Pulmonary kinematics from tagged hyperpolarized helium-3 MRI

Purpose: To propose and test the feasibility of a novel method for quantifying 3D regional pulmonary kinematics from hyperpolarized helium-3 tagged MRI in human subjects using a tailored image processing pipeline and a recently developed nonrigid registration framework. Materials and Methods: Following image acquisition, inspiratory and expiratory tagged3He magnetic resonance (MR) images were preprocessed using various image filtering techniques to enhance the tag surfaces. Segmentation of the three orthogonal sets of tag planes in each lung produced distinct point-set representations of the tag surfaces. Using these labeled point-sets, deformation fields and corresponding strain maps were obtained via nonrigid point-set registration. Kinematic analysis was performed on three volunteers. Results: Tag lines in inspiratory and expiratory images were coregistered producing a continuous 3D correspondence mapping. Average displacement and directional strains were calculated in three subjects in the inferior, mid, and superior portions of the right and left lungs. As expected, the predominant direction of displacements with expiration is from inferior to superior. Conclusion: Kinematic quantitation of pulmonary motion using tagged3He MRI is feasible using the applied image preprocessing filtering techniques and nonrigid point-set registration. Potential benefits from regional pulmonary kinematic quantitation include the facilitation of diagnosis and local assessment of disease progression.