Holmes James H, O'Halloran Rafael L, Brodsky Ethan K, Jung Youngkyoo, Block Walter F, Fain Sean B
Department of Medical Physics, University of Wisconsin-Madison, 600 Highland Avenue, Madison, WI 53792, USA.
Magn Reson Med. 2008 May;59(5):1062-71. doi: 10.1002/mrm.21437.
A method is presented for high-resolution 3D imaging of the whole lung using inhaled hyperpolarized (HP) He-3 MR with multiple half-echo radial trajectories that can accelerate imaging through undersampling. A multiple half-echo radial trajectory can be used to reduce the level of artifact for undersampled 3D projection reconstruction (PR) imaging by increasing the amount of data acquired per unit time for HP He-3 lung imaging. The point spread functions (PSFs) for breath-held He-3 MRI using multiple half-echo trajectories were evaluated using simulations to predict the effects of T(2)* and gas diffusion on image quality. Results from PSF simulations were consistent with imaging results in volunteer studies showing improved image quality with increasing number of echoes using up to 8 half-echoes. The 8-half-echo acquisition is shown to accommodate lost breath-holds as short as 6 sec using a retrospective reconstruction at reduced resolution and also to allow reduced breath-hold time compared with an equivalent Cartesian trajectory. Furthermore, preliminary results from a 3D dynamic inhalation-exhalation maneuver are demonstrated using the 8-half-echo trajectory. Results demonstrate the first high-resolution 3D PR imaging of ventilation and respiratory dynamics in humans using HP He-3 MR.
本文介绍了一种使用吸入式超极化（HP）氦-3磁共振成像（MR）对全肺进行高分辨率三维成像的方法，该方法采用多个半回波径向轨迹，可通过欠采样加速成像。多个半回波径向轨迹可用于减少欠采样三维投影重建（PR）成像中的伪影水平，通过增加单位时间内采集的用于HP氦-3肺部成像的数据量来实现。使用模拟评估了使用多个半回波轨迹的屏气氦-3磁共振成像的点扩散函数（PSF），以预测T(2)*和气体扩散对图像质量的影响。PSF模拟结果与志愿者研究中的成像结果一致，表明随着回波数量增加（最多使用8个半回波），图像质量得到改善。结果表明，使用8个半回波采集时，通过降低分辨率的回顾性重建，可以适应短至6秒的屏气丢失情况，并且与等效的笛卡尔轨迹相比，还可以缩短屏气时间。此外，使用8个半回波轨迹展示了三维动态吸气-呼气动作的初步结果。结果证明了首次使用HP氦-3 MR对人体通气和呼吸动力学进行高分辨率三维PR成像。
