| 摘要: | 本計劃為五年期前瞻性研究。目標為發展一系列快速磁振造影技術，利用多重迴訊信號的特性，取得高品質的參數圖譜及多重對比影像。研究內容包含磁振物理原理探討，數學模型設計，擷取序列研發，重建計算設計及臨床應用。此計劃五年內的五個特定目標為：一、發展單次激發的梯度自旋迴訊序列， 快速擷取不同 T2 權重的數據，並使其不受刺激及高階迴旋訊號污染。配合多工與指數訊號模型，重建出準確的 T2 參數圖譜。二、發展利用反向回復技術的梯度自旋迴訊序列，配合多次不同 T1 弛緩時間的資料擷取，增加 T2 訊號的採樣，可同時提供質子密度及 T1 參數圖譜，及可分析腦部隨鞘內水分比例的雙重指數 T2 參數圖譜，並利用多重參數圖譜產生合成多重對比影像。三、發展可分離多重迴訊信號的的單次激發梯度自旋迴訊序列，同時產生不同對比的迴訊信號，包含質子密度對比、T1權重對比、T2權重對比及液體衰減反轉恢復對比。四、發展多次激發梯度自旋迴訊序列，同時產生不同對比的迴訊信號，配合射頻脈衝方向的組合，減低影像的幾何扭曲，提高影像解析度，並提供更短的迴訊時間。五、發展技術將應用於腦部組織特徵化，腦部、腹部及心臟影像。本計劃提供高效率的參數圖譜與多重對比磁振造影技術，可為許多臨床應用帶來立即且重大的效益，減少造影成本，使磁振造影成為更流通與可負擔的臨床檢查技術。 ;This is a five-year prospective project on developing a series of highly-efficient magnetic resonance imaging (MRI) technologies, with the aims to acquire high-resolution and high-quality parametric and multi-contrast data through multiple echo pathways. Our project includes analysis of MR physics, development of signal models, sequence design, design of reconstruction algorithm and clinical applications. Our project has five specific aims: Aim 1: Highly-efficient T2 parametric MRI with single-shot imaging scan: We will develop an echo-split gradient-spin-echo imaging (ES-GRASE) technique, capable of generating multi-T2-contrast data from a single-shot scan without contamination of stimulated and high-order echoes. An accurate T2 map will be calculated from the multi-T2-contrast data with multiplexed and exponential signal model.Aim 2: Simultaneous proton density (PD), T1 and double-exponential T2 parametric MRI: Built upon the Aim 1, we will further perform simultaneous PD, T1 and T2 mapping using multiple inversion-recovery (IR) prepared ES-GRASE data sets corresponding to different inversion times. The multiple ES-GRASE acquisition will improve the T2 sampling density, providing enough samples for double-exponential T2 fitting for myelin water fraction mapping. Synthetic multi-contrast images will also be generated from the measured parametric maps. Aim 3: Multi-contrast MRI (PD-weighted, T1-weighted, T2-weighted and FLAIR images) with single-shot ES-GRASE scan: We will develop a single-shot multi-contrast ES-GRASE technique, capable of separating multiple echo pathways to generate echo signals with different contrast. Images with multiple contrasts will be generated from a single set of ES-GRASE data.Aim 4: High-resolution multi-contrast MRI with multi-shot ES-GRASE scan: Built upon Aim 3, we will further develop a multi-shot multi-contrast ES-GRASE technique, with multiple excitation direction of RF pulses, to reduce geometric distortion, improve signal-to-noise ratio and image resolution, and enable shorter echo time.Aim 5: Applications of the newly developed high-speed parametric and multi-contrast MRI: We will validate the developed MRI techniques in brain tissue characterization, brain imaging, abdominal imaging and cardiac imaging.This project enables highly-efficient parametric and multi-contrast MRI that cannot be achieved with existing approaches. The impact of our proposed MR imaging techniques is expected to be immediate and significant for various clinical applications. We also expect that the new highly-efficient MRI technologies, with the reduction in scan time, can reduce the overall cost for MRI procedures for each individual, thus making MRI a more accessible and affordable modality. |
