3D hyperpolarized He-3 MRI of ventilation using a multi-echo projection acquisition.

Area of Science:

• Medical Imaging
• Pulmonary Medicine
• Magnetic Resonance Imaging

Background:

• High-resolution 3D imaging of the lungs is crucial for diagnosing respiratory diseases.
• Current MRI techniques face challenges with speed and image quality for lung applications.

Purpose of the Study:

• To develop and evaluate a novel accelerated 3D projection reconstruction (PR) imaging method for hyperpolarized (HP) Helium-3 (He-3) MRI of the whole lung.
• To improve image quality and reduce artifacts in HP He-3 lung imaging through undersampled radial trajectories.

Main Methods:

• Utilized multiple half-echo radial trajectories for accelerated 3D PR imaging.
• Evaluated point spread functions (PSFs) via simulations to assess T(2)* and gas diffusion effects on image quality.
• Acquired data using up to 8 half-echoes and performed retrospective reconstruction.

Main Results:

• Simulations predicted and volunteer studies confirmed improved image quality with an increased number of echoes.
• The 8-half-echo acquisition accommodated short breath-holds (as short as 6 sec) with retrospective reconstruction.
• Demonstrated the first high-resolution 3D PR imaging of human lung ventilation and respiratory dynamics using HP He-3 MR.

Conclusions:

• Multiple half-echo radial trajectories significantly enhance image quality and data acquisition speed for HP He-3 lung MRI.
• This accelerated imaging method allows for robust 3D visualization of lung ventilation and dynamic respiratory maneuvers.
• The developed technique represents a significant advancement for non-invasive pulmonary imaging.