Quantitative lung perfusion mapping at 0.2 T using FAIR True-FISP MRI

Area of Science:

• Magnetic Resonance Imaging (MRI)
• Medical Physics
• Pulmonary Medicine

Background:

• Arterial spin labeling (ASL) techniques for lung perfusion imaging face challenges from microscopic field gradients caused by susceptibility differences between alveolar air and lung parenchyma.
• These field inhomogeneities significantly impact imaging accuracy, particularly at higher magnetic field strengths.

Purpose of the Study:

• To adapt a true fast imaging with steady precession (True-FISP) sequence for flow-sensitive alternating inversion recovery (FAIR) lung perfusion imaging.
• To assess the feasibility of noninvasive lung perfusion measurements using this adapted sequence at different field strengths (0.2 T and 1.5 T).

Main Methods:

• Assessed microscopic static field distribution in healthy volunteers at 0.2 T and 1.5 T using multiecho gradient-echo sequences.
• Simulated the influence of microscopic field inhomogeneities on True-FISP signal.
• Developed and optimized a FAIR True-FISP sequence for lung perfusion imaging at 0.2 T.

Main Results:

• Microscopic field inhomogeneities were significantly greater at 1.5 T (FWHM 180–277 Hz) compared to 0.2 T (FWHM 39–109 Hz).
• The developed FAIR True-FISP sequence at 0.2 T allowed for successful lung perfusion measurements.
• Average perfusion rates in peripheral lung regions ranged from 368 to 418 ml/100 g/min across different slice orientations.

Conclusions:

• Microscopic field inhomogeneities at 1.5 T were too pronounced for effective FAIR True-FISP lung perfusion imaging.
• The optimized FAIR True-FISP sequence at low field strength (0.2 T) is suitable for noninvasive lung perfusion examinations.