應用漏溢聲波波束成像技術進行影像導引

Abstract

超音波針導引技術已經廣泛地被醫師們使用於手術中，由於超音波影像對人體影響較小的優勢，使得醫師能夠藉由影像即時了解組織的解剖資訊及針在組織中相對應位置。在先前研究中提出了一種利用雷射激發漏溢聲波，並利用超音波探頭定位的方法，然而此方法並無法應用在非線性的物體上，為了克服這個現象，此研究提出一種利用雷射激發漏溢聲波，並對漏溢聲波進行波束成像的定位方法。收到訊號時間可分成兩個部分，一個是導波在針或是導絲上走的時間，另外一個是在水中傳遞的時間，知道導波在針上走的時間，並配合合適波束成像的時間延遲，得到類似傳統的光聲訊號。在不鏽鋼針實驗結果中，結果顯示漏溢聲波定位方法做到51 mm的定位深度，並且最大的針插入角度能夠到達47度，顯示本方法優於現有的超音波與光聲方法。而此方法可進一步用在心導管導絲的定位，在實驗結果中，顯示此方法可比傳統超音波影像在大角度有更好的定位效果，且可以達到跟傳統超音波影像在大深度有相同表現水準，同樣優於現有的超音波與光聲方法。最後此方法可應用在長度達1268 mm導絲針尖定位，足以在體外產生超音波導波傳遞至體內形成點波源。

Ultrasound-guided needle operation is widely used for real-time visualization of the needle position during tissue biopsy and localized drug delivery. Conventionally B-mode imaging is used for needle visualization. However, its practical use has been limited due to acoustic reflection at the needle surface. To overcome this problem, we previously proposed a method to exploit the laser generated guided wave and the leaky acoustic waves. Although successful, the method is only applicable to linear objects and cannot be used for nonlinear objects, thus limiting its applications in areas such as guidewire visualization. The purpose of the current research is to improve the original approach by using ultrasound array beam formation. In this case, irradiated laser pulse generates acoustic waves on the top of a needle or a guidewire. These acoustic waves propagate along the metal surface. Then, the waves leak into the surrounding medium that can be detected by an ultrasound array transducer. The main challenge of the proposed method is to account for the propagation time of the guided waves for accurate beamforming. In other words, the echo arrival time between laser irradiation and array detection consists of two parts. One is the propagation time of the guided waves. The second component is the ultrasound propagation time of the leaky waves in the tissue. In principle, an image of the needle or the guidewire can be formed based on array beam formation after the propagation times on the metal are taken into consideration. Using the proposed beamforming method, results showed that the detection depth was up to 51 mm and the insertion angle was up to 47.3 degrees with needles of different diameters. On the other hand, results of the guidewires showed that the detection depth was up to 63 mm, the insertion angle was up to 56.31 degrees and the propagation distance of the guide waves was up to 1268 mm.