下背痛一直是臨床外科醫師最常遇到的問題，根據統
計，大約有80％的成年人皆曾經有過下背痛的經驗，其發
病的年齡層大多集中在四十五至六十歲。當病人因下背痛
就醫時，醫師最常利用電腦斷層攝影(CT)和磁振造影(MRI)
的檢查來輔助做臨床診斷。在診斷病情時，通常都是藉由
交互觀察電腦斷層影像和磁振影像以找出真正的病因，但
此種觀察方式需要來回切換影像，實感不便。因此本論文
的重點在於利用影像登錄(Image Registration)技術將此
兩種醫療影像做一整合，在醫學臨床研究與診斷上提供更
完整的資訊。

在方法上，先將電腦斷層影像中之腰椎硬質骨切割出
來，再經由Laplacian邊緣檢測擷取出腰椎輪廓圖以當作參
考模組；而磁振影像則是先利用Canny邊緣檢測來突顯出其
特徵後，再使用距離轉換將其轉換為視距圖(Distance
Map)；最後，將參考模組套入視距圖中，並利用chamfer
matching來找尋電腦斷層影像與磁振影像之幾何位置相對
應的關係。同時，我們利用外部標記來評估本論文所提出
之影像登錄演算法的準確性和可靠性，以確認登錄後之結
果在臨床應用上具有實用的價值。除此之外，為了方便醫
師作病情上的觀察，我們也設計一套多樣化顯示系統，包
括二維顯示、三維重構顯示和登錄後影像之重合顯示等，
使醫師能夠更容易觀察椎神經與腰椎硬質骨邊緣之間相對
應的關係。

Low back pain is one of the most common health
problems treated by orthopedic surgeons. According
to the experience, about eighty percent of adults
have had low back pain and the age is mostly
located between forty-five and sixty. For those low
back pain patients, Computer Tomography (CT) and
Magnetic Resonance Imaging (MRI) are two helpful
instruments for clinical diagnosis. In general, CT
and MRI images are inspected by turns for finding
the causes. However, it is inconvenient to change
images frequently back and forth. Thus, the purpose
of this study is to use image registration
technique for integrating both of the information
of CT and MRI images to provide more complete
information for diagnosis.

For CT images, the lumbar vertebra is firstly
segmented out. Then the Laplacian edge detector is
used to extract the contours of the segmented
images. These extracted contours from CT images are
used as the reference models. For those MRI images,
their gradient images are obtained. Then they are
converted into its corresponding distance maps by
using distance transformation. Finally, the
corresponding relationship of spatial position
between the reference models and the distance maps
is found by using chamfer matching techniques for
registration. External landmarks are also used to
estimate the accuracy and robustness of the
registered result of the proposed algorithm for
confirming the application of clinic. For helping
the observation, a visualization system, including
2D image, 3D reconstruction and registered image
display. It shows the doctor the corresponding
relationship between nerve roots and the edge of
lumbar vertebra more easily.

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