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Abstract：
Brain imaging exams typically take 10-20 min and involve multiple sequential acquisitions. A low-distortion whole-brain echo planar imaging (EPI)-based approach was developed to efficiently encode multiple contrasts in one acquisition, allowing for calculation of quantitative parameter maps and synthetic contrast-weighted images.
Inversion prepared spin- and gradient-echo EPI was developed with slice-order shuffling across measurements for efficient acquisition with T1 , T2 , and T2∗ weighting. A dictionary-matching approach was used to fit the images to quantitative parameter maps, which in turn were used to create synthetic weighted images with typical clinical contrasts. Dynamic slice-optimized multi-coil shimming with a B0 shim array was used to reduce B0 inhomogeneity and, therefore, image distortion by >50%. Multi-shot EPI was also implemented to minimize distortion and blurring while enabling high in-plane resolution. A low-rank reconstruction approach was used to mitigate errors from shot-to-shot phase variation.
The slice-optimized shimming approach was combined with in-plane parallel-imaging acceleration of 4× to enable single-shot EPI with more than eight-fold distortion reduction. The proposed sequence efficiently obtained 40 contrasts across the whole-brain in just over 1 min at 1.2 × 1.2 × 3 mm resolution. The multi-shot variant of the sequence achieved higher in-plane resolution of 1 × 1 × 4 mm with good image quality in 4 min. Derived quantitative maps showed comparable values to conventional mapping methods.
The approach allows fast whole-brain imaging with quantitative parameter maps and synthetic weighted contrasts. The slice-optimized multi-coil shimming and multi-shot reconstruction approaches result in minimal EPI distortion, giving the sequence the potential to be used in rapid screening applications.
Inversion prepared spin- and gradient-echo EPI was developed with slice-order shuffling across measurements for efficient acquisition with T1 , T2 , and T2∗ weighting. A dictionary-matching approach was used to fit the images to quantitative parameter maps, which in turn were used to create synthetic weighted images with typical clinical contrasts. Dynamic slice-optimized multi-coil shimming with a B0 shim array was used to reduce B0 inhomogeneity and, therefore, image distortion by >50%. Multi-shot EPI was also implemented to minimize distortion and blurring while enabling high in-plane resolution. A low-rank reconstruction approach was used to mitigate errors from shot-to-shot phase variation.
The slice-optimized shimming approach was combined with in-plane parallel-imaging acceleration of 4× to enable single-shot EPI with more than eight-fold distortion reduction. The proposed sequence efficiently obtained 40 contrasts across the whole-brain in just over 1 min at 1.2 × 1.2 × 3 mm resolution. The multi-shot variant of the sequence achieved higher in-plane resolution of 1 × 1 × 4 mm with good image quality in 4 min. Derived quantitative maps showed comparable values to conventional mapping methods.
The approach allows fast whole-brain imaging with quantitative parameter maps and synthetic weighted contrasts. The slice-optimized multi-coil shimming and multi-shot reconstruction approaches result in minimal EPI distortion, giving the sequence the potential to be used in rapid screening applications.
摘要：
脑成像检查通常需要10-20分钟，并涉及多个顺序采集。开发了一种基于低失真全脑回波平面成像（EPI）的方法，以在一次采集中有效地编码多个对比度，允许计算定量参数图和合成对比度加权图像。
反转准备的自旋和梯度回波EPI通过跨测量的切片顺序混洗开发，以实现T1的有效采集，T2,和T2*权重。使用字典匹配方法将图像拟合到定量参数图，这反过来被用来创建合成加权图像与典型的临床对比。采用B0匀场阵列的动态切片优化多线圈匀场来减少B0的不均匀性，因此,图像失真>50%。还实现了多次发射EPI以最小化失真和模糊,同时实现高的平面内分辨率。使用低秩重建方法来减轻镜头到镜头相位变化的误差。
切片优化的匀场方法与4倍的面内平行成像加速度相结合，以使单次发射EPI具有八倍以上的失真减少。所提出的序列以1.2×1.2×3mm的分辨率在短短1分钟内有效地在整个大脑中获得了40个对比度。序列的多次拍摄变体在4分钟内实现了1×1×4mm的更高的面内分辨率，并具有良好的图像质量。衍生的定量图显示出与常规作图方法相当的值。
该方法允许具有定量参数图和合成加权对比的快速全脑成像。切片优化的多线圈匀场和多激发重建方法导致最小的EPI失真，赋予序列用于快速筛查应用的潜力。
反转准备的自旋和梯度回波EPI通过跨测量的切片顺序混洗开发，以实现T1的有效采集，T2,和T2*权重。使用字典匹配方法将图像拟合到定量参数图，这反过来被用来创建合成加权图像与典型的临床对比。采用B0匀场阵列的动态切片优化多线圈匀场来减少B0的不均匀性，因此,图像失真>50%。还实现了多次发射EPI以最小化失真和模糊,同时实现高的平面内分辨率。使用低秩重建方法来减轻镜头到镜头相位变化的误差。
切片优化的匀场方法与4倍的面内平行成像加速度相结合，以使单次发射EPI具有八倍以上的失真减少。所提出的序列以1.2×1.2×3mm的分辨率在短短1分钟内有效地在整个大脑中获得了40个对比度。序列的多次拍摄变体在4分钟内实现了1×1×4mm的更高的面内分辨率，并具有良好的图像质量。衍生的定量图显示出与常规作图方法相当的值。
该方法允许具有定量参数图和合成加权对比的快速全脑成像。切片优化的多线圈匀场和多激发重建方法导致最小的EPI失真，赋予序列用于快速筛查应用的潜力。
