Free-breathing time-resolved 4D MRI with improved T1-weighting contrast

Area of Science:

• Magnetic Resonance Imaging (MRI)
• Medical Imaging Technology
• Radiology

Background:

• Time-resolved 4D MRI techniques are crucial for capturing dynamic physiological processes, particularly in free-breathing scenarios.
• Standard 4D MRI methods often face challenges with motion artifacts and suboptimal contrast, limiting diagnostic accuracy.
• Improving T1-weighted contrast in dynamic MRI is essential for better tissue characterization and lesion detection.

Purpose of the Study:

• To introduce and evaluate MP-Grasp4D (magnetization-prepared golden-angle radial sparse parallel 4D) MRI, a novel free-breathing, time-resolved 4D MRI technique.
• To assess the capability of MP-Grasp4D MRI in improving T1-weighted contrast and image quality compared to standard 4D MRI.
• To demonstrate the potential for accelerated acquisition with preserved image quality using MP-Grasp4D MRI.

Main Methods:

• MP-Grasp4D MRI integrates inversion recovery (IR) preparation into a golden-angle radial gradient echo sequence with navigator data.
• A low-rank subspace-constrained reconstruction using navigator stacks enables simultaneous capture of contrast changes and respiratory motion.
• Temporal resolution of 0.16 seconds per volume is achieved, allowing retrospective selection of optimal inversion times (TI) for contrast enhancement.

Main Results:

• MP-Grasp4D MRI demonstrated significantly higher image quality scores compared to standard Grasp4D MRI in reader studies (P < 0.05).
• Reader agreement for image quality assessment was moderate to almost perfect (kappa coefficient 0.42–0.9).
• MP-Grasp4D MRI maintained image contrast and quality even with reduced scan times, indicating acceleration capabilities.

Conclusions:

• MP-Grasp4D MRI significantly improves T1-weighted contrast for free-breathing, time-resolved 4D MRI.
• The technique effectively captures dynamic contrast changes and respiratory motion without requiring explicit motion compensation.
• MP-Grasp4D MRI shows promise for various applications, including MR-guided radiotherapy, due to its enhanced contrast and motion-robustness.