Bankson James A, Wright Steven M
Department of Electrical Engineering, Texas A&M University, College Station, Texas, USA.
Magn Reson Med. 2002 Apr;47(4):777-86. doi: 10.1002/mrm.10113.
Partially parallel imaging strategies such as SMASH, SENSE, and PILS rely on the sensitivity distribution of phased array RF coils to reduce MRI imaging time. Using an N-element phased array, these techniques allow maximum accelerations, L, such that L < or = N, with acceleration defined as the factor by which scan time is reduced in comparison to traditional, fully gradient encoded acquisitions. As N increases in modern MRI facilities or using special hardware extensions, its role as the primary limitation in partially parallel imaging will be reduced and other limiting factors will become dominant. Two such factors include available SNR and the variation of sensitivity distributions with imaging depth. Simulations have been conducted to evaluate the impact of slice depth and noise on partially parallel reconstructions for the case of a square linear array of overlapped elements that are parallel to the imaging plane. Results indicate that even when sensitivity distributions are exactly known, the linear surface array can only provide high accelerations over a limited imaging depth due to changing suitability of the sensitivity distributions for partially parallel reconstruction. This work emphasizes the importance of simulations for target-based partially parallel array design.
部分并行成像策略，如SMASH、SENSE和PILS，依赖相控阵射频线圈的灵敏度分布来减少MRI成像时间。使用N元相控阵，这些技术允许最大加速因子L，使得L≤N，加速定义为与传统的完全梯度编码采集相比扫描时间减少的因子。随着现代MRI设备中N的增加或使用特殊硬件扩展，其作为部分并行成像主要限制因素的作用将降低，其他限制因素将变得占主导地位。其中两个因素包括可用的信噪比以及灵敏度分布随成像深度的变化。对于与成像平面平行的重叠元件方形线性阵列的情况，已经进行了模拟以评估切片深度和噪声对部分并行重建的影响。结果表明，即使灵敏度分布完全已知，由于灵敏度分布对于部分并行重建的适用性不断变化，线性表面阵列也只能在有限的成像深度上提供高加速因子。这项工作强调了针对基于目标的部分并行阵列设计进行模拟的重要性。
