略介於舌骨和下顎骨之間。影像擷取後即可利用本篇所發展的基於光流法之斑點追蹤演算法於每一張超音波B-mode影像上追蹤所有舌根興趣點之動態變化。結果中顯示正常組的舌根位移較OSA組相對大且越靠近下頦骨(Mandible bone)的舌根組織比靠近舌骨(Hyoid bone)的舌根組織位移來的大。本研究未來會致力於收集更多臨床病例以便更全方面的分析OSA組與正常組之差異並發展更多臨床參數。

Obstructive sleep apnea (OSA), a breathing disorder characterized by repetitive collapse of the pharyngeal airway during sleep, can cause intermittent hypoxemia and frequent arousal. Several studies have demonstrated that the deformation of tongue base plays an important role in OSA. In our previous study, tongue base thickness (TBT) was measured as a significant index by ultrasound image to identify the person with or without OSA. However, TBT cannot provide the dynamic deformation of whole tongue base in detail. Therefore, the purpose of this study is to develop a suitable speckle tracking algorithm to track the dynamic motion of tongue base in ultrasound images. Results were obtained from patients which can help physician to understand the anatomical change of tongue base.
The performance characteristics of proposed optical flow-based method was compared with block matching method, which was commonly used for tissue motion tracking, in both commercial ultrasonic phantom and synthetic data. Calculation of error value and error ratio from the estimated displacement line indicate that proposed optical flow-based method exhibit a better accuracy than block matching method.
Finally, in human experiment, all subjects were required to perform the Mueller Maneuver (MM) to cause the temporal collapsibility of the tongue base. The dynamic B-mode images were recorded during the subjects in the state from eupnea to the MM by a 3.5 MHz ultrasound array probe. The ultrasonic probe was placed on the submental skin of the neck, between the hyoid bone and the symphysis of the mandible. The dynamic deformation of tongue base was tracked by the proposed optical flow-based method in continuous ultrasound image sequences. Subsequently, the dynamic deformation of tongue base with all-cared point during different states of the MM can be obtained. The results obtained in the human experiments indicated that the motion of the normal group is large than the OSA group, and that the tongue base motion near the hyoid bone is less than the motion near the mandible bone. Future work will focus on collect more clinical data to analyze the human tongue base in aims to discover more clinical parameters.

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