Two-dimensional spatially selective radiofrequency (2DRF) pulse is a type of excitation radiofrequency (RF) pulse in magnetic resonance imaging (MRI) which selects and excites spins in two dimensions simultaneously. Due to its extra selectivity on the second dimension compared with conventional one-dimensional RF pulse, 2DRF pulse could realize reduced field of view (rFOV) imaging. 2DRF-enabled rFOV imaging can accelerate imaging speed, and improve image quality significantly. Advances of 2DRF pulse have been achieved in recent years. However, its wide application in routine clinical practice is hindered by rigid design of 2DRF pulse, the long pulse duration, the inflexibility in excitation pattern, and the user-unfriendliness for non-specialists. The objective of this thesis work is to develop a high-efficient and user-friendly 2DRF pulse to improve its usability and efficiency in routine clinical practice, especially for non-specialists. Finally, the feasibility and applicability of the developed 2DRF pulse was verified in human spine T₁ₚ MR imaging and chemical exchange saturation transfer (CEST) imaging. / A high-low echo planar (EP) 2DRF pulse was first developed to realize rFOV imaging. Developed 2DRF pulse was evaluated in both phantom and human brain. The advantages of being robust to moderate gradient system delay and higher image signal to noise ratio (SNR) of the proposed 2DRF pulse were characterized by the better excitation profiles compared with conventional EP 2DRF pulse sequence. Additionally, the flexibility of the developed 2DRF pulse was verified by the constant image qualities and excitation profiles at different on-line setups. These results demonstrated the feasibility and user-friendliness of the high-low EP 2DRF pulse and revealed its potential application in routine clinical practice. / The high-low EP 2DRF pulse was then incorporated into T₁ₚ sequence to realize rFOV spine T₁ₚ imaging. Quantitative T₁ₚ imaging is time consuming in particular for high spatial resolution images obtained with high spin-lock frequency (FSL) though fast acquisition techniques could be employed. In addition, spine T₁ₚ imaging is vulnerable to the artifact induced by respiration and fat-water chemical shift. Reduced field of view in phase encoding (PE) direction helps to shorten the acquisition time, while preserving the SNR and resolution. The respiration artifact can be eliminated as no spin in chest or abdomen is excited. The 2DRF-enabled rFOV T₁ₚ imaging shortened scan time to the half and minimized respiration artifacts. rFOV CEST imaging was realized by the high-low EP 2DRF pulse. The feasibility of 2DRF pulse enabled rFOV CEST imaging was demonstrated. / 二維空間選擇射頻脈衝（2DRF）是一種磁共振成像中的激發脈衝。它能夠在兩個維度上同時地選擇性激發自旋。和傳統的一維選擇射頻脈衝相比，2DRF 在另一維度上額外的選擇能力使之能夠實現小視域成像。2DRF小視域成像能夠大幅加快成像速度以及提高圖像質量。近年來，2DRF的理論和實驗成果日益豐碩，但2DRF的廣泛臨床應用受到了其相對複雜的設計，較長的激發時間，不夠靈活的激發模式，對組織磁敏感性的過於靈敏以及對於非專業人士的難以操控性等諸多因素的阻礙。這篇碩士論文所述工作的目的是開發一種高效以及易操控的2DRF,以提高它在臨床應用中的實用性和易用性。而後，在人體脊柱T1ₚ磁共振成像和化學轉移飽和交換（CEST）成像技術中，驗證了所提出的2DRF的可行性和適用性。 / 一種高-低回波平面2DRF被首次提出并用於實現小視域成像。這種2DRF在水模和人體腦部成像中得以檢驗。相較於一般的平面回波2DRF，其具有對梯度線圈系統延遲的魯棒性，以及較高的信噪比。這些優勢體現于較好的激發圖樣中。此外，此種2DRF的靈活性在多種設定中取得的穩定的圖像質量和激發圖樣中得到體現。 / 所提出的高-低回波平面2DRF隨後與T1ₚ磁共振成像序列相結合實現了小視域脊柱T1ₚ成像。量化T1ₚ成像比較費時，特別是在使用較高自旋鎖定頻率或者較高的成像分辨率時。此外，脊柱T1ₚ成像容易受到呼吸運動以及水脂化學位移導致的偽影的影像。小視域成像在相位編碼方向上減少了成像範圍，從而在保證圖像信噪比和分辨率的同時減少了圖像採集時間。由於沒有腹部的自選電子被激發，呼吸運動偽影也得以消除。小視域脊柱T1ₚ成像大幅減少成像時間至常規時間的一半以下且最大程度地消除了呼吸運動偽影。通過應用這種2DRF,小視域化學轉移飽和交換轉移成像隨後也得以實現。在研究中，這種成像技術的可行性得到了證明。 / Zhang, Qinwei. / Thesis M.Phil. Chinese University of Hong Kong 2014. / Includes bibliographical references (leaves 69-79). / Abstracts also in Chinese. / Title from PDF title page (viewed on 11, October, 2016). / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only.
| Identifer | oai:union.ndltd.org:cuhk.edu.hk/oai:cuhk-dr:cuhk_1291505 |
| Date | January 2014 |
| Contributors | Zhang, Qinwei , active 2014 (author.), Yuan, Jing , active 2014 (thesis advisor.), Wang, Yi-Xiang (thesis advisor.), Chinese University of Hong Kong Graduate School. Division of Imaging and Interventional Radiology. (degree granting institution.) |
| Source Sets | The Chinese University of Hong Kong |
| Language | English, Chinese |
| Detected Language | English |
| Type | Text, bibliography, text |
| Format | electronic resource, electronic resource, remote, 1 online resource (xvi, 79 leaves) : illustrations (some color), computer, online resource |
| Rights | Use of this resource is governed by the terms and conditions of the Creative Commons "Attribution-NonCommercial-NoDerivatives 4.0 International" License (http://creativecommons.org/licenses/by-nc-nd/4.0/) |
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