Basha Tamer A, Akçakaya Mehmet, Goddu Beth, Berg Sophie, Nezafat Reza
Department of Medicine (Cardiovascular Division), Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA, USA.
NMR Biomed. 2015 Jan;28(1):30-9. doi: 10.1002/nbm.3225. Epub 2014 Oct 16.
The aim of this study was to implement and evaluate an accelerated three-dimensional (3D) cine phase contrast MRI sequence by combining a randomly sampled 3D k-space acquisition sequence with an echo planar imaging (EPI) readout. An accelerated 3D cine phase contrast MRI sequence was implemented by combining EPI readout with randomly undersampled 3D k-space data suitable for compressed sensing (CS) reconstruction. The undersampled data were then reconstructed using low-dimensional structural self-learning and thresholding (LOST). 3D phase contrast MRI was acquired in 11 healthy adults using an overall acceleration of 7 (EPI factor of 3 and CS rate of 3). For comparison, a single two-dimensional (2D) cine phase contrast scan was also performed with sensitivity encoding (SENSE) rate 2 and approximately at the level of the pulmonary artery bifurcation. The stroke volume and mean velocity in both the ascending and descending aorta were measured and compared between two sequences using Bland-Altman plots. An average scan time of 3 min and 30 s, corresponding to an acceleration rate of 7, was achieved for 3D cine phase contrast scan with one direction flow encoding, voxel size of 2 × 2 × 3 mm(3) , foot-head coverage of 6 cm and temporal resolution of 30 ms. The mean velocity and stroke volume in both the ascending and descending aorta were statistically equivalent between the proposed 3D sequence and the standard 2D cine phase contrast sequence. The combination of EPI with a randomly undersampled 3D k-space sampling sequence using LOST reconstruction allows a seven-fold reduction in scan time of 3D cine phase contrast MRI without compromising blood flow quantification.
本研究的目的是通过将随机采样的三维（3D）k空间采集序列与回波平面成像（EPI）读出相结合，来实现并评估一种加速三维（3D）电影相位对比磁共振成像序列。通过将EPI读出与适用于压缩感知（CS）重建的随机欠采样3D k空间数据相结合，实现了一种加速3D电影相位对比磁共振成像序列。然后使用低维结构自学习和阈值处理（LOST）对欠采样数据进行重建。在11名健康成年人中采集了3D相位对比磁共振成像，总体加速倍数为7（EPI因子为3，CS率为3）。为作比较，还使用灵敏度编码（SENSE）率2并大致在肺动脉分叉水平进行了单次二维（2D）电影相位对比扫描。使用Bland-Altman图测量并比较了两个序列中升主动脉和降主动脉的每搏输出量和平均速度。对于具有一个方向血流编码、体素大小为2×2×3 mm³、足头覆盖范围为6 cm且时间分辨率为30 ms的3D电影相位对比扫描，实现了平均扫描时间3分30秒，对应加速率为7。所提出的3D序列与标准2D电影相位对比序列之间，升主动脉和降主动脉的平均速度和每搏输出量在统计学上相当。EPI与使用LOST重建的随机欠采样3D k空间采样序列相结合，可使3D电影相位对比磁共振成像的扫描时间减少7倍，且不影响血流定量分析。
