FID-based lung MRI at 0.5 T: theoretical considerations and practical implications

Area of Science:

• Magnetic Resonance Imaging (MRI)
• Medical Physics
• Biomedical Engineering

Background:

• Magnetic Resonance Imaging (MRI) is crucial for non-invasive anatomical imaging.
• Lung MRI presents unique challenges due to motion and low proton density.
• Projection Reconstruction (PR) techniques offer potential for fast imaging but can be susceptible to artifacts.

Purpose of the Study:

• To investigate artifacts in lung MRI at 0.5 T using Free Induction Decay (FID) signals and PR.
• To evaluate the impact of k-space mismapping, cardiac motion, and respiratory motion on image quality.
• To determine the suitability of FID-based PR techniques for clinical lung MRI at this field strength.

Main Methods:

• Simulated and experimentally confirmed non-structured artifacts in lung MRI.
• Utilized FID signals and PR techniques at a 0.5 T magnetic field strength.
• Assessed artifacts arising from readout gradient waveform distortions and physiological motion.

Main Results:

• Non-structured artifacts were identified, simulated, and experimentally confirmed for the first time in this context.
• These artifacts did not prevent visualization of high signal-to-noise ratio (SNR) structures.
• Quantitative analysis of lung parenchyma intensity was significantly affected by these artifacts, leading to errors.

Conclusions:

• FID-based PR techniques are not justified for lung MRI at 0.5 T.
• Artifacts, particularly non-structured ones, introduce quantitative inaccuracies in lung parenchyma imaging.
• Further development of artifact mitigation strategies is needed for low-field lung MRI.