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Author Spotlight: Advancing Human Brain Modulation – Optimized Protocols for Transcranial Ultrasound Stimulation Experiments
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Enhancing transcranial ultrasound stimulation planning with MRI-derived skull masks: a comparative analysis with
Ali K Zadeh1,2, Oula Puonti3,4, Björn Sigurðsson3,5
1Department of Clinical Neurosciences, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada.
Journal of Neural Engineering
|January 30, 2025
Summary
Magnetic resonance imaging (MRI)-derived skull masks offer accurate transcranial ultrasound stimulation (TUS) planning, especially with custom settings. Careful site selection is crucial due to location-specific errors, improving TUS safety and efficacy.
Area of Science:
- Neuroscience
- Biomedical Engineering
- Medical Imaging
Background:
- Transcranial ultrasound stimulation (TUS) faces challenges in ultrasound wave transmission due to skull aberration and attenuation.
- Current 3D computed tomography (CT) based planning involves radiation exposure, raising ethical concerns.
- Magnetic resonance imaging (MRI) offers a radiation-free alternative for generating skull models.
Purpose of the Study:
- To compare ultrasound field predictions using CT-derived versus MRI-derived skull masks for TUS planning.
- To evaluate the accuracy of MRI-derived skull masks generated with different segmentation settings.
- To assess the impact of skull density variations on TUS simulation accuracy.
Main Methods:
- Ultrasound simulations were conducted using BabelBrain software with a single-element transducer across various frequencies (250, 500, 750 kHz).
- CT scans provided acoustic skull properties, while MRI scans were segmented using the Charm tool (default and custom settings).
- Simulations targeted 30 mm below the skull surface at 54 electroencephalogram (EEG) locations for five participants with diverse skull density ratios.
Main Results:
- Custom Charm settings significantly improved the Dice coefficient and reduced maximum pressure error compared to default settings (p < 0.001).
- Focus location errors were comparable between CT- and MRI-derived masks using custom settings, averaging 2.08, 1.38, and 1.44 mm for 250, 500, and 750 kHz.
- MRI-derived masks demonstrated satisfactory accuracy at many EEG sites, with custom settings enhancing precision.
Conclusions:
- MRI-derived skull masks, particularly with custom segmentation, provide a viable, radiation-free alternative for TUS planning.
- While generally accurate, significant location-specific errors necessitate careful consideration of stimulation targets.
- The findings support the use of MRI-based skull modeling to improve TUS planning while minimizing participant radiation exposure.
