Deoni Sean C L
Centre for Neuroimaging Research, Institute of Psychiatry, King's College London, London, UK.
J Magn Reson Imaging. 2009 Aug;30(2):411-7. doi: 10.1002/jmri.21849.
To investigate a new approach for more completely accounting for off-resonance affects in the DESPOT2 (driven equilibrium single pulse observation of T(2)) mapping technique.
The DESPOT2 method derives T(2) information from fully balanced steady-state free precession (bSSFP) images acquired over multiple flip angles. Off-resonance affects, which present as bands of altered signal intensity throughout the bSSFP images, results in erroneous T(2) values in the corresponding calculated maps. Radiofrequency (RF) phase-cycling, in which the phase of the RF pulse is incremented along the pulse train, offers a potential method for eliminating these artifacts. In this work we present a general method, referred to as DESPOT2, with full modeling (DESPOT2-FM), for deriving T(2), as well as off-resonance frequency, from dual flip angle bSSFP data acquired with two RF phase increments.
The method is demonstrated in vivo through the acquisition of whole-brain, 1 mm(3) isotropic T(2) maps at 3T and shown to provide near artifact-free maps, even in areas with steep susceptibility-induced gradients.
DESPOT2-FM offers an efficient method for acquiring high spatial resolution, whole-brain T(2) maps at 3T with high precision and free of artifact.
研究一种新方法，以便在DESPOT2（T(2)的驱动平衡单脉冲观测）成像技术中更全面地考虑失谐效应。
DESPOT2方法从在多个翻转角采集的完全平衡稳态自由进动（bSSFP）图像中获取T(2)信息。失谐效应在整个bSSFP图像中表现为信号强度改变的条带，会在相应计算图像中导致错误的T(2)值。射频（RF）相位循环，即RF脉冲的相位沿脉冲序列递增，提供了一种消除这些伪影的潜在方法。在本研究中，我们提出一种通用方法，称为带全模型的DESPOT2（DESPOT2-FM），用于从以两个RF相位增量采集的双翻转角bSSFP数据中推导T(2)以及失谐频率。
通过在3T下采集全脑1mm(3)各向同性T(2)图像在体内验证了该方法，结果表明即使在存在陡峭的磁化率诱导梯度的区域也能提供几乎无伪影的图像。
DESPOT2-FM提供了一种高效方法，可在3T下高精度、无伪影地获取高空间分辨率的全脑T(2)图像。
