Ming Hsieh Department of Electrical Engineering, Viterbi School of Engineering, University of Southern California, Los Angeles, California.
Magn Reson Med. 2019 Jan;81(1):234-246. doi: 10.1002/mrm.27373. Epub 2018 Jul 29.
To improve the depiction and tracking of vocal tract articulators in spiral real-time MRI (RT-MRI) of speech production by estimating and correcting for dynamic changes in off-resonance.
The proposed method computes a dynamic field map from the phase of single-TE dynamic images after a coil phase compensation where complex coil sensitivity maps are estimated from the single-TE dynamic scan itself. This method is tested using simulations and in vivo data. The depiction of air-tissue boundaries is evaluated quantitatively using a sharpness metric and visual inspection.
Simulations demonstrate that the proposed method provides robust off-resonance correction for spiral readout durations up to 5 ms at 1.5T. In -vivo experiments during human speech production demonstrate that image sharpness is improved in a majority of data sets at air-tissue boundaries including the upper lip, hard palate, soft palate, and tongue boundaries, whereas the lower lip shows little improvement in the edge sharpness after correction.
Dynamic off-resonance correction is feasible from single-TE spiral RT-MRI data, and provides a practical performance improvement in articulator sharpness when applied to speech production imaging.
通过估计和校正离频动态变化，提高螺旋式实时 MRI（RT-MRI）在言语产生中对声道构音器官的描绘和跟踪。
所提出的方法从经过线圈相位补偿的单回波动态图像的相位中计算动态场图，其中复杂的线圈灵敏度图是从单回波动态扫描本身估计的。该方法使用模拟和体内数据进行了测试。使用锐度度量和视觉检查对空气-组织边界的描绘进行定量评估。
模拟表明，该方法在 1.5T 时提供了长达 5ms 的螺旋读出时间的稳健离频校正。在人类言语产生过程中的体内实验表明，在大多数数据集的空气-组织边界处，包括上唇、硬腭、软腭和舌边界，图像锐度得到了改善，而校正后下唇的边缘锐度改善较小。
从单回波螺旋 RT-MRI 数据中进行动态离频校正是可行的，并且在应用于言语产生成像时，在构音器官锐度方面提供了实际的性能提高。
