Phase-cycled balanced SSFP imaging for non-contrast-enhanced functional lung imaging.

Area of Science:

• Magnetic Resonance Imaging
• Medical Imaging Physics
• Pulmonary Function Testing

Background:

• Fourier decomposition MRI is crucial for lung function assessment.
• Field inhomogeneities can cause signal loss and artifacts in MRI.
• Balanced steady-state free precession (bSSFP) is a common MRI sequence.

Purpose of the Study:

• To introduce phase-cycled bSSFP as an alternative MRI technique.
• To improve robustness against magnetic field inhomogeneities.
• To enhance lung function assessment using MRI.

Main Methods:

• Acquired 2D dynamic lung images in 5 volunteers at 1.5 T and 3 T.
• Utilized bSSFP sequence with multiple RF phase increments.
• Compared phase-cycled acquisitions with conventional single-phase acquisitions.
• Evaluated functional map homogeneity, SNR, and contrast-to-noise ratio.

Main Results:

• Phase-cycled acquisitions showed improved robustness against signal loss at both field strengths.
• Ventilation maps demonstrated significantly better homogeneity with phase-cycled bSSFP.
• Coefficient of variation in ventilation maps was lower for phase-cycled acquisitions (29.7±2.6 at 1.5 T, 37.5±3.1 at 3 T) compared to single-phase (39.9±5.2 at 1.5 T, 49.5±3.7 at 3 T).

Conclusions:

• Phase-cycled bSSFP enhances robustness against field inhomogeneity artifacts.
• This method significantly improves ventilation map homogeneity in lung imaging.
• Phase-cycled bSSFP offers a robust alternative for lung function assessment.