Human lung air spaces: potential for MR imaging with hyperpolarized He-3

Area of Science:

• Medical Imaging
• Pulmonary Medicine
• Nuclear Magnetic Resonance

Background:

• Laser-polarized noble gases, such as helium-3 (³He), offer unique contrast mechanisms for magnetic resonance imaging (MRI).
• Pulmonary MRI is crucial for diagnosing and monitoring lung diseases, but traditional MRI faces challenges due to the low proton density and rapid motion within the lungs.

Purpose of the Study:

• To evaluate the feasibility and image quality of 1.5 T MRI using inhaled laser-polarized helium-3 gas in healthy volunteers.
• To assess the potential of this technique for both qualitative and quantitative imaging of lung structures.

Main Methods:

• Two healthy volunteers inhaled approximately 0.75 L of laser-polarized helium-3 gas.
• Magnetic resonance imaging was performed at 1.5 T using fast gradient-echo pulse sequences with small flip angles (<10 degrees).
• Thick-section (20 mm) coronal images, time-course data (30 images/1.8 sec), and thin-section (6 mm) images were acquired.

Main Results:

• Subjects tolerated the 12% polarized helium-3 gas inhalation without difficulty.
• Thick-section images demonstrated good quality with signal-to-noise ratios (S/N) of 32:1 (near coil) and 16:1 (farther away).
• Time-course images revealed regional differences, suggesting quantitative potential, while high-resolution images provided greater detail (S/N ~6:1).

Conclusions:

• Inhaled laser-polarized helium-3 MRI is a well-tolerated and effective method for imaging the lungs in healthy individuals.
• The technique provides good image quality and shows promise for quantitative assessment of lung ventilation and regional differences.