Department of Medical Physics, University of Wisconsin-Madison, Madison, Wisconsin, USA.
Magn Reson Med. 2009 Dec;62(6):1543-56. doi: 10.1002/mrm.22150.
The purpose of this work is to detect dynamic gas trapping in three dimensions during forced exhalation at isotropic high spatial resolution and high temporal resolution using hyperpolarized helium-3 MRI. Ten subjects underwent hyperpolarized helium-3 MRI and multidetector CT. MRI was performed throughout inspiration, breath-hold, and forced expiration. A multiecho three-dimensional projection acquisition was used to improve data collection efficiency and an iterative constrained reconstruction was implemented to improve signal to noise ratio (SNR) and increase robustness to motion. Two radiologists evaluated the dynamic MRI and breath-held multidetector CT data for gas and air trapping, respectively. Phantom studies showed the proposed technique significantly improved depiction of moving objects compared to view-sharing methods. Gas trapping was detected using MRI in five of the six asthmatic subjects who displayed air trapping with multidetector CT. Locations in disagreement were found to represent small to moderate regions of air trapping. The proposed technique provides whole-lung three-dimensional imaging of respiration dynamics at high spatial and temporal resolution and compares well to the current standard, multidetector CT. While multidetector CT can provide information about static regional air trapping, it is unable to depict dynamics in a setting more comparable to a spirometry maneuver and explore the longitudinal time evolution of the trapped regions.
本研究旨在使用极化氦-3 MRI 以各向同性高空间分辨率和高时间分辨率检测强制呼气过程中的动态气体陷闭。 10 名受试者接受了极化氦-3 MRI 和多排 CT 检查。 MRI 检查贯穿吸气、屏气和用力呼气。使用多回波三维投影采集来提高数据采集效率，并实施迭代约束重建以提高信噪比（SNR）并增强对运动的鲁棒性。两位放射科医生分别评估动态 MRI 和屏气多排 CT 数据中的气体和空气陷闭。 体模研究表明，与视图共享方法相比，所提出的技术显著改善了运动物体的描绘。在 6 名哮喘患者中，有 5 名患者通过 MRI 检测到气体陷闭，而多排 CT 检测到空气陷闭。不一致的部位被认为代表较小至中度的空气陷闭区域。所提出的技术可在高空间和时间分辨率下提供整个肺部呼吸动力学的三维成像，与当前标准的多排 CT 相比效果良好。 虽然多排 CT 可以提供关于静态区域性空气陷闭的信息，但它无法在更类似于肺活量测定操作的环境中描绘动态情况，并探索陷闭区域的纵向时间演变。
