Oxygen-enhanced functional lung imaging using a contemporary 0.55 T MRI system.

Area of Science:

• Medical Imaging
• Pulmonary Medicine
• Magnetic Resonance Imaging

Background:

• Oxygen-enhanced MRI uses inhaled oxygen as a contrast agent to measure regional lung ventilation and perfusion.
• Low-field MRI systems (0.55T) with contemporary hardware can produce high-quality lung imaging due to prolonged T2*.
• Oxygen's T1 relaxivity increases at lower field strengths, potentially enhancing oxygen-enhanced lung MRI sensitivity.

Purpose of the Study:

• To evaluate oxygen-enhanced pulmonary imaging at 0.55T using a 3D stack-of-spirals ultrashort-TE (UTE) acquisition.
• To assess the repeatability of oxygen-enhanced lung MRI measurements.
• To compare signal enhancement in healthy volunteers and patients with lymphangioleiomyomatosis (LAM).

Main Methods:

• Implemented a breath-held T1-weighted 3D stack-of-spirals UTE acquisition with a 7ms spiral-out readout.
• Assessed measurement repeatability using five repetitions in healthy volunteers (n=7).
• Compared percent signal enhancement maps in healthy volunteers (n=15) and LAM patients (n=10), with voxel-wise correction for lung tissue density.

Main Results:

• Voxel-wise correction for lung tissue density improved the repeatability of percent signal enhancement maps (CV=34±16%).
• Healthy volunteers showed a mean percent signal enhancement of 9.0±3.5% at 0.55T.
• LAM patients exhibited reduced signal enhancement (5.4±4.8%, p=0.02) and significantly increased heterogeneity (30.5±13.1%, p=0.01) compared to healthy volunteers.

Conclusions:

• Oxygen-enhanced pulmonary MRI at 0.55T is feasible and repeatable with density correction.
• The technique can differentiate between healthy volunteers and LAM patients based on regional lung function.
• This method shows potential for measuring regional functional deficits in pulmonary diseases like LAM.