Hyperpolarized ¹²⁹Xe MRI at low field: Current status and future directions

Area of Science:

• Medical Imaging
• Biophysics
• Pulmonary Medicine

Background:

• Magnetic Resonance Imaging (MRI) traditionally suffers from low sensitivity due to sample magnetization.
• Hyperpolarized (HP) noble gases (helium-3, xenon-129) offer a non-invasive, radiation-free alternative for high-resolution lung imaging.
• HP gases provide significantly higher MR signal, independent of tissue concentration, and improved signal at low magnetic fields.

Approach:

• This review details the spin-exchange optical-pumping method for hyperpolarization.
• It examines the field dependence of the MR signal for HP gases in human lung imaging.
• Advancements in low-field MRI hardware (scanners, RF coils, polarizers) and pulse sequences are explored.

Key Points:

• HP gas MRI achieves high sensitivity at low field strengths (<0.5 T), optimal for pulmonary imaging.
• Longer T2* relaxation times of HP gases allow for fewer RF pulses and larger flip angles.
• In vivo imaging of human and animal lungs is feasible with this high-sensitivity approach.

Conclusions:

• Low-field hyperpolarized gas MRI is a promising, clinically accessible tool for pulmonary diagnostics.
• It overcomes siting limitations of high-field scanners, enabling point-of-care imaging globally.
• Future developments focus on hardware and acquisition techniques for versatile pulmonary MRI applications.