Please use this identifier to cite or link to this item: http://hdl.handle.net/11455/8014
標題: 即時螺旋軌跡磁振造影之非同步傳送機制設計
Distributed Reconstruction for Real-Time Spiral Magnetic Resonance Imaging
作者: 徐新鈞
CHUN, HSU HSIN
關鍵字: MRI
出版社: 電機工程學系
摘要: 
在各種醫學影像造影方法中,磁振造影是一種非常多用途的造影
方法。主要的原因是由於磁振造影的影像品質高,而且其造影參數眾
多,可以根據不同的診斷需求而改變。因為磁振造影的過程必須經過
一連串激發核磁共振信號而後接收此信號的過程,所以造影時間長。
因此,加快造影速度乃成為現今磁振造影中的重要問題。許多快速造
影方法也因此而發明,螺旋軌跡磁振造影即為其中之─。此方法乃是
以螺旋型軌跡涵蓋較大區域的資料,因而減少所需激發核磁共振信號
的次數,從而加快造影速度。相較於其他快速造影方法,螺旋軌跡造
影的優點是它比較不會受到因物體運動所產生的影像瑕疵所干擾。因
為即時影像的目的即在觀察人體內的動態,螺旋軌跡造影對運動瑕疵
的容忍性使得它非常適合於即時影像的應用上。但是由於螺旋軌跡所
取得資料並沒有落在格子點上,必須將資料重新安排在格子點上,才
能以高速傅立葉轉換的方式重建影像,此方法便稱之為格化(Gridding)。
JAVA RMI提供一套在JAVA環境下,不同機器彼此進行資訊交換的機制,本論文是研究以JAVA RMI 建立一非同步傳送機制,並作到跨平台的功能,以期能達到即時影像重建的目標。本論文所設計的系統架構是先將個人電腦上的螺旋軌跡磁振造影重建參數內需耗費時間的定點格化運算及反快速傳立葉轉換分送到各RMI SERVER,計算完成之後再將格化資料回傳至個人電腦以重建影像,達到即時影像重建的目標。在完成系統架構設計後,並以 JAVA程式成功地驗証模擬結果之正確性,影像重建時間為48.8ms,影像重建效率為20.5張影像的速度,較原系統提高16%的效能。

Magnetic resonance imaging(MRI)is a very versatile medical imaging tool.The main reasons are twofold.First,It can produce high-quality images.Second,it has many imaging parameters that can be changed to fit different imaging needs.Because MRI requires a long process of exciting and receiving the nuclear magnetic resonance signal, the main hurdle for MRI today is its slow imaging speed. To overcome the problem,many fast imaging methods have been invented.Spiral MRI is one of these methods. Spiral imaging uses a spiral trajectory to quickly cover a large portion of k-space so that the number of times required to excite the NMR signal is reduced.Therefore,It can finish much faster than other methods.Comparing to other fast imaging methods,the benefit of the spiral imaging is that it is insensitive to motion-related artifacts. The problem is that spiral trajectory does not acquire data at rectilinear grid and it is necessary to re-grid the acquired data before fast Fourier transform. This process is often also called "gridding".
This thesis describes an implementation of the gridding algorithm and inverse fourier transform using JAVA RMI on multiple platfomrs.
The system architecture,we used is to pass the reconstruction parameters to RMI SERVER for gridding computation and transmit reconstructed data back to a personal computer for post processing.We validate that the system can successfully reconstruct spiral images distributedly.
URI: http://hdl.handle.net/11455/8014
Appears in Collections:電機工程學系所

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