本文選題：磁共振成像 + EPI序列　； 參考：《電子科技大學》2014年碩士論文

【摘要】：核磁共振成像(Magnetic Resonance Imaging,MRI)技術是目前一種先進的醫(yī)學成像方法,利用磁共振信號能夠獲得任何部位、任意方向的組織切片的醫(yī)學圖像。在核磁共振成像的過程中,需要成像序列控制譜儀產生相應的射頻脈沖、選層梯度、相位編碼梯度和頻率編碼梯度來產生圖像。為了追求質量更高的圖像,設計更好的成像序列是一個非常重要的條件,所以磁共振序列是磁共振成像技術最直接的載體。伴隨著MRI在醫(yī)學診斷領域的深入發(fā)展,序列從上世紀中期的自旋回波成像(spin echo,簡寫為SE)發(fā)展到20世紀80年代中期的梯度回波成像(gradient echo,簡寫為GRE),再發(fā)展到90年代的平面回波成像(echo planar imaging,簡稱EPI)。MRI序列為解剖結構的顯示、組織的功能成像、分子成像等的最基本的支撐平臺。所以,本文立足于現(xiàn)今MRI序列的需求狀況,在EPI成像和真實穩(wěn)態(tài)自由進動序列成像(true steady state free precession,True-SSFP)的基礎上,設計出成像時間和成像質量相比于基礎序列(EPI序列和True-SSFP序列)都有所改善的序列。本文主要研究內容如下:1、核磁共振成像的基本原理分析。本文分別從相位編碼、頻率編碼、選層梯度和K空間等幾個方面介紹了核磁共振序列的基本成像原理。2、EPI序列和True-SSFP序列分析。本文從序列成像原理、所用參數(shù)及其特點、臨床適用范圍等方面對EPI序列和True-SSFP序列分別進行分析。針對EPI,本文分別從單次激勵的平面回波序列(single-shot EPI,SS-EPI)和多次激勵的平面回波序列(multi-shot EPI,MS-EPI)兩種情況進行詳解。并且,本文在ODIN仿真軟件上實現(xiàn)了EPI序列和True-SSFP序列的序列圖仿真、K空間仿真以及圖像仿真。3、single-shot EPI-SSFP序列的設計與實現(xiàn)。本文通過對EPI-SSFP序列的深入分析,針對multi-shot EPI-SSFP序列成像速度還不能滿足心臟動態(tài)成像這一特點,設計了single-shot EPI-SSFP序列。本文解決了新序列中EPI序列的選擇、射頻脈沖激勵方式的選擇等問題,并運用梯度橋接技術解決了序列的重復時間太短無法實現(xiàn)雙向補償?shù)膯栴},還解決了具體實現(xiàn)穩(wěn)態(tài)過程這一技術難題。本文基于ODIN軟件平臺仿真出了single-shot EPI-SSFP序列的序列圖、K空間數(shù)據(jù)填充過程及其成像效果圖。4、快速成像序列的偽影消除方法研究與序列評估。本文對快速成像序列所產生偽影進行分析研究,結合EPI序列獨有的消除Ghost偽影方法,對single-shot EPI-SSFP序列產生的偽影提出消除方法,并仿真實現(xiàn)所提出的偽影消除方法。最后,文章還就序列的成像時間和成像質量對所提出的偽影消除方法進行評估,結果顯示所設計的新序列在成像時間和成像質量上與EPI序列、True-SSFP序列相比有較為明顯的改善。
[Abstract]:Magnetic Resonance Imaging (MRI) is an advanced medical imaging method, which can obtain medical images of tissue sections in any position and any direction by using magnetic resonance signal. In the process of nuclear magnetic resonance imaging, it is necessary for the imaging sequence to produce the corresponding RF pulse, layer selection gradient, phase coding gradient and frequency coding gradient to generate the image. In order to achieve better image quality, it is very important to design better imaging sequence, so magnetic resonance sequence is the most direct carrier of magnetic resonance imaging technology. With the development of MRI in the field of medical diagnosis, The sequence developed from spin echo imaging (spin echo,) in the middle of the last century to gradient echo imaging (gradient echo,) in the mid-1980s, and then to planar echo imaging (echo planar imaging,) in the 1990s. Tissue functional imaging, molecular imaging and so on the most basic support platform. Therefore, this paper is based on the demand of (true steady state free sequence, based on EPI imaging and true steady-state free precession sequence imaging (true steady state free precession True-SSFP). The imaging time and quality are improved compared with the basic sequence (EPI sequence and True-SSFP sequence). The main contents of this paper are as follows: 1: 1, the basic principle of nuclear magnetic resonance imaging. In this paper, the basic imaging principles of nuclear magnetic resonance sequences, such as phase coding, frequency coding, layer selection gradient and K-space, are introduced, respectively. The analysis of EPI sequence and True-SSFP sequence of nuclear magnetic resonance sequences are presented. In this paper, EPI sequence and True-SSFP sequence are analyzed from the aspects of imaging principle, parameters and characteristics, clinical application range and so on. In this paper, the single excitation plane echo sequence (single-shot EPI SS-EPI) and the multiple excitation plane echo sequence (multi-shot EPI MS-EPI) are analyzed in detail. Furthermore, the design and implementation of EPI sequence and True-SSFP sequence are implemented in ODIN software. The design and implementation of EPI sequence and True-SSFP sequence are also presented in this paper, as well as the design and implementation of the image simulation of single-shot EPI-SSFP sequence. Based on the deep analysis of EPI-SSFP sequence, the single-shot EPI-SSFP sequence is designed in view of the fact that the imaging speed of EPI-SSFP sequence can not meet the requirement of dynamic cardiac imaging. In this paper, the selection of EPI sequence and the mode of RF pulse excitation in the new sequence are solved, and the gradient bridging technique is used to solve the problem that the repetition time of the sequence is too short to realize bidirectional compensation. The technical problem of realizing the steady-state process is also solved. Based on the ODIN software platform, this paper simulates the filling process of single-shot EPI-SSFP sequence map K spatial data and its imaging effect figure .4. the research on the method of fast imaging sequence artifact elimination and sequence evaluation is presented. In this paper, the artifact produced by fast imaging sequence is analyzed and studied. Combined with the unique method of eliminating ghost artifacts in single-shot EPI-SSFP sequence, the method of eliminating artifacts produced by EPI sequence is proposed, and the proposed method is realized by simulation. Finally, the image time and quality of the proposed method are evaluated. The results show that the new sequence has better imaging time and quality than the EPI sequence and True-SSFP sequence.
【學位授予單位】：電子科技大學
【學位級別】：碩士
【學位授予年份】：2014
【分類號】：R445.2
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本文編號：2056337