Transcranial phase aberration correction using beam simulations and MR-ARFI.

Area of Science:

• Medical Imaging
• Acoustic Physics
• Neurosurgery

Background:

• Transcranial MR-guided focused ultrasound surgery (MRgFUS) offers noninvasive tissue ablation.
• Skull variations distort the focused ultrasound beam, impacting treatment precision.
• Accurate focusing is crucial for therapeutic efficacy and minimizing off-target effects.

Purpose of the Study:

• To develop and validate a hybrid simulation-MR-ARFI technique for correcting skull-induced phase aberrations in MRgFUS.
• To improve the accuracy of focal zone targeting during transcranial MRgFUS procedures.
• To enhance the safety and effectiveness of noninvasive ultrasound surgery.

Main Methods:

• A hybrid approach combining ultrasound beam propagation simulations with MR Acoustic Radiation Force Imaging (MR-ARFI) was employed.
• Numerical skull-based aberrations were applied to a focused ultrasound transducer model.
• MR-ARFI was used to estimate and correct for phase aberrations caused by the skull.
• Experiments were conducted using 16 and 1024 aberration elements, with repetitions for robustness.

Main Results:

• The hybrid technique demonstrated significant improvements in focal MR-ARFI phase.
• An average increase in focal MR-ARFI phase of 44% (16 aberrations) and 52% (1024 aberrations) was achieved.
• The method recovered 83% of ideal MR-ARFI phase for 16 aberrations and 39% for 1024 aberrations.

Conclusions:

• The hybrid simulation-MR-ARFI technique effectively corrects skull-induced phase aberrations in MRgFUS.
• This method enhances the maximum MR-ARFI phase at the beam's focus without prior aberration data.
• The technique holds promise for improving the precision of transcranial focused ultrasound therapies.