二維超音波影像定位的厚度解析度之改善

Abstract

超音波影像為目前常用之醫療檢測儀器，它具有即時成像、無放射線傷害且成本低等優點。超音波影像可檢視身體內部結構，其成像原理為量測聲波發送至物體反射之時間差與強度，形成二維灰階影像。若在超音波探頭上裝設位置感測器，將可了解超音波影像所掃描的切面位置，進而推測出影像中物體在空間中位置，此稱為超音波影像定位。但超音波影像只能提供兩維度之資訊，若想利用一張超音波影像定位出物體在空間三維位置是非常困難的。本論文提出一創新之方法，利用兩相互正交之探頭，得到一組正交超音波影像，若物體在兩影像重疊之區域將可結合兩影像之位置資訊，得到準確之三維定位點。本研究將設計兩種不同類型之實驗，依照被掃描物之特性可區分為靜態定位實驗與動態定位實驗；在靜態定位實驗中將驗證使用雙超音波影像定位可提升定位準確度，靜態定位誤差皆小於1 mm；在動態定位實驗中將模擬肝臟移動軌跡作為標的，動態追蹤定位誤差皆小於1.8 mm。

The ultrasound image is the common medical diagnostic equipment with a lot of advantages including real time imaging, low cost and nonradioactive. The theorem of ultrasound imaging is that a transducer receives the sound wave reflected from the target. The ultrasound system estimates the distance according to the information of reflected sound waves. Then, the system presents the distance information using a two dimension image. The ultrasound image can show the structure of human body, and it could be combined with position sensors, which are attached to an ultrasound probe, to find the target position. This positioning approach is called ultrasound image positioning. Positioning using single ultrasound image cannot be accurate since the thickness problem. In this thesis, a novel ultrasound positioning approach is proposed. This research used two ultrasound systems that are placed orthogonally. The proposed system can obtain an accurate target position using dual ultrasound images. For fixed target, the positioning error was less than 1 mm. For moving target, the positioning error was less than 1.8 mm.