Please use this identifier to cite or link to this item: http://hdl.handle.net/11455/7460
標題: 以立體血管顯像術重建三維血管模型
Using Stereoscopic Magnetic Resonance Angiography to Reconstruct Blood Vessels
作者: 黃世輝
關鍵字: 醫學影像;立體血管影像
出版社: 電機工程學系
摘要: 
由於以往的立體醫學影像所需的造影時間過長,而二維平面的醫學影像又缺乏影像深度的資訊,因此我們將在此篇論文中探討如何由二維平面影像的資料重建出原始三維空間的立體血管影像。
磁振造影血管顯影術是一種只顯示出人體血管影像而不顯示其它組織的造影技術。其影像的類別有兩種,一種是將三維空間的血管投影至二維平面上的投影影像(二維血管顯影術),另一種則是取得完整的三度空間資訊的三度空間醫學影像(三維血管顯影術)。立體影像的優點在於可隨心所欲地去觀察任一角度的資訊,缺點則是造影的時間過長。當時間受到限制時,只能犧牲掉深度資訊,以二維的投影影像來診斷病變。為了能滿足造影時間的限制,且保有影像深度的資訊,將研究以二維平面的影像重建立體醫學影像。
立體磁振造影血管顯像術,是利用兩個角度的血管投影影像,來重建立體血管影像。由於X光投影影像中像素亮度值,可視為光線行進路徑上所有物質衰減值的積分,因此可由此積分進而反推物體的形狀。但是磁振造影影像中成像的參數很多(例如:T1、T2、質子密度、與共振偏移等),會影響像素亮度的參數也非常多,所以很難由像素亮度值直接推得與物體形狀的關係。因此我們將設法以空間幾何的方法,由血管的邊界值重建出原始影像的形狀,進而重建出原始的立體血管影像。
本篇論文將以實際的例子,來重建實際的三度空間血管影像。由從台中榮總醫院所獲得的80張磁振造影血管影像,我們取其中50張影像,分別作左右各150的投影,當作實際血管投影影像。然後取得投影影像之血管邊界值,再以推導出的演算法算出各血管切面的參數,重建三維空間的立體血管影像。再以同樣的演算方法求出血管的分支,並將重建後的主血管投影影像的血管邊界值與原來的投影影像邊界值作誤差比較,而改良的求解法所重建出的影像平均誤差為0.844。

There are two approaches to acquire an image of MRA(Magnetic Resonance Angiography) which is an imaging technique to show the blood vessels but suppress signals from all the other tissues.One is projecting the 3-D vessels onto 2-D plane.The other is to directly obtain the complete 3-D information.The advantage of 3-D MRA is that we can view the data from arbitrary direction.However,the scan time is usually very long for 3-D MRA.Due to the scan time is limited,we could use 2-D MRA only and the depth of information is sacrificed.In this thesis,we research how to recover the depth information by reconstructing 3-D vessels image from two projective MRA images.
Stereoscopic angiography utilizes two images by projecting blood vessels onto 2-D plane in two angles to reconstruct 3-D vessel image. For DSA, the pixel value is the integration of the attenuation value in the path of the X-ray. We can use this property to derive the shape of the vessels by solving the integrals. On the other hands, there are many imaging parameters in MRA(such as T1 , T2 and proton density). Therefore, it is difficult to obtain the relation between the shape of the vessels and the pixel intensity. For this reason, we attempt to reconstruct the shape of the vessels by geometry.
In the thesis, eighty images of MRA were used to demonstrate the capability of our algorithm. From these images, we use fifty images to make two projective images. The two projections are 300 apart. Then we employ our algorithm to estimate all the ellipses and reconstruct the 3-D model of the vessels. Comparing the boundaries of the original projective images with the boundaries of the reconstructed 3-D model by proved appro-
ach, the average error is 0.844.
URI: http://hdl.handle.net/11455/7460
Appears in Collections:電機工程學系所

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