跳到主要內容

臺灣博碩士論文加值系統

(34.204.169.230) 您好!臺灣時間:2024/02/28 08:34
字體大小: 字級放大   字級縮小   預設字形  
回查詢結果 :::

詳目顯示

我願授權國圖
: 
twitterline
研究生:葉秩光
研究生(外文):Yeh, Jyh Guang
論文名稱:電偶極模型定位癲癇焦點之初始值估計法
論文名稱(外文):Initial Estimation Methods for Dipole Modeling in Localization of Epileptogenic Focus
指導教授:陳家進陳家進引用關係
指導教授(外文):Chen Jia Jin
學位類別:碩士
校院名稱:國立成功大學
系所名稱:醫學工程學系
學門:工程學門
學類:綜合工程學類
論文種類:學術論文
論文出版年:1997
畢業學年度:86
語文別:中文
論文頁數:70
中文關鍵詞:腦波圖電偶極模型奇異值分解法初始值估計法
外文關鍵詞:EEGDipole ModelingSingular Value DecompositionInitial Estimation
相關次數:
  • 被引用被引用:0
  • 點閱點閱:303
  • 評分評分:
  • 下載下載:0
  • 收藏至我的研究室書目清單書目收藏:0
在大腦中,一個過度放電的焦點可以用電流電偶極源來等效視之,而
藉由腦波圖所對映的電偶極模型即可以定位出癲癇焦點。通常電偶極的位
置和偶極矩方向可藉由最佳化演繹法的疊代計算在價值函數中找出的最小
部份加以決定。然而,初始值估計值對於最佳化演繹法疊代過程有著極為
重要的影響,因此,本研究將利用電偶極模型,發展一改良式初始值估計
法應用於非侵入式癲癇焦點的定位上。
本研究以目前廣泛被使用的奇異值分解技術,在多重焦點及具有背景波的
腦波訊號當中,萃取出單一電偶極成份做為分析。另外,配合三度空間腦
波圖映射及三度空間雲彩內差方法,將可以得到比標準平面映射較佳的初
始估計值。一般來說,電偶極的位置都在零電位面上,為了取得零電位面
,本研究在三度空間拓樸圖映射中找出多點零電位點,然後採用最小平方
法,找出一個線性平面通過這些零電位點當做零電位面。而電偶極參數的
初始值估計可由零電位面和三度空間電位的波峰、波谷分佈兩者連線的交
點來決定。
為了驗證這裡所提出方法的正確性,腦波模擬訊號是由電偶極在理想的均
勻介質頭顱模型下所得到;定位偏移量及偶極矩方向偏移量兩參數被用來
當做估計值準確度的指標,另外,初始值估計法的偏移量分佈可用數學中
的珈瑪方程式描述出分佈的特性。初始值估計法的各種模擬情況包括有:
雜訊的資料、雜訊資料加上奇異值分解法以及無雜訊資料等,模擬的結果
將三者加以比較。在臨床腦波分析上,我們取兩種焦點來自於不同頭顱深
度的例子做為比較,分別為近中顳葉癲癇焦點及外側顳葉癲癇焦點。最後
實驗的結果我們可以指出,擁有好的電偶極起始參值估計法,確實能夠提
供快速收斂並且能夠找到正確的位置。

Assuming over-discharge of a focus in the brain as an
equivalent current dipole source, localization of epileptic
focus can be obtained from EEG dipole modeling. Usually, the
location and orientation of the dipoles can be determined by
iterative calculations using optimization algorithm
minimizing a cost function. However, the critical dependence
on the initial estimation is an inherent feature of iterative
dipole optimization algorithms. Improved initial estimation
method for noninvasive localization of epileptic
focus, modeled as electrical dipole, is proposed in this
research. This study was
accomplished by using singular value decomposition (SVD)
technique which has been commonly used for extracting the single
dipole component from multiple dipoles and background noise. In
addition, a 3-diomensional (3-D) representation of EEG maps and
reliable 3-D spline interpolation method makes it possible to
obtain better initial estimation than those with
standard planar mapping. In general, the dipolecomponents are
located at the zero potential plane, called null plane.
However, for 3D topographic mapping, many zero potential points
can be detected. Instead of testing all the possible points,
the proposed approach is to fit the selected zero
potentials in terms of a linear plane, i.e. null plane, via
least square approach. The initial estimates of the parameters
which determine the dipole modeling can be computed from the
intersection between null plane and the line connecting the
peak and valley potentials.
For verifying the proposed approach, the EEG potential simulated
from current dipoles in an ideal homogeneous medium are
generated. The localization discrepancy and the moment
orientation discrepancy are used as index for measuring the
estimation accuracy. The distribution of initial estimation
discrepancy was further modeled as a mathematical gamma
function so that distribution features could be characterized.
The initial estimation of various simulation data, including
noise data, noise data with SVD, and noise free data are
compared. For clinical EEG, subjects with different layer such
as mesiotemporal lobe and temporal lobe epilepsy are
compared. Our experimental results indicate that having
good initial estimates for the dipole parameters is essential to
ensure rapid convergence to the correct solution.


QRCODE
 
 
 
 
 
                                                                                                                                                                                                                                                                                                                                                                                                               
第一頁 上一頁 下一頁 最後一頁 top