采用二维交错多层减少视野单次激发扩散加权回波平面成像(2D ss-rFOV-DWEPI)的高分辨率扩散张量成像。

High-resolution DTI with 2D interleaved multislice reduced FOV single-shot diffusion-weighted EPI (2D ss-rFOV-DWEPI).

作者信息

Jeong Eun-Kee, Kim Seong-Eun, Guo Junyu, Kholmovski Eugene G, Parker Dennis L

机构信息

Department of Radiology, Utah Center for Advanced Imaging Research, University of Utah, Salt Lake City, Utah 84108, USA.

出版信息

Magn Reson Med. 2005 Dec;54(6):1575-9. doi: 10.1002/mrm.20711.

Abstract

Diffusion tensor MRI (DTI), using single-shot 2D diffusion weighted-EPI (2D ss-DWEPI), is limited to intracranial (i.c.) applications far from the sinuses and bony structures, due to the severe geometric distortions caused by significant magnetic field inhomogeneities at or near the tissue-air or tissue-bone interfaces. Reducing these distortions in single-shot EPI by shortening the readout period generally requires a reduced field of view (and the potential of wraparound artifact) in the phase-encoding direction and/or reduced spatial resolution. To resolve the problem, a novel 2D reduced FOV single-shot diffusion-weighted EPI (2D ss-rFOV-DWEPI) pulse sequence applicable for high resolution diffusion-weighted MRI of local anatomic regions, such as brainstem, cervical spinal cord, and optic nerve, has been developed. In the proposed technique, time-efficient interleaved acquisition of multiple slices with a limited FOV was achieved by applying an even number of refocusing 180 degrees pulses with the slice-selection gradient applied in the phase-encoding direction. The two refocusing pulses used for each slice acquisition were separated by a short time interval (typically less than 45 ms) required for the 2D EPI echotrain acquisition. The new technique can be useful for high resolution DTI of various anatomies, such as localized brain structures, cervical spinal cord, optic nerve, heart, or other extra-cerebral organ, where conventional 2D ss-DWEPI is limited in usage due to the severity of image distortions.

摘要

使用单次激发二维扩散加权回波平面成像(2D ss-DWEPI)的扩散张量磁共振成像(DTI),由于在组织-空气或组织-骨界面处或其附近存在显著磁场不均匀性而导致严重的几何畸变,因此仅限于远离鼻窦和骨结构的颅内(i.c.)应用。通过缩短读出时间来减少单次激发回波平面成像中的这些畸变,通常需要在相位编码方向上减小视野(以及存在卷绕伪影的可能性)和/或降低空间分辨率。为了解决这个问题,已经开发出一种新颖的二维缩小视野单次激发扩散加权回波平面成像(2D ss-rFOV-DWEPI)脉冲序列,适用于对局部解剖区域(如脑干、颈脊髓和视神经)进行高分辨率扩散加权磁共振成像。在所提出的技术中,通过应用偶数个180度重聚焦脉冲并在相位编码方向上应用切片选择梯度,实现了在有限视野下对多个切片进行时间高效的交错采集。用于每个切片采集的两个重聚焦脉冲由二维回波平面成像回波链采集所需的短时间间隔(通常小于45毫秒)隔开。这项新技术可用于对各种解剖结构进行高分辨率DTI,例如局部脑结构、颈脊髓、视神经、心脏或其他脑外器官,在这些部位,由于图像畸变严重,传统的2D ss-DWEPI在使用上受到限制。

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