Steerable transcranial ultrasound stimulation (TUS) validated by acoustic radiation force imaging
Poster No:
95
Submission Type:
Abstract Submission
Authors:
Bernardo Campilho1, Holger Hewener2, Aidin Arbabi3, Sarah Grosshagauer1, Christoph Risser2, Dann Heuvel3, Jose Marques4, Christian Degel2, Steffen Tretbar2, David Norris4, Christian Windischberger5
Institutions:
1Medical University of Vienna, Vienna, Vienna, 2Department Ultrasound, Fraunhofer Institute for Biomedical Engineering IBMT, Sankt Ingbert, Saarland, 3Donders Institute, Radboud University, Nijmegen, Gelderland, 4Donders Institute for Brain, Cognition and Behaviour, Radboud University, Nijmegen, Gelderland, 5Medical University of Vienna, Vienna, Austria
First Author:
Co-Author(s):
Holger Hewener
Department Ultrasound, Fraunhofer Institute for Biomedical Engineering IBMT
Sankt Ingbert, Saarland
Department Ultrasound, Fraunhofer Institute for Biomedical Engineering IBMT
Sankt Ingbert, Saarland
Christoph Risser
Department Ultrasound, Fraunhofer Institute for Biomedical Engineering IBMT
Sankt Ingbert, Saarland
Department Ultrasound, Fraunhofer Institute for Biomedical Engineering IBMT
Sankt Ingbert, Saarland
Jose Marques
Donders Institute for Brain, Cognition and Behaviour, Radboud University
Nijmegen, Gelderland
Donders Institute for Brain, Cognition and Behaviour, Radboud University
Nijmegen, Gelderland
Christian Degel
Department Ultrasound, Fraunhofer Institute for Biomedical Engineering IBMT
Sankt Ingbert, Saarland
Department Ultrasound, Fraunhofer Institute for Biomedical Engineering IBMT
Sankt Ingbert, Saarland
Steffen Tretbar
Department Ultrasound, Fraunhofer Institute for Biomedical Engineering IBMT
Sankt Ingbert, Saarland
Department Ultrasound, Fraunhofer Institute for Biomedical Engineering IBMT
Sankt Ingbert, Saarland
David Norris
Donders Institute for Brain, Cognition and Behaviour, Radboud University
Nijmegen, Gelderland
Donders Institute for Brain, Cognition and Behaviour, Radboud University
Nijmegen, Gelderland
Introduction:
Transcranial Ultrasound Stimulation (TUS) is a non-invasive technique that has considerable potential in the field of neuromodulation, given its spatial precision in the millimetre range and ability to reach deep targets in the human brain (Yaakub et al., 2023). Combining TUS with Magnetic Resonance Acoustic Radiation Force Imaging (MR-ARFI; Darmani et al., 2022) potentially enables the assessment of stimulation focus and intensity, both of which are extremely important for stimulation validation. Different to monitoring approaches based on temperature rises as used in high-intensity focussed ultrasound (HIFU), MR-ARFI assesses TUS effects via MR signal phase changes from subtle tissue displacements (Pauly, 2015). Due to the correlation between tissue displacement (quantified by phase difference maps) at a given position and the acoustic intensity of the beam there, MR-ARFI offers an opportunity for real-time target validation. This is essential not only for safety reasons, but also to validate the acoustic simulations and make sure the desired stimulation outcomes are reached. We extend our previous work on MR-ARFI (van den Heuvel et al., 2023) by showing how a novel using 256-element transducers allows for well-defined steering of the TUS focus by changing stimulation parameters without any change in the setup.
Methods:
Our method uses a novel setup consisting of a custom-made MR-compatible, 256-element TUS system for precise beam steering, as well as a developed framework for TUS stimulation control, from which the desired acoustic intensity can be controlled. The focus localization is done using an MR-ARFI sequence (van den Heuvel, 2023) as the imaging method. Images (1.5x1.5x5mm3 voxel size, TE/TR=80/1000, 32 averages) are acquired with and without TUS sonication, in an interleaved scheme. A soft tofu phantom (e.g., McGarry et al., 2013) is used to simulate brain tissue, given their similar density and acoustic properties. Sonication was performed at 283kHz with a duration of 19ms.
This study involves two separate experiments, designed to address the current challenges encountered in TUS implementation. Beam steering capabilities of the system are verified by varying the specified focus coordinates to the corners of a 10mm by 10mm square. Intensity effects were tested by varying voltages from 20V to 80V (Figure 2).
This study involves two separate experiments, designed to address the current challenges encountered in TUS implementation. Beam steering capabilities of the system are verified by varying the specified focus coordinates to the corners of a 10mm by 10mm square. Intensity effects were tested by varying voltages from 20V to 80V (Figure 2).
Results:
Our beam steering experiment validates the ability of the developed system to precisely control the location of the ultrasound focus (Figure 1), as well as its intensity (Figure 2). From Figure 1, we can see that the focus shifts to the desired position with a high degree of accuracy. Moreover, despite the presence of slight artefacts arising from the fragile structure of the used tofu phantom, it is clear that the focus intensity is quadrant-independent, which suggests consistent results regardless of the chosen steering direction.
Regarding the voltage experiment (Figure 2), the gradual transition of the intensity of the focus is in agreement with the linear relationship found in previous studies (e.g., Li et al., 2022). This predictability is important for acoustic dose planning, particularly in clinical applications, where precise knowledge of the acoustic intensity is critical.
Regarding the voltage experiment (Figure 2), the gradual transition of the intensity of the focus is in agreement with the linear relationship found in previous studies (e.g., Li et al., 2022). This predictability is important for acoustic dose planning, particularly in clinical applications, where precise knowledge of the acoustic intensity is critical.
Conclusions:
Here we have shown that MR-ARFI can be used to measure TUS effects with high spatial resolution. As expected, phase changes at the focus were increasing with the voltage used. Beam steering capabilities were successfully demonstrated by shifting focus location around the initial central target. Our proposed TUS-MRI setup shows that multi-element TUS transducers enable precise steering of the TUS focus without any change in the mechanical setup. This enables online adjustments to not only compensate for discrepancies between simulation results and accrual sonication effects, but also to switch stimulation targets on-the-fly, i.e. during an TUS/MR experiment.
Brain Stimulation:
Sonic/Ultrasound 1
Modeling and Analysis Methods:
Methods Development 2
Novel Imaging Acquisition Methods:
Imaging Methods Other
Keywords:
HIGH FIELD MR
ULTRASOUND
Other - ARFI, TUS
1|2Indicates the priority used for review
Provide references using author date format
Li, N., Gaur, P., Quah, K., & Butts Pauly, K. (2022), “Improving in situ acoustic intensity estimates using MR acoustic radiation force imaging in combination with multifrequency MR elastography”, Magnetic Resonance in Medicine, 88(4), 1673-1689.
McGarry, Matthew, et al. (2013), "Including spatial information in nonlinear inversion MR elastography using soft prior regularization", IEEE transactions on medical imaging, 32.10: 1901-1909.
Pauly, K. B. (2015), “Magnetic resonance acoustic radiation force (impulse) imaging (MR-ARFI)”, Journal of Therapeutic Ultrasound, 3(1), 1-1.
van den Heuvel, D., et al (2023), Proc. of the ESMRMB, P204
Yaakub, Siti N., et al. (2023), "Transcranial focused ultrasound-mediated neurochemical and functional connectivity changes in deep cortical regions in humans.", Nature Communications: 5318.