以時域有限差分法模擬雷射產生之漏溢聲波定位針在生物組織內之位置

Abstract

利用雷射產生之漏溢聲波能偵測針在組織內的位置以及傾角。在模擬上，利用時域有限差分法 (finite-difference time-domain, FDTD) 模擬超音波在針壁介質傳遞狀態以及由針壁邊界漏溢出去形成的漏溢聲波在組織介質中的傳遞狀態。首先，我們利用超音波之控制方程式 (governing equations) 模擬出超音波傳遞模型，並加以驗證，進而建構出實驗之架構並吻合實驗操作。我們將超音波源置於針壁介質內，改變針之厚度以及位置、組織介質以及密度、波源之頻率以及波長，分析在不同超音波參數下的傳遞現象差異。最後，將模擬結果與實驗數據做比對分析，有助於實驗操作端之分析研究。

Here we model acoustic waves by employing the finite-difference time-domain (FDTD) simulation technique. We model acoustic waves source at the position of the needle emitting waves out of the needle and propagating through the scattering medium. In simulation, we analyze the phenomenon for leaky acoustic waves propagating out of the needle and leaking to the surrounding medium that can be detected by the ultrasound (US) transducer. The needle angle and position are calculated based on characteristics of guided waves and leaky acoustic waves. Further, we change the wavelength of the acoustic wave, the speed of sound and the density of medium of wave propagation, the size of needle and the location of sensors. We can analyze the different phenomenon of acoustics for different material parameters. Finally, the simulation results are used to help analyze experimental measurements.