Design of a 16-channel TUS/MR head coil for concurrent neuromodulation and imaging
Poster No:
57
Submission Type:
Abstract Submission
Authors:
Lena Nohava1, Onisim Soanca1, Sarah Grosshagauer1, Michael Obermann1, Shota Hodono2, Bernardo Campilho1, Holger Hewener3, Steffen Tretbar3, Arno Schmitgen4, Sven Arnold4, Christian Windischberger5, Elmar Laistler1
Institutions:
1Medical University of Vienna, Vienna, Austria, 2Donders Centre for Cognitive Neuroimaging, Radboud University, Nijmegen, Nijmegen, 3Fraunhofer Institute for Biomedical Engineering IBMT, St. Ingbert, Germany, 4Localite GmbH, Bonn, Germany, 5Medical University of Vienna, Vienna, Vienna
First Author:
Co-Author(s):
Introduction:
Low intensity transcranical focused ultrasound (TUS) presents a novel non-invasive methodology for precise stimulation of deep brain targets (Baek et al., 2017; Fomenko et al., 2018). Due to its precision and penetration depth, TUS is a promising tool for the treatment of various psychiatric and neurological disorders. When combined with MRI, TUS displacement effects can be precisely localized with MR acoustic radiation force imaging (MR-ARFI) (McDannold & Maier, 2008; D. van den Heuvel et al., 2023) while TUS neuromodulatory effects can be assessed using fMRI (Lee et al., 2016; Yang et al., 2018).
In this work we introduce our novel 16-channel TUS/MR radiofrequency (RF) coil tailored for closed-loop individualized image-guided transcranial ultrasound stimulation (CITRUS). The coil accommodates up to two transducers with a stable yet highly flexible fixation mechanism to allow for precise positioning of transducers. In addition, it includes trackers for continuous tracking of transducer positions with neuronavigation setups. Performance was assessed in terms of signal-to-noise ratios (SNRs) and compared to a standard 20-channel reference coil.
In this work we introduce our novel 16-channel TUS/MR radiofrequency (RF) coil tailored for closed-loop individualized image-guided transcranial ultrasound stimulation (CITRUS). The coil accommodates up to two transducers with a stable yet highly flexible fixation mechanism to allow for precise positioning of transducers. In addition, it includes trackers for continuous tracking of transducer positions with neuronavigation setups. Performance was assessed in terms of signal-to-noise ratios (SNRs) and compared to a standard 20-channel reference coil.
Methods:
The RF coil design includes 16 receive channels in a custom 3D printed housing integrating two transducer fixation mechanisms which are placed over the temporal window for ideal stimulation of clinically relevant brain regions. Two of the 16 coil elements were designed as flexible coil segments, allowing for easier access in transducer mounting while maintaining full brain coverage. The CITRUS transducer fixation mechanism can be adjusted in multiple degrees of freedom from outside the RF coil housing without the need to manipulate in the limited space between coil and scalp. In the final setting, TUS is performed with up to two custom-made 256-element transducers operating at a frequency of 283 kHz (Fraunhofer IBMT, Sankt Ingbert, Germany). Importantly, these beam-steering transducers allow for moving the TUS focus without changing the mechanical setup. Both transducers can be employed individually or in cross-beam mode.
Coil performance was assessed in phantoms and in vivo via SNR and g-factor mapping. Following IRB-approval by Radboud University (Nijmegen, Netherlands) and written informed consent, a healthy volunteer was scanned at 3T MAGNETOM Prisma with the CITRUS coil and a standard 20-channel head coil (Siemens Healthineers, Erlangen, Germany). Anatomical scans (MP-RAGE, TR=2300 ms, TE=3 ms, flip angle=8˚, 1 mm3 isotropic resolution, FOV=256x256x192 mm3, GRAPPA=2) as well as GRE sequences were acquired to assess SNR and g-factors.
Coil performance was assessed in phantoms and in vivo via SNR and g-factor mapping. Following IRB-approval by Radboud University (Nijmegen, Netherlands) and written informed consent, a healthy volunteer was scanned at 3T MAGNETOM Prisma with the CITRUS coil and a standard 20-channel head coil (Siemens Healthineers, Erlangen, Germany). Anatomical scans (MP-RAGE, TR=2300 ms, TE=3 ms, flip angle=8˚, 1 mm3 isotropic resolution, FOV=256x256x192 mm3, GRAPPA=2) as well as GRE sequences were acquired to assess SNR and g-factors.
Results:
The coil design is shown in Figure 1. In Figure 2, the in-vivo imaging performance of the CITRUS coil is shown in comparison to the reference 20-channel coil. Imaging performance in terms of SNR is comparable to a 20-channel head coil, except for the smaller neck coverage. If transducers are present, this affects SNR only directly underneath the transducer due to RF transmit field shielding effects. The CITRUS coil provides slightly superior acceleration capabilities (lower g-factors) compared to the reference coil. This is of high importance for future applications of concurrent TUS and functional MRI.
Conclusions:
We have successfully built and tested a dedicated coil for concurrent TUS/MR measurements. With its flexible yet stable mounting options for up to two transducers, this coil provides the ideal characteristics for performing TUS/MR studies. Therefore, the CITRUS coil will enable efficient combined TUS/MRI studies and therefore contribute to the deeper investigation of TUS neuromodulation effects and optimized therapeutic applications.
Brain Stimulation:
Sonic/Ultrasound 1
Non-Invasive Stimulation Methods Other 2
Keywords:
FUNCTIONAL MRI
MRI
ULTRASOUND
Other - hardware development; MR coil; transcranial focused ultrasound
1|2Indicates the priority used for review
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Were any human subjects research approved by the relevant Institutional Review Board or ethics panel? NOTE: Any human subjects studies without IRB approval will be automatically rejected.
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Provide references using APA citation style.
van den Heuvel, D., Arbabi, A., Meijer, S., Kop, B., Chetverikov, A., Verhagen, L. & Norris, D.G. (2023). MR-ARFI using single-shot HASTE imaging to detect displacement due to transcranial ultrasound. Proceedings of the ESMRMB, 2023.
Fomenko, A., Neudorfer, C., Dallapiazza, R. F., Kalia, S. K., & Lozano, A. M. (2018). Low-intensity ultrasound neuromodulation: An overview of mechanisms and emerging human applications. Brain Stimulation, 11(6), 1209–1217. https://doi.org/10.1016/j.brs.2018.08.013
Lee, W., Kim, H.-C., Jung, Y., Chung, Y. A., Song, I.-U., Lee, J.-H., & Yoo, S.-S. (2016). Transcranial focused ultrasound stimulation of human primary visual cortex. Scientific Reports, 6(1), 34026. https://doi.org/10.1038/srep34026
McDannold, N., & Maier, S. E. (2008). Magnetic resonance acoustic radiation force imaging. Medical Physics, 35(8), 3748–3758. https://doi.org/10.1118/1.2956712
Yang, P.-F., Phipps, M. A., Newton, A. T., Chaplin, V., Gore, J. C., Caskey, C. F., & Chen, L. M. (2018). Neuromodulation of sensory networks in monkey brain by focused ultrasound with MRI guidance and detection. Scientific Reports, 8(1), 7993. https://doi.org/10.1038/s41598-018-26287-7