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Zhou J, Guo Y, Sun Q, Lin F, Jiang C, Xu K, Ta D. Transcranial ultrafast ultrasound Doppler imaging: A phantom study. ULTRASONICS 2024; 144:107430. [PMID: 39173276 DOI: 10.1016/j.ultras.2024.107430] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/25/2024] [Revised: 07/02/2024] [Accepted: 08/09/2024] [Indexed: 08/24/2024]
Abstract
Ultrafast ultrasound Doppler imaging facilitates the assessment of cerebral hemodynamics with high spatio-temporal resolution. However, the significant acoustic impedance mismatch between the skull and soft tissue results in phase aberrations, which can compromise the quality of transcranial imaging and introduce biases in velocity and direction quantification of blood flow. This paper proposed an aberration correction method that combines deep learning-based skull sound speed modelling with ray theory to realize transcranial plane-wave imaging and ultrafast Doppler imaging. The method was validated through phantom experiments using a linear array with a center frequency of 6.25 MHz, 128 elements, and a pitch of 0.3 mm. The results demonstrated an improvement in the imaging quality of intracranial targets when using the proposed method. After aberration correction, the average locating deviation decreased from 1.40 mm to 0.27 mm in the axial direction, from 0.50 mm to 0.20 mm in the lateral direction, and the average full-width-at-half-maximum (FWHM) decreased from 1.37 mm to 0.97 mm for point scatterers. For circular inclusions, the average contrast-to-noise ratio (CNR) improved from 8.1 dB to 11.0 dB, and the average eccentricity decreased from 0.36 to 0.26. Furthermore, the proposed method was applied to transcranial ultrafast Doppler flow imaging. The results showed a significant improvement in accuracy and quality for blood Doppler flow imaging. The results in the absence of the skull were considered as the reference, and the average normalized root-mean-square errors of the axial velocity component on the five selected axial profiles were reduced from 17.67% to 8.02% after the correction.
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Affiliation(s)
- Jiangjin Zhou
- Department of Biomedical Engineering, School of Information Science and Technology, Fudan University, Shanghai 200438, China
| | - Yuanyang Guo
- Department of Biomedical Engineering, School of Information Science and Technology, Fudan University, Shanghai 200438, China
| | - Qiandong Sun
- Department of Biomedical Engineering, School of Information Science and Technology, Fudan University, Shanghai 200438, China
| | - Fanglue Lin
- Ultrasound BU, Wuhan United Imaging Healthcare Co., Ltd., Wuhan 430206, China
| | - Chen Jiang
- Yiwu Research Institute of Fudan University, Zhejiang 322000, China.
| | - Kailiang Xu
- Department of Biomedical Engineering, School of Information Science and Technology, Fudan University, Shanghai 200438, China; Yiwu Research Institute of Fudan University, Zhejiang 322000, China; PodaMed Medical Technology Co., Ltd., Shanghai 200433, China.
| | - Dean Ta
- Department of Biomedical Engineering, School of Information Science and Technology, Fudan University, Shanghai 200438, China; Yiwu Research Institute of Fudan University, Zhejiang 322000, China
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In A, Strohman A, Payne B, Legon W. Low-intensity focused ultrasound to the posterior insula reduces temporal summation of pain. Brain Stimul 2024; 17:911-924. [PMID: 39089647 DOI: 10.1016/j.brs.2024.07.020] [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: 01/13/2024] [Revised: 07/24/2024] [Accepted: 07/29/2024] [Indexed: 08/04/2024] Open
Abstract
BACKGROUND The insula and dorsal anterior cingulate cortex (dACC) are core brain regions involved in pain processing and central sensitization, a shared mechanism across various chronic pain conditions. Methods to modulate these regions may serve to reduce central sensitization, though it is unclear which target may be most efficacious for different measures of central sensitization. OBJECTIVE/HYPOTHESIS Investigate the effect of low-intensity focused ultrasound (LIFU) to the anterior insula (AI), posterior insula (PI), or dACC on conditioned pain modulation (CPM) and temporal summation of pain (TSP). METHODS N = 16 volunteers underwent TSP and CPM pain tasks pre/post a 10 min LIFU intervention to either the AI, PI, dACC or Sham stimulation. Pain ratings were collected pre/post LIFU. RESULTS Only LIFU to the PI significantly attenuated pain ratings during the TSP protocol. No effects were found for the CPM task for any of the LIFU targets. LIFU pressure modulated group means but did not affect overall group differences. CONCLUSIONS LIFU to the PI reduced temporal summation of pain. This may, in part, be due to dosing (pressure) of LIFU. Inhibition of the PI with LIFU may be a future potential therapy in chronic pain populations demonstrating central sensitization. The minimal effective dose of LIFU for efficacious neuromodulation will help to translate LIFU for therapeutic options.
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Affiliation(s)
- Alexander In
- Virginia Tech Carilion School of Medicine, Roanoke, VA, 24016, USA
| | - Andrew Strohman
- Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, VA, 24016, USA; Virginia Tech Carilion School of Medicine, Roanoke, VA, 24016, USA; Graduate Program in Translational Biology, Medicine, and Health, Virginia Polytechnic Institute and State University, Roanoke, VA, 24016, USA
| | - Brighton Payne
- Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, VA, 24016, USA
| | - Wynn Legon
- Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, VA, 24016, USA; Virginia Tech Carilion School of Medicine, Roanoke, VA, 24016, USA; Center for Human Neuroscience Research, Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, VA, 24016, USA; Center for Health Behaviors Research, Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, VA, 24016, USA; School of Neuroscience, Virginia Polytechnic Institute and State University, Blacksburg, VA, 24016, USA; Graduate Program in Translational Biology, Medicine, and Health, Virginia Polytechnic Institute and State University, Roanoke, VA, 24016, USA; Department of Neurosurgery, Carilion Clinic, Roanoke, VA, 24016, USA.
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Strohman A, Isaac G, Payne B, Verdonk C, Khalsa SS, Legon W. Low-intensity focused ultrasound to the human insular cortex differentially modulates the heartbeat-evoked potential: a proof-of-concept study. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.03.08.584152. [PMID: 38559271 PMCID: PMC10979877 DOI: 10.1101/2024.03.08.584152] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/04/2024]
Abstract
Background The heartbeat evoked potential (HEP) is a brain response time-locked to the heartbeat and a potential marker of interoceptive processing. The insula and dorsal anterior cingulate cortex (dACC) are brain regions that may be involved in generating the HEP. Low-intensity focused ultrasound (LIFU) is a non-invasive neuromodulation technique that can selectively target sub-regions of the insula and dACC to better understand their contributions to the HEP. Objective Proof-of-concept study to determine whether LIFU modulation of the anterior insula (AI), posterior insula (PI), and dACC influences the HEP. Methods In a within-subject, repeated-measures design, healthy human participants (n=16) received 10 minutes of stereotaxically targeted LIFU to the AI, PI, dACC or Sham at rest during continuous electroencephalography (EEG) and electrocardiography (ECG) recording on separate days. Primary outcome was change in HEP amplitudes. Relationships between LIFU pressure and HEP changes were examined using linear mixed modelling. Peripheral indices of visceromotor output including heart rate and heart rate variability (HRV) were explored between conditions. Results Relative to sham, LIFU to the PI, but not AI or dACC, decreased HEP amplitudes; this was partially explained by increased LIFU pressure. LIFU did not affect time or frequency dependent measures of HRV. Conclusions These results demonstrate the ability to modulate HEP amplitudes via non-invasive targeting of key interoceptive brain regions. Our findings have implications for the causal role of these areas in bottom-up heart-brain communication that could guide future work investigating the HEP as a marker of interoceptive processing in healthy and clinical populations.
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Affiliation(s)
- Andrew Strohman
- Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, VA, 24016, USA
- Virginia Tech Carilion School of Medicine, Roanoke, VA, 24016, USA
- Graduate Program in Translational Biology, Medicine, and Health, Virginia Polytechnic Institute and State University, Roanoke, VA, 24016, USA
| | - Gabriel Isaac
- Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, VA, 24016, USA
- School of Neuroscience, Virginia Polytechnic Institute and State University, Blacksburg, VA, 24016, USA
| | - Brighton Payne
- Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, VA, 24016, USA
| | - Charles Verdonk
- Laureate Institute for Brain Research, Tulsa, OK, USA
- VIFASOM (EA 7330 Vigilance Fatigue, Sommeil et Santé Publique), Université Paris Cité, Paris, France
- French Armed Forces Biomedical Research Institute, Brétigny-sur-Orge, France
| | - Sahib S. Khalsa
- Laureate Institute for Brain Research, Tulsa, OK, USA
- Oxley College of Health Sciences, University of Tulsa, Tulsa, OK, USA
| | - Wynn Legon
- Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, VA, 24016, USA
- Center for Human Neuroscience Research, Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, VA, 24016, USA
- Center for Health Behaviors Research, Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, VA, 24016, USA
- School of Neuroscience, Virginia Polytechnic Institute and State University, Blacksburg, VA, 24016, USA
- Virginia Tech Carilion School of Medicine, Roanoke, VA, 24016, USA
- Graduate Program in Translational Biology, Medicine, and Health, Virginia Polytechnic Institute and State University, Roanoke, VA, 24016, USA
- Department of Neurosurgery, Carilion Clinic, Roanoke, VA, 24016, USA
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Bancel T, Tiennot T, Aubry JF. Adaptive Ultrasound Focusing Through the Cranial Bone for Non-invasive Treatment of Brain Disorders. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2022; 1364:397-409. [DOI: 10.1007/978-3-030-91979-5_18] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Jiang C, Li Y, Xu K, Ta D. Full-Matrix Phase Shift Migration Method for Transcranial Ultrasonic Imaging. IEEE TRANSACTIONS ON ULTRASONICS, FERROELECTRICS, AND FREQUENCY CONTROL 2021; 68:72-83. [PMID: 32795967 DOI: 10.1109/tuffc.2020.3016382] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
A spectrum-domain method, called full-matrix phase shift migration (FM-PSM), is presented for transcranial ultrasound phase correction and imaging with ideal synthetic aperture focusing technology. The simulated data obtained using the pseudospectral time-domain method are used to evaluate the feasibility of the method. The experimental data measured from a 3-D printed skull phantom are used to evaluate the algorithm performance in terms of resolution, contrast-to-noise ratio (CNR), and eccentricity comparing with the classical ray-tracing delay and sum (DAS) method. In wire imaging experiment, FM-PSM has a lateral resolution of 0.22 mm and ray-tracing DAS has a lateral resolution of 0.24 mm measured at -6-dB drop using a transducer with a center frequency of 6.25 MHz. In cylinder imaging experiment, FM-PSM has a CNR of 2.14 and ray-tracing DAS has a CNR of 1.82, which illustrates about 17% improvement. For a J -element array and an output image with pixels M ×N (lateral × axial), the computational cost of the DAS is of O(J ×M2×N2) ; on the contrary, it reduces to O(J ×M ×N2) with the proposed FM-PSM. The results suggest that FM-PSM is an efficiency method for transcranial ultrasonic imaging.
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Schoen S, Arvanitis CD. Heterogeneous Angular Spectrum Method for Trans-Skull Imaging and Focusing. IEEE TRANSACTIONS ON MEDICAL IMAGING 2020; 39:1605-1614. [PMID: 31751231 PMCID: PMC10710012 DOI: 10.1109/tmi.2019.2953872] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Ultrasound, alone or in concert with circulating microbubble contrast agents, has emerged as a promising modality for therapy and imaging of brain diseases. While this has become possible due to advancements in aberration correction methods, a range of applications, including adaptive focusing and tracking of the microbubble dynamics through the human skull, may benefit from even more computationally efficient methods to account for skull aberrations. Here, we derive a general method for the angular spectrum approach (ASA) in a heterogeneous medium, based on a numerical marching scheme to approximate the full implicit solution. We then demonstrate its functionality with simulations for (human) skull-related aberration correction and trans-skull passive acoustic mapping. Our simulations show that the general solution provides accurate trans-skull focusing as compared to the uncorrected case (error in focal point location of 1.0 ± 0.4 mm vs 2.2 ± 0.7 mm) for clinically relevant frequencies (0.25-1.5MHz), apertures (50-100 mm), and targets, with peak focal pressures approximately 30 ± 17% of the free field case, with the effects of skull attenuation and amplitude shading included. In the case of source localization, our method leads to an average of 75% error reduction (from 2.9 ± 1.8 mm to 0.7 ± 0.5 mm) and 40-60% increase in peak intensity, evaluated over the range of frequencies (0.4-1.2 MHz), apertures (50-100 mm), and point source locations (40 mm by 50 mm grid) as compared to the homogeneous medium ASA. Overall, total computation times for both focusing and point source localization of the order milliseconds (166 ± 37 ms, compared with 44 ± 4 ms for the homogeneous ASA formulation) can be attained with this approach. Collectively our findings indicate that the proposed phase correction method based on the ASA could provide a computationally efficient and accurate method for trans-skull transmit focusing and imaging of point scatterers, potentially opening new possibilities for treatment and diagnosis of brain diseases.
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Gallay MN, Moser D, Federau C, Jeanmonod D. Radiological and Thermal Dose Correlations in Pallidothalamic Tractotomy With MRgFUS. Front Surg 2019; 6:28. [PMID: 31157233 PMCID: PMC6533852 DOI: 10.3389/fsurg.2019.00028] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2019] [Accepted: 05/02/2019] [Indexed: 12/05/2022] Open
Abstract
Background: MR-guided focused ultrasound (MRgFUS) offers the possibility of safe and accurate lesioning inside the brain. Until now, most MRgFUS thermal applications have been based on temperature or energy protocols. Experimental studies support however an approach centered on thermal dose control. Objective: To show the technical feasibility and lesion size predictability of a thermal dose approach during MRgFUS pallidothalamic tractotomy (PTT) against chronic therapy-resistant Parkinson's disease (PD). Methods: MR and thermal dose data were analyzed in 31 MRgFUS interventions between January and December 2017 in patients suffering from chronic therapy-resistant Parkinson's disease (PD) using a standardized PTT target covered by 5 to 7 target lesion sub-units. Results: Good correlations were found between (1) the mean axial T2 lesion diameter intraoperatively and the mean 240 cumulative equivalent min at 43°C (240 CEM) thermal dose diameter (r = 0.52), (2) the mean axial T2 diameter 48 h post-treatment and the mean 18 CEM thermal dose diameter (r = 0.62), and (3) the mean axial T2 diameter intraoperatively and 48 h post-treatment (r = 0.62). Conclusion: Our current approach using a thermal dose steering for multiple target lesion sub-units could be reproduced in 31 interventions with a good lesion size predictability.
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Affiliation(s)
- Marc N Gallay
- SoniModul, Center for Ultrasound Functional Neurosurgery, Solothurn, Switzerland
| | - David Moser
- SoniModul, Center for Ultrasound Functional Neurosurgery, Solothurn, Switzerland
| | - Christian Federau
- ETH Zurich, Institute for Biomedical Engineering, University Zurich, Zurich, Switzerland.,Department of Radiology, University Hospital Basel, Basel, Switzerland
| | - Daniel Jeanmonod
- SoniModul, Center for Ultrasound Functional Neurosurgery, Solothurn, Switzerland
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Maimbourg G, Houdouin A, Deffieux T, Tanter M, Aubry JF. Steering Capabilities of an Acoustic Lens for Transcranial Therapy: Numerical and Experimental Studies. IEEE Trans Biomed Eng 2019; 67:27-37. [PMID: 30932823 DOI: 10.1109/tbme.2019.2907556] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
For successful brain therapy, transcranial focused ultrasound must compensate for the time shifts induced locally by the skull. The patient-specific phase profile is currently generated by multi-element arrays which, over time, have tended toward increasing element count. We recently introduced a new approach, consisting of a single-element transducer coupled to an acoustic lens of controlled thickness. By adjusting the local thickness of the lens, we were able to induce phase differences which compensated those induced by the skull. Nevertheless, such an approach suffers from an apparent limitation: the lens is a priori designed for one specific target. In this paper, we demonstrate the possibility of taking advantage of the isoplanatic angle of the aberrating skull in order to steer the focus by mechanically moving the transducer/acoustic lens pair around its initial focusing position. This study, conducted on three human skull samples, demonstrates that tilting of the transducer with the lens restores a single -3 dB focal volume at 914 kHz for a steering up to ±11 mm in the transverse direction, and ±10 mm in the longitudinal direction, around the initial focal region.
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Maimbourg G, Houdouin A, Santin M, Lehericy S, Tanter M, Aubry JF. Inside/outside the brain binary cavitation localization based on the lowpass filter effect of the skull on the harmonic content: a proof of concept study. Phys Med Biol 2018; 63:135012. [PMID: 29864024 DOI: 10.1088/1361-6560/aaca21] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Cavitation activity induced by ultrasound may occur during high intensity focused ultrasound (HIFU) treatment, due to bubble nucleation under high peak negative pressure, and during blood-brain-barrier (BBB) disruption, due to injected ultrasound contrast agents (UCAs). Such microbubble activity has to be monitored to assess the safety and efficiency of ultrasonic brain treatments. In this study, we aim at assessing whether cavitation occurs within cerebral tissue by binary discriminating cavitation activity originating from the inside or the outside of the skull. The results were obtained from both in vitro experiments mimicking BBB opening, by using UCA flow, and in vitro thermal necrosis in calf brain samples. The sonication was applied using a 1 MHz focused transducer and the acoustic response of the microbubbles was recorded with a wideband passive cavitation detector. The spectral content of the recorded signal was used to localize microbubble activity. Since the skull acts as a low pass filter, the ratio of high harmonics to low harmonics is lower for cavitation events located inside the skull compared to events outside the skull. Experiments showed that the ratio of the 5/2 ultraharmonic to the 1/2 subharmonic for binary localization cavitation activity achieves 100% sensitivity and specificity for both monkey and human skulls. The harmonic ratio of the fourth to the second harmonic provided 100% sensitivity and 96% and 46% specificity on a non-human primate for thermal necrosis and BBB opening, respectively. Nonetheless, the harmonic ratio remains promising for human applications, as the experiments showed 100% sensitivity and 100% specificity for both thermal necrosis and BBB opening through the human skull. The study requires further validation on a larger number of skull samples.
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Affiliation(s)
- Guillaume Maimbourg
- Institut Langevin, ESPCI Paris, CNRS UMR7587, INSERM U 979, F-75012, PSL Research University, Paris, France. Université Paris Diderot, Sorbonne Paris Cité, F-75013, Paris, France
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Maimbourg G, Houdouin A, Deffieux T, Tanter M, Aubry JF. 3D-printed adaptive acoustic lens as a disruptive technology for transcranial ultrasound therapy using single-element transducers. Phys Med Biol 2018; 63:025026. [PMID: 29219124 DOI: 10.1088/1361-6560/aaa037] [Citation(s) in RCA: 56] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The development of multi-element arrays for better control of the shape of ultrasonic beams has opened the way for focusing through highly aberrating media, such as the human skull. As a result, the use of brain therapy with transcranial-focused ultrasound has rapidly grown. Although effective, such technology is expensive. We propose a disruptive, low-cost approach that consists of focusing a 1 MHz ultrasound beam through a human skull with a single-element transducer coupled with a tailored silicone acoustic lens cast in a 3D-printed mold and designed using computed tomography-based numerical acoustic simulation. We demonstrate on N = 3 human skulls that adding lens-based aberration correction to a single-element transducer increases the deposited energy on the target 10 fold.
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Affiliation(s)
- Guillaume Maimbourg
- INSERM U979, Institut Langevin, Paris, France. ESPCI Paris, Institut Langevin, PSL Research University, Paris, France. CNRS UMR 7587, Institut Langevin, Paris, France. Université Paris Diderot, Paris, France
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Constans C, Deffieux T, Pouget P, Tanter M, Aubry JF. A 200-1380-kHz Quadrifrequency Focused Ultrasound Transducer for Neurostimulation in Rodents and Primates: Transcranial In Vitro Calibration and Numerical Study of the Influence of Skull Cavity. IEEE TRANSACTIONS ON ULTRASONICS, FERROELECTRICS, AND FREQUENCY CONTROL 2017; 64:717-724. [PMID: 28092531 DOI: 10.1109/tuffc.2017.2651648] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Low intensity transcranial focused ultrasound has been demonstrated to produce neuromodulation in both animals and humans. Primarily for technical reasons, frequency is one of the most poorly investigated critical wave parameters. We propose the use of a quadri-band transducer capable of operating at 200, 320, 850, and 1380 kHz for further investigation of the frequency dependence of neuromodulation efficacy while keeping the position of the transducer fixed with respect to the subject's head. This paper presents the results of the transducer calibration in water, in vitro transmission measurements through a monkey skull flap, 3-D simulations based on both a μ -computed tomography ( μ CT)-scan of a rat and on CT-scans of two macaques. A maximum peak pressure greater than 0.52 MPa is expected at each frequency in rat and macaque heads. According to the literature, our transducer can achieve neuromodulation in rodents and primates at each four frequencies. The impact of standing waves is shown to be most prominent at the lowest frequencies.
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Deng L, O'Reilly MA, Jones RM, An R, Hynynen K. A multi-frequency sparse hemispherical ultrasound phased array for microbubble-mediated transcranial therapy and simultaneous cavitation mapping. Phys Med Biol 2016; 61:8476-8501. [PMID: 27845920 DOI: 10.1088/0031-9155/61/24/8476] [Citation(s) in RCA: 49] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Focused ultrasound (FUS) phased arrays show promise for non-invasive brain therapy. However, the majority of them are limited to a single transmit/receive frequency and therefore lack the versatility to expose and monitor the treatment volume. Multi-frequency arrays could offer variable transmit focal sizes under a fixed aperture, and detect different spectral content on receive for imaging purposes. Here, a three-frequency (306, 612, and 1224 kHz) sparse hemispherical ultrasound phased array (31.8 cm aperture; 128 transducer modules) was constructed and evaluated for microbubble-mediated transcranial therapy and simultaneous cavitation mapping. The array is able to perform effective electronic beam steering over a volume spanning (-40, 40) and (-30, 50) mm in the lateral and axial directions, respectively. The focal size at the geometric center is approximately 0.9 (2.1) mm, 1.7 (3.9) mm, and 3.1 (6.5) mm in lateral (axial) pressure full width at half maximum (FWHM) at 1224, 612, and 306 kHz, respectively. The array was also found capable of dual-frequency excitation and simultaneous multi-foci sonication, which enables the future exploration of more complex exposure strategies. Passive acoustic mapping of dilute microbubble clouds demonstrated that the point spread function of the receive array has a lateral (axial) intensity FWHM between 0.8-3.5 mm (1.7-11.7 mm) over a volume spanning (-25, 25) mm in both the lateral and axial directions, depending on the transmit/receive frequency combination and the imaging location. The device enabled both half and second harmonic imaging through the intact skull, which may be useful for improving the contrast-to-tissue ratio or imaging resolution, respectively. Preliminary in vivo experiments demonstrated the system's ability to induce blood-brain barrier opening and simultaneously spatially map microbubble cavitation activity in a rat model. This work presents a tool to investigate optimal strategies for non-thermal FUS brain therapy and concurrent microbubble cavitation monitoring through the availability of multiple frequencies.
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Affiliation(s)
- Lulu Deng
- Physical Sciences Platform, Sunnybrook Research Institute, Toronto, ON M4N 3M5, Canada
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Hynynen K, Jones RM. Image-guided ultrasound phased arrays are a disruptive technology for non-invasive therapy. Phys Med Biol 2016; 61:R206-48. [PMID: 27494561 PMCID: PMC5022373 DOI: 10.1088/0031-9155/61/17/r206] [Citation(s) in RCA: 78] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Focused ultrasound offers a non-invasive way of depositing acoustic energy deep into the body, which can be harnessed for a broad spectrum of therapeutic purposes, including tissue ablation, the targeting of therapeutic agents, and stem cell delivery. Phased array transducers enable electronic control over the beam geometry and direction, and can be tailored to provide optimal energy deposition patterns for a given therapeutic application. Their use in combination with modern medical imaging for therapy guidance allows precise targeting, online monitoring, and post-treatment evaluation of the ultrasound-mediated bioeffects. In the past there have been some technical obstacles hindering the construction of large aperture, high-power, densely-populated phased arrays and, as a result, they have not been fully exploited for therapy delivery to date. However, recent research has made the construction of such arrays feasible, and it is expected that their continued development will both greatly improve the safety and efficacy of existing ultrasound therapies as well as enable treatments that are not currently possible with existing technology. This review will summarize the basic principles, current statures, and future potential of image-guided ultrasound phased arrays for therapy.
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Affiliation(s)
- Kullervo Hynynen
- Physical Sciences Platform, Sunnybrook Research Institute, Toronto, Canada. Department of Medical Biophysics, University of Toronto, Toronto, Canada. Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, Canada
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Kamimura HAS, Wang S, Wu SY, Karakatsani ME, Acosta C, Carneiro AAO, Konofagou EE. Chirp- and random-based coded ultrasonic excitation for localized blood-brain barrier opening. Phys Med Biol 2016; 60:7695-712. [PMID: 26394091 DOI: 10.1088/0031-9155/60/19/7695] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Chirp- and random-based coded excitation methods have been proposed to reduce standing wave formation and improve focusing of transcranial ultrasound. However, no clear evidence has been shown to support the benefits of these ultrasonic excitation sequences in vivo. This study evaluates the chirp and periodic selection of random frequency (PSRF) coded-excitation methods for opening the blood-brain barrier (BBB) in mice. Three groups of mice (n = 15) were injected with polydisperse microbubbles and sonicated in the caudate putamen using the chirp/PSRF coded (bandwidth: 1.5–1.9 MHz, peak negative pressure: 0.52 MPa, duration: 30 s) or standard ultrasound (frequency: 1.5 MHz, pressure: 0.52 MPa, burst duration: 20 ms, duration: 5 min) sequences. T1-weighted contrast-enhanced MRI scans were performed to quantitatively analyze focused ultrasound induced BBB opening. The mean opening volumes evaluated from the MRI were mm3, mm3and mm3 for the chirp, random and regular sonications, respectively. The mean cavitation levels were V.s, V.s and V.s for the chirp, random and regular sonications, respectively. The chirp and PSRF coded pulsing sequences improved the BBB opening localization by inducing lower cavitation levels and smaller opening volumes compared to results of the regular sonication technique. Larger bandwidths were associated with more focused targeting but were limited by the frequency response of the transducer, the skull attenuation and the microbubbles optimal frequency range. The coded methods could therefore facilitate highly localized drug delivery as well as benefit other transcranial ultrasound techniques that use higher pressure levels and higher precision to induce the necessary bioeffects in a brain region while avoiding damage to the surrounding healthy tissue.
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Miller GW, Eames M, Snell J, Aubry JF. Ultrashort echo-time MRI versus CT for skull aberration correction in MR-guided transcranial focused ultrasound: In vitro comparison on human calvaria. Med Phys 2016; 42:2223-33. [PMID: 25979016 DOI: 10.1118/1.4916656] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE Transcranial magnetic resonance-guided focused ultrasound (TcMRgFUS) brain treatment systems compensate for skull-induced beam aberrations by adjusting the phase and amplitude of individual ultrasound transducer elements. These corrections are currently calculated based on a preacquired computed tomography (CT) scan of the patient's head. The purpose of the work presented here is to demonstrate the feasibility of using ultrashort echo-time magnetic resonance imaging (UTE MRI) instead of CT to calculate and apply aberration corrections on a clinical TcMRgFUS system. METHODS Phantom experiments were performed in three ex-vivo human skulls filled with tissue-mimicking hydrogel. Each skull phantom was imaged with both CT and UTE MRI. The MR images were then segmented into "skull" and "not-skull" pixels using a computationally efficient, threshold-based algorithm, and the resulting 3D binary skull map was converted into a series of 2D virtual CT images. Each skull was mounted in the head transducer of a clinical TcMRgFUS system (ExAblate Neuro, Insightec, Israel), and transcranial sonications were performed using a power setting of approximately 750 acoustic watts at several different target locations within the electronic steering range of the transducer. Each target location was sonicated three times: once using aberration corrections calculated from the actual CT scan, once using corrections calculated from the MRI-derived virtual CT scan, and once without applying any aberration correction. MR thermometry was performed in conjunction with each 10-s sonication, and the highest single-pixel temperature rise and surrounding-pixel mean were recorded for each sonication. RESULTS The measured temperature rises were ∼ 45% larger for aberration-corrected sonications than for noncorrected sonications. This improvement was highly significant (p < 10(-4)). The difference between the single-pixel peak temperature rise and the surrounding-pixel mean, which reflects the sharpness of the thermal focus, was also significantly larger for aberration-corrected sonications. There was no significant difference between the sonication results achieved using CT-based and MR-based aberration correction. CONCLUSIONS The authors have demonstrated that transcranial focal heating can be significantly improved in vitro by using UTE MRI to compute skull-induced ultrasound aberration corrections. Their results suggest that UTE MRI could be used instead of CT to implement such corrections on current 0.7 MHz clinical TcMRgFUS devices. The MR image acquisition and segmentation procedure demonstrated here would add less than 15 min to a clinical MRgFUS treatment session.
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Affiliation(s)
- G Wilson Miller
- Department of Radiology and Medical Imaging, University of Virginia, Charlottesville, Virginia 22908 and Department of Biomedical Engineering, University of Virginia, Charlottesville, Virginia 22908
| | - Matthew Eames
- Focused Ultrasound Foundation, Charlottesville, Virginia 22903
| | - John Snell
- Department of Neurosurgery, University of Virginia, Charlottesville, Virginia 22908 and Focused Ultrasound Foundation, Charlottesville, Virginia 22903
| | - Jean-François Aubry
- Department of Radiation Oncology, University of Virginia, Charlottesville, Virginia 22908 and Institut Langevin Ondes et Images, ESPCI ParisTech, CNRS UMR 7587, INSERM U979, Paris 75005, France
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Aubry JF, Tanter M. MR-Guided Transcranial Focused Ultrasound. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2016; 880:97-111. [PMID: 26486334 DOI: 10.1007/978-3-319-22536-4_6] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Previous chapters introduced the ability of using focused ultrasound to ablate tissues. It has led to various clinical applications in the treatment of uterine fibroid, prostate or liver cancers. Nevertheless, treating the brain non-invasively with focused ultrasound has been considered beyond reach for almost a century: The skull bone protects the brain from mechanical injuries, but it also reflects and refracts ultrasound, making it difficult to target the brain with focused ultrasound. Fortunately, aberration correction techniques have been developed recently and thermal lesioning in the thalamus has been achieved clinically. This chapter introduces the aberration effect of the skull bone and how it can be corrected non-invasively. It also presents the latest clinical results obtained with thermal ablation and introduces novel non-thermal approaches that could revolutionize brain therapy in the future.
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Affiliation(s)
- Jean-François Aubry
- Institut Langevin, ESPCI ParisTech, CNRS UMR 7587, INSERM U979, Paris, France. .,Department of Radiation Oncology, University of Virginia, Charlottesville, VA, USA.
| | - Mickael Tanter
- Institut Langevin, ESPCI ParisTech, CNRS UMR 7587, INSERM U979, Paris, France.
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Ding X, Wang Y, Zhang Q, Zhou W, Wang P, Luo M, Jian X. Modulation of transcranial focusing thermal deposition in nonlinear HIFU brain surgery by numerical simulation. Phys Med Biol 2015; 60:3975-98. [DOI: 10.1088/0031-9155/60/10/3975] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
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Sea JC, Bahler CD, Ring JD, Amstutz S, Sanghvi NT, Cheng L, Sundaram CP. Calibration of a Novel, Laparoscopic, 12-mm, Ultrasound, Image-guided, High-intensity Focused Ultrasound Probe for Ablation of Renal Neoplasms. Urology 2015; 85:953-8. [DOI: 10.1016/j.urology.2014.10.063] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2014] [Revised: 09/29/2014] [Accepted: 10/14/2014] [Indexed: 12/25/2022]
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Xu Z, Carlson C, Snell J, Eames M, Hananel A, Lopes MB, Raghavan P, Lee CC, Yen CP, Schlesinger D, Kassell NF, Aubry JF, Sheehan J. Intracranial inertial cavitation threshold and thermal ablation lesion creation using MRI-guided 220-kHz focused ultrasound surgery: preclinical investigation. J Neurosurg 2015; 122:152-61. [PMID: 25380106 DOI: 10.3171/2014.9.jns14541] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
OBJECT In biological tissues, it is known that the creation of gas bubbles (cavitation) during ultrasound exposure is more likely to occur at lower rather than higher frequencies. Upon collapsing, such bubbles can induce hemorrhage. Thus, acoustic inertial cavitation secondary to a 220-kHz MRI-guided focused ultrasound (MRgFUS) surgery is a serious safety issue, and animal studies are mandatory for laying the groundwork for the use of low-frequency systems in future clinical trials. The authors investigate here the in vivo potential thresholds of MRgFUS-induced inertial cavitation and MRgFUS-induced thermal coagulation using MRI, acoustic spectroscopy, and histology. METHODS Ten female piglets that had undergone a craniectomy were sonicated using a 220-kHz transcranial MRgFUS system over an acoustic energy range of 5600-14,000 J. For each piglet, a long-duration sonication (40-second duration) was performed on the right thalamus, and a short sonication (20-second duration) was performed on the left thalamus. An acoustic power range of 140-300 W was used for long-duration sonications and 300-700 W for short-duration sonications. Signals collected by 2 passive cavitation detectors were stored in memory during each sonication, and any subsequent cavitation activity was integrated within the bandwidth of the detectors. Real-time 2D MR thermometry was performed during the sonications. T1-weighted, T2-weighted, gradient-recalled echo, and diffusion-weighted imaging MRI was performed after treatment to assess the lesions. The piglets were killed immediately after the last series of posttreatment MR images were obtained. Their brains were harvested, and histological examinations were then performed to further evaluate the lesions. RESULTS Two types of lesions were induced: thermal ablation lesions, as evidenced by an acute ischemic infarction on MRI and histology, and hemorrhagic lesions, associated with inertial cavitation. Passive cavitation signals exhibited 3 main patterns identified as follows: no cavitation, stable cavitation, and inertial cavitation. Low-power and longer sonications induced only thermal lesions, with a peak temperature threshold for lesioning of 53°C. Hemorrhagic lesions occurred only with high-power and shorter sonications. The sizes of the hemorrhages measured on macroscopic histological examinations correlated with the intensity of the cavitation activity (R2 = 0.74). The acoustic cavitation activity detected by the passive cavitation detectors exhibited a threshold of 0.09 V·Hz for the occurrence of hemorrhages. CONCLUSIONS This work demonstrates that 220-kHz ultrasound is capable of inducing a thermal lesion in the brain of living swines without hemorrhage. Although the same acoustic energy can induce either a hemorrhage or a thermal lesion, it seems that low-power, long-duration sonication is less likely to cause hemorrhage and may be safer. Although further study is needed to decrease the likelihood of ischemic infarction associated with the 220-kHz ultrasound, the threshold established in this work may allow for the detection and prevention of deleterious cavitations.
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Menikou G, Dadakova T, Pavlina M, Bock M, Damianou C. MRI compatible head phantom for ultrasound surgery. ULTRASONICS 2015; 57:144-152. [PMID: 25482534 DOI: 10.1016/j.ultras.2014.11.004] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/19/2014] [Revised: 09/29/2014] [Accepted: 11/09/2014] [Indexed: 06/04/2023]
Abstract
OBJECTIVE Develop a magnetic resonance imaging (MRI) compatible head phantom with acoustic attenuation closely matched to the human attenuation, and suitable for testing focused ultrasound surgery protocols. MATERIALS AND METHODS Images from an adult brain CT scan were used to segment the skull bone from adjacent cerebral tissue. The segmented model was manufactured in a 3-D printer using (Acrylonitrile Butadiene Styrene) ABS plastic. The cerebral tissue was mimicked by an agar-evaporated milk-silica gel (2% w/v-25% v/v-1.2% w/v) which was molded inside a skull model. RESULTS The measured attenuation of the ABS skull was 16 dB/cm MHz. The estimated attenuation coefficient of the gel replicating brain tissue was 0.6 dB/cm MHz. The estimated agar-silica gel's T1 and T2 relaxation times in a 1.5 Tesla magnetic field were 852 ms and 66 ms respectively. The effectiveness of the skull to reduce ultrasonic heating was demonstrated using MRI thermometry. CONCLUSION Due to growing interest in using MRI guided focused ultrasound (MRgFUS) for treating brain cancer and its application in sonothrombolysis, the proposed head phantom can be utilized as a very useful tool for evaluating ultrasonic protocols, thus minimizing the need for animal models and cadavers.
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Affiliation(s)
| | - Tetiana Dadakova
- University Medical Center Freiburg, Radiology - Medical Physics, Freiburg, Germany
| | - Matt Pavlina
- University Medical Center Freiburg, Radiology - Medical Physics, Freiburg, Germany
| | - Michael Bock
- University Medical Center Freiburg, Radiology - Medical Physics, Freiburg, Germany
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Zhang Y, Aubry JF, Zhang J, Wang Y, Roy J, Mata JF, Miller W, Dumont E, Xie M, Lee K, Zuo Z, Wintermark M. Defining the optimal age for focal lesioning in a rat model of transcranial HIFU. ULTRASOUND IN MEDICINE & BIOLOGY 2015; 41:449-55. [PMID: 25542495 DOI: 10.1016/j.ultrasmedbio.2014.09.029] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/10/2014] [Revised: 09/22/2014] [Accepted: 09/22/2014] [Indexed: 05/17/2023]
Abstract
This study aimed at determining the optimal age group for high-intensity focused ultrasound (HIFU) experiments for producing lesions in rats. Younger rats have thinner skulls, allowing for the acoustic waves to propagate easily through the skull without causing burns of the skin and brain surface. Younger rats however, have a smaller brain that can make HIFU focusing in the brain parenchyma challenging because of the focus size. In this study, we conducted transcranial HIFU sonications in rat pups of different ages (from 9 to 43 d) with a 1.5MHz MR compatible transducer. The electric power was selected to always reach a target temperature of at least 50°C in the parenchyma. The thickness of the skull and of the brain parenchyma was measured using T2-weighted MR imaging. Results showed that the thickness of the brain parenchyma increased quickly from P9 to P12, reaching 8.5 mm at P16, and then increasing gradually along with age. The skull thickness increased gradually from P9 to P26, and then more quickly after P30. The ratio between brain parenchyma thickness and skull thickness decreased gradually with age. For the pups at 30 d, the temperature in the brain tissue adjacent to the skull increased to 48.9°C, and those from the rodents older than 33 d reached 60°C or higher, which can produce undesired irreversible damage in this location. We conclude that young rats aged 16-26 d are optimal for experiments producing transcranial HIFU lesions in rats with an intact skull.
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Affiliation(s)
- Yanrong Zhang
- Department of Ultrasound, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China; Neuroradiology Division, Department of Radiology, University of Virginia, Charlottesville, VA, USA
| | - Jean-François Aubry
- Department of Radiation Oncology, University of Virginia, Charlottesville, VA, USA; ESPCI ParisTech, PSL Research University, Institut Langevin, Paris, France; CNRS, Institut Langevin, Paris, France; INSERM, Institut Langevin, Paris, France
| | - Junfeng Zhang
- Department of Anesthesiology, University of Virginia, Charlottesville, VA, USA; Department of Anesthesiology, Shanghai Sixth Hospital, Shanghai Jiaotong University, Shanghai, China
| | - Yi Wang
- Departments of Neuroscience and Neurologic Surgery, University of Virginia, Charlottesville, VA, USA
| | - Jack Roy
- Department of Radiology, University of Virginia, Charlottesville, VA, USA
| | - Jaime F Mata
- Department of Radiology, University of Virginia, Charlottesville, VA, USA
| | - Wilson Miller
- Department of Radiology, University of Virginia, Charlottesville, VA, USA
| | | | - Mingxing Xie
- Department of Ultrasound, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China
| | - Kevin Lee
- Departments of Neuroscience and Neurologic Surgery, University of Virginia, Charlottesville, VA, USA
| | - Zhiyi Zuo
- Department of Anesthesiology, University of Virginia, Charlottesville, VA, USA
| | - Max Wintermark
- Neuroradiology Division, Department of Radiology, University of Virginia, Charlottesville, VA, USA.
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Chang JW, Min BK, Kim BS, Chang WS, Lee YH. Neurophysiologic correlates of sonication treatment in patients with essential tremor. ULTRASOUND IN MEDICINE & BIOLOGY 2015; 41:124-131. [PMID: 25438838 DOI: 10.1016/j.ultrasmedbio.2014.08.008] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/25/2013] [Revised: 07/23/2014] [Accepted: 08/12/2014] [Indexed: 06/04/2023]
Abstract
Transcranial magnetic resonance imaging-guided high-intensity focused ultrasound (MRgHIFU) is gaining attention as a potent substitute for surgical intervention in the treatment of neurologic disorders. To discern the neurophysiologic correlates of its therapeutic effects, we applied MRgHIFU to an intractable neurologic disorder, essential tremor, while measuring magnetoencephalogram mu rhythms from the motor cortex. Focused ultrasound sonication destroyed tissues by focusing a high-energy beam on the ventralis intermedius nucleus of the thalamus. The post-treatment effectiveness was also evaluated using the clinical rating scale for tremors. Thalamic MRgHIFU had substantial therapeutic effects on patients, based on MRgHIFU-mediated improvements in movement control and significant changes in brain mu rhythms. Ultrasonic thalamotomy may reduce hyper-excitable activity in the motor cortex, resulting in normalized behavioral activity after sonication treatment. Thus, non-invasive and spatially accurate MRgHIFU technology can serve as a potent therapeutic tool with broad clinical applications.
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Affiliation(s)
- Jin Woo Chang
- Department of Neurosurgery, Yonsei University College of Medicine, Seoul, Korea
| | - Byoung-Kyong Min
- Department of Brain and Cognitive Engineering, Korea University, Seoul, Korea.
| | - Bong-Soo Kim
- Department of Neurosurgery, Yonsei University College of Medicine, Seoul, Korea
| | - Won Seok Chang
- Department of Neurosurgery, Yonsei University College of Medicine, Seoul, Korea
| | - Yong-Ho Lee
- Korea Research Institute of Standards and Science, Daejeon, Korea
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Pajek D, Hynynen K. The application of sparse arrays in high frequency transcranial focused ultrasound therapy: a simulation study. Med Phys 2014; 40:122901. [PMID: 24320540 DOI: 10.1118/1.4829510] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE Transcranial focused ultrasound is an emerging therapeutic modality that can be used to perform noninvasive neurosurgical procedures. The current clinical transcranial phased array operates at 650 kHz, however the development of a higher frequency array would enable more precision, while reducing the risk of standing waves. However, the smaller wavelength and the skull's increased distortion at this frequency are problematic. It would require an order of magnitude more elements to create such an array. Random sparse arrays enable steering of a therapeutic array with fewer elements. However, the tradeoffs inherent in the use of sparsity in a transcranial phased array have not been systematically investigated and so the objective of this simulation study is to investigate the effect of sparsity on transcranial arrays at a frequency of 1.5 MHz that provides small focal spots for precise exposure control. METHODS Transcranial sonication simulations were conducted using a multilayer Rayleigh-Sommerfeld propagation model. Element size and element population were varied and the phased array's ability to steer was assessed. RESULTS The focal pressures decreased proportionally as elements were removed. However, off-focus hotspots were generated if a high degree of steering was attempted with very sparse arrays. A phased array consisting of 1588 elements 3 mm in size, a 10% population, was appropriate for steering up to 4 cm in all directions. However, a higher element population would be required if near-skull sonication is desired. CONCLUSIONS This study demonstrated that the development of a sparse, hemispherical array at 1.5 MHz could enable more precision in therapies that utilize lower intensity sonications.
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Affiliation(s)
- Daniel Pajek
- Physical Sciences Platform, Sunnybrook Research Institute, Toronto, Ontario M4N 3M5, Canada and Department of Medical Biophysics, University of Toronto, Toronto, Ontario M4N3M5, Canada
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Wintermark M, Tustison NJ, Elias WJ, Patrie JT, Xin W, Demartini N, Eames M, Sumer S, Lau B, Cupino A, Snell J, Hananel A, Kassell N, Aubry JF. T1-weighted MRI as a substitute to CT for refocusing planning in MR-guided focused ultrasound. Phys Med Biol 2014; 59:3599-614. [DOI: 10.1088/0031-9155/59/13/3599] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Kyriakou A, Neufeld E, Werner B, Paulides MM, Szekely G, Kuster N. A review of numerical and experimental compensation techniques for skull-induced phase aberrations in transcranial focused ultrasound. Int J Hyperthermia 2013; 30:36-46. [PMID: 24325307 DOI: 10.3109/02656736.2013.861519] [Citation(s) in RCA: 83] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The development of phased array transducers and their integration with magnetic resonance (MR) guidance and thermal monitoring has established transcranial MR-guided focused ultrasound (tcMRgFUS) as an attractive non-invasive modality for neurosurgical interventions. The presence of the skull, however, compromises the efficiency of transcranial FUS (tcFUS) therapy, as its heterogeneous nature and acoustic characteristics induce significant phase aberrations and energy attenuation, especially at the higher acoustic frequencies employed in tcFUS thermal therapy. These aberrations may distort and shift the acoustic focus as well as induce heating at the patient's scalp and skull bone. Phased array transducers feature hundreds of elements that can be driven individually, each with its own phase and amplitude. This feature allows for compensation of skull-induced aberrations by calculation and application of appropriate phase and amplitude corrections. In this paper, we illustrate the importance of precise refocusing and provide a comprehensive review of the wide variety of numerical and experimental techniques that have been used to estimate these corrections.
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Affiliation(s)
- Adamos Kyriakou
- IT'IS Foundation for Research on Information Technologies in Society , Zurich , Switzerland
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