Conklin John, Winter Jeff D, Thompson R Terry, Gelman Neil
Imaging Division, Lawson Health Research Institute, London, Ontario, Canada.
Magn Reson Med. 2008 May;59(5):1190-6. doi: 10.1002/mrm.21548.
Optimization of magnetization-prepared rapid gradient-echo (MP-RAGE) sequence variations for maximum white matter (WM) versus gray matter (GM) contrast in neonates at 3T was investigated. Numerical simulations were applied to optimize and compare three contrast preparation modules and to assess the effect of phase encoding (PE) order on contrast between WM and thin cortical GM layers. Simulations predict that a new sequence, which combines both T(1)- and T(2)-weighting into the contrast preparation and utilizes an interleaved elliptical-spiral PE order, should provide the strongest contrast between neonatal WM and cortical GM. This sequence was compared to a conventional MP-RAGE acquisition (i.e., T(1)-weighted preparation, centric PE order) for in vivo imaging of seven preterm newborn infants. Regional measurements of the contrast-to-noise ratio (CNR) between WM and GM demonstrated an increase of 50-70% (depending on GM region) using the new sequence, in good agreement with theoretical predictions. This improved contrast resulted in superior WM versus GM discrimination in intensity-based brain tissue segmentations.
研究了在3T场强下优化磁化准备快速梯度回波（MP-RAGE）序列变体，以实现新生儿白质（WM）与灰质（GM）对比度最大化。应用数值模拟来优化和比较三个对比度准备模块，并评估相位编码（PE）顺序对WM和薄皮质GM层之间对比度的影响。模拟预测，一种新序列，它将T(1)加权和T(2)加权都纳入对比度准备中，并采用交错椭圆螺旋PE顺序，应该能在新生儿WM和皮质GM之间提供最强的对比度。将该序列与传统的MP-RAGE采集（即T(1)加权准备，中心PE顺序）进行比较，用于对七名早产新生儿进行体内成像。WM和GM之间对比度噪声比（CNR）的区域测量表明，使用新序列时，CNR增加了50-70%（取决于GM区域），与理论预测高度一致。这种改善的对比度在基于强度的脑组织分割中导致了WM与GM之间更好的区分。
