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Daneshzand M, Guerin B, Kotlarz P, Chou T, Dougherty DD, Edlow BL, Nummenmaa A. Model-based navigation of transcranial focused ultrasound neuromodulation in humans: Application to targeting the amygdala and thalamus. Brain Stimul 2024; 17:958-969. [PMID: 39094682 DOI: 10.1016/j.brs.2024.07.019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2024] [Revised: 07/22/2024] [Accepted: 07/29/2024] [Indexed: 08/04/2024] Open
Abstract
BACKGROUND Transcranial focused ultrasound (tFUS) neuromodulation has shown promise in animals but is challenging to translate to humans because of the thicker skull that heavily scatters ultrasound waves. OBJECTIVE We develop and disseminate a model-based navigation (MBN) tool for acoustic dose delivery in the presence of skull aberrations that is easy to use by non-specialists. METHODS We pre-compute acoustic beams for thousands of virtual transducer locations on the scalp of the subject under study. We use the hybrid angular spectrum solver mSOUND, which runs in ∼4 s per solve per CPU yielding pre-computation times under 1 h for scalp meshes with up to 4000 faces and a parallelization factor of 5. We combine this pre-computed set of beam solutions with optical tracking, thus allowing real-time display of the tFUS beam as the operator freely navigates the transducer around the subject' scalp. We assess the impact of MBN versus line-of-sight targeting (LOST) positioning in simulations of 13 subjects. RESULTS Our navigation tool has a display refresh rate of ∼10 Hz. In our simulations, MBN increased the acoustic dose in the thalamus and amygdala by 8-67 % compared to LOST and avoided complete target misses that affected 10-20 % of LOST cases. MBN also yielded a lower variability of the deposited dose across subjects than LOST. CONCLUSIONS MBN may yield greater and more consistent (less variable) ultrasound dose deposition than transducer placement with line-of-sight targeting, and thus could become a helpful tool to improve the efficacy of tFUS neuromodulation.
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Affiliation(s)
- Mohammad Daneshzand
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Charlestown, MA, USA; Harvard Medical School, Boston, MA, USA
| | - Bastien Guerin
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Charlestown, MA, USA; Harvard Medical School, Boston, MA, USA.
| | - Parker Kotlarz
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Charlestown, MA, USA; Harvard Medical School, Boston, MA, USA
| | - Tina Chou
- Harvard Medical School, Boston, MA, USA; Department of Psychiatry, Massachusetts General Hospital, Charlestown, MA, USA
| | - Darin D Dougherty
- Harvard Medical School, Boston, MA, USA; Department of Psychiatry, Massachusetts General Hospital, Charlestown, MA, USA
| | - Brian L Edlow
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Charlestown, MA, USA; Harvard Medical School, Boston, MA, USA; Center for Neurotechnology and Neurorecovery, Department of Neurology, Massachusetts General Hospital, Boston, MA, USA
| | - Aapo Nummenmaa
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Charlestown, MA, USA; Harvard Medical School, Boston, MA, USA
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2
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Xu R, Bestmann S, Treeby BE, Martin E. Strategies and safety simulations for ultrasonic cervical spinal cord neuromodulation. Phys Med Biol 2024; 69:125011. [PMID: 38788727 DOI: 10.1088/1361-6560/ad506f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2024] [Accepted: 05/24/2024] [Indexed: 05/26/2024]
Abstract
Objective. Focused ultrasound spinal cord neuromodulation has been demonstrated in small animals. However, most of the tested neuromodulatory exposures are similar in intensity and exposure duration to the reported small animal threshold for possible spinal cord damage. All efforts must be made to minimize the risk and assure the safety of potential human studies, while maximizing potential treatment efficacy. This requires an understanding of ultrasound propagation and heat deposition within the human spine.Approach. Combined acoustic and thermal modelling was used to assess the pressure and heat distributions produced by a 500 kHz source focused to the C5/C6 level via two approaches (a) the posterior acoustic window between vertebral posterior arches, and (b) the lateral intervertebral foramen from which the C6 spinal nerve exits. Pulse trains of fifty 0.1 s pulses (pulse repetition frequency: 0.33 Hz, free-field spatial peak pulse-averaged intensity: 10 W cm-2) were simulated for four subjects and for ±10 mm translational and ±10∘rotational source positioning errors.Main results.Target pressures ranged between 20%-70% of free-field spatial peak pressures with the posterior approach, and 20%-100% with the lateral approach. When the posterior source was optimally positioned, peak spine heating values were below 1 ∘C, but source mispositioning resulted in bone heating up to 4 ∘C. Heating with the lateral approach did not exceed 2 ∘C within the mispositioning range. There were substantial inter-subject differences in target pressures and peak heating values. Target pressure varied three to four-fold between subjects, depending on approach, while peak heating varied approximately two-fold between subjects. This results in a nearly ten-fold range between subjects in the target pressure achieved per degree of maximum heating.Significance. This study highlights the utility of trans-spine ultrasound simulation software and need for precise source-anatomy positioning to assure the subject-specific safety and efficacy of focused ultrasound spinal cord therapies.
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Affiliation(s)
- Rui Xu
- Department of Medical Physics and Biomedical Engineering, University College London, London, United Kingdom
- Wellcome/EPSRC Centre for Interventional and Surgical Sciences, University College London, London, United Kingdom
| | - Sven Bestmann
- Department of Clinical and Movement Neuroscience, University College London, London, United Kingdom
| | - Bradley E Treeby
- Department of Medical Physics and Biomedical Engineering, University College London, London, United Kingdom
| | - Eleanor Martin
- Department of Medical Physics and Biomedical Engineering, University College London, London, United Kingdom
- Wellcome/EPSRC Centre for Interventional and Surgical Sciences, University College London, London, United Kingdom
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Yang Y, Duan H, Zheng Y. Improved Transcranial Plane-Wave Imaging With Learned Speed-of-Sound Maps. IEEE TRANSACTIONS ON MEDICAL IMAGING 2024; 43:2191-2201. [PMID: 38271172 DOI: 10.1109/tmi.2024.3358307] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2024]
Abstract
Although transcranial ultrasound plane-wave imaging (PWI) has promising clinical application prospects, studies have shown that variable speed-of-sound (SoS) would seriously damage the quality of ultrasound images. The mismatch between the conventional constant velocity assumption and the actual SoS distribution leads to the general blurring of ultrasound images. The optimization scheme for reconstructing transcranial ultrasound image is often solved using iterative methods like full-waveform inversion. These iterative methods are computationally expensive and based on prior magnetic resonance imaging (MRI) or computed tomography (CT) information. In contrast, the multi-stencils fast marching (MSFM) method can produce accurate time travel maps for the skull with heterogeneous acoustic speed. In this study, we first propose a convolutional neural network (CNN) to predict SoS maps of the skull from PWI channel data. Then, use these maps to correct the travel time to reduce transcranial aberration. To validate the performance of the proposed method, numerical, phantom and intact human skull studies were conducted using a linear array transducer (L11-5v, 128 elements, pitch = 0.3 mm). Numerical simulations demonstrate that for point targets, the lateral resolution of MSFM-restored images increased by 65%, and the center position shift decreased by 89%. For the cyst targets, the eccentricity of the fitting ellipse decreased by 75%, and the center position shift decreased by 58%. In the phantom study, the lateral resolution of MSFM-restored images was increased by 49%, and the position shift was reduced by 1.72 mm. This pipeline, termed AutoSoS, thus shows the potential to correct distortions in real-time transcranial ultrasound imaging, as demonstrated by experiments on the intact human skull.
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4
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Seo H, Han M, Choi JR, Kim S, Park J, Lee EH. Numerical Investigation of Layered Homogeneous Skull Model for Simulations of Transcranial Focused Ultrasound. Neuromodulation 2024:S1094-7159(24)00072-2. [PMID: 38691075 DOI: 10.1016/j.neurom.2024.04.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2024] [Revised: 03/24/2024] [Accepted: 04/02/2024] [Indexed: 05/03/2024]
Abstract
BACKGROUND AND OBJECTIVES The influence of the intracranial pressure field must be discussed with the development of a single-element transducer for low-intensity transcranial focused ultrasound because the skull plays a significant role in blocking and dispersing ultrasound wave propagation. Ultrasound propagation is mainly affected by the structure and acoustic properties of the skull; thus, we aimed to investigate the impact of simplifying the acoustic properties of the skull on the simulation of the transcranial pressure field to present guidance for efficient skull modeling in full-wave simulations. MATERIALS AND METHODS We constructed a three-dimensional computational model for ultrasound transmission with the same structure but varying acoustic properties of the skull. The structural information and heterogeneous acoustic properties of the skull were acquired from computed tomography images, and we segmented the skull into three layers (3 L), including spongy and compact bones. We then assigned homogeneous acoustic properties to a single layer (1 L) or 3 L of the skull. In addition, we investigated the influence of different types of transducers and different ultrasound frequencies (1.1 MHz, 0.5 MHz, and 0.25 MHz) on the intracranial pressure field to provide a comparison of the heterogenous and homogeneous models. RESULTS We indicated the importance of numerical simulations in estimating the intracranial pressure field of the skull owing to beam distortions. When we simplified the skull model, both the 1 L and 3 L models showed contours of the acoustic focus comparable to those of the heterogeneous model. When we evaluated the peak pressure and volume of the acoustic focus, the 1 L model produced a better estimation of peak pressure with a difference <10%, and the 3 L model is suitable to obtain smaller errors in the volume of the acoustic focus. CONCLUSIONS In conclusion, we examined the possibility of simplification of skull models using 1 L and 3 L homogeneous properties in the numerical simulation for focused ultrasound. The results show that the layered homogeneous model can provide characteristics comparable to those of the acoustic focus in heterogeneous models.
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Affiliation(s)
- Hyeon Seo
- Department of AI Convergence Engineering, Gyeongsang National University, Jinju, Republic of Korea; Department of Computer Science, Gyeongsang National University, Jinju, Republic of Korea
| | - Mun Han
- Medical Device Development Center, Daegu-Gyeongbuk Medical Innovation Foundation (K-MEDI hub), Daegu, Korea
| | - Jong-Ryul Choi
- Medical Device Development Center, Daegu-Gyeongbuk Medical Innovation Foundation (K-MEDI hub), Daegu, Korea
| | - Seungmin Kim
- Medical Device Development Center, Daegu-Gyeongbuk Medical Innovation Foundation (K-MEDI hub), Daegu, Korea
| | - Juyoung Park
- Medical Device Development Center, Daegu-Gyeongbuk Medical Innovation Foundation (K-MEDI hub), Daegu, Korea; Department of High-Tech Medical Device, College of Future Industry, Gachon University, Seongnam, Korea
| | - Eun-Hee Lee
- Medical Device Development Center, Daegu-Gyeongbuk Medical Innovation Foundation (K-MEDI hub), Daegu, Korea.
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5
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Shen F, Fan F, Li F, Wang L, Wang R, Wang Y, Liu T, Wei C, Niu H. An efficient method for transcranial ultrasound focus correction based on the coupling of boundary integrals and finite elements. ULTRASONICS 2024; 137:107181. [PMID: 37847943 DOI: 10.1016/j.ultras.2023.107181] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/09/2023] [Revised: 09/21/2023] [Accepted: 10/08/2023] [Indexed: 10/19/2023]
Abstract
Transcranial focused ultrasound is a novel technique for the noninvasive treatment of brain diseases. The success of the treatment greatly depends on achieving precise and efficient intraoperative focus. However, compensating for aberrated ultrasound waves caused by the skull through numerical simulation-based phase corrections is a challenging task due to the significant computational burden involved in solving the acoustic wave equation. In this article, we propose a promising strategy using the coupling of the boundary integral equation method (BIEM) and the finite element method (FEM) to overcome the above limitation. Specifically, we adopt the BIEM to obtain the Robin-to-Dirichlet maps on the boundaries of the skull and then couple the maps to the FEM matrices via a dual interpolation technique, resulting in a computational domain including only the skull. Three simulation experiments were conducted to evaluate the effectiveness of the proposed method, including a convergence test and two skull-induced aberration corrections in 2D and 3D ultrasound. The results show that the method's convergence is guaranteed as the element size decreases, leading to a decrease in pressure error. The computation times for simulating a 500 kHz ultrasound field on a regular desktop computer were found to be 0.47 ± 0.01 s in the 2D case and 43.72 ± 1.49 s in the 3D case, provided that lower-upper decomposition (approximately 13 s in 2D and 2.5 h in 3D) was implemented in advance. We also demonstrated that more accurate transcranial focusing can be achieved by phase correction compared to the noncorrected results (with errors of 1.02 mm vs. 6.45 mm in 2D and 0.28 mm vs. 3.07 mm in 3D). The proposed strategy is valuable for enabling online ultrasound simulations during treatment, facilitating real-time adjustments and interventions.
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Affiliation(s)
- Fei Shen
- School of Biological Science and Medical Engineering, Beihang University, Beijing, China
| | - Fan Fan
- School of Biological Science and Medical Engineering, Beihang University, Beijing, China
| | - Fengji Li
- School of Biological Science and Medical Engineering, Beihang University, Beijing, China
| | - Li Wang
- School of Biological Science and Medical Engineering, Beihang University, Beijing, China
| | - Rui Wang
- School of Biological Science and Medical Engineering, Beihang University, Beijing, China
| | - Yue Wang
- School of Biological Science and Medical Engineering, Beihang University, Beijing, China
| | - Tao Liu
- School of Biological Science and Medical Engineering, Beihang University, Beijing, China
| | - Cuibai Wei
- Department of Neurology, Xuan Wu Hospital, Capital Medical University, Beijing 100050, China
| | - Haijun Niu
- School of Biological Science and Medical Engineering, Beihang University, Beijing, China.
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6
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Xu P, Wu N, Shen G. A rapid element pressure field simulation method for transcranial phase correction in focused ultrasound therapy. Phys Med Biol 2023; 68:235015. [PMID: 37934058 DOI: 10.1088/1361-6560/ad0a59] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2023] [Accepted: 11/07/2023] [Indexed: 11/08/2023]
Abstract
Transcranial focused ultrasound ablation has emerged as a promising technique for treating neurological disorders. The clinical system exclusively employed the ray tracing method to compute phase aberrations induced by the human skull, taking into account computational time constraints. However, this method compromises slightly on accuracy compared to simulation-based methods. This study evaluates a fast simulation method that simulates the time-harmonic pressure field within the region of interest for effective phase correction. Experimental validation was carried out using a 512-element, 670 kHz hemispherical transducer for fourex vivoskulls. The ray tracing method achieved a restoration ratio of 64.81% ± 4.33% of acoustic intensity normalized to hydrophone measurements. In comparison, the rapid simulation method demonstrated improved results with a restoration ratio of 73.10% ± 7.46%, albeit slightly lower than the full-wave simulation which achieved a restoration ratio of 75.87% ± 5.40%. The rapid simulation methods exhibited computational times that were less than five minutes for parallel computation with 8 threads. The incident angle was calculated, and a maximum difference of 6.8 degrees was found when the fixed position of the skull was changed. Meanwhile, the restoration ratio of acoustic intensity was validated to be above 70% for different target positions away from the geometrical focus of the transducer. The favorable balance between time consumption and correction accuracy makes this method valuable for clinical treatment applications.
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Affiliation(s)
- Peng Xu
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, People's Republic of China
| | - Nan Wu
- Shanghai Shende Green Medical Era Healthcare Technology Co., Ltd., Shanghai, People's Republic of China
| | - Guofeng Shen
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, People's Republic of China
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7
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Robins TC, Cueto C, Cudeiro J, Bates O, Agudo OC, Strong G, Guasch L, Warner M, Tang MX. Dual-Probe Transcranial Full-Waveform Inversion: A Brain Phantom Feasibility Study. ULTRASOUND IN MEDICINE & BIOLOGY 2023; 49:2302-2315. [PMID: 37474432 PMCID: PMC7616382 DOI: 10.1016/j.ultrasmedbio.2023.06.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/05/2022] [Revised: 05/29/2023] [Accepted: 06/02/2023] [Indexed: 07/22/2023]
Abstract
OBJECTIVE Despite being a low-cost, portable and safe medical imaging technique, transcranial ultrasound imaging is not used widely in adults because of the severe degradation and distortion of signals caused by the skull. Full-waveform inversion (FWI) has recently been found to have potential as an effective method for transcranial ultrasound tomography to obtain high-quality, subwavelength-resolution acoustic models of the brain using low-frequency ultrasound data. In this study is the first demonstration of this method in recovering a high-resolution 2-D reconstruction of a brain and skull ultrasound imaging phantom using experimentally acquired data. METHODS A 2:5 scale brain phantom encased within a 3-D-printed skull-mimicking layer was created to simulate a clinical transcranial imaging target. To obtain tomographic ultrasound data on the brain and skull phantom, a tomographic ultrasound acquisition system was designed and implemented using commercially available low-frequency cardiac probes. FWI reconstructions of the brain and skull phantom were performed using the acquired tomographic data and were compared with corresponding synthetic reconstructions. This comparison was used to evaluate the feasibility of the proposed imaging system when employing different transducer array configurations. RESULTS We demonstrate the successful FWI reconstruction of the brain phantom within the skull mimic from experimentally acquired tomographic ultrasound data. To mitigate the effects of the skull-mimicking material, a reflection-matching algorithm was applied to model the morphology of the skull layer prior to performing the inversion. CONCLUSION The findings of this study provide a promising step toward the clinical use of FWI for transcranial ultrasound imaging in adults.
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Affiliation(s)
- Thomas Caradoc Robins
- Department of Bioengineering, Faculty of Engineering, Imperial College London, London, UK.
| | - Carlos Cueto
- Department of Bioengineering, Faculty of Engineering, Imperial College London, London, UK
| | - Javier Cudeiro
- Department of Earth Science and Engineering, Faculty of Engineering, Imperial College London, London, UK
| | - Oscar Bates
- Department of Bioengineering, Faculty of Engineering, Imperial College London, London, UK
| | - Oscar Calderon Agudo
- Department of Earth Science and Engineering, Faculty of Engineering, Imperial College London, London, UK
| | - George Strong
- Department of Earth Science and Engineering, Faculty of Engineering, Imperial College London, London, UK
| | - Lluis Guasch
- Department of Earth Science and Engineering, Faculty of Engineering, Imperial College London, London, UK
| | - Michael Warner
- Department of Earth Science and Engineering, Faculty of Engineering, Imperial College London, London, UK
| | - Meng-Xing Tang
- Department of Bioengineering, Faculty of Engineering, Imperial College London, London, UK
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8
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Sigona MK, Manuel TJ, Anthony Phipps M, Boroujeni KB, Treuting RL, Womelsdorf T, Caskey CF. Generating Patient-Specific Acoustic Simulations for Transcranial Focused Ultrasound Procedures Based on Optical Tracking Information. IEEE OPEN JOURNAL OF ULTRASONICS, FERROELECTRICS, AND FREQUENCY CONTROL 2023; 3:146-156. [PMID: 38222464 PMCID: PMC10785958 DOI: 10.1109/ojuffc.2023.3318560] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/16/2024]
Abstract
Optical tracking is a real-time transducer positioning method for transcranial focused ultrasound (tFUS) procedures, but the predicted focus from optical tracking typically does not incorporate subject-specific skull information. Acoustic simulations can estimate the pressure field when propagating through the cranium but rely on accurately replicating the positioning of the transducer and skull in a simulated space. Here, we develop and characterize the accuracy of a workflow that creates simulation grids based on optical tracking information in a neuronavigated phantom with and without transmission through an ex vivo skull cap. The software pipeline could replicate the geometry of the tFUS procedure within the limits of the optical tracking system (transcranial target registration error (TRE): 3.9 ± 0.7 mm). The simulated focus and the free-field focus predicted by optical tracking had low Euclidean distance errors of 0.5±0.1 and 1.2±0.4 mm for phantom and skull cap, respectively, and some skull-specific effects were captured by the simulation. However, the TRE of simulation informed by optical tracking was 4.6±0.2, which is as large or greater than the focal spot size used by many tFUS systems. By updating the position of the transducer using the original TRE offset, we reduced the simulated TRE to 1.1 ± 0.4 mm. Our study describes a software pipeline for treatment planning, evaluates its accuracy, and demonstrates an approach using MR-acoustic radiation force imaging as a method to improve dosimetry. Overall, our software pipeline helps estimate acoustic exposure, and our study highlights the need for image feedback to increase the accuracy of tFUS dosimetry.
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Affiliation(s)
- Michelle K Sigona
- Department of Biomedical Engineering, Vanderbilt University, Nashville, TN 37212, USA
- Vanderbilt University Institute of Imaging Science, Nashville, TN 37232, USA
| | - Thomas J Manuel
- Department of Biomedical Engineering, Vanderbilt University, Nashville, TN 37212, USA
- Vanderbilt University Institute of Imaging Science, Nashville, TN 37232, USA
| | - M Anthony Phipps
- Vanderbilt University Institute of Imaging Science, Nashville, TN 37232, USA
- Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, TN 37212, USA
| | | | - Robert Louie Treuting
- Department of Biomedical Engineering, Vanderbilt University, Nashville, TN 37212, USA
| | - Thilo Womelsdorf
- Department of Biomedical Engineering, Vanderbilt University, Nashville, TN 37212, USA
- Department of Psychology, Vanderbilt University, Nashville, TN 37240, USA
| | - Charles F Caskey
- Department of Biomedical Engineering, Vanderbilt University, Nashville, TN 37212, USA
- Vanderbilt University Institute of Imaging Science, Nashville, TN 37232, USA
- Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, TN 37212, USA
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9
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Fan B, Goodman W, Cho RY, Sheth SA, Bouchard RR, Aazhang B. Computational modeling and minimization of unintended neuronal excitation in a LIFU stimulation. Sci Rep 2023; 13:13403. [PMID: 37591991 PMCID: PMC10435497 DOI: 10.1038/s41598-023-40522-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2023] [Accepted: 08/11/2023] [Indexed: 08/19/2023] Open
Abstract
The neuromodulation effect of low-intensity focused ultrasound (LIFU) is highly target-specific. Unintended off-target neuronal excitation can be elicited when the beam focusing accuracy and resolution are limited, whereas the resulted side effect has not been evaluated quantitatively. There is also a lack of methods addressing the minimization of such side effects. Therefore, this work introduces a computational model of unintended neuronal excitation during LIFU neuromodulation, which evaluates the off-target activation area (OTAA) by integrating an ultrasound field model with the neuronal spiking model. In addition, a phased array beam focusing scheme called constrained optimal resolution beamforming (CORB) is proposed to minimize the off-target neuronal excitation area while ensuring effective stimulation in the target brain region. A lower bound of the OTAA is analytically approximated in a simplified homogeneous medium, which could guide the selection of transducer parameters such as aperture size and operating frequency. Simulations in a human head model using three transducer setups show that CORB markedly reduces the OTAA compared with two benchmark beam focusing methods. The high neuromodulation resolution demonstrates the capability of LIFU to effectively limit the side effects during neuromodulation, allowing future clinical applications such as treatment of neuropsychiatric disorders.
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Affiliation(s)
- Boqiang Fan
- Department of Electrical and Computer Engineering, Rice University, Houston, TX, 77005, USA.
| | - Wayne Goodman
- Department of Electrical and Computer Engineering, Rice University, Houston, TX, 77005, USA
- Department of Psychiatry and Behavioral Science, Baylor College of Medicine, Houston, TX, 77030, USA
| | - Raymond Y Cho
- Department of Psychiatry and Behavioral Science, Baylor College of Medicine, Houston, TX, 77030, USA
| | - Sameer A Sheth
- Department of Electrical and Computer Engineering, Rice University, Houston, TX, 77005, USA
- Department of Neurosurgery, Baylor College of Medicine, Houston, TX, 77030, USA
| | - Richard R Bouchard
- Department of Imaging Physics, University of Texas MD Anderson Cancer Center, Houston, TX, 77030, USA
| | - Behnaam Aazhang
- Department of Electrical and Computer Engineering, Rice University, Houston, TX, 77005, USA
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10
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Hosseini S, Puonti O, Treeby B, Hanson LG, Thielscher A. A head template for computational dose modelling for transcranial focused ultrasound stimulation. Neuroimage 2023; 277:120227. [PMID: 37321357 DOI: 10.1016/j.neuroimage.2023.120227] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2023] [Revised: 06/04/2023] [Accepted: 06/12/2023] [Indexed: 06/17/2023] Open
Abstract
Transcranial focused Ultrasound Stimulation (TUS) at low intensities is emerging as a novel non-invasive brain stimulation method with higher spatial resolution than established transcranial stimulation methods and the ability to selectively stimulate also deep brain areas. Accurate control of the focus position and strength of the TUS acoustic waves is important to enable a beneficial use of the high spatial resolution and to ensure safety. As the human skull causes strong attenuation and distortion of the waves, simulations of the transmitted waves are needed to accurately determine the TUS dose distribution inside the cranial cavity. The simulations require information of the skull morphology and its acoustic properties. Ideally, they are informed by computed tomography (CT) images of the individual head. However, suited individual imaging data is often not readily available. For this reason, we here introduce and validate a head template that can be used to estimate the average effects of the skull on the TUS acoustic wave in the population. The template was created from CT images of the heads of 29 individuals of different ages (between 20-50 years), gender and ethnicity using an iterative non-linear co-registration procedure. For validation, we compared acoustic and thermal simulations based on the template to the average of the simulation results of all 29 individual datasets. Acoustic simulations were performed for a model of a focused transducer driven at 500 kHz, placed at 24 standardized positions by means of the EEG 10-10 system. Additional simulations at 250 kHz and 750 kHz at 16 of the positions were used for further confirmation. The amount of ultrasound-induced heating at 500 kHz was estimated for the same 16 transducer positions. Our results show that the template represents the median of the acoustic pressure and temperature maps from the individuals reasonably well in most cases. This underpins the usefulness of the template for the planning and optimization of TUS interventions in studies of healthy young adults. Our results further indicate that the amount of variability between the individual simulation results depends on the position. Specifically, the simulated ultrasound-induced heating inside the skull exhibited strong interindividual variability for three posterior positions close to the midline, caused by a high variability of the local skull shape and composition. This should be taken into account when interpreting simulation results based on the template.
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Affiliation(s)
- Seyedsina Hosseini
- Department of Health Technology, Technical University of Denmark, Kgs. Lyngby, Denmark; Danish Research Centre for Magnetic Resonance, Centre for Functional and Diagnostic Imaging and Research, Copenhagen University Hospital Amager and Hvidovre, Denmark
| | - Oula Puonti
- Danish Research Centre for Magnetic Resonance, Centre for Functional and Diagnostic Imaging and Research, Copenhagen University Hospital Amager and Hvidovre, Denmark
| | - Bradley Treeby
- Department of Medical Physics and Biomedical Engineering, University College London, GowerStreet, London, WC1E 6BT, United Kingdom
| | - Lars G Hanson
- Department of Health Technology, Technical University of Denmark, Kgs. Lyngby, Denmark; Danish Research Centre for Magnetic Resonance, Centre for Functional and Diagnostic Imaging and Research, Copenhagen University Hospital Amager and Hvidovre, Denmark
| | - Axel Thielscher
- Department of Health Technology, Technical University of Denmark, Kgs. Lyngby, Denmark; Danish Research Centre for Magnetic Resonance, Centre for Functional and Diagnostic Imaging and Research, Copenhagen University Hospital Amager and Hvidovre, Denmark.
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11
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Drainville RA, Chatillon S, Moore D, Snell J, Padilla F, Lafon C. A simulation study on the sensitivity of transcranial ray-tracing ultrasound modeling to skull properties. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2023; 154:1211-1225. [PMID: 37610718 DOI: 10.1121/10.0020761] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/14/2023] [Accepted: 08/08/2023] [Indexed: 08/24/2023]
Abstract
In transcranial focused ultrasound therapies, such as treating essential tremor via thermal ablation in the thalamus, acoustic energy is focused through the skull using a phased-array transducer. Ray tracing is a computationally efficient method that can correct skull-induced phase aberrations via per-element phase delay calculations using patient-specific computed tomography (CT) data. However, recent studies show that variations in CT-derived Hounsfield unit may account for only 50% of the speed of sound variability in human skull specimens, potentially limiting clinical transcranial ultrasound applications. Therefore, understanding the sensitivity of treatment planning methods to material parameter variations is essential. The present work uses a ray-tracing simulation model to explore how imprecision in model inputs, arising from clinically significant uncertainties in skull properties or considerations of acoustic phenomena, affects acoustic focusing quality through the skull. We propose and validate new methods to optimize ray-tracing skull simulations for clinical treatment planning, relevant for predicting intracranial target's thermal rise, using experimental data from ex-vivo human skulls.
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Affiliation(s)
| | | | - David Moore
- Focused Ultrasound Foundation, Charlottesville, Virginia 22903, USA
| | - John Snell
- Histosonics, Ann Arbor, Michigan 48103, USA
| | - Frederic Padilla
- Focused Ultrasound Foundation, Charlottesville, Virginia 22903, USA
| | - Cyril Lafon
- LabTAU, INSERM, Centre Léon Bérard, Université Lyon 1, Univ Lyon, F-69003, Lyon, France
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12
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Preston C, Alvarez AM, Allard M, Barragan A, Witte RS. Acoustoelectric Time-Reversal for Ultrasound Phase-Aberration Correction. IEEE TRANSACTIONS ON ULTRASONICS, FERROELECTRICS, AND FREQUENCY CONTROL 2023; 70:854-864. [PMID: 37405897 PMCID: PMC10493188 DOI: 10.1109/tuffc.2023.3292595] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/07/2023]
Abstract
Acoustoelectric imaging (AEI) is a technique that combines ultrasound (US) with radio frequency recording to detect and map local current source densities. This study demonstrates a new method called acoustoelectric time reversal (AETR), which uses AEI of a small current source to correct for phase aberrations through a skull or other US-aberrating layers with applications to brain imaging and therapy. Simulations conducted at three different US frequencies (0.5, 1.5, and 2.5 MHz) were performed through media layered with different sound speeds and geometries to induce aberrations of the US beam. Time delays of the acoustoelectric (AE) signal from a monopole within the medium were calculated for each element to enable corrections using AETR. Uncorrected aberrated beam profiles were compared with those after applying AETR corrections, which demonstrated a strong recovery (29%-100%) of lateral resolution and increases in focal pressure up to 283%. To further demonstrate the practical feasibility of AETR, we further conducted bench-top experiments using a 2.5 MHz linear US array to perform AETR through 3-D-printed aberrating objects. These experiments restored lost lateral restoration up to 100% for the different aberrators and increased focal pressure up to 230% after applying AETR corrections. Cumulatively, these results highlight AETR as a powerful tool for correcting focal aberrations in the presence of a local current source with applications to AEI, US imaging, neuromodulation, and therapy.
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13
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Nicholls JK, Turner P, Lecchini-Visintini A, Ince J, de Vries G, Cappellugola L, Oura M, Ebirim KU, Pallett E, Ramnarine KV, Chung EML. Effects of Blood Pressure on Brain Tissue Pulsation Amplitude in a Phantom Model. ULTRASOUND IN MEDICINE & BIOLOGY 2023:S0301-5629(23)00200-4. [PMID: 37400302 DOI: 10.1016/j.ultrasmedbio.2023.06.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/17/2022] [Revised: 06/05/2023] [Accepted: 06/07/2023] [Indexed: 07/05/2023]
Abstract
OBJECTIVE The precise mechanism and determinants of brain tissue pulsations (BTPs) are poorly understood, and the impact of blood pressure (BP) on BTPs is relatively unexplored. This study aimed to explore the relationship between BP parameters (mean arterial pressure [MAP] and pulse pressure [PP]) and BTP amplitude, using a transcranial tissue Doppler prototype. METHODS A phantom brain model generating arterial-induced BTPs was developed to observe BP changes in the absence of confounding variables and cerebral autoregulation feedback processes. A regression model was developed to investigate the relationship between bulk BTP amplitude and BP. The separate effects of PP and MAP were evaluated and quantified. RESULTS The regression model (R2 = 0.978) revealed that bulk BTP amplitude measured from 27 gates significantly increased with PP but not with MAP. Every 1 mm Hg increase in PP resulted in a bulk BTP amplitude increase of 0.29 µm. CONCLUSION Increments in BP were significantly associated with increments in bulk BTP amplitude. Further work should aim to confirm the relationship between BP and BTPs in the presence of cerebral autoregulation and explore further physiological factors having an impact on BTP measurements, such as cerebral blood flow volume, tissue distensibility and intracranial pressure.
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Affiliation(s)
- Jennifer K Nicholls
- Cerebral Haemodynamics in Ageing and Stroke Medicine (CHiASM) Research Group, Department of Cardiovascular Sciences, University of Leicester, Leicester, UK; Department of Medical Physics, University Hospitals of Leicester NHS Trust, Leicester, UK
| | - Poppy Turner
- Cerebral Haemodynamics in Ageing and Stroke Medicine (CHiASM) Research Group, Department of Cardiovascular Sciences, University of Leicester, Leicester, UK; School of Engineering, University of Leicester, Leicester, UK
| | - Andrea Lecchini-Visintini
- Cerebral Haemodynamics in Ageing and Stroke Medicine (CHiASM) Research Group, Department of Cardiovascular Sciences, University of Leicester, Leicester, UK; School of Electronics and Computer Science, University of Southampton, Southampton, UK
| | - Jonathan Ince
- Cerebral Haemodynamics in Ageing and Stroke Medicine (CHiASM) Research Group, Department of Cardiovascular Sciences, University of Leicester, Leicester, UK
| | - Georgina de Vries
- Department of Medical Physics, University Hospitals of Leicester NHS Trust, Leicester, UK
| | - Laurie Cappellugola
- Cerebral Haemodynamics in Ageing and Stroke Medicine (CHiASM) Research Group, Department of Cardiovascular Sciences, University of Leicester, Leicester, UK
| | - Mitsuhiro Oura
- Nihon Kohden Corporation, Tokorozawa-shi, Saitama, Japan
| | | | - Edward Pallett
- Department of Medical Physics, University Hospitals of Leicester NHS Trust, Leicester, UK
| | - Kumar V Ramnarine
- Department of Medical Physics, University Hospitals of Leicester NHS Trust, Leicester, UK; Medical Physics Department, Guy's and St Thomas' NHS Foundation Trust, London, UK
| | - Emma M L Chung
- Cerebral Haemodynamics in Ageing and Stroke Medicine (CHiASM) Research Group, Department of Cardiovascular Sciences, University of Leicester, Leicester, UK; Department of Medical Physics, University Hospitals of Leicester NHS Trust, Leicester, UK; NIHR Leicester Biomedical Research Centre, University of Leicester, Leicester, UK; Faculty of Life Sciences and Medicine, King's College London, London, UK.
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14
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Yeats E, Lu N, Sukovich JR, Xu Z, Hall TL. Soft Tissue Aberration Correction for Histotripsy Using Acoustic Emissions From Cavitation Cloud Nucleation and Collapse. ULTRASOUND IN MEDICINE & BIOLOGY 2023; 49:1182-1193. [PMID: 36759271 PMCID: PMC10082475 DOI: 10.1016/j.ultrasmedbio.2023.01.004] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/26/2022] [Revised: 12/01/2022] [Accepted: 01/03/2023] [Indexed: 05/11/2023]
Abstract
OBJECTIVE Phase aberration from soft tissue limits the efficacy of histotripsy, a therapeutic ultrasound technique based on acoustic cavitation. Previous work has shown that the acoustic emissions from cavitation can serve as "point sources" for aberration correction (AC). This study compared the efficacy of soft tissue AC for histotripsy using acoustic cavitation emissions (ACE) from bubble cloud nucleation and collapse. METHODS A 750-kHz, receive-capable histotripsy array was pulsed to generate cavitation in ex vivo porcine liver through an intervening abdominal wall. Received ACE signals were used to determine the arrival time differences to the focus and compute corrective delays. Corrections from single pulses and from the median of multiple pulses were tested. DISCUSSION On average, ACE AC obtained 96% ± 3% of the pressure amplitude obtained by hydrophone-based correction (compared with 71% ± 5% without AC). Both nucleation- and collapse-based corrections obtained >96% of the hydrophone-corrected pressure when using medians of ≥10 pulses. When using single-pulse corrections, nucleation obtained a range of 49%-99% of the hydrophone-corrected pressure, while collapse obtained 95%-99%. CONCLUSION The results suggest that (i) ACE AC can recover nearly all pressure amplitude lost owing to soft tissue aberration and that (ii) the collapse signal permits robust AC using a small number of pulses.
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Affiliation(s)
- Ellen Yeats
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA.
| | - Ning Lu
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA
| | - Jonathan R Sukovich
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA
| | - Zhen Xu
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA
| | - Timothy L Hall
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA
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15
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Wang L, Wang H, Liang L, Li J, Zeng Z, Liu Y. Physics-informed neural networks for transcranial ultrasound wave propagation. ULTRASONICS 2023; 132:107026. [PMID: 37137219 DOI: 10.1016/j.ultras.2023.107026] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2022] [Revised: 04/09/2023] [Accepted: 04/24/2023] [Indexed: 05/05/2023]
Abstract
Transcranial ultrasound imaging has been playing an increasingly important role in the non-invasive treatment of brain disorders. However, the conventional mesh-based numerical wave solvers, which are an integral part of imaging algorithms, suffer from limitations such as high computational cost and discretization error in predicting the wavefield passing through the skull. In this paper, we explore the use of physics-informed neural networks (PINNs) for predicting the transcranial ultrasound wave propagation. The wave equation, two sets of time snapshots data and a boundary condition (BC) are embedded as physical constraints in the loss function during training. The proposed approach has been validated by solving the two-dimensional (2D) acoustic wave equation under three increasingly complex spatially varying velocity models. Our cases demonstrate that due to the meshless nature of PINNs, they can be flexibly applied to different wave equations and types of BCs. By adding physics constraints to the loss function, PINNs can predict wavefields far outside the training data, providing ideas for improving the generalization capability of existing deep learning methods. The proposed approach offers exciting perspectives because of the powerful framework and simple implementation. We conclude with a summary of the strengths, limitations and further research directions of this work.
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Affiliation(s)
- Linfeng Wang
- State Key Laboratory of Precision Measuring Technology and Instruments, Tianjin University, Tianjin 300072, China
| | - Hao Wang
- State Key Laboratory of Precision Measuring Technology and Instruments, Tianjin University, Tianjin 300072, China
| | - Lin Liang
- Schlumberger-Doll Research, One Hampshire St, Cambridge, MA 02139, USA
| | - Jian Li
- State Key Laboratory of Precision Measuring Technology and Instruments, Tianjin University, Tianjin 300072, China
| | - Zhoumo Zeng
- State Key Laboratory of Precision Measuring Technology and Instruments, Tianjin University, Tianjin 300072, China
| | - Yang Liu
- State Key Laboratory of Precision Measuring Technology and Instruments, Tianjin University, Tianjin 300072, China.
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16
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Jing B, Strassle Rojas S, Lindsey BD. Effect of skull porosity on ultrasound transmission and wave mode conversion at large incidence angles. Med Phys 2023; 50:3092-3102. [PMID: 36810723 DOI: 10.1002/mp.16318] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2022] [Revised: 01/19/2023] [Accepted: 02/06/2023] [Indexed: 02/24/2023] Open
Abstract
BACKGROUND Transcranial ultrasound imaging and therapy depend on the efficient transmission of acoustic energy through the skull. Multiple previous studies have concluded that a large incidence angle should be avoided during transcranial-focused ultrasound therapy to ensure transmission through the skull. Alternatively, some other studies have shown that longitudinal-to-shear wave mode conversion might improve transmission through the skull when the incidence angle is increased above the critical angle (i.e., 25° to 30°). PURPOSE The effect of skull porosity on the transmission of ultrasound through the skull at varying incidence angles was investigated for the first time to elucidate why transmission through the skull at large angles of incidence is decreased in some cases but improved in other cases. METHODS Transcranial ultrasound transmission at varying incidence angles (0°-50°) was investigated in phantoms and ex vivo skull samples with varying bone porosity (0% to 28.54% ± 3.36%) using both numerical and experimental methods. First, the elastic acoustic wave transmission through the skull was simulated using micro-computed tomography data of ex vivo skull samples. The trans-skull pressure was compared between skull segments having three levels of porosity, that is, low porosity (2.65% ± 0.03%), medium porosity (13.41% ± 0.12%), and high porosity (26.9%). Next, transmission through two 3D-printed resin skull phantoms (compact vs. porous phantoms) was experimentally measured to test the effect of porous microstructure alone on ultrasound transmission through flat plates. Finally, the effect of skull porosity on ultrasound transmission was investigated experimentally by comparing transmission through two ex vivo human skull segments having similar thicknesses but different porosities (13.78% ± 2.05% vs. 28.54% ± 3.36%). RESULTS Numerical simulations indicated that an increase in transmission pressure occurs at large incidence angles for skull segments having low porosities but not for those with high porosity. In experimental studies, a similar phenomenon was observed. Specifically, for the low porosity skull sample (13.78% ± 2.05%), the normalized pressure was 0.25 when the incidence angle increased to 35°. However, for the high porosity sample (28.54% ± 3.36%), the pressure was no more than 0.1 at large incidence angles. CONCLUSIONS These results indicate that the skull porosity has an evident effect on the transmission of ultrasound at large incidence angles. The wave mode conversion at large, oblique incidence angles could enhance the transmission of ultrasound through parts of the skull having lower porosity in the trabecular layer. However, for transcranial ultrasound therapy in the presence of highly porous trabecular bone, transmission at a normal incidence angle is preferable relative to oblique incidence angles due to the higher transmission efficiency.
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Affiliation(s)
- Bowen Jing
- Wallace H Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, Georgia, USA
| | - Stephan Strassle Rojas
- School of Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta, Georgia, USA
| | - Brooks D Lindsey
- Wallace H Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, Georgia, USA.,School of Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta, Georgia, USA
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He J, Zhu Y, Wu C, Wu J, Chen Y, Yuan M, Cheng Z, Zeng L, Ji X. Simultaneous multi-target ultrasound neuromodulation in freely-moving mice based on a single-element ultrasound transducer. J Neural Eng 2023; 20. [PMID: 36608340 DOI: 10.1088/1741-2552/acb104] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2022] [Accepted: 01/06/2023] [Indexed: 01/07/2023]
Abstract
Objective.Ultrasound neuromodulation has become an emerging method for the therapy of neurodegenerative and psychiatric diseases. The phased array ultrasonic transducer enables multi-target ultrasound neuromodulation in small animals, but the relatively large size and mass and the thick cables of the array limit the free movement of small animals. Furthermore, spatial interference may occur during multi-target ultrasound brain stimulation with multiple micro transducers.Approach.In this study, we developed a miniature power ultrasound transducer and used the virtual source time inversion method and 3D printing technology to design, optimize, and manufacture the acoustic holographic lens to construct a multi-target ultrasound neuromodulation system for free-moving mice. The feasibility of the system was verified byin vitrotranscranial ultrasound field measurements,in vivodual-target blood-brain barrier (BBB) opening experiments, andin vivodual-target ultrasound neuromodulation experiments.Main results.The developed miniature transducer had a diameter of 4.0 mm, a center frequency of 1.1 MHz, and a weight of 1.25 g. The developed miniature acoustic holographic lens had a weight of 0.019 g to generate dual-focus transcranial ultrasound. The ultrasonic field measurements' results showed that the bifocal's horizontal distance was 3.0 mm, the -6 dB focal spot width in thex-direction was 2.5 and 2.25 mm, and 2.12 and 2.24 mm in they-direction. Finally, thein vivoexperimental results showed that the system could achieve dual-target BBB opening and ultrasound neuromodulation in freely-moving mice.Significance.The ultrasonic neuromodulation system based on a miniature single-element transducer and the miniature acoustic holographic lens could achieve dual-target neuromodulation in awake small animals, which is expected to be applied to the research of non-invasive dual-target ultrasonic treatment of brain diseases in awake small animals.
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Affiliation(s)
- Jiaru He
- State Key Laboratory of Precision Electronic Manufacturing Technology and Equipment, Guangdong University of Technology, Guangzhou 510006, People's Republic of China
| | - Yiyue Zhu
- State Key Laboratory of Precision Electronic Manufacturing Technology and Equipment, Guangdong University of Technology, Guangzhou 510006, People's Republic of China
| | - Canwen Wu
- State Key Laboratory of Precision Electronic Manufacturing Technology and Equipment, Guangdong University of Technology, Guangzhou 510006, People's Republic of China
| | - Junwei Wu
- State Key Laboratory of Precision Electronic Manufacturing Technology and Equipment, Guangdong University of Technology, Guangzhou 510006, People's Republic of China
| | - Yan Chen
- State Key Laboratory of Precision Electronic Manufacturing Technology and Equipment, Guangdong University of Technology, Guangzhou 510006, People's Republic of China
| | - Maodan Yuan
- State Key Laboratory of Precision Electronic Manufacturing Technology and Equipment, Guangdong University of Technology, Guangzhou 510006, People's Republic of China
| | - Zhongwen Cheng
- State Key Laboratory of Precision Electronic Manufacturing Technology and Equipment, Guangdong University of Technology, Guangzhou 510006, People's Republic of China
| | - Lvming Zeng
- State Key Laboratory of Precision Electronic Manufacturing Technology and Equipment, Guangdong University of Technology, Guangzhou 510006, People's Republic of China
| | - Xuanrong Ji
- State Key Laboratory of Precision Electronic Manufacturing Technology and Equipment, Guangdong University of Technology, Guangzhou 510006, People's Republic of China
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18
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Chen M, Peng C, Wu H, Huang CC, Kim T, Traylor Z, Muller M, Chhatbar PY, Nam CS, Feng W, Jiang X. Numerical and experimental evaluation of low-intensity transcranial focused ultrasound wave propagation using human skulls for brain neuromodulation. Med Phys 2023; 50:38-49. [PMID: 36342303 PMCID: PMC10099743 DOI: 10.1002/mp.16090] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2022] [Revised: 10/20/2022] [Accepted: 10/21/2022] [Indexed: 11/09/2022] Open
Abstract
BACKGROUND Low-intensity transcranial focused ultrasound (tFUS) has gained considerable attention as a promising noninvasive neuromodulatory technique for human brains. However, the complex morphology of the skull hinders scholars from precisely predicting the acoustic energy transmitted and the region of the brain impacted during the sonication. This is due to the fact that different ultrasound frequencies and skull morphology variations greatly affect wave propagation through the skull. PURPOSE Although the acoustic properties of human skull have been studied for tFUS applications, such as tumor ablation using a multielement phased array, there is no consensus about how to choose a single-element focused ultrasound (FUS) transducer with a suitable frequency for neuromodulation. There are interests in exploring the magnitude and dimension of tFUS beam through human parietal bone for modulating specific brain lobes. Herein, we aim to investigate the wave propagation of tFUS on human skulls to understand and address the concerns above. METHODS Both experimental measurements and numerical modeling were conducted to investigate the transmission efficiency and beam pattern of tFUS on five human skulls (C3 and C4 regions) using single-element FUS transducers with six different frequencies (150-1500 kHz). The degassed skull was placed in a water tank, and a calibrated hydrophone was utilized to measure acoustic pressure past it. The cranial computed tomography scan data of each skull were obtained to derive a high-resolution acoustic model (grid point spacing: 0.25 mm) in simulations. Meanwhile, we modified the power-law exponent of acoustic attenuation coefficient to validate numerical modeling and enabled it to be served as a prediction tool, based on the experimental measurements. RESULTS The transmission efficiency and -6 dB beamwidth were evaluated and compared for various frequencies. An exponential decrease in transmission efficiency and a logarithmic decrease of -6 dB beamwidth with an increase in ultrasound frequency were observed. It is found that a >750 kHz ultrasound leads to a relatively lower tFUS transmission efficiency (<5%), whereas a <350 kHz ultrasound contributes to a relatively broader beamwidth (>5 mm). Based on these observations, we further analyzed the dependence of tFUS wave propagation on FUS transducer aperture size. CONCLUSIONS We successfully studied tFUS wave propagation through human skulls at different frequencies experimentally and numerically. The findings have important implications to predict tFUS wave propagation for ultrasound neuromodulation in clinical applications, and guide researchers to develop advanced ultrasound transducers as neural interfaces.
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Affiliation(s)
- Mengyue Chen
- Department of Mechanical and Aerospace Engineering, North Carolina State University, Raleigh, North Carolina, USA
| | - Chang Peng
- Department of Mechanical and Aerospace Engineering, North Carolina State University, Raleigh, North Carolina, USA.,School of Biomedical Engineering, ShanghaiTech University, Shanghai, China
| | - Huaiyu Wu
- Department of Mechanical and Aerospace Engineering, North Carolina State University, Raleigh, North Carolina, USA
| | - Chih-Chung Huang
- Department of Mechanical and Aerospace Engineering, North Carolina State University, Raleigh, North Carolina, USA.,Department of Biomedical Engineering, National Cheng Kung University, Tainan, Taiwan
| | - Taewon Kim
- Department of Neurology, Duke University School of Medicine, Durham, North Carolina, USA
| | - Zachary Traylor
- Edward P. Fitts Department of Industrial and Systems Engineering, North Carolina State University, Raleigh, North Carolina, USA
| | - Marie Muller
- Department of Mechanical and Aerospace Engineering, North Carolina State University, Raleigh, North Carolina, USA
| | - Pratik Y Chhatbar
- Department of Neurology, Duke University School of Medicine, Durham, North Carolina, USA
| | - Chang S Nam
- Edward P. Fitts Department of Industrial and Systems Engineering, North Carolina State University, Raleigh, North Carolina, USA
| | - Wuwei Feng
- Department of Neurology, Duke University School of Medicine, Durham, North Carolina, USA
| | - Xiaoning Jiang
- Department of Mechanical and Aerospace Engineering, North Carolina State University, Raleigh, North Carolina, USA
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Attali D, Tiennot T, Schafer M, Fouragnan E, Sallet J, Caskey CF, Chen R, Darmani G, Bubrick EJ, Butler C, Stagg CJ, Klein-Flügge M, Verhagen L, Yoo SS, Pauly KB, Aubry JF. Three-layer model with absorption for conservative estimation of the maximum acoustic transmission coefficient through the human skull for transcranial ultrasound stimulation. Brain Stimul 2023; 16:48-55. [PMID: 36549480 DOI: 10.1016/j.brs.2022.12.005] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2022] [Revised: 12/05/2022] [Accepted: 12/12/2022] [Indexed: 12/23/2022] Open
Abstract
Transcranial ultrasound stimulation (TUS) has been shown to be a safe and effective technique for non-invasive superficial and deep brain stimulation. Safe and efficient translation to humans requires estimating the acoustic attenuation of the human skull. Nevertheless, there are no international guidelines for estimating the impact of the skull bone. A tissue independent, arbitrary derating was developed by the U.S. Food and Drug Administration to take into account tissue absorption (0.3 dB/cm-MHz) for diagnostic ultrasound. However, for the case of transcranial ultrasound imaging, the FDA model does not take into account the insertion loss induced by the skull bone, nor the absorption by brain tissue. Therefore, the estimated absorption is overly conservative which could potentially limit TUS applications if the same guidelines were to be adopted. Here we propose a three-layer model including bone absorption to calculate the maximum pressure transmission through the human skull for frequencies ranging between 100 kHz and 1.5 MHz. The calculated pressure transmission decreases with the frequency and the thickness of the bone, with peaks for each thickness corresponding to a multiple of half the wavelength. The 95th percentile maximum transmission was calculated over the accessible surface of 20 human skulls for 12 typical diameters of the ultrasound beam on the skull surface, and varies between 40% and 78%. To facilitate the safe adjustment of the acoustic pressure for short ultrasound pulses, such as transcranial imaging or transcranial ultrasound stimulation, a table summarizes the maximum pressure transmission for each ultrasound beam diameter and each frequency.
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Affiliation(s)
- David Attali
- Physics for Medicine Paris, Inserm U1273, ESPCI Paris, CNRS UMR8063, PSL University, Paris, France; Pôle Paris 16 (Secteurs 17-18) et Pôle Neuro Sainte-Anne, Centre Hospitalier Sainte-Anne, GHU Paris Psychiatrie & Neurosciences, Université Paris Cité, Paris, France
| | - Thomas Tiennot
- Physics for Medicine Paris, Inserm U1273, ESPCI Paris, CNRS UMR8063, PSL University, Paris, France
| | - Mark Schafer
- School of Biomedical Engineering, Science and Health Systems, Drexel University, Philadelphia, PA, USA
| | - Elsa Fouragnan
- Brain Research Imaging Center and School of Psychology, University of Plymouth, Plymouth, UK; School of Psychology, Portland Square, Plymouth PL4 8AA, UK
| | - Jérôme Sallet
- Univ Lyon, Université Lyon 1, Inserm, Stem Cell and Brain Research Institute U1208, Bron, France
| | - Charles F Caskey
- Vanderbilt University Institute of Imaging Sciences, VU Medical Center, Nashville, TN, United States
| | - Robert Chen
- Division of Neurology, Department of Medicine, University of Toronto, Canada; Krembil Research Institute, University Health Network, Toronto, Ontario, Canada
| | - Ghazaleh Darmani
- Krembil Research Institute, University Health Network, Toronto, Ontario, Canada
| | - Ellen J Bubrick
- Brigham and Women's Hospital, Harvard Medical School, Department of Neurology, 75 Francis St., Boston, MA, USA
| | - Christopher Butler
- Department of Brain Sciences, Imperial College London, 9th Floor, Sir Michael Uren Hub, 86 Wood Lane, London, W12 0BZ, UK
| | - Charlotte J Stagg
- Wellcome Centre for Integrative Neuroimaging (WIN), Centre for Functional MRI of the Brain (FMRIB), University of Oxford, Nuffield Department of Clinical Neurosciences, Level 6, West Wing, John Radcliffe Hospital, Oxford OX3 9DU, UK
| | - Miriam Klein-Flügge
- Wellcome Centre for Integrative Neuroimaging (WIN), Centre for Functional MRI of the Brain (FMRIB), University of Oxford, Nuffield Department of Clinical Neurosciences, Level 6, West Wing, John Radcliffe Hospital, Oxford OX3 9DU, UK; Wellcome Centre for Integrative Neuroimaging (WIN), Department of Experimental Psychology, University of Oxford, Tinsley Building, Mansfield Road, Oxford OX1 3TA, UK
| | - Lennart Verhagen
- Donders Institute for Brain, Cognition and Behaviour, Radboud University, 6525 GD Nijmegen, the Netherlands
| | - Seung-Schik Yoo
- Brigham and Women's Hospital, Harvard Medical School, Department of Radiology, 75 Francis St., Boston, MA, USA
| | - Kim Butts Pauly
- Stanford University, Department of Radiology, Stanford CA, 94305, USA
| | - Jean-Francois Aubry
- Physics for Medicine Paris, Inserm U1273, ESPCI Paris, CNRS UMR8063, PSL University, Paris, France.
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20
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Cain JA, Visagan S, Monti MM. S.M.A.R.T. F.U.S: Surrogate Model of Attenuation and Refraction in Transcranial Focused Ultrasound. PLoS One 2022; 17:e0264101. [PMID: 36302034 PMCID: PMC9612531 DOI: 10.1371/journal.pone.0264101] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2022] [Accepted: 09/19/2022] [Indexed: 11/05/2022] Open
Abstract
Low-intensity focused ultrasound (LIFU) is an increasingly applied method for achieving non-invasive brain stimulation. However, transmission of ultrasound through the human skull can substantially affect focal point characteristics of LIFU, including dramatic attenuation in intensity and refraction of focal point location. These effects depend on a high-dimensional parameter space, making these effects difficult to estimate from previous work. Instead, focal point properties of LIFU experiments are often estimated using numerical simulation of LIFU sonication through skull. However, this procedure presents many entry barriers to even computationally savvy investigators and often requires expensive computational hardware, impeding LIFU research. We present a novel MATLAB toolbox (data: doi:10.5068/D1QD60; Matlab Scripts: https://doi.org/10.5281/zenodo.5811122) for rapidly estimating beam properties of LIFU transmitted through bone. Users provide specific values for frequency of LIFU, bone thickness, angle at which LIFU is applied, depth of the LIFU focal point, and diameter of the transducer used and receive an estimation of the degree of refraction/attenuation expected for the given parameters.
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Affiliation(s)
- Joshua A. Cain
- Department of Psychology, University of California Los Angeles, Los Angeles, California, United States of America
- * E-mail:
| | - Shakthi Visagan
- Department of Neurology, University of California Los Angeles, Los Angeles, California, United States of America
| | - Martin M. Monti
- Department of Psychology, University of California Los Angeles, Los Angeles, California, United States of America
- Department of Neurosurgery, University of California Los Angeles, Los Angeles, California, United States of America
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Comparison between MR and CT imaging used to correct for skull-induced phase aberrations during transcranial focused ultrasound. Sci Rep 2022; 12:13407. [PMID: 35927449 PMCID: PMC9352781 DOI: 10.1038/s41598-022-17319-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2021] [Accepted: 07/25/2022] [Indexed: 11/08/2022] Open
Abstract
Transcranial focused ultrasound with the InSightec Exablate system uses thermal ablation for the treatment of movement and mood disorders and blood brain barrier disruption for tumor therapy. The system uses computed tomography (CT) images to calculate phase corrections that account for aberrations caused by the human skull. This work investigates whether magnetic resonance (MR) images can be used as an alternative to CT images to calculate phase corrections. Phase corrections were calculated using the gold standard hydrophone method and the standard of care InSightec ray tracing method. MR binary image mask, MR-simulated-CT (MRsimCT), and CT images of three ex vivo human skulls were supplied as inputs to the InSightec ray tracing method. The degassed ex vivo human skulls were sonicated with a 670 kHz hemispherical phased array transducer (InSightec Exablate 4000). 3D raster scans of the beam profiles were acquired using a hydrophone mounted on a 3-axis positioner system. Focal spots were evaluated using six metrics: pressure at the target, peak pressure, intensity at the target, peak intensity, positioning error, and focal spot volume. Targets at the geometric focus and 5 mm lateral to the geometric focus were investigated. There was no statistical difference between any of the metrics at either target using either MRsimCT or CT for phase aberration correction. As opposed to the MRsimCT, the use of CT images for aberration correction requires registration to the treatment day MR images; CT misregistration within a range of ± 2 degrees of rotation error along three dimensions was shown to reduce focal spot intensity by up to 9.4%. MRsimCT images used for phase aberration correction for the skull produce similar results as CT-based correction, while avoiding both CT to MR registration errors and unnecessary patient exposure to ionizing radiation.
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22
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Chen H, Felix C, Folloni D, Verhagen L, Sallet J, Jerusalem A. Modelling transcranial ultrasound neuromodulation: an energy-based multiscale framework. Acta Biomater 2022; 151:317-332. [PMID: 35902037 DOI: 10.1016/j.actbio.2022.07.034] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2022] [Revised: 07/18/2022] [Accepted: 07/19/2022] [Indexed: 11/26/2022]
Abstract
Several animal and human studies have now established the potential of low intensity, low frequency transcranial ultrasound (TUS) for non-invasive neuromodulation. Paradoxically, the underlying mechanisms through which TUS neuromodulation operates are still unclear, and a consensus on the identification of optimal sonication parameters still remains elusive. One emerging hypothesis based on thermodynamical considerations attributes the acoustic-induced nerve activity alterations to the mechanical energy and/or entropy conversions occurring during TUS action. Here, we propose a multiscale modelling framework to examine the energy states of neuromodulation under TUS. First, macroscopic tissue-level acoustic simulations of the sonication of a whole monkey brain are conducted under different sonication protocols. For each one of them, mechanical loading conditions of the received waves in the anterior cingulate cortex region are recorded and exported into a microscopic cell-level 3D viscoelastic finite element model of neuronal axon embedded extracellular medium. Pulse-averaged elastically stored and viscously dissipated energy rate densities during axon deformation are finally computed under different sonication incident angles and are mapped against distinct combinations of sonication parameters of the TUS. The proposed multiscale framework allows for the analysis of vibrational patterns of the axons and its comparison against the spectrograms of stimulating ultrasound. The results are in agreement with literature data on neuromodulation, demonstrating the potential of this framework to identify optimised acoustic parameters in TUS neuromodulation. The proposed approach is finally discussed in the context of multiphysics energetic considerations, argued here to be a promising avenue towards a scalable framework for TUS in silico predictions. STATEMENT OF SIGNIFICANCE: Low-intensity transcranial ultrasound (TUS) is poised to become a leading neuromodulation technique for the treatment of neurological disorders. Paradoxically, how it operates at the cellular scale remains unknown, hampering progress in personalised treatment. To this end, models of the multiphysics of neurons able to upscale results to the organ scale are required. We propose here to achieve this by considering an axon submitted to an ultrasound wave extracted from a simulation at the organ scale. Doing so, information pertaining to both stored and dissipated axonal energies can be extracted for a given head/brain morphology. This two-scale multiphysics energetic approach is a promising scalable framework for in silico predictions in the context of personalised TUS treatment.
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Affiliation(s)
- Haoyu Chen
- Department of Engineering Science, University of Oxford, Oxford, UK
| | - Ciara Felix
- Department of Engineering Science, University of Oxford, Oxford, UK
| | - Davide Folloni
- Wellcome Centre for Integrative Neuroimaging (WIN), Department of Experimental Psychology, University of Oxford, Oxford, UK; Department of Neuroscience and Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Lennart Verhagen
- Wellcome Centre for Integrative Neuroimaging (WIN), Department of Experimental Psychology, University of Oxford, Oxford, UK; Donders Institute, Radboud University, Nijmegen, Netherlands
| | - Jérôme Sallet
- Wellcome Centre for Integrative Neuroimaging (WIN), Department of Experimental Psychology, University of Oxford, Oxford, UK; Inserm, Stem Cell and Brain Research Institute, Université Lyon 1, Bron, France
| | - Antoine Jerusalem
- Department of Engineering Science, University of Oxford, Oxford, UK.
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Yeats E, Gupta D, Xu Z, Hall TL. Effects of phase aberration on transabdominal focusing for a large aperture, low f-number histotripsy transducer. Phys Med Biol 2022; 67:10.1088/1361-6560/ac7d90. [PMID: 35772383 PMCID: PMC9396534 DOI: 10.1088/1361-6560/ac7d90] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2022] [Accepted: 06/30/2022] [Indexed: 11/12/2022]
Abstract
Objective. Soft tissue phase aberration may be particularly severe for histotripsy due to large aperture and lowf-number transducer geometries. This study investigated how phase aberration from human abdominal tissue affects focusing of a large, strongly curved histotripsy transducer.Approach.A computational model (k-Wave) was experimentally validated withex vivoporcine abdominal tissue and used to simulate focusing a histotripsy transducer (radius: 14.2 cm,f-number: 0.62, central frequencyfc: 750 kHz) through the human abdomen. Abdominal computed tomography images from 10 human subjects were segmented to create three-dimensional acoustic property maps. Simulations were performed focusing at 3 target locations in the liver of each subject with ideal phase correction, without phase correction, and after separately matching the sound speed of water and fat to non-fat soft tissue.Main results.Experimental validation in porcine abdominal tissue showed that simulated and measured arrival time differences agreed well (average error, ∼0.10 acoustic cycles atfc). In simulations with human tissue, aberration created arrival time differences of 0.65μs (∼0.5 cycles) at the target and shifted the focus from the target by 6.8 mm (6.4 mm pre-focally along depth direction), on average. Ideal phase correction increased maximum pressure amplitude by 95%, on average. Matching the sound speed of water and fat to non-fat soft tissue decreased the average pre-focal shift by 3.6 and 0.5 mm and increased pressure amplitude by 2% and 69%, respectively.Significance.Soft tissue phase aberration of large aperture, lowf-number histotripsy transducers is substantial despite low therapeutic frequencies. Phase correction could potentially recover substantial pressure amplitude for transabdominal histotripsy. Additionally, different heterogeneity sources distinctly affect focusing quality. The water path strongly affects the focal shift, while irregular tissue boundaries (e.g. fat) dominate pressure loss.
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Affiliation(s)
- Ellen Yeats
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, United States of America
| | - Dinank Gupta
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, United States of America
| | - Zhen Xu
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, United States of America
| | - Timothy L Hall
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, United States of America
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Lu H. Radiomics-Informed Modeling for Transcranial Ultrasound Stimulation: Age Matters. Front Neurosci 2022; 16:935283. [PMID: 35784843 PMCID: PMC9240751 DOI: 10.3389/fnins.2022.935283] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2022] [Accepted: 05/27/2022] [Indexed: 11/15/2022] Open
Affiliation(s)
- Hanna Lu
- Department of Psychiatry, The Chinese University of Hong Kong, Hong Kong, Hong Kong SAR, China
- Centre for Neuromodulation and Rehabilitation, The Affiliated Brain Hospital of Guangzhou Medical University, Guangzhou, China
- The Affiliated Brain Hospital of Guangzhou Medical University, Guangzhou, China
- *Correspondence: Hanna Lu
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25
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Andrés D, Jiménez N, Benlloch JM, Camarena F. Numerical Study of Acoustic Holograms for Deep-Brain Targeting through the Temporal Bone Window. ULTRASOUND IN MEDICINE & BIOLOGY 2022; 48:872-886. [PMID: 35221196 DOI: 10.1016/j.ultrasmedbio.2022.01.010] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/24/2021] [Revised: 01/14/2022] [Accepted: 01/16/2022] [Indexed: 06/14/2023]
Abstract
Acoustic holograms can encode complex wavefronts to compensate the aberrations of a therapeutical ultrasound beam propagating through heterogeneous tissues such as the skull, and simultaneously, they can generate diffraction-limited acoustic images, that is, arbitrary shaped focal spots. In this work, we numerically study the performance of acoustic holograms focusing at the thalamic nuclei when the source is located at the temporal bone window. The temporal window is the thinnest area of the lateral skull and it is mainly hairless, so it is a desirable area through which to transmit ultrasonic waves to the deep brain. However, in targeting from this area the bilateral thalamic nuclei are not aligned with the elongated focal spots of conventional focused transducers, and in addition, skull aberrations can distort the focal spot. We found that by using patient-specific holographic lenses coupled to a single-element 650-kHz-frequency 65-mm-aperture source, the focal spot can be sharply adapted to the thalamic nuclei in a bilateral way while skull aberrations are mitigated. Furthermore, the performance of these holograms was studied under misalignment errors between the source and the skull, concluding that for misalignments up to 5°, acoustic images are correctly restored. This work paves the way to designing clinical applications of transcranial ultrasound such as blood-brain barrier opening for drug delivery or deep-brain neuromodulation using this low-cost and personalized technology, presenting desirable aspects for long-term treatments because the patient's head does not need to be shaved completely and skull heating is low.
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Affiliation(s)
- Diana Andrés
- Instituto de Instrumentación para Imagen Molecular (i3M), Universitat Politècnica de València, Consejo Superior de Investigaciones Científicas (CSIC), València, Spain
| | - Noé Jiménez
- Instituto de Instrumentación para Imagen Molecular (i3M), Universitat Politècnica de València, Consejo Superior de Investigaciones Científicas (CSIC), València, Spain.
| | - José M Benlloch
- Instituto de Instrumentación para Imagen Molecular (i3M), Universitat Politècnica de València, Consejo Superior de Investigaciones Científicas (CSIC), València, Spain
| | - Francisco Camarena
- Instituto de Instrumentación para Imagen Molecular (i3M), Universitat Politècnica de València, Consejo Superior de Investigaciones Científicas (CSIC), València, Spain
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Darmani G, Bergmann T, Butts Pauly K, Caskey C, de Lecea L, Fomenko A, Fouragnan E, Legon W, Murphy K, Nandi T, Phipps M, Pinton G, Ramezanpour H, Sallet J, Yaakub S, Yoo S, Chen R. Non-invasive transcranial ultrasound stimulation for neuromodulation. Clin Neurophysiol 2022; 135:51-73. [DOI: 10.1016/j.clinph.2021.12.010] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2021] [Revised: 12/20/2021] [Accepted: 12/22/2021] [Indexed: 12/13/2022]
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27
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Zhuang X, He J, Wu J, Ji X, Chen Y, Yuan M, Zeng L. A Spatial Multitarget Ultrasound Neuromodulation System Using High-Powered 2-D Array Transducer. IEEE TRANSACTIONS ON ULTRASONICS, FERROELECTRICS, AND FREQUENCY CONTROL 2022; 69:998-1007. [PMID: 34990356 DOI: 10.1109/tuffc.2022.3140889] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Transcranial focused ultrasound (tFUS) is increasingly used in experimental neuroscience due to its neuromodulatory effectiveness in animal studies. However, achieving multitarget tFUS in small animals is typically limited by transducer size, energy transfer efficiency, and brain volume. The objective of this work was to construct an ultrasound system for multitarget neuromodulation in small animals. First, a miniaturized high-powered 2-D array transducer was developed. The phase delay of each array element was calculated based on the multifocal time-reversal method, generating multiple foci simultaneously in a 3-D field. The effects of the axial focal length, interfocus spacing (lateral distance between the two focal centers), and the number of foci on the focal properties of the pressure field were examined through numerical simulations. In-vitro ultrasonic measurements and transcranial simulations on a rat skull were conducted. The minimum interfocus spacing separating two -6-dB foci and the peak full-width at half-maximum were positively correlated with axial focal length; the relative relationship between the interfocus spacing and pressure field properties was similar for each axial focal length. The maximum acoustic pressure and spatial average intensity at focus in deionized water were 2.21 MPa and 133 W/cm2, respectively. The simulated and experimental results were compared, demonstrating agreement in both peak position and focus shape. The ultrasound system can provide a neuroscientific platform for evaluating the feasibility of multitarget ultrasound stimulation treatment protocols, thus improving the understanding of functional neuroanatomy.
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Guo J, Song X, Chen X, Xu M, Ming D. Mathematical Model of Ultrasound Attenuation With Skull Thickness for Transcranial-Focused Ultrasound. Front Neurosci 2022; 15:778616. [PMID: 35250434 PMCID: PMC8891811 DOI: 10.3389/fnins.2021.778616] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2021] [Accepted: 12/16/2021] [Indexed: 11/23/2022] Open
Abstract
Transcranial-focused ultrasound (tFUS) has potential for both neuromodulation and neuroimaging. Due to the influence of head tissue, especially the skull, its attenuation is a key issue affecting precise focusing. The objective of the present study was to construct a mathematical model of ultrasound attenuation inclusive of skull thickness. First, combined with real skull phantom experiments and simulation experiments, tFUS attenuation of different head tissues was investigated. Furthermore, based on the system identification method, a mathematical model of ultrasound attenuation was constructed taking skull thickness into account. Finally, the performance of the mathematical model was tested, and its potential applications were investigated. For different head tissues, including scalp, skull, and brain tissue, the skull was found to be the biggest influencing factor for ultrasound attenuation, the attenuation caused by it being 4.70 times and 7.06 times that of attenuation caused by the brain and scalp, respectively. Consistent with the results of both the simulation and phantom experiments, the attenuation of the mathematical model increased as the skull thickness increased. The average error of the mathematical model was 1.87% in the phantom experiment. In addition, the experimental results show that the devised mathematical model is suitable for different initial pressures and different skulls with correlation coefficients higher than 0.99. Both simulation and phantom experiments validated the effectiveness of the proposed mathematical model. It can be concluded from this experiment that the proposed mathematical model can accurately calculate the tFUS attenuation and can significantly contribute to further research and application of tFUS.
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Affiliation(s)
- Jiande Guo
- Academy of Medical Engineering and Translational Medicine, Tianjin University, Tianjin, China
| | - Xizi Song
- Academy of Medical Engineering and Translational Medicine, Tianjin University, Tianjin, China
| | - Xinrui Chen
- Academy of Medical Engineering and Translational Medicine, Tianjin University, Tianjin, China
| | - Minpeng Xu
- Department of Biomedical Engineering, College of Precision Instruments and Optoelectronics Engineering, Tianjin University, Tianjin, China
| | - Dong Ming
- Academy of Medical Engineering and Translational Medicine, Tianjin University, Tianjin, China
- Department of Biomedical Engineering, College of Precision Instruments and Optoelectronics Engineering, Tianjin University, Tianjin, China
- *Correspondence: Dong Ming,
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29
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Seo H, Huh H, Lee EH, Park J. Numerical Evaluation of the Effects of Transducer Displacement on Transcranial Focused Ultrasound in the Rat Brain. Brain Sci 2022; 12:216. [PMID: 35203979 PMCID: PMC8870101 DOI: 10.3390/brainsci12020216] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2021] [Revised: 01/15/2022] [Accepted: 02/03/2022] [Indexed: 02/04/2023] Open
Abstract
Focused ultrasound is a promising therapeutic technique, as it involves the focusing of an ultrasonic beam with sufficient acoustic energy into a target brain region with high precision. Low-intensity ultrasound transmission by a single-element transducer is mostly established for neuromodulation applications and blood-brain barrier disruption for drug delivery. However, transducer positioning errors can occur without fine control over the sonication, which can affect repeatability and lead to reliability problems. The objective of this study was to determine whether the target brain region would be stable under small displacement (0.5 mm) of the transducer based on numerical simulations. Computed-tomography-derived three-dimensional models of a rat head were constructed to investigate the effects of transducer displacement in the caudate putamen (CP) and thalamus (TH). Using three different frequencies (1.1, 0.69, and 0.25 MHz), the transducer was displaced by 0.5 mm in each of the following six directions: superior, interior, anterior, posterior, left, and right. The maximum value of the intracranial pressure field was calculated, and the targeting errors were determined by the full-width-at-half-maximum (FWHM) overlap between the free water space (FWHMwater) and transcranial transmission (FWHMbase). When the transducer was positioned directly above the target region, a clear distinction between the target regions was observed, resulting in 88.3%, 81.5%, and 84.5% FWHMwater for the CP and 65.6%, 76.3%, and 64.4% FWHMwater for the TH at 1.1, 0.69, and 0.25 MHz, respectively. Small transducer displacements induced both enhancement and reduction of the peak pressure and targeting errors, compared with when the transducer was displaced in water. Small transducer displacement to the left resulted in the lowest stability, with 34.8% and 55.0% targeting accuracy (FWHMwater) at 1.1 and 0.69 MHz in the TH, respectively. In addition, the maximum pressure was reduced by up to 11% by the transducer displacement. This work provides the targeting errors induced by transducer displacements through a preclinical study and recommends that attention be paid to determining the initial sonication foci in the transverse plane in the cases of small animals.
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Affiliation(s)
- Hyeon Seo
- Medical Device Development Center, Daegu-Gyeongbuk Medical Innovation Foundation, Daegu 41061, Korea; (H.S.); (H.H.); (E.-H.L.)
| | - Hyungkyu Huh
- Medical Device Development Center, Daegu-Gyeongbuk Medical Innovation Foundation, Daegu 41061, Korea; (H.S.); (H.H.); (E.-H.L.)
| | - Eun-Hee Lee
- Medical Device Development Center, Daegu-Gyeongbuk Medical Innovation Foundation, Daegu 41061, Korea; (H.S.); (H.H.); (E.-H.L.)
| | - Juyoung Park
- Medical Device Development Center, Daegu-Gyeongbuk Medical Innovation Foundation, Daegu 41061, Korea; (H.S.); (H.H.); (E.-H.L.)
- Department of High-Tech Medical Device, College of Future Industry, Gachon University, Seongnam-si 13120, Korea
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30
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Kong C, Park SH, Shin J, Baek HG, Park J, Na YC, Chang WS, Chang JW. Factors Associated with Energy Efficiency of Focused Ultrasound Through the Skull: A Study of 3D-Printed Skull Phantoms and Its Comparison with Clinical Experiences. Front Bioeng Biotechnol 2021; 9:783048. [PMID: 34957077 PMCID: PMC8708563 DOI: 10.3389/fbioe.2021.783048] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2021] [Accepted: 11/15/2021] [Indexed: 11/24/2022] Open
Abstract
While focused ultrasound (FUS) is non-invasive, the ultrasound energy is attenuated by the skull which results in differences in energy efficiency among patients. In this study, we investigated the effect of skull variables on the energy efficiency of FUS. The thickness and density of the skull and proportion of the trabecular bone were selected as factors that could affect ultrasound energy transmittance. Sixteen 3D-printed skull models were designed and fabricated to reflect the three factors. The energy of each phantom was measured using an ultrasonic sound field energy measurement system. The thickness and proportion of trabecular bone affected the attenuation of transmitted energy. There was no difference in the density of the trabecular bone. In clinical data, the trabecular bone ratio showed a significantly greater correlation with dose/delivered energy than that of thickness and the skull density ratio. Currently, for clinical non-thermal FUS, the data are not sufficient, but we believe that the results of this study will be helpful in selecting patients and appropriate parameters for FUS treatment.
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Affiliation(s)
- Chanho Kong
- Department of Neurosurgery, Brain Research Institute, Yonsei University College of Medicine, Seoul, South Korea
| | - So Hee Park
- Department of Neurosurgery, Brain Research Institute, Yonsei University College of Medicine, Seoul, South Korea
| | - Jaewoo Shin
- Department of Neurosurgery, Brain Research Institute, Yonsei University College of Medicine, Seoul, South Korea
| | - Hee Gyu Baek
- Medical Device Development Center, Daegu-Gyeongbuk Medical Innovation Foundation, Daegu, South Korea
| | - Juyoung Park
- Medical Device Development Center, Daegu-Gyeongbuk Medical Innovation Foundation, Daegu, South Korea
| | - Young Cheol Na
- Department of Neurosurgery, Catholic Kwandong University College of Medicine, International St Mary's Hospital, Incheon, South Korea
| | - Won Seok Chang
- Department of Neurosurgery, Brain Research Institute, Yonsei University College of Medicine, Seoul, South Korea
| | - Jin Woo Chang
- Department of Neurosurgery, Brain Research Institute, Yonsei University College of Medicine, Seoul, South Korea
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Bakaric M, Miloro P, Javaherian A, Cox BT, Treeby BE, Brown MD. Measurement of the ultrasound attenuation and dispersion in 3D-printed photopolymer materials from 1 to 3.5 MHz. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2021; 150:2798. [PMID: 34717448 DOI: 10.1121/10.0006668] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/31/2021] [Accepted: 09/21/2021] [Indexed: 06/13/2023]
Abstract
Over the past decade, the range of applications in biomedical ultrasound exploiting 3D printing has rapidly expanded. For wavefront shaping specifically, 3D printing has enabled a diverse range of new, low-cost approaches for controlling acoustic fields. These methods rely on accurate knowledge of the bulk acoustic properties of the materials; however, to date, robust knowledge of these parameters is lacking for many materials that are commonly used. In this work, the acoustic properties of eight 3D-printed photopolymer materials were characterised over a frequency range from 1 to 3.5 MHz. The properties measured were the frequency-dependent phase velocity and attenuation, group velocity, signal velocity, and mass density. The materials were fabricated using two separate techniques [PolyJet and stereolithograph (SLA)], and included Agilus30, FLXA9960, FLXA9995, Formlabs Clear, RGDA8625, RGDA8630, VeroClear, and VeroWhite. The range of measured density values across all eight materials was 1120-1180 kg · m-3, while the sound speed values were between 2020 to 2630 m · s-1, and attenuation values typically in the range 3-9 dB · MHz-1· cm-1.
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Affiliation(s)
- Marina Bakaric
- Department of Medical Physics and Biomedical Engineering, University College London, Gower Street, London WC1E 6BT, United Kingdom
| | - Piero Miloro
- Ultrasound and Underwater Acoustics, National Physical Laboratory, Hampton Road, Teddington TW11 0LW, United Kingdom
| | - Ashkan Javaherian
- Department of Medical Physics and Biomedical Engineering, University College London, Gower Street, London WC1E 6BT, United Kingdom
| | - Ben T Cox
- Department of Medical Physics and Biomedical Engineering, University College London, Gower Street, London WC1E 6BT, United Kingdom
| | - Bradley E Treeby
- Department of Medical Physics and Biomedical Engineering, University College London, Gower Street, London WC1E 6BT, United Kingdom
| | - Michael D Brown
- Department of Medical Physics and Biomedical Engineering, University College London, Gower Street, London WC1E 6BT, United Kingdom
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32
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Zhang H, Zhang Y, Xu M, Song X, Chen S, Jian X, Ming D. The Effects of the Structural and Acoustic Parameters of the Skull Model on Transcranial Focused Ultrasound. SENSORS 2021; 21:s21175962. [PMID: 34502853 PMCID: PMC8434628 DOI: 10.3390/s21175962] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/17/2021] [Revised: 09/02/2021] [Accepted: 09/02/2021] [Indexed: 01/02/2023]
Abstract
Transcranial focused ultrasound (tFUS) has great potential in brain imaging and therapy. However, the structural and acoustic differences of the skull will cause a large number of technical problems in the application of tFUS, such as low focus energy, focal shift, and defocusing. To have a comprehensive understanding of the skull effect on tFUS, this study investigated the effects of the structural parameters (thickness, radius of curvature, and distance from the transducer) and acoustic parameters (density, acoustic speed, and absorption coefficient) of the skull model on tFUS based on acrylic plates and two simulation methods (self-programming and COMSOL). For structural parameters, our research shows that as the three factors increase the unit distance, the attenuation caused from large to small is the thickness (0.357 dB/mm), the distance to transducer (0.048 dB/mm), and the radius of curvature (0.027 dB/mm). For acoustic parameters, the attenuation caused by density (0.024 dB/30 kg/m3) and acoustic speed (0.021 dB/30 m/s) are basically the same. Additionally, as the absorption coefficient increases, the focus acoustic pressure decays exponentially. The thickness of the structural parameters and the absorption coefficient of the acoustic parameters are the most important factors leading to the attenuation of tFUS. The experimental and simulation trends are highly consistent. This work contributes to the comprehensive and quantitative understanding of how the skull influences tFUS, which further enhances the application of tFUS in neuromodulation research and treatment.
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Affiliation(s)
- Hao Zhang
- Laboratory of Neural Engineering and Rehabilitation, Department of Biomedical Engineering, College of Precision Instruments and Optoelectronics Engineering, Tianjin University, Tianjin 300072, China; (H.Z.); (M.X.); (S.C.)
| | - Yanqiu Zhang
- School of Biomedical Engineering and Technology, Tianjin Medical University, Tianjin 300070, China; (Y.Z.); (X.J.)
| | - Minpeng Xu
- Laboratory of Neural Engineering and Rehabilitation, Department of Biomedical Engineering, College of Precision Instruments and Optoelectronics Engineering, Tianjin University, Tianjin 300072, China; (H.Z.); (M.X.); (S.C.)
- Academy of Medical Engineering and Translational Medicine, Tianjin University, Tianjin 300072, China;
| | - Xizi Song
- Academy of Medical Engineering and Translational Medicine, Tianjin University, Tianjin 300072, China;
| | - Shanguang Chen
- Laboratory of Neural Engineering and Rehabilitation, Department of Biomedical Engineering, College of Precision Instruments and Optoelectronics Engineering, Tianjin University, Tianjin 300072, China; (H.Z.); (M.X.); (S.C.)
- Academy of Medical Engineering and Translational Medicine, Tianjin University, Tianjin 300072, China;
- National Key Laboratory of Human Factors Engineering, China Astronaut Research and Training Center, Beijing 100094, China
| | - Xiqi Jian
- School of Biomedical Engineering and Technology, Tianjin Medical University, Tianjin 300070, China; (Y.Z.); (X.J.)
| | - Dong Ming
- Laboratory of Neural Engineering and Rehabilitation, Department of Biomedical Engineering, College of Precision Instruments and Optoelectronics Engineering, Tianjin University, Tianjin 300072, China; (H.Z.); (M.X.); (S.C.)
- Academy of Medical Engineering and Translational Medicine, Tianjin University, Tianjin 300072, China;
- Correspondence:
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Michimoto I, Miyashita K, Suzuyama H, Yano K, Kobayashi Y, Saito K, Matsukawa M. Simulation study on the effects of cancellous bone structure in the skull on ultrasonic wave propagation. Sci Rep 2021; 11:17592. [PMID: 34475422 PMCID: PMC8413454 DOI: 10.1038/s41598-021-96502-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2020] [Accepted: 08/11/2021] [Indexed: 12/15/2022] Open
Abstract
The transcranial Doppler method (TCD) enables the measurement of cerebral blood flow velocity and detection of emboli by applying an ultrasound probe to the temporal bone window, or the orbital or greater occipital foramina. TCD is widely used for evaluation of cerebral vasospasm after subarachnoid hemorrhage, early detection of patients with arterial stenosis, and the assessment of brain death. However, measurements often become difficult in older women. Among various factors contributing to this problem, we focused on the effect of the diploe in the skull bone on the penetration of ultrasound into the brain. In particular, the effect of the cancellous bone structure in the diploe was investigated. Using a 2D digital bone model, wave propagation through the skull bone was investigated using the finite-difference time-domain (FDTD) method. We fabricated digital bone models with similar structure but different BV/TV (bone volume/total volume) values in the diploe. At a BV/TV of approximately 50–60% (similar to that of older women), the minimum ultrasound amplitude was observed as a result of scattering and multiple reflections in the cancellous diploe. These results suggest that structural changes such as osteoporosis may be one factor hampering TCD measurements.
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Jing B, Lindsey BD. Effect of Skull Porous Trabecular Structure on Transcranial Ultrasound Imaging in the Presence of Elastic Wave Mode Conversion at Varying Incidence Angle. ULTRASOUND IN MEDICINE & BIOLOGY 2021; 47:2734-2748. [PMID: 34140169 DOI: 10.1016/j.ultrasmedbio.2021.05.010] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/15/2020] [Revised: 05/04/2021] [Accepted: 05/07/2021] [Indexed: 06/12/2023]
Abstract
With the advancement of aberration correction techniques, transcranial ultrasound imaging has exhibited great potential in applications such as imaging neurological function and guiding therapeutic ultrasound. However, the feasibility of transcranial imaging varies among individuals because of the differences in skull acoustic properties. To better understand the fundamental mechanisms underlying the variation in imaging performance, the effect of the structure of the porous trabecular bone on transcranial imaging performance (i.e., target localization errors and resolution) was investigated for the first time through the use of elastic wave simulations and experiments. Simulation studies using high-resolution computed tomography data from ex vivo skull samples revealed that imaging at large incidence angles reduced the target localization error for skulls having low porosity; however, as skull porosity increased, large angles of incidence resulted in degradation of resolution and increased target localization errors. Experimental results indicate that imaging at normal incidence introduced a localization error of 1.85 ± 0.10 mm, while imaging at a large incidence angle (40°) resulted in an increased localization error of 6.54 ± 1.33 mm and caused a single point target to no longer appear as a single, coherent target in the resulting image, which is consistent with simulation results. This first investigation of the effects of skull microstructure on transcranial ultrasound imaging indicates that imaging performance is highly dependent on the porosity of the skull, particularly at non-normal angles of incidence.
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Affiliation(s)
- Bowen Jing
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, Georgia, USA
| | - Brooks D Lindsey
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, Georgia, USA; School of Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta, Georgia, USA.
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Bancel T, Houdouin A, Annic P, Rachmilevitch I, Shapira Y, Tanter M, Aubry JF. Comparison Between Ray-Tracing and Full-Wave Simulation for Transcranial Ultrasound Focusing on a Clinical System Using the Transfer Matrix Formalism. IEEE TRANSACTIONS ON ULTRASONICS, FERROELECTRICS, AND FREQUENCY CONTROL 2021; 68:2554-2565. [PMID: 33651688 DOI: 10.1109/tuffc.2021.3063055] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Only one high-intensity focused ultrasound device has been clinically approved for transcranial brain surgery at the time of writing. The device operates within 650 and 720 kHz and corrects the phase distortions induced by the skull of each patient using a multielement phased array. Phase correction is estimated adaptively using a proprietary algorithm based on computed-tomography (CT) images of the patient's skull. In this article, we assess the performance of the phase correction computed by the clinical device and compare it to: 1) the correction obtained with a previously validated full-wave simulation algorithm using an open-source pseudo-spectral toolbox and 2) a hydrophone-based correction performed invasively to measure the aberrations induced by the skull at 650 kHz. For the full-wave simulation, three different mappings between CT Hounsfield units and the longitudinal speed of sound inside the skull were tested. All methods are compared with the exact same setup due to transfer matrices acquired with the clinical system for N = 5 skulls and T = 2 different targets for each skull. We show that the clinical ray-tracing software and the full-wave simulation restore, respectively, 84% ± 5% and 86% ± 5% of the pressure obtained with hydrophone-based correction for targets located in central brain regions. On the second target (off-center), we also report that the performance of both algorithms degrades when the average incident angles of the acoustic beam at the skull surface increase. When incident angles are higher than 20°, the restored pressure drops below 75% of the pressure restored with hydrophone-based correction.
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36
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Montanaro H, Pasquinelli C, Lee HJ, Kim H, Siebner HR, Kuster N, Thielscher A, Neufeld E. The impact of CT image parameters and skull heterogeneity modeling on the accuracy of transcranial focused ultrasound simulations. J Neural Eng 2021; 18. [PMID: 33836508 DOI: 10.1088/1741-2552/abf68d] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2020] [Accepted: 04/09/2021] [Indexed: 11/12/2022]
Abstract
Objective. Low-intensity transcranial ultrasound stimulation (TUS) is a promising non-invasive brain stimulation (NIBS) technique. TUS can reach deeper areas and target smaller regions in the brain than other NIBS techniques, but its application in humans is hampered by the lack of a straightforward and reliable procedure to predict the induced ultrasound exposure. Here, we examined how skull modeling affects computer simulations of TUS.Approach. We characterized the ultrasonic beam after transmission through a sheep skull with a hydrophone and performed computed tomography (CT) image-based simulations of the experimental setup. To study the skull model's impact, we varied: CT acquisition parameters (tube voltage, dose, filter sharpness), image interpolation, segmentation parameters, acoustic property maps (speed-of-sound, density, attenuation), and transducer-position mismatches. We compared the impact of modeling parameter changes on model predictions and on measurement agreement. Spatial-peak intensity and location, total power, and the Gamma metric (a measure for distribution differences) were used as quantitative criteria. Modeling-based sensitivity analysis was also performed for two human head models.Main results. Sheep skull attenuation assignment and transducer positioning had the most important impact on spatial peak intensity (overestimation up to 300%, respectively 30%), followed by filter sharpness and tube voltage (up to 20%), requiring calibration of the mapping functions. Positioning and skull-heterogeneity-structure strongly affected the intensity distribution (gamma tolerances exceeded in>80%, respectively>150%, of the focus-volume in water), necessitating image-based personalized modeling. Simulation results in human models consistently demonstrate a high sensitivity to the skull-heterogeneity model, attenuation tuning, and transducer shifts, the magnitude of which depends on the underlying skull structure complexity.Significance. Our study reveals the importance of properly modeling the skull-heterogeneity and its structure and of accurately reproducing the transducer position. The results raise red flags when translating modeling approaches among clinical sites without proper standardization and/or recalibration of the imaging and modeling parameters.
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Affiliation(s)
- Hazael Montanaro
- Foundation for Research on Information Technologies in Society (IT'IS), Zurich, Switzerland.,Department of Information Technology and Electrical Engineering , Swiss Federal Institute of Technology (ETH), Zurich, Switzerland.,Laboratory for Acoustics/Noise Control, EMPA, Swiss Federal Laboratories for Materials Science and Technology, Dubendorf, Switzerland.,The authors contributed equally to the work
| | - Cristina Pasquinelli
- Danish Research Centre for Magnetic Resonance, Centre for Functional and Diagnostic Imaging and Research, Copenhagen University Hospital - Amager and Hvidovre, Copenhagen, Denmark.,Center for Magnetic Resonance, Department of Health Technology, Technical University of Denmark, Kgs. Lyngby, Denmark.,The authors contributed equally to the work
| | - Hyunjoo J Lee
- School of Electrical Engineering, Korea Advanced Institute of Science and Technology, Daejeon, Republic of Korea
| | - Hyunggug Kim
- School of Electrical Engineering, Korea Advanced Institute of Science and Technology, Daejeon, Republic of Korea
| | - Hartwig R Siebner
- Danish Research Centre for Magnetic Resonance, Centre for Functional and Diagnostic Imaging and Research, Copenhagen University Hospital - Amager and Hvidovre, Copenhagen, Denmark.,Department of Neurology , Copenhagen University Hospital Bispebjerg, Copenhagen, Denmark.,Institute of Clinical Medicine, Faculty of Health and Medical Sciences, University of Copenhagen , Copenhagen, Denmark
| | - Niels Kuster
- Foundation for Research on Information Technologies in Society (IT'IS), Zurich, Switzerland.,Department of Information Technology and Electrical Engineering , Swiss Federal Institute of Technology (ETH), Zurich, Switzerland
| | - Axel Thielscher
- Danish Research Centre for Magnetic Resonance, Centre for Functional and Diagnostic Imaging and Research, Copenhagen University Hospital - Amager and Hvidovre, Copenhagen, Denmark.,Center for Magnetic Resonance, Department of Health Technology, Technical University of Denmark, Kgs. Lyngby, Denmark
| | - Esra Neufeld
- Foundation for Research on Information Technologies in Society (IT'IS), Zurich, Switzerland.,Department of Information Technology and Electrical Engineering , Swiss Federal Institute of Technology (ETH), Zurich, Switzerland
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Leung SA, Moore D, Webb TD, Snell J, Ghanouni P, Butts Pauly K. Transcranial focused ultrasound phase correction using the hybrid angular spectrum method. Sci Rep 2021; 11:6532. [PMID: 33753771 PMCID: PMC7985511 DOI: 10.1038/s41598-021-85535-5] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2020] [Accepted: 02/25/2021] [Indexed: 12/17/2022] Open
Abstract
The InSightec Exablate system is the standard of care used for transcranial focused ultrasound ablation treatments in the United States. The system calculates phase corrections that account for aberrations caused by the human skull. This work investigates whether skull aberration correction can be improved by comparing the standard of care InSightec ray tracing method with the hybrid angular spectrum (HAS) method and the gold standard hydrophone method. Three degassed ex vivo human skulls were sonicated with a 670 kHz hemispherical phased array transducer (InSightec Exablate 4000). Phase corrections were calculated using four different methods (straight ray tracing, InSightec ray tracing, HAS, and hydrophone) and were used to drive the transducer. 3D raster scans of the beam profiles were acquired using a hydrophone mounted on a 3-axis positioner system. Focal spots were evaluated using six metrics: pressure at the target, peak pressure, intensity at the target, peak intensity, positioning error, and focal spot volume. For three skulls, the InSightec ray tracing method achieved 52 ± 21% normalized target intensity (normalized to hydrophone), 76 ± 17% normalized peak intensity, and 0.72 ± 0.47 mm positioning error. The HAS method achieved 74 ± 9% normalized target intensity, 81 ± 9% normalized peak intensity, and 0.35 ± 0.09 mm positioning error. The InSightec-to-HAS improvement in focal spot targeting provides promise in improving treatment outcomes. These improvements to skull aberration correction are also highly relevant for the applications of focused ultrasound neuromodulation and blood brain barrier opening, which are currently being translated for human use.
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Affiliation(s)
- Steven A Leung
- Department of Bioengineering, Stanford University, Stanford, CA, USA.
| | - David Moore
- Focused Ultrasound Foundation, Charlottesville, VA, USA
| | - Taylor D Webb
- Department of Electrical Engineering, Stanford University, Stanford, CA, USA
| | - John Snell
- Focused Ultrasound Foundation, Charlottesville, VA, USA
- Department of Neurological Surgery, University of Virginia, Charlottesville, VA, USA
| | - Pejman Ghanouni
- Department of Radiology, Stanford University, Stanford, CA, USA
| | - Kim Butts Pauly
- Department of Bioengineering, Stanford University, Stanford, CA, USA
- Department of Electrical Engineering, Stanford University, Stanford, CA, USA
- Department of Radiology, Stanford University, Stanford, CA, USA
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38
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Wu N, Shen G, Qu X, Wu H, Qiao S, Wang E, Chen Y, Wang H. Design of a Versatile Angle-Rotatable Skull-Shaped Conformal Transcranial Focused Ultrasound Transducer for Noninvasive Brain Therapy. IEEE TRANSACTIONS ON ULTRASONICS, FERROELECTRICS, AND FREQUENCY CONTROL 2021; 68:116-126. [PMID: 32396086 DOI: 10.1109/tuffc.2020.2993810] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Phase-controlled focused ultrasound transducers have opened up a new way to noninvasively treat brain diseases. However, due to the geometry and the heterogeneous medium of the human skull, the currently used hemispherical transducers cannot guarantee that the ultrasound emitted by the transducer penetrates the skull normally; consequently, the impact of the shear wave on the treatment area has to be considered. The usual approach is to turn off elements in the transducer with excessively large incident angles, but this approach reduces the efficiency of the transducer. This article presents the design of a novel transducer that can be rotated according to the different geometric shapes of the skull. The incident angles of the elements in the transducer are modified so that the effect of the shear wave on the treatment area can be ignored and the efficiency of the transducer is improved. The results of computed tomography (CT) model simulation of nine skulls verify the versatility and feasibility of the new transducer. We believe that this kind of rotatable transducer has clinical and engineering significance.
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39
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Fomenko A, Chen KHS, Nankoo JF, Saravanamuttu J, Wang Y, El-Baba M, Xia X, Seerala SS, Hynynen K, Lozano AM, Chen R. Systematic examination of low-intensity ultrasound parameters on human motor cortex excitability and behavior. eLife 2020; 9:e54497. [PMID: 33236981 PMCID: PMC7728443 DOI: 10.7554/elife.54497] [Citation(s) in RCA: 60] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2019] [Accepted: 11/24/2020] [Indexed: 12/23/2022] Open
Abstract
Low-intensity transcranial ultrasound (TUS) can non-invasively modulate human neural activity. We investigated how different fundamental sonication parameters influence the effects of TUS on the motor cortex (M1) of 16 healthy subjects by probing cortico-cortical excitability and behavior. A low-intensity 500 kHz TUS transducer was coupled to a transcranial magnetic stimulation (TMS) coil. TMS was delivered 10 ms before the end of TUS to the left M1 hotspot of the first dorsal interosseous muscle. Varying acoustic parameters (pulse repetition frequency, duty cycle, and sonication duration) on motor-evoked potential amplitude were examined. Paired-pulse measures of cortical inhibition and facilitation, and performance on a visuomotor task was also assessed. TUS safely suppressed TMS-elicited motor cortical activity, with longer sonication durations and shorter duty cycles when delivered in a blocked paradigm. TUS increased GABAA-mediated short-interval intracortical inhibition and decreased reaction time on visuomotor task but not when controlled with TUS at near-somatosensory threshold intensity.
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Affiliation(s)
- Anton Fomenko
- Krembil Research Institute, University Health NetworkTorontoCanada
| | - Kai-Hsiang Stanley Chen
- Krembil Research Institute, University Health NetworkTorontoCanada
- Department of Neurology, National Taiwan University Hospital Hsin-Chu BranchHsin-ChuTaiwan
| | | | | | - Yanqiu Wang
- Krembil Research Institute, University Health NetworkTorontoCanada
| | - Mazen El-Baba
- Krembil Research Institute, University Health NetworkTorontoCanada
| | - Xue Xia
- Division of Neurology, Department of Medicine, University of TorontoTorontoCanada
| | | | | | - Andres M Lozano
- Krembil Research Institute, University Health NetworkTorontoCanada
- Division of Neurosurgery, Department of Surgery, Toronto Western Hospital, University of TorontoTorontoCanada
| | - Robert Chen
- Krembil Research Institute, University Health NetworkTorontoCanada
- Division of Neurology, Department of Medicine, University of TorontoTorontoCanada
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40
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Wu N, Shen G, Qu X, Wu H, Qiao S, Wang E, Chen Y, Wang H. An efficient and accurate parallel hybrid acoustic signal correction method for transcranial ultrasound. Phys Med Biol 2020; 65:215019. [PMID: 32721943 DOI: 10.1088/1361-6560/abaa25] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Phased-control focused ultrasound transducers provide a new and noninvasive treatment method for brain disease. However, improving the accuracy of phase correction and reducing the calculation time during treatment have always been contradictory constraints. In this paper, a hybrid acoustic signal correction (HASC) method combined with k-Wave stage and holography stage was introduced for phase correction and simulation of transcranial focused ultrasound. The k-Wave stage is mainly used to calculate the sound field in a heterogeneous medium (skull), which divides the sound field calculation process into paths that can be calculated in parallel, and the transcranial correction phase can also be obtained during the calculation. The holography stage is sufficient to simulate the acoustic field in the homogenous intracranial medium after ultrasound transmitting through the skull. The agreement of the k-space corrected pseudospectral time domain method and HASC method was assessed by statistical methods: linear regression between the two methods provided a slope of 0.9735, intercept of 0.0078, and R 2 of 0.9982. The Bland-Altman method provided a bias of 0.0015 and 95% limits of agreement 0.065 apart. We demonstrated that the difference in sound intensity at the focal point corrected by HASC and time reversal phase correction method was 0.2% and 0.5% in the results of simulation and experiment, respectively. Not only that, the phase calculation time by the HASC phase correction method can be reduced to 11 min on a multi GPU array, which has clinical potential for ultrasound treatment of brain therapy.
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Affiliation(s)
- Nan Wu
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai 200030 People's Republic of China
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41
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Maimbourg G, Guilbert J, Bancel T, Houdouin A, Raybaud G, Tanter M, Aubry JF. Computationally Efficient Transcranial Ultrasonic Focusing: Taking Advantage of the High Correlation Length of the Human Skull. IEEE TRANSACTIONS ON ULTRASONICS, FERROELECTRICS, AND FREQUENCY CONTROL 2020; 67:1993-2002. [PMID: 32396081 DOI: 10.1109/tuffc.2020.2993718] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
The phase correction necessary for transcranial ultrasound therapy requires numerical simulation to noninvasively assess the phase shift induced by the skull bone. Ideally, the numerical simulations need to be fast enough for clinical implementation in a brain therapy protocol and to provide accurate estimation of the phase shift to optimize the refocusing through the skull. In this article, we experimentally performed transcranial ultrasound focusing at 900 kHz on N = 5 human skulls. To reduce the computation time, we propose here to perform the numerical simulation at 450 kHz and use the corresponding phase shifts experimentally at 900 kHz. We demonstrate that a 450-kHz simulation restores 94.2% of the pressure when compared with a simulation performed at 900 kHz and 85.0% of the gold standard pressure obtained by an invasive time reversal procedure based on the signal recorded by a hydrophone placed at the target. From a 900- to 450-kHz simulation, the grid size is divided by 8, and the computation time is divided by 10.
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42
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Jones RM, Huang Y, Meng Y, Scantlebury N, Schwartz ML, Lipsman N, Hynynen K. Echo-Focusing in Transcranial Focused Ultrasound Thalamotomy for Essential Tremor: A Feasibility Study. Mov Disord 2020; 35:2327-2333. [PMID: 32815611 DOI: 10.1002/mds.28226] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2020] [Revised: 06/30/2020] [Accepted: 07/02/2020] [Indexed: 11/06/2022] Open
Abstract
BACKGROUND Transcranial magnetic resonance-guided focused ultrasound (TcMRgFUS) systems currently employ computed tomography (CT)-based aberration corrections, which may provide suboptimal trans-skull focusing. OBJECTIVES The objective of this study was to evaluate a contrast agent microbubble imaging-based transcranial focusing method, echo-focusing (EF), during TcMRgFUS for essential tremor. METHODS A clinical trial of TcMRgFUS thalamotomy using EF for the treatment of essential tremor was conducted (NCT03935581; funded by InSightec [Tirat Carmel, Israel]). Patients (n = 12) were injected with Definity (Lantheus Medical Imaging, North Billerica, MA) microbubbles, and EF was performed using a research feature add-on to a commercial TcMRgFUS system (ExAblate Neuro, InSightec). Subablative thermal sonications carried out using (1) EF and (2) CT-based aberration corrections were compared via magnetic resonance thermometry, and the optimal focusing method for each patient was employed for TcMRgFUS thalamotomy. RESULTS EF aberration corrections provided increased sonication efficiency, decreased focal size, and equivalent targeting accuracy relative to CT-based focusing. EF aberration corrections were employed successfully for lesion formation in all 12 patients, 3 of whom had previously undergone unsuccessful TcMRgFUS thalamotomy via CT-based focusing. There were no adverse events related directly to the EF procedure. CONCLUSIONS EF is feasible and appears safe during TcMRgFUS thalamotomy for essential tremor and improves on the trans-skull focal quality provided by existing CT-based focusing methods. © 2020 International Parkinson and Movement Disorder Society.
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Affiliation(s)
- Ryan M Jones
- Physical Sciences Platform, Sunnybrook Research Institute, Toronto, Ontario, Canada
| | - Yuexi Huang
- Physical Sciences Platform, Sunnybrook Research Institute, Toronto, Ontario, Canada
| | - Ying Meng
- Division of Neurosurgery, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada.,Department of Surgery, University of Toronto, Toronto, Ontario, Canada
| | - Nadia Scantlebury
- Division of Neurosurgery, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada
| | - Michael L Schwartz
- Division of Neurosurgery, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada.,Department of Surgery, University of Toronto, Toronto, Ontario, Canada
| | - Nir Lipsman
- Division of Neurosurgery, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada.,Department of Surgery, University of Toronto, Toronto, Ontario, Canada
| | - Kullervo Hynynen
- Physical Sciences Platform, Sunnybrook Research Institute, Toronto, Ontario, Canada.,Department of Medical Biophysics, University of Toronto, Toronto, Ontario, Canada.,Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, Ontario, Canada
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43
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Yabe T, Yamamoto S, Oda M, Mori K, Toshito T, Akagi T. Prediction of dose distribution from luminescence image of water using a deep convolutional neural network for particle therapy. Med Phys 2020; 47:3882-3891. [DOI: 10.1002/mp.14372] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2020] [Revised: 06/19/2020] [Accepted: 06/25/2020] [Indexed: 12/15/2022] Open
Affiliation(s)
- Takuya Yabe
- Radiological and Medical Laboratory Sciences Nagoya University Graduate School of Medicine Nagoya Japan
- Department of Medical Technology Nagoya University Hospital Nagoya Japan
| | - Seiichi Yamamoto
- Radiological and Medical Laboratory Sciences Nagoya University Graduate School of Medicine Nagoya Japan
| | - Masahiro Oda
- Graduate School of Informatics Nagoya University Nagoya Japan
| | - Kensaku Mori
- Graduate School of Informatics Nagoya University Nagoya Japan
| | - Toshiyuki Toshito
- Nagoya Proton Therapy Center Nagoya City West Medical Center Nagoya Japan
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44
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Pasquinelli C, Montanaro H, Lee HJ, Hanson LG, Kim H, Kuster N, Siebner HR, Neufeld E, Thielscher A. Transducer modeling for accurate acoustic simulations of transcranial focused ultrasound stimulation. J Neural Eng 2020; 17:046010. [DOI: 10.1088/1741-2552/ab98dc] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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45
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Farcito S, Lloyd BA, Thielscher A, Puonti O, Montanaro H, Saturnino GB, Nielsen JD, Madsen CG, Siebner HR, Neufeld E, Kuster N. Accurate anatomical head segmentations: a data set for biomedical simulations. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2020; 2019:6118-6123. [PMID: 31947240 DOI: 10.1109/embc.2019.8857041] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Detailed computational anatomical models of the entire head are needed for accurate in silico modeling in a variety of transcranial stimulation applications. Models from different subjects help to understand and account for population variability. To this end, we have developed a new library of head models of 20 individuals, segmented from co-aligned multi-modal medical image data. The acquired image modalities allow to accurately model tissues with different material properties, such as electrical conductivity or spatially varying acoustic properties. The usefulness of the models is illustrated for two example applications.
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46
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Martin E, Jaros J, Treeby BE. Experimental Validation of k-Wave: Nonlinear Wave Propagation in Layered, Absorbing Fluid Media. IEEE TRANSACTIONS ON ULTRASONICS, FERROELECTRICS, AND FREQUENCY CONTROL 2020; 67:81-91. [PMID: 31535990 DOI: 10.1109/tuffc.2019.2941795] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
Models of ultrasound propagation in biologically relevant media have applications in planning and verification of ultrasound therapies and computational dosimetry. To be effective, the models must be able to accurately predict both the spatial distribution and amplitude of the acoustic pressure. This requires that the models are validated in absolute terms, which for arbitrarily heterogeneous media should be performed by comparison with measurements of the acoustic field. In this article, simulations performed using the open-source k-Wave acoustics toolbox, with a measurement-based source definition, were quantitatively validated against measurements of acoustic pressure in water and layered absorbing fluid media. In water, the measured and simulated spatial-peak pressures agreed to within 3% under linear conditions and 7% under nonlinear conditions. After propagation through a planar or wedge-shaped glycerol-filled phantom, the difference in spatial-peak pressure was 8.5% and 10.7%, respectively. These differences are within or close to the expected uncertainty of the acoustic pressure measurement. The -6 dB width and length of the focus agreed to within 4% in all cases, and the focal positions were within 0.7 mm for the planar phantom and 1.2 mm for the wedge-shaped phantom. These results demonstrate that when the acoustic medium properties and geometry are well known, accurate quantitative predictions of the acoustic field can be made using k-Wave.
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47
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McDannold N, White PJ, Cosgrove R. Elementwise approach for simulating transcranial MRI-guided focused ultrasound thermal ablation. PHYSICAL REVIEW RESEARCH 2019; 1:033205. [PMID: 34164625 PMCID: PMC8218657 DOI: 10.1103/physrevresearch.1.033205] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
This work explored an elementwise approach to model transcranial MRI-guided focused ultrasound (TcMRgFUS) thermal ablation, a noninvasive approach to neurosurgery. Each element of the phased array transducer was simulated individually and could be simultaneously loaded into computer memory, allowing for rapid (~2.5 s) calculation of the pressure field for different phase offsets used for beam steering and aberration correction. We simulated the pressure distribution for 431 sonications in 32 patients, applied the phase and magnitude values used during treatment, and estimated the resulting temperature rise. We systematically varied the relationship between CT (computerized tomography)-derived skull density and the acoustic attenuation and sound speed to obtain the best agreement between the predictions and MR temperature imaging (MRTI). The optimization was validated with simulations of 396 sonications from 40 additional treatments. After optimization, the predicted and measured heating agreed well (R 2: 0.74 patients 1-32; 0.71 patients 33-72). The dimensions and obliquity of the heating in the simulated temperature maps were correlated with the MRTI (R 2: 0.62, 0.74, respectively), but the measured heating was more spatially diffuse. The energy needed to achieve ablation varied by an order of magnitude (3.3-36.1 kJ). While this elementwise approach required more computation time up front (the combined simulation matrices were approximately 4.6 times higher than a single large simulation), it could be performed in parallel on a computing cluster. It allows for rapid calculation of the three-dimensional heating at the focus for different phase and magnitude values on the array. We also show how this approach can be used to optimize the relationship between CT-derived skull density and acoustic properties. While the relationships found here need further validation in a larger patient population, these results demonstrate the promise of this approach to model TcMRgFUS.
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Affiliation(s)
- Nathan McDannold
- Department of Radiology, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts 02115, USA
| | - P Jason White
- Department of Radiology, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts 02115, USA
| | - Rees Cosgrove
- Department of Neurosurgery, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts 02115, USA
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Acquaticci F, Lew SE, Gwirc SN. Ultrasound Axicon: Systematic Approach to Optimize Focusing Resolution through Human Skull Bone. MATERIALS (BASEL, SWITZERLAND) 2019; 12:ma12203433. [PMID: 31635195 PMCID: PMC6829233 DOI: 10.3390/ma12203433] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/16/2019] [Revised: 10/16/2019] [Accepted: 10/17/2019] [Indexed: 06/10/2023]
Abstract
The use of axicon lenses is useful in many high-resolution-focused ultrasound applications, such as mapping, detection, and have recently been extended to ultrasonic brain therapies. However, in order to achieve high spatial resolution with an axicon lens, it is necessary to adjust the separation, called stand-off (δ), between a conventional transducer and the lens attached to it. Comprehensive ultrasound simulations, using the open-source k-Wave toolbox, were performed for an axicon lens attached to a piezo-disc type transducer with a radius of 14 mm, and a frequency of about 0.5 MHz, that is within the range of optimal frequencies for transcranial transmission. The materials properties were measured, and the lens geometry was modelled. Hydrophone measurements were performed through a human skull phantom. We obtained an initial easygoing design model for the lens angle and optimal stand-off using relatively simple formulas. The skull is not an obstacle for focusing of ultrasound with optimized axicon lenses that achieve an identical resolution to spherical transducers, but with the advantage that the focusing distance is shortened. An adequate stand-off improves the lateral resolution of the acoustic beam by approximately 50%. The approach proposed provides an effective way of designing polydimethylsiloxane (PDMS)-based axicon lenses equipped transducers.
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Affiliation(s)
- Fabián Acquaticci
- Instituto de Ingeniería Biomédica, Universidad de Buenos Aires, Buenos Aires C1063ACV, Argentina.
- Instituto Nacional de Tecnología Industrial, Ministerio de Producción y Trabajo, San Martín, Buenos Aires B1650WAB, Argentina.
| | - Sergio E Lew
- Instituto de Ingeniería Biomédica, Universidad de Buenos Aires, Buenos Aires C1063ACV, Argentina.
| | - Sergio N Gwirc
- Departamento de Investigaciones Tecnológicas, Universidad Nacional de La Matanza, San Justo, Buenos Aires B1754JEC, Argentina.
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Park TY, Pahk KJ, Kim H. Method to optimize the placement of a single-element transducer for transcranial focused ultrasound. COMPUTER METHODS AND PROGRAMS IN BIOMEDICINE 2019; 179:104982. [PMID: 31443869 DOI: 10.1016/j.cmpb.2019.104982] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2019] [Revised: 06/25/2019] [Accepted: 07/09/2019] [Indexed: 06/10/2023]
Abstract
BACKGROUND AND OBJECTIVE Transcranial focused ultrasound (tFUS) is a promising neuromodulation technique because of its non-invasiveness and high spatial resolution (within millimeter scale). However, the presence of the skull can lead to disrupting and shifting the acoustic focus in the brain. In this study, we propose a computationally efficient way to determine the optimal position of a single-element focused ultrasound transducer which can effectively deliver acoustic energy to the brain target. We hypothesized that the placement of a single element transducer with the lowest average reflection coefficient would be the optimal position. METHODS The reflection coefficient is defined by the ratio of the amplitude of the reflected wave to the incident wave. To calculate the reflection coefficient, we assumed ultrasound waves as straight lines (beam lines). At each beam line, the reflection coefficient was calculated from the incidence angle at the skull interface (outer/inner skull surfaces). The average reflection coefficient (ARC) was calculated at each possible placement of the transducer using a custom-built software. For comparison purposes, acoustic simulations (k-Wave MATLAB toolbox) which numerically solved the linear wave equation were performed with the same transducer positions used in the ARC calculation. In addition, the experimental validation of our proposed method was also performed by measuring acoustic wave propagation through the calvaria skull phantom in water. The accuracy of our method was defined as the distance between the two optimal transducer placements which were determined from the acoustic simulations and from the ARC method. RESULT Simulated acoustic pressure distribution corresponding to each ARC showed an inverse relationship with peak acoustic pressures produced in the brain. In comparison to the acoustic simulations, the accuracy of our method was 5.07 ± 4.27 mm when targeting the cortical region in the brain. The computing time of ARC calculations were 0.08% of the time required for acoustic pressure simulations. CONCLUSION We calculated the ARC to find the optimal position of the tFUS transducer used in the present study. The optimal placement of the transducer was found when the ARC was the lowest. Our numerical and experimental results showed that the proposed ARC method can effectively be used to find the optimal position of a single-element tFUS transducer for targeting the cortex region of the brain in a computationally inexpensive way.
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Affiliation(s)
- Tae Young Park
- Center for Bionics, Biomedical Research Institute, Korea Institute Science and Technology (KIST), 5, Hwarangro 14-gil, Seongbuk-gu, Seoul 02792, Republic of Korea; Division of Bio-Medical Science & Technology, KIST School, Korea University of Science and Technology, 5, Hwarangro 14-gil, Seongbuk-gu, Seoul 02792, Republic of Korea
| | - Ki Joo Pahk
- Center for Bionics, Biomedical Research Institute, Korea Institute Science and Technology (KIST), 5, Hwarangro 14-gil, Seongbuk-gu, Seoul 02792, Republic of Korea
| | - Hyungmin Kim
- Center for Bionics, Biomedical Research Institute, Korea Institute Science and Technology (KIST), 5, Hwarangro 14-gil, Seongbuk-gu, Seoul 02792, Republic of Korea; Division of Bio-Medical Science & Technology, KIST School, Korea University of Science and Technology, 5, Hwarangro 14-gil, Seongbuk-gu, Seoul 02792, Republic of Korea.
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Pasquinelli C, Hanson LG, Siebner HR, Lee HJ, Thielscher A. Safety of transcranial focused ultrasound stimulation: A systematic review of the state of knowledge from both human and animal studies. Brain Stimul 2019; 12:1367-1380. [PMID: 31401074 DOI: 10.1016/j.brs.2019.07.024] [Citation(s) in RCA: 77] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2019] [Revised: 07/24/2019] [Accepted: 07/29/2019] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND Low-intensity transcranial focused ultrasound stimulation (TFUS) holds great promise as a highly focal technique for transcranial stimulation even for deep brain areas. Yet, knowledge about the safety of this novel technique is still limited. OBJECTIVE To systematically review safety related aspects of TFUS. The review covers the mechanisms-of-action by which TFUS may cause adverse effects and the available data on the possible occurrence of such effects in animal and human studies. METHODS Initial screening used key term searches in PubMed and bioRxiv, and a review of the literature lists of relevant papers. We included only studies where safety assessment was performed, and this results in 33 studies, both in humans and animals. RESULTS Adverse effects of TFUS were very rare. At high stimulation intensity and/or rate, TFUS may cause haemorrhage, cell death or damage, and unintentional blood-brain barrier (BBB) opening. TFUS may also unintentionally affect long-term neural activity and behaviour. A variety of methods was used mainly in rodents to evaluate these adverse effects, including tissue staining, magnetic resonance imaging, temperature measurements and monitoring of neural activity and behaviour. In 30 studies, adverse effects were absent, even though at least one Food and Drug Administration (FDA) safety index was frequently exceeded. Two studies reported microhaemorrhages after long or relatively intense stimulation above safety limits. Another study reported BBB opening and neuronal damage in a control condition, which intentionally and substantially exceeded the safety limits. CONCLUSION Most studies point towards a favourable safety profile of TFUS. Further investigations are warranted to establish a solid safety framework for the therapeutic window of TFUS to reliably avoid adverse effects while ensuring neural effectiveness. The comparability across studies should be improved by a more standardized reporting of TFUS parameters.
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Affiliation(s)
- Cristina Pasquinelli
- Danish Research Centre for Magnetic Resonance, Centre for Functional and Diagnostic Imaging and Research, Copenhagen University Hospital Hvidovre, Denmark; Center for Magnetic Resonance, Department of Health Technology, Technical University of Denmark, Kgs, Lyngby, Denmark
| | - Lars G Hanson
- Danish Research Centre for Magnetic Resonance, Centre for Functional and Diagnostic Imaging and Research, Copenhagen University Hospital Hvidovre, Denmark; Center for Magnetic Resonance, Department of Health Technology, Technical University of Denmark, Kgs, Lyngby, Denmark
| | - Hartwig R Siebner
- Danish Research Centre for Magnetic Resonance, Centre for Functional and Diagnostic Imaging and Research, Copenhagen University Hospital Hvidovre, Denmark; Department of Neurology, Copenhagen University Hospital Bispebjerg, Copenhagen, Denmark; Institute of Clinical Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Hyunjoo J Lee
- School of Electrical Engineering, Korea Advanced Institute of Science and Technology, Daejeon, South Korea
| | - Axel Thielscher
- Danish Research Centre for Magnetic Resonance, Centre for Functional and Diagnostic Imaging and Research, Copenhagen University Hospital Hvidovre, Denmark; Center for Magnetic Resonance, Department of Health Technology, Technical University of Denmark, Kgs, Lyngby, Denmark.
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