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Evaluation of a three-dimensional MR acoustic radiation force imaging pulse sequence using a novel unbalanced bipolar
Joshua T de Bever1, Henrik Odéen2, Nick Todd2
1School of Computing, Utah Center for Advanced Imaging Research, University of Utah, Salt Lake City, Utah, USA.
Magnetic Resonance in Medicine
|October 8, 2015
Summary
This study introduces a novel 3D pulse sequence for acoustic radiation force imaging (ARFI) to accurately localize the focal spot in MR guided focused ultrasound. The method ensures safety and efficiency, reducing tissue heating by 51%.
Area of Science:
- Medical Imaging
- Ultrasound Technology
- Magnetic Resonance Imaging
Background:
- Accurate focal spot localization is critical for MR guided focused ultrasound procedures.
- Current methods may lack precision or efficiency in three-dimensional localization.
Purpose of the Study:
- To present a novel three-dimensional (3D) pulse sequence for acoustic radiation force imaging (ARFI).
- To enable efficient and accurate focal spot localization using ultrasound-induced tissue displacement over a large field-of-view.
Main Methods:
- Implemented a novel unbalanced bipolar motion encoding gradient to optimize motion encoding time and reduce echo times.
- Utilized kz reduction factor (KZRF) and kz-level interleaving to minimize tissue heating.
- Compared displacement and temperature measurements in gelatin phantoms using 3D MR thermometry.
Main Results:
- Peak displacement and temperature rise locations agreed within 0.2 ± 0.1 mm (transverse) and 0.5 ± 0.3 mm (longitudinal).
- KZRF and kz-level interleaving reduced tissue heating by 51%.
- High-quality 3D displacement maps were acquired despite respiration and tissue inhomogeneities.
Conclusions:
- The developed sequence offers a safe, accurate, and simple method for 3D focal spot localization in a single scan.
- This advancement enhances the precision and safety of MR guided focused ultrasound treatments.
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