Simultaneous MR thermometry and acoustic radiation force imaging using interleaved acquisition.

Area of Science:

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

Background:

• MR-guided focused ultrasound (MRgFUS) procedures require precise monitoring of tissue temperature and mechanical properties.
• Current methods may not offer simultaneous, dynamic assessment of both parameters.

Purpose of the Study:

• To develop and validate a novel method for simultaneous MR acoustic radiation force imaging (ARFI) and proton resonance frequency (PRF)-shift thermometry.
• To assess the utility of this combined technique for evaluating MRgFUS treatments.

Main Methods:

• A gradient recalled echo segmented echo-planar imaging sequence with bipolar motion encoding gradients was employed.
• Simultaneous ARFI displacement and PRF temperature maps were acquired by interleaving ultrasound ON/OFF acquisitions.
• Constrained reconstruction and subsampled k-space were utilized to improve temporal resolution.

Main Results:

• Simultaneous 2D and 3D maps of tissue displacement and temperature were successfully acquired with minimal heating (<1°C).
• Temperature map accuracy was comparable to standard PRF thermometry.
• 3D simultaneous mapping was achieved every 4.7 seconds with constrained reconstruction and subsampled k-space (R=4.33).

Conclusions:

• The developed sequence enables simultaneous, dynamic monitoring of tissue temperature and mechanical properties during procedures like thermal ablation.
• This technique offers a practical tool for assessing the efficacy and safety of MRgFUS treatments.