基於誘發複合動作電位與電場成像的個人化模型

Abstract

透過電腦斷層獲得人工電子耳使用者的耳蝸的物理尺寸之後，結合人工電子耳臨床量測，使得建立一個更精確的電神經模型是可行的。這篇論文提出眾多方法中的其中一種。一個精確的個人化電神經模型能夠被用來微調電刺激參數，或者能夠不需要繁瑣的人工電子耳調頻動作而完成調頻。明顯地這對於應用在兒童的人工電子耳使用者來說具有極大的意義。

這篇論文的目的是在評估對於使用人工電子耳的人類而言，其相對的螺旋神經節密度。透過對人工電子耳使用者進行電場成像的量測，可以獲得延著耳蝸的電位能。而且對人工電子耳使用者而言，誘發複合動作電位的閾值和聽覺閾值有很大的關聯。誘發複合動作電位量測方法是客觀的且較快速的方法來獲得相對應的閾值。再一次地說，這對於兒童的人工電子耳使用者的調頻應用有很大的意義，因為無法要求他們會有所回饋。由於刺激的範圍很大，因此提出「蘋果核」-誘發複合動作電位的方法，其方法限制被刺激的聽神經能夠狹小到相鄰兩電極之間的區域。因為聽神經被激發的區域和電極與螺旋神經節的距離都已固定，透過比較不同的刺激電極所量測到的螺旋神經節訊號，可獲得相對螺旋神經節密度。

With physiological dimensions of the cochlear implant (CI) patient’s cochlea from computed tomography (CT), it is possible to build a more accurate patient-specific electro-neural model of CI patients based on clinical measurements. One of such methods is proposed in this thesis. An accurate patient specific electro-neural model could be used for fine tuning the electrical stimulation parameters or “maps” of a CI patient without needing many CI mapping sessions. This has enormous implication for CI pediatric applications due to obvious reason.

The goal of this thesis is to evaluate the relative spiral ganglion cells (SGC) density of a human CI patient. The electric potential along the cochlea in a CI patient can be measured via electric field imaging (EFI). Also, there is a significant correlation between evoked compound action potential (ECAP) threshold and behavior threshold (T) level for a CI patient. ECAP measurement approach is an objective and faster way to obtain the relative T level of a CI patient. This again has important implication for pediatric CI mapping application since it does not require feedback from pediatric CI patients. Due to a large stimulating range, we propose to use the idea of using “apple-core”-ECAP paradigm which can limit the auditory nerves being stimulated to a narrower volume between neighboring two electrodes. Since the volume of auditory nerves activated and the distance between electrode and SGC are fixed, we can obtain the relative SGC density through comparing with every SGC signal at different electrodes.