Multiple-point magnetic resonance acoustic radiation force imaging.

Area of Science:

• Medical Imaging
• Biophysics
• Ultrasound Technology

Background:

• Magnetic Resonance Acoustic Radiation Force Imaging (MR-ARFI) is vital for non-invasive tissue stiffness assessment.
• Current MR-ARFI methods often require lengthy acquisition times, limiting clinical applicability.
• Efficient volumetric tissue property mapping is essential for advanced therapeutic monitoring.

Purpose of the Study:

• To implement and validate an efficient multiple-point MR-ARFI pulse sequence.
• To enable volumetric measurement of tissue displacement and stiffness evaluation.
• To integrate MR-ARFI with focused ultrasound (FUS) for simultaneous temperature mapping.

Main Methods:

• Developed a gradient-recalled echo segmented EPI pulse sequence with bipolar motion-encoding gradients.
• Incorporated 2D and 3D acquisition modes with interleaved FUS-ON/FUS-OFF imaging.
• Implemented efficiency improvements: partial Fourier, parallel imaging, and multi-position encoding.

Main Results:

• Achieved 16-point MR-ARFI map acquisition in 5-10s (2D) and 60s (3D) in phantoms.
• Acquired 16-point MR-ARFI maps in 20s (3D) in ex vivo porcine brain.
• Observed a ~22% decrease in ex vivo brain tissue displacement post-FUS ablation.

Conclusions:

• Volumetric multiple-point MR-ARFI with simultaneous MR thermometry is feasible in clinically acceptable times.
• Efficiency improvements enable rapid, simultaneous measurement of tissue displacement and temperature.
• This technique holds promise for precise monitoring in FUS-based therapies.