Two-step aberration correction: application to transcranial histotripsy

Area of Science:

• Medical Physics
• Acoustic Imaging
• Neurosurgery

Background:

• Transcranial histotripsy requires accurate focusing through the skull.
• Skull bone heterogeneity causes significant focal distortion.
• Existing aberration correction methods have limitations in clinical settings.

Purpose of the Study:

• To improve a 2-step aberration correction (AC) method for transcranial histotripsy.
• To develop a clinically applicable AC workflow.
• To compensate for focal distortion caused by skull bone heterogeneity.

Main Methods:

• Implemented a 2-step AC workflow: computed tomography (CT)-based analytical approach followed by acoustic cavitation emission (ACE)-based approach.
• Utilized a 700 kHz, 360-element hemispherical transducer array for cavitation generation and ACE shockwave acquisition.
• Investigated forward and backward ray-tracing models for CT-based AC and cross-correlation for ACE-based AC.

Main Results:

• The 2-step AC achieved 90 ± 7% peak focal pressure compared to hydrophone correction.
• Reduced average focal shift from 0.84 mm to 0.30 mm.
• Decreased average focal volume from 10.6 mm³ to 2.0 mm³ compared to no AC.

Conclusions:

• The 2-step AC method provides superior refocusing compared to CT-AC or ACE-AC alone.
• This improved method can be implemented in real-time for transcranial histotripsy.
• The workflow is suitable for clinical application in brain therapy.