Design and Validation of a Patient-Specific Stereotactic Frame for Transcranial Ultrasound Therapy

Area of Science:

• Neurosurgery and Medical Devices
• Biomedical Engineering
• Medical Imaging and Ultrasound

Background:

• Transcranial-focused ultrasound (tFUS) requires precise brain targeting for procedures like neuromodulation and blood-brain barrier (BBB) opening.
• Magnetic Resonance Imaging (MRI) is the current standard for focus localization but is impractical for repeated therapies.
• Existing methods lack the precision and repeatability needed for frequent tFUS treatments outside of an MRI suite.

Purpose of the Study:

• To design, fabricate, and characterize a patient-specific, 3D-printed stereotactic frame for repeatable tFUS therapy.
• To enable precise transcranial FUS treatment without continuous MR-guidance after initial calibration.
• To assess the accuracy and consistency of focus placement using the novel stereotactic frame.

Main Methods:

• Developed and fabricated a compact, patient-specific 3D-printed stereotactic frame for tFUS.
• Assessed focus localization and repeatability using MR-thermometry (ex vivo) and MR-acoustic radiation force imaging (ARFI) (in vivo nonhuman primates).
• Performed initial MRI calibration for focal localization, registration, and steering, then tested re-steering accuracy.

Main Results:

• The stereotactic frame demonstrated sub-millimeter accuracy in target registration error (TRE) (1.2 ± 0.3 mm ex vivo, 1.0 ± 0.5 mm in vivo).
• Focus position remained consistent across sessions, with sub-millimeter variation in each dimension.
• The frame allowed for reliable positioning and orientation of the ultrasound transducer for repeated targeting.

Conclusions:

• The 3D-printed, patient-specific stereotactic frame provides reliable, high-precision targeting for repeated tFUS brain therapies.
• This innovative frame facilitates tFUS procedures outside of MRI scanners, potentially reducing treatment costs.
• The technology supports precise and repeatable transcranial FUS applications, advancing neuromodulation and BBB opening therapies.