Han S H, Cho F H, Song Y K, Paulsen J, Song Y Q, Kim Y R, Kim J K, Cho G, Cho H
Department of Biomedical Engineering, UNIST, Ulsan, South Korea.
Schlumberger Doll Research Center, Cambridge, MA, USA.
Sci Rep. 2014 May 27;4:5061. doi: 10.1038/srep05061.
Long scan times of 3D volumetric MR acquisitions usually necessitate ultrafast in vivo gradient-echo acquisitions, which are intrinsically susceptible to magnetic field inhomogeneities. This is especially problematic for contrast-enhanced (CE)-MRI applications, where non-negligible T2* effect of contrast agent deteriorates the positive signal contrast and limits the available range of MR acquisition parameters and injection doses. To overcome these shortcomings without degrading temporal resolution, ultrafast spin-echo acquisitions were implemented. Specifically, a multiplicative acceleration factor from multiple spin echoes (×32) and compressed sensing (CS) sampling (×8) allowed highly-accelerated 3D Multiple-Modulation-Multiple-Echo (MMME) acquisition. At the same time, the CE-MRI of kidney with Gd-DOTA showed significantly improved signal enhancement for CS-MMME acquisitions (×7) over that of corresponding FLASH acquisitions (×2). Increased positive contrast enhancement and highly accelerated acquisition of extended volume with reduced RF irradiations will be beneficial for oncological and nephrological applications, in which the accurate in vivo 3D quantification of contrast agent concentration is necessary with high temporal resolution.
3D容积磁共振成像采集的长扫描时间通常需要进行超快速的活体梯度回波采集，而这种采集本质上容易受到磁场不均匀性的影响。对于对比增强（CE）-MRI应用而言，这一问题尤为突出，因为造影剂不可忽略的T2*效应会降低正信号对比度，并限制磁共振采集参数和注射剂量的可用范围。为了在不降低时间分辨率的情况下克服这些缺点，实施了超快速自旋回波采集。具体而言，来自多个自旋回波的乘法加速因子（×32）和压缩感知（CS）采样（×8）实现了高度加速的3D多调制多回波（MMME）采集。同时，使用钆双胺的肾脏CE-MRI显示，与相应的快速小角度激发（FLASH）采集（×2）相比，CS-MMME采集（×7）的信号增强显著改善。增强的正对比度和在减少射频辐射的情况下对更大容积进行高度加速采集，将有利于肿瘤学和肾脏病学应用，在这些应用中，需要以高时间分辨率对造影剂浓度进行准确的活体3D定量。
