Free-breathing self-gated 4D lung MRI using wave-CAIPI

Area of Science:

• Medical Imaging
• Radiology
• Magnetic Resonance Imaging

Background:

• Accelerated MRI techniques are crucial for reducing scan times and improving patient comfort.
• Free-breathing 4D lung MRI presents challenges due to respiratory motion.
• Optimizing k-space trajectories is key to enhancing image quality in accelerated MRI.

Purpose of the Study:

• To compare the performance of the wave-CAIPI (controlled aliasing in parallel imaging) trajectory against standard Cartesian sampling for accelerated free-breathing 4D lung MRI.
• To evaluate the impact of wave-CAIPI on image quality metrics such as information loss and artifact levels.

Main Methods:

• Wave-CAIPI k-space trajectory implemented in a respiratory self-gated 3D spoiled gradient echo sequence.
• Image reconstruction using iterative conjugate gradient SENSE (CG SENSE) with trajectory correction.
• Quantitative comparison using normalized mutual information and RMS error in five healthy volunteers and one patient.

Main Results:

• Wave-CAIPI demonstrated 10% higher normalized mutual information, indicating lower information loss during acceleration.
• Root-mean-square (RMS) error was 19% lower, and signal-to-noise ratio (SNR) was 14% higher with wave-CAIPI.
• Undersampled Cartesian images showed increased artifacts at short acquisition times (down to 1 minute) compared to wave-CAIPI.

Conclusions:

• Wave-CAIPI effectively reduces undersampling artifacts in 4D lung MRI compared to Cartesian acquisition at the same scan time.
• The benefits of wave-CAIPI allow for either shorter scan durations or improved image quality in accelerated 4D lung MRI acquisitions.
• Wave-CAIPI is a promising technique for enhancing accelerated free-breathing 4D lung MRI.