Rydén Henric, Berglund Johan, Norbeck Ola, Avventi Enrico, Sprenger Tim, van Niekerk Adam, Skare Stefan
Department of Neuroradiology, Karolinska University Hospital, Stockholm, Sweden.
Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden.
Magn Reson Med. 2020 Nov;84(5):2456-2468. doi: 10.1002/mrm.28293. Epub 2020 Apr 25.
To investigate the impact of dual readout bandwidths (dBW) in a dual echo fat/water acquisition and describe a dBW-rapid acquisition relaxation enhanced, or turbo spin echo sequence where the concept is used to improve SNR by removing dead times between refocusing pulses and avoiding redundant Chemical-shift encoded.
Cramér-Rao bounds and Monte Carlo simulations were used to investigate a two-point fat/water model where the difference in bandwidths is incorporated. In vivo images were acquired at 1.5 and 3 T with the dBW-rapid acquisition relaxation enhanced, or turbo spin echo sequence. Typical bandwidth ratios were 1:2. SNR was compared with a single bandwidth sequence under identical scan parameters at 3T.
Monte Carlo simulations and Cramér-Rao analysis demonstrate that number of signal averages can be improved with dual bandwidths compared to conventional single bandwidth acquisitions. The dBW-rapid acquisition relaxation enhanced, or turbo spin echo sequence can acquire images with high readout resolutions with well-conditioned sampling. An SNR improvement of 52% was measured, in line with the theoretical gain of 54%.
The proposed dBW-rapid acquisition relaxation enhanced, or turbo spin echo sequence is a highly SNR-efficient two-point rapid acquisition relaxation enhanced, or turbo spin echo sequence without dead times, and can acquire images at higher resolutions than current vendor-supplied alternatives.
研究双回波脂肪/水采集过程中双读出带宽（dBW）的影响，并描述一种采用该概念的dBW快速采集弛豫增强（或涡轮自旋回波）序列，通过消除重聚焦脉冲之间的死时间并避免冗余化学位移编码来提高信噪比。
使用克拉美罗界和蒙特卡罗模拟研究纳入带宽差异的两点脂肪/水模型。采用dBW快速采集弛豫增强或涡轮自旋回波序列在1.5和3T场强下采集体内图像。典型带宽比为1:2。在3T场强下，将相同扫描参数下的信噪比与单带宽序列进行比较。
蒙特卡罗模拟和克拉美罗分析表明，与传统单带宽采集相比，双带宽可提高信号平均次数。dBW快速采集弛豫增强或涡轮自旋回波序列能够以良好的采样条件采集具有高读出分辨率的图像。实测信噪比提高了52%，与理论增益54%一致。
所提出的dBW快速采集弛豫增强或涡轮自旋回波序列是一种高信噪比效率的两点快速采集弛豫增强或涡轮自旋回波序列，无死时间，且能以比当前供应商提供的替代方案更高的分辨率采集图像。
