Fourier decomposition pulmonary MRI using a variable flip angle balanced steady-state free precession technique

Area of Science:

• Medical Imaging
• Pulmonary Function Assessment
• Biophysics

Background:

• Fourier decomposition (FD) is a noninvasive technique for evaluating lung ventilation and perfusion.
• A key limitation of FD is its low signal-to-noise ratio (SNR) in lung parenchyma.
• Improving SNR is crucial for enhancing the diagnostic value of FD imaging.

Purpose of the Study:

• To develop and validate an approach for increasing SNR in both morphological and functional FD lung images.
• To optimize the balanced steady-state free precession (bSSFP) sequence for FD imaging.
• To assess the impact of the proposed method on image artifacts and resolution.

Main Methods:

• Utilized a variable flip angle approach within a bSSFP sequence to optimize FD image acquisition.
• Standard bSSFP sequences are limited by specific absorption rate (SAR) constraints on flip angles.
• Validated the method using phantom measurements and imaging of six healthy volunteers.

Main Results:

• Achieved a 32% increase in SNR for both morphological and functional FD images.
• Maintained existing SAR limitations while enhancing image quality.
• Observed a visible improvement in the effective resolution of functional images due to higher SNR.
• The variable flip angle approach minimized blurring artifacts and did not introduce new transient artifacts.

Conclusions:

• The FD method, when combined with a variable flip angle optimized bSSFP sequence, effectively increases SNR in functional lung images.
• This optimization leads to a significant gain in effective resolution for functional lung imaging.
• The proposed approach offers a promising method for improved noninvasive assessment of lung ventilation and perfusion.