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Xu R, Treeby BE, Martin E. Safety Review of Therapeutic Ultrasound for Spinal Cord Neuromodulation and Blood-Spinal Cord Barrier Opening. ULTRASOUND IN MEDICINE & BIOLOGY 2024; 50:317-331. [PMID: 38182491 DOI: 10.1016/j.ultrasmedbio.2023.11.007] [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: 06/18/2023] [Revised: 11/07/2023] [Accepted: 11/10/2023] [Indexed: 01/07/2024]
Abstract
New focused ultrasound spinal cord applications have emerged, particularly those improving therapeutic agent delivery to the spinal cord via blood-spinal cord barrier opening and the neuromodulation of spinal cord tracts. One hurdle in the development of these applications is safety. It may be possible to use safety trends from seminal and subsequent works in focused ultrasound to guide the development of safety guidelines for spinal cord applications. We collated data from decades of pre-clinical studies and illustrate a clear relationship between damage, time-averaged spatial peak intensity and exposure duration. This relationship suggests a thermal mechanism underlies ultrasound-induced spinal cord damage. We developed minimum and mean thresholds for damage from these pre-clinical studies. When these thresholds were plotted against the parameters used in recent pre-clinical ultrasonic spinal cord neuromodulation studies, the majority of the neuromodulation studies were near or above the minimum threshold. This suggests that a thermal neuromodulatory effect may exist for ultrasonic spinal cord neuromodulation, and that the thermal dose must be carefully controlled to avoid damage to the spinal cord. By contrast, the intensity-exposure duration threshold had no predictive value when applied to blood-spinal cord barrier opening studies that employed injected contrast agents. Most blood-spinal cord barrier opening studies observed slight to severe damage, except for small animal studies that employed an active feedback control method to limit pressures based on measured bubble oscillation behavior. The development of new focused ultrasound spinal cord applications perhaps reflects the recent success in the development of focused ultrasound brain applications, and recent work has begun on the translation of these technologies from brain to spinal cord. However, a great deal of work remains to be done, particularly with respect to developing and accepting safety standards for these applications.
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Affiliation(s)
- Rui Xu
- Department of Medical Physics and Biomedical Engineering, University College London, London, UK.
| | - Bradley E Treeby
- Department of Medical Physics and Biomedical Engineering, University College London, London, UK
| | - Eleanor Martin
- Department of Medical Physics and Biomedical Engineering, University College London, London, UK
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2
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Yeats E, Hall TL. Aberration correction in abdominal histotripsy. Int J Hyperthermia 2023; 40:2266594. [PMID: 37813397 PMCID: PMC10637766 DOI: 10.1080/02656736.2023.2266594] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2023] [Accepted: 09/28/2023] [Indexed: 10/11/2023] Open
Abstract
In transabdominal histotripsy, ultrasound pulses are focused on the body to noninvasively destroy soft tissues via cavitation. However, the ability to focus is limited by phase aberration, or decorrelation of the ultrasound pulses due to spatial variation in the speed of sound throughout heterogeneous tissue. Phase aberration shifts, broadens, and weakens the focus, thereby reducing the safety and efficacy of histotripsy therapy. This paper reviews and discusses aberration effects in histotripsy and in related therapeutic ultrasound techniques (e.g., high intensity focused ultrasound), with an emphasis on aberration by soft tissues. Methods for aberration correction are reviewed and can be classified into two groups: model-based methods, which use segmented images of the tissue as input to an acoustic propagation model to predict and compensate phase differences, and signal-based methods, which use a receive-capable therapy array to detect phase differences by sensing acoustic signals backpropagating from the focus. The relative advantages and disadvantages of both groups of methods are discussed. Importantly, model-based methods can correct focal shift, while signal-based methods can restore substantial focal pressure, suggesting that both methods should be combined in a 2-step approach. Aberration correction will be critical to improving histotripsy treatments and expanding the histotripsy treatment envelope to enable non-invasive, non-thermal histotripsy therapy for more patients.
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Affiliation(s)
- Ellen Yeats
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan, United States
| | - Timothy L. Hall
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan, United States
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3
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Zheng H, Niu L, Qiu W, Liang D, Long X, Li G, Liu Z, Meng L. The Emergence of Functional Ultrasound for Noninvasive Brain-Computer Interface. RESEARCH (WASHINGTON, D.C.) 2023; 6:0200. [PMID: 37588619 PMCID: PMC10427153 DOI: 10.34133/research.0200] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/13/2023] [Accepted: 07/04/2023] [Indexed: 08/18/2023]
Abstract
A noninvasive brain-computer interface is a central task in the comprehensive analysis and understanding of the brain and is an important challenge in international brain-science research. Current implanted brain-computer interfaces are cranial and invasive, which considerably limits their applications. The development of new noninvasive reading and writing technologies will advance substantial innovations and breakthroughs in the field of brain-computer interfaces. Here, we review the theory and development of the ultrasound brain functional imaging and its applications. Furthermore, we introduce latest advancements in ultrasound brain modulation and its applications in rodents, primates, and human; its mechanism and closed-loop ultrasound neuromodulation based on electroencephalograph are also presented. Finally, high-frequency acoustic noninvasive brain-computer interface is prospected based on ultrasound super-resolution imaging and acoustic tweezers.
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Affiliation(s)
- Hairong Zheng
- Institute of Biomedical and Health Engineering, Shenzhen Institutes of Advanced Technology,
Chinese Academy of Sciences, Shenzhen, 518055, China
| | - Lili Niu
- Institute of Biomedical and Health Engineering, Shenzhen Institutes of Advanced Technology,
Chinese Academy of Sciences, Shenzhen, 518055, China
| | - Weibao Qiu
- Institute of Biomedical and Health Engineering, Shenzhen Institutes of Advanced Technology,
Chinese Academy of Sciences, Shenzhen, 518055, China
| | - Dong Liang
- Institute of Biomedical and Health Engineering, Shenzhen Institutes of Advanced Technology,
Chinese Academy of Sciences, Shenzhen, 518055, China
| | - Xiaojing Long
- Institute of Biomedical and Health Engineering, Shenzhen Institutes of Advanced Technology,
Chinese Academy of Sciences, Shenzhen, 518055, China
| | - Guanglin Li
- Shenzhen Institute of Advanced Integration Technology, Chinese Academy of Sciences and The Chinese University of Hong Kong, Shenzhen, 518055, China
| | - Zhiyuan Liu
- Shenzhen Institute of Advanced Integration Technology, Chinese Academy of Sciences and The Chinese University of Hong Kong, Shenzhen, 518055, China
| | - Long Meng
- Institute of Biomedical and Health Engineering, Shenzhen Institutes of Advanced Technology,
Chinese Academy of Sciences, Shenzhen, 518055, China
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4
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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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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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Angla C, Larrat B, Gennisson JL, Chatillon S. Transcranial ultrasound simulations: A review. Med Phys 2023; 50:1051-1072. [PMID: 36047387 DOI: 10.1002/mp.15955] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2022] [Revised: 08/12/2022] [Accepted: 08/15/2022] [Indexed: 11/06/2022] Open
Abstract
Transcranial ultrasound is more and more used for therapy and imaging of the brain. However, the skull is a highly attenuating and aberrating medium, with different structures and acoustic properties among samples and even within a sample. Thus, case-specific simulations are needed to perform transcranial focused ultrasound interventions safely. In this article, we provide a review of the different methods used to model the skull and to simulate ultrasound propagation through it.
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Affiliation(s)
| | - Benoit Larrat
- Université Paris Saclay, CNRS, CEA, DRF/JOLIOT/NEUROSPIN/BAOBAB, Gif-sur-Yvette, France
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Tan L, Pan J, Jiang Q, Liu F. Application of Time-Reversal in Electromagnetic Power Synthesis under Distributed Motion Platform. Heliyon 2022; 8:e11822. [DOI: 10.1016/j.heliyon.2022.e11822] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2022] [Revised: 05/30/2022] [Accepted: 11/15/2022] [Indexed: 11/20/2022] Open
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Thomas GPL, Khokhlova TD, Sapozhnikov OA, Wang YN, Totten SI, Khokhlova VA. In Vivo Aberration Correction for Transcutaneous HIFU Therapy Using a Multielement Array. IEEE TRANSACTIONS ON ULTRASONICS, FERROELECTRICS, AND FREQUENCY CONTROL 2022; 69:2955-2964. [PMID: 35981067 PMCID: PMC9714798 DOI: 10.1109/tuffc.2022.3200309] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
One of the challenges of transcutaneous high-intensity focused ultrasound (HIFU) therapies, especially ones relying heavily on shock formation, such as boiling histotripsy (BH), is the loss of focusing from aberration induced by the heterogeneities of the body wall. Here, a methodology to execute aberration correction in vivo is proposed. A custom BH system consisting of a 1.5-MHz phased array of 256 elements connected to a Verasonics V1 system is used in pulse/echo mode on a porcine model under general anesthesia. Estimation of the time shifts needed to correct for aberration in the liver and kidney is done by maximizing the value of the coherence factor on the acquired backscattered signals. As this process requires multiple pulse/echo sequences on a moving target to converge to a solution, tracking is also implemented to ensure that the same target is used between each iteration. The method was validated by comparing the acoustic power needed to generate a boiling bubble at one target with aberration correction and at another target within a 5-mm radius without aberration correction. Results show that the aberration correction effectively lowers the acoustic power required to reach boiling by up to 45%, confirming that it indeed restored formation of the nonlinear shock front at the focus.
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Lu N, Hall TL, Sukovich JR, Choi SW, Snell J, McDannold N, Xu Z. Two-step aberration correction: application to transcranial histotripsy. Phys Med Biol 2022; 67:10.1088/1361-6560/ac72ed. [PMID: 35609619 PMCID: PMC9234948 DOI: 10.1088/1361-6560/ac72ed] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2022] [Accepted: 05/24/2022] [Indexed: 11/11/2022]
Abstract
Objective: Phase aberration correction is essential in transcranial histotripsy to compensate for focal distortion caused by the heterogeneity of the intact skull bone. This paper improves the 2-step aberration correction (AC) method that has been previously presented and develops an AC workflow that fits in the clinical environment, in which the computed tomography (CT)-based analytical approach was first implemented, followed by a cavitation-based approach using the shockwaves from the acoustic cavitation emission (ACE).Approach:A 700 kHz, 360-element hemispherical transducer array capable of transmit-and-receive on all channels was used to transcranially generate histotripsy-induced cavitation and acquire ACE shockwaves. For CT-AC, two ray-tracing models were investigated: a forward ray-tracing model (transducer-to-focus) in the open-source software Kranion, and an in-house backward ray-tracing model (focus-to-transducer) accounting for refraction and the sound speed variation in skulls. Co-registration was achieved by aligning the skull CT data to the skull surface map reconstructed using the acoustic pulse-echo method. For ACE-AC, the ACE signals from the collapses of generated bubbles were aligned by cross-correlation to estimate the corresponding time delays.Main results:The performance of the 2-step method was tested with 3 excised human calvariums placed at 2 different locations in the transducer array. Results showed that the 2-step AC achieved 90 ± 7% peak focal pressure compared to the gold standard hydrophone correction. It also reduced the focal shift from 0.84 to 0.30 mm and the focal volume from 10.6 to 2.0 mm3on average compared to the no AC cases.Significance:The 2-step AC yielded better refocusing compared to either CT-AC or ACE-AC alone and can be implemented in real-time for transcranial histotripsy brain therapy.
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Affiliation(s)
- Ning Lu
- 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
| | - Jonathan R Sukovich
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, United States of America
| | - Sang Won Choi
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, United States of America
| | - John Snell
- Focused Ultrasound Foundation, Charlottesville, United States of America
| | - Nathan McDannold
- Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Zhen Xu
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, United States of America
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10
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Deng L, Yang SD, O’Reilly MA, Jones RM, Hynynen K. An Ultrasound-Guided Hemispherical Phased Array for Microbubble-Mediated Ultrasound Therapy. IEEE Trans Biomed Eng 2022; 69:1776-1787. [PMID: 34855582 PMCID: PMC9092225 DOI: 10.1109/tbme.2021.3132014] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
GOAL To develop a low-cost magnetic resonance imaging (MRI)-free transcranial focused ultrasound (FUS) system for microbubble-mediated therapy. METHODS A 128-element 11 MHz array for skull localization was integrated within a 256-module multi-frequency (306/612/1224 kHz) dual-mode phased array. The system's transcranial transmit and receive performance was evaluated with ex-vivo human skullcaps using phase aberration corrections calculated from computed tomography (CT)-based simulations via ultrasound-based (USCT) and landmark-based (LMCT) registrations, and a gold-standard fixed source emitter (FSE)-based method. RESULTS Displacement and rotation registration errors of 1.4 ± 0.4 mm and 2.1 ± 0.2 ° were obtained using USCT, resulting in sub-millimeter transmit targeting errors driven at 306 kHz (0.9 ± 0.2 mm) and 612 kHz (0.9 ± 0.3 mm), and source localization errors of 1.0 ± 0.3 mm and 0.6 ± 0.2 mm at receive frequencies of 306 kHz and 612 kHz, respectively (mean ± SD). Similar errors were obtained using LMCT and no significant differences between these two approaches were found on either transmit (p = 0.64/0.99) or receive (p = 0.45/0.36) at 306 kHz/612kHz. During volumetric multi-point exposures, approximately 70% and 60% of the transmit frames in which microbubble activity was detected via FSE were recovered using USCT when imaging at the second-harmonic and half-harmonic, respectively, compared to 60% and 69% using LMCT. CONCLUSION This low-cost ultrasound-guided transcranial FUS system affords USCT skull registration with accuracy comparable to LMCT methods. SIGNIFICANCE Such systems have great potential to advance the adoption of microbubble-mediated FUS brain therapy by improving access to the technology.
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Affiliation(s)
| | - Steven D. Yang
- Physical Sciences Platform, Sunnybrook Research Institute, Toronto, ON, Canada
| | - Meaghan A. O’Reilly
- Physical Sciences Platform, Sunnybrook Research Institute and the Department of Medical Biophysics, University of Toronto, ON, Canada
| | - Ryan M. Jones
- Physical Sciences Platform, Sunnybrook Research Institute, Toronto, ON, Canada
| | - Kullervo Hynynen
- Physical Sciences Platform, Sunnybrook Research Institute, the Department of Medical Biophysics, and the Institute of Biomedical Engineering, University of Toronto, Toronto, ON, Canada
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Schoen S, Dash P, Arvanitis CD. Experimental Demonstration of Trans-Skull Volumetric Passive Acoustic Mapping With the Heterogeneous Angular Spectrum Approach. IEEE TRANSACTIONS ON ULTRASONICS, FERROELECTRICS, AND FREQUENCY CONTROL 2022; 69:534-542. [PMID: 34748486 PMCID: PMC10243207 DOI: 10.1109/tuffc.2021.3125670] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Real-time, 3-D, passive acoustic mapping (PAM) of microbubble dynamics during transcranial focused ultrasound (FUS) is essential for optimal treatment outcomes. The angular spectrum approach (ASA) potentially offers a very efficient method to perform PAM, as it can reconstruct specific frequency bands pertinent to microbubble dynamics and may be extended to correct aberrations caused by the skull. Here, we experimentally assess the abilities of heterogeneous ASA (HASA) to perform trans-skull PAM. Our experimental investigations demonstrate that the 3-D PAMs of a known 1-MHz source, constructed with HASA through an ex vivo human skull segment, reduced both the localization error (from 4.7 ± 2.3 to 2.3 ± 1.6 mm) and the number, size, and energy of spurious lobes caused by aberration, with the modest additional computational expense. While further improvements in the localization errors are expected with arrays with denser elements and larger aperture, our analysis revealed that experimental constraints associated with the array pitch and aperture (here, 1.8 mm and 2.5 cm, respectively) can be ameliorated by interpolation and peak finding techniques. Beyond the array characteristics, our analysis also indicated that errors in the registration (translation and rotation of ±5 mm and ±5°, respectively) of the skull segment to the array can lead to peak localization errors of the order of a few wavelengths. Interestingly, errors in the spatially dependent speed of sound in the skull (±20%) caused only subwavelength errors in the reconstructions, suggesting that registration is the most important determinant of point source localization accuracy. Collectively, our findings show that HASA can address source localization problems through the skull efficiently and accurately under realistic conditions, thereby creating unique opportunities for imaging and controlling the microbubble dynamics in the brain.
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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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Gupta S, Haiat G, Laporte C, Belanger P. Effect of the Acoustic Impedance Mismatch at the Bone-Soft Tissue Interface as a Function of Frequency in Transcranial Ultrasound: A Simulation and In Vitro Experimental Study. IEEE TRANSACTIONS ON ULTRASONICS, FERROELECTRICS, AND FREQUENCY CONTROL 2021; 68:1653-1663. [PMID: 33306464 DOI: 10.1109/tuffc.2020.3043893] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
The transcranial Doppler (TCD) ultrasound is a method that uses a handheld low-frequency (2-2.5 MHz), pulsed Doppler phased array probe to measure blood velocity within the arteries located inside the brain. The problem with TCD lies in the low ultrasonic energy penetrating inside the brain through the skull, which leads to a low signal-to-noise ratio. This is due to several effects, including phase aberration, variations in the speed of sound in the skull, scattering, the acoustic impedance mismatch, and absorption of the three-layer medium constituted by soft tissues, the skull, and the brain. The goal of this article is to study the effect of transmission losses due to the acoustic impedance mismatch on the transmitted energies as a function of frequency. To do so, wave propagation was modeled from the ultrasonic transducer into the brain. This model calculates transmission coefficients inside the brain, leading to a frequency-dependent transmission coefficient for a given skin and bone thickness. This approach was validated experimentally by comparing the analytical results with measurements obtained from a bone phantom plate mimicking the skull. The average position error of the occurrence of the maximum amplitude between the experiment and analytical result was equivalent to a 0.06-mm error on the skin thickness given a fixed bone thickness. The similarity between the experimental and analytical results was also demonstrated by calculating correlation coefficients. The average correlation between the experimental and analytical results came out to be 0.50 for a high-frequency probe and 0.78 for a low-frequency probe. Further analysis of the simulation showed that an optimized excitation frequency can be chosen based on skin and bone thicknesses, thereby offering an opportunity to improve the image quality of TCD.
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Thomas GPL, Khokhlova TD, Bawiec CR, Peek AT, Sapozhnikov OA, O'Donnell M, Khokhlova VA. Phase-Aberration Correction for HIFU Therapy Using a Multielement Array and Backscattering of Nonlinear Pulses. IEEE TRANSACTIONS ON ULTRASONICS, FERROELECTRICS, AND FREQUENCY CONTROL 2021; 68:1040-1050. [PMID: 33052845 PMCID: PMC8476183 DOI: 10.1109/tuffc.2020.3030890] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Phase aberrations induced by heterogeneities in body wall tissues introduce a shift and broadening of the high-intensity focused ultrasound (HIFU) focus, associated with decreased focal intensity. This effect is particularly detrimental for HIFU therapies that rely on shock front formation at the focus, such as boiling histotripsy (BH). In this article, an aberration correction method based on the backscattering of nonlinear ultrasound pulses from the focus is proposed and evaluated in tissue-mimicking phantoms. A custom BH system comprising a 1.5-MHz 256-element array connected to a Verasonics V1 engine was used as a pulse/echo probe. Pulse inversion imaging was implemented to visualize the second harmonic of the backscattered signal from the focus inside a phantom when propagating through an aberrating layer. Phase correction for each array element was derived from an aberration-correction method for ultrasound imaging that combines both the beamsum and the nearest neighbor correlation method and adapted it to the unique configuration of the array. The results were confirmed by replacing the target tissue with a fiber-optic hydrophone. Comparing the shock amplitude before and after phase-aberration correction showed that the majority of losses due to tissue heterogeneity were compensated, enabling fully developed shocks to be generated while focusing through aberrating layers. The feasibility of using a HIFU phased-array transducer as a pulse-echo probe in harmonic imaging mode to correct for phase aberrations was demonstrated.
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Demené C, Robin J, Dizeux A, Heiles B, Pernot M, Tanter M, Perren F. Transcranial ultrafast ultrasound localization microscopy of brain vasculature in patients. Nat Biomed Eng 2021; 5:219-228. [PMID: 33723412 PMCID: PMC7610356 DOI: 10.1038/s41551-021-00697-x] [Citation(s) in RCA: 108] [Impact Index Per Article: 36.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2020] [Accepted: 02/05/2021] [Indexed: 12/23/2022]
Abstract
Changes in cerebral blood flow are associated with stroke, aneurysms, vascular cognitive impairment, neurodegenerative diseases and other pathologies. Brain angiograms, typically performed via computed tomography or magnetic resonance imaging, are limited to millimetre-scale resolution and are insensitive to blood-flow dynamics. Here we show that ultrafast ultrasound localization microscopy of intravenously injected microbubbles enables transcranial imaging of deep vasculature in the adult human brain at microscopic resolution and the quantification of haemodynamic parameters. Adaptive speckle tracking to correct for micrometric brain-motion artefacts and ultrasonic-wave aberrations induced during transcranial propagation allowed us to map the vascular network of tangled arteries to functionally characterize blood-flow dynamics at a resolution of up to 25 μm and to detect blood vortices in a small deep-seated aneurysm in a patient. Ultrafast ultrasound localization microscopy may facilitate the understanding of brain haemodynamics and of how vascular abnormalities in the brain are related to neurological pathologies.
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Affiliation(s)
- Charlie Demené
- Physics for Medicine Paris, Inserm, ESPCI Paris, PSL Research University, CNRS, Paris, France.,Department of Clinical Neurosciences, HUG, LUNIC Laboratory Geneva Neurocenter, Faculty of Medicine, University of Geneva, Geneva, Switzerland
| | - Justine Robin
- Physics for Medicine Paris, Inserm, ESPCI Paris, PSL Research University, CNRS, Paris, France.,Department of Clinical Neurosciences, HUG, LUNIC Laboratory Geneva Neurocenter, Faculty of Medicine, University of Geneva, Geneva, Switzerland
| | - Alexandre Dizeux
- Physics for Medicine Paris, Inserm, ESPCI Paris, PSL Research University, CNRS, Paris, France
| | - Baptiste Heiles
- Physics for Medicine Paris, Inserm, ESPCI Paris, PSL Research University, CNRS, Paris, France
| | - Mathieu Pernot
- Physics for Medicine Paris, Inserm, ESPCI Paris, PSL Research University, CNRS, Paris, France
| | - Mickael Tanter
- Physics for Medicine Paris, Inserm, ESPCI Paris, PSL Research University, CNRS, Paris, France.
| | - Fabienne Perren
- Department of Clinical Neurosciences, HUG, LUNIC Laboratory Geneva Neurocenter, Faculty of Medicine, University of Geneva, Geneva, Switzerland
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16
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Mozaffarzadeh M, Minonzio C, de Jong N, Verweij MD, Hemm S, Daeichin V. Lamb Waves and Adaptive Beamforming for Aberration Correction in Medical Ultrasound Imaging. IEEE TRANSACTIONS ON ULTRASONICS, FERROELECTRICS, AND FREQUENCY CONTROL 2021; 68:84-91. [PMID: 32746204 DOI: 10.1109/tuffc.2020.3007345] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Phase aberration in transcranial ultrasound imaging (TUI) caused by the human skull leads to an inaccurate image reconstruction. In this article, we present a novel method for estimating the speed of sound and an adaptive beamforming technique for phase aberration correction in a flat polyvinylchloride (PVC) slab as a model for the human skull. First, the speed of sound of the PVC slab is found by extracting the overlapping quasi-longitudinal wave velocities of symmetrical Lamb waves in the frequency-wavenumber domain. Then, the thickness of the plate is determined by the echoes from its front and back side. Next, an adaptive beamforming method is developed, utilizing the measured sound speed map of the imaging medium. Finally, to minimize reverberation artifacts caused by strong scatterers (i.e., needles), a dual probe setup is proposed. In this setup, we image the medium from two opposite directions, and the final image can be the minimum intensity projection of the inherently co-registered images of the opposed probes. Our results confirm that the Lamb wave method estimates the longitudinal speed of the slab with an error of 3.5% and is independent of its shear wave speed. Benefiting from the acquired sound speed map, our adaptive beamformer reduces (in real time) a mislocation error of 3.1, caused by an 8 mm slab, to 0.1 mm. Finally, the dual probe configuration shows 7 dB improvement in removing reverberation artifacts of the needle, at the cost of only 2.4-dB contrast loss. The proposed image formation method can be used, e.g., to monitor deep brain stimulation procedures and localization of the electrode(s) deep inside the brain from two temporal bones on the sides of the human skull.
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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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18
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Jin C, Moore D, Snell J, Paeng DG. An open-source phase correction toolkit for transcranial focused ultrasound. BMC Biomed Eng 2020; 2:9. [PMID: 32903384 PMCID: PMC7427913 DOI: 10.1186/s42490-020-00043-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2020] [Accepted: 08/03/2020] [Indexed: 01/01/2023] Open
Abstract
BACKGROUND The phase correction on transcranial focused ultrasound is essential to regulate unwanted focal point shift caused by skull bone aberration. The aim of the current study was to design and investigate the feasibility of a ray-based phase correction toolkit for transcranial focused ultrasound. RESULTS The peak pressure at focal area was improved by 140.5 ± 7.0% on target I and 134.8 ± 19.1% on target II using proposed phase correction toolkit, respectively. A total computation time of 402.1 ± 24.5 milliseconds was achieved for each sonication. CONCLUSION The designed ray-based phase correction software can be used as a lightweight toolkit to compensate aberrated phase within clinical environment.
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Affiliation(s)
- Changzhu Jin
- Department of Robotics Engineering, DGIST, Daegu, 42988 Korea
- DGIST-ETH Microrobot Research Center, DGIST, Daegu, 42988 Korea
| | - David Moore
- Focused Ultrasound Foundation, Charlottesville, VA 22903 USA
| | - John Snell
- Focused Ultrasound Foundation, Charlottesville, VA 22903 USA
| | - Dong-Guk Paeng
- Focused Ultrasound Foundation, Charlottesville, VA 22903 USA
- Department of Radiology and Medical Imaging, University of Virginia, Charlottesville, VA 22903 USA
- Ocean System, Engineering/ Biomedical Engineering, Jeju National University, Jeju, 63243 Korea
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19
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Sukovich JR, Macoskey JJ, Lundt JE, Gerhardson TI, Hall TL, Xu Z. Real-Time Transcranial Histotripsy Treatment Localization and Mapping Using Acoustic Cavitation Emission Feedback. IEEE TRANSACTIONS ON ULTRASONICS, FERROELECTRICS, AND FREQUENCY CONTROL 2020; 67:1178-1191. [PMID: 31976885 PMCID: PMC7398266 DOI: 10.1109/tuffc.2020.2967586] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Cavitation events generated during histotripsy therapy generate large acoustic cavitation emission (ACE) signals that can be detected through the skull. This article investigates the feasibility of using these ACE signals, acquired using the elements of a 500-kHz, 256-element hemispherical histotripsy transducer as receivers, to localize and map the cavitation activity in real time through the human skullcap during transcranial histotripsy therapy. The locations of the generated cavitation events predicted using the ACE feedback signals in this study were found to be accurate to within <1.5 mm of the centers of masses detected by optical imaging and found to lie to within the measured volumes of the generated cavitation events in >~80 % of cases. Localization results were observed to be biased in the prefocal direction of the histotripsy array and toward its transverse origin but were only weakly affected by focal steering location. The choice of skullcap and treatment pulse repetition frequency (PRF) were both observed to affect the accuracy of the localization results in the low PRF regime (1-10 Hz), but the localization accuracy was seen to stabilize at higher PRFs (≥10 Hz). Tests of the localization algorithm in vitro, for treatment delivered to a bovine brain sample mounted within the skullcap, revealed good agreement between the ACE feedback-generated treatment map and the morphological characteristics of the treated volume of the brain sample. Localization during experiments was achieved in real time for pulses delivered at rates up to 70 Hz, but benchmark tests indicate that the localization algorithm is scalable, indicating that higher rates are possible with more powerful hardware. The results of this article demonstrate the feasibility of using ACE feedback signals to localize and map transcranially generated cavitation events during histotripsy. Such capability has the potential to greatly simplify transcranial histotripsy treatments, as it may provide a non-MRI-based method for monitoring and localizing transcranial histotripsy treatments in real time.
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20
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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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21
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Deng L, Hughes A, Hynynen K. A Noninvasive Ultrasound Resonance Method for Detecting Skull Induced Phase Shifts May Provide a Signal for Adaptive Focusing. IEEE Trans Biomed Eng 2020; 67:2628-2637. [PMID: 31976875 DOI: 10.1109/tbme.2020.2967033] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
OBJECTIVE There may be a need to perform dynamic skull aberration corrections during the non-invasive high-intensity transcranial treatment with magnetic resonance imaging (MRI) -guided focused ultrasound in order to accurately and rapidly restore the focus in the brain. METHODS This could possibly be accomplished by using an ultrasound-based correction method based on the skulls' thickness resonance frequencies. The focus of a 500 kHz transducer was centered in the ex vivo human skull caps at different temperatures. The pulse-echoed signals reflected from the skulls were analyzed in the frequency domain to reveal the resonance frequencies for the phase shift calculation. The accuracy was compared to both hydrophone and computed tomography (CT) based analytical methods. RESULTS Around 73% of the measurements (n = 784) were in the optimal constructive interference region, with a 15° decrease in the average phase error compared to the previous study. In the best implementation, it performed approximately the same or better than the CT based analytical method currently in clinical use. Linear correlation was found between the resonance frequencies or skull induced phase shifts and the skull temperature with an average rate of -0.4 kHz/°C and 2.6 deg/°C, respectively. CONCLUSION The ultrasound based resonance method has shown the feasibility of detecting heating-induced changes of skull phase shift non-invasively and accurately. SIGNIFICANCE Since the technique can be made MRI compatible and integrated in the therapy arrays, it may enable temperature tracking and adaptive focusing during high-intensity transcranial ultrasound treatments, to prevent skull overheating and preserve the transcranial focusing integrity.
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22
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Qiao S, Elbes D, Boubriak O, Urban JPG, Coussios CC, Cleveland RO. Delivering Focused Ultrasound to Intervertebral Discs Using Time-Reversal. ULTRASOUND IN MEDICINE & BIOLOGY 2019; 45:2405-2416. [PMID: 31155405 DOI: 10.1016/j.ultrasmedbio.2019.04.023] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/16/2018] [Revised: 04/18/2019] [Accepted: 04/25/2019] [Indexed: 06/09/2023]
Abstract
Chronic low back pain causes more disability worldwide than any other condition and is thought to arise in part through loss of biomechanical function of degenerate intervertebral discs (IVDs). Current treatments can involve replacing part or all of the degenerate IVDs by invasive surgery. Our vision is to develop a minimally invasive approach in which high intensity focused ultrasound (HIFU) is used to mechanically fractionate degenerate tissue in an IVD; a fine needle is then used to first remove the fractionated tissue and then inject a biomaterial able to restore normal physiologic function. The goal of this manuscript is to demonstrate the feasibility of trans-spinal HIFU delivery using simulations of 3-D ultrasound propagation in models derived from patient computed tomography (CT) scans. The CT data were segmented into bone, fat and other soft tissue for three patients. Ultrasound arrays were placed around the waist of each patient model, and time-reversal was used to determine the source signals necessary to create a focus in the center of the disc. The simulations showed that for 0.5 MHz ultrasound, a focus could be created in most of the lumbar IVDs, with the pressure focal gain ranging from 3.2-13.7. In conclusion, it is shown that with patient-specific planning, focusing ultrasound into an IVD is possible in the majority of patients despite the complex acoustic path introduced by the bony structures of the spine.
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Affiliation(s)
- S Qiao
- Institute of Biomedical Engineering, Department of Engineering Science, University of Oxford, UK
| | - D Elbes
- Institute of Biomedical Engineering, Department of Engineering Science, University of Oxford, UK
| | - O Boubriak
- Institute of Biomedical Engineering, Department of Engineering Science, University of Oxford, UK
| | - J P G Urban
- Department of Physiology, Anatomy & Genetics, University of Oxford, UK
| | - C-C Coussios
- Institute of Biomedical Engineering, Department of Engineering Science, University of Oxford, UK
| | - R O Cleveland
- Institute of Biomedical Engineering, Department of Engineering Science, University of Oxford, UK.
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23
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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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Gerhardson T, Sukovich JR, Pandey AS, Hall TL, Cain CA, Xu Z. Catheter Hydrophone Aberration Correction for Transcranial Histotripsy Treatment of Intracerebral Hemorrhage: Proof-of-Concept. IEEE TRANSACTIONS ON ULTRASONICS, FERROELECTRICS, AND FREQUENCY CONTROL 2017; 64:1684-1697. [PMID: 28880166 PMCID: PMC5681355 DOI: 10.1109/tuffc.2017.2748050] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Histotripsy is a minimally invasive ultrasound therapy that has shown rapid liquefaction of blood clots through human skullcaps in an in vitro intracerebral hemorrhage model. However, the efficiency of these treatments can be compromised if the skull-induced aberrations are uncorrected. We have developed a catheter hydrophone which can perform aberration correction (AC) and drain the liquefied clot following histotripsy treatment. Histotripsy pulses were delivered through an excised human skullcap using a 256-element, 500-kHz hemisphere array transducer with a 15-cm focal distance. A custom hydrophone was fabricated using a mm PZT-5h crystal interfaced to a coaxial cable and integrated into a drainage catheter. An AC algorithm was developed to correct the aberrations introduced between histotripsy pulses from each array element. An increase in focal pressure of up to 60% was achieved at the geometric focus and 27%-62% across a range of electronic steering locations. The sagittal and axial -6-dB beam widths decreased from 4.6 to 2.2 mm in the sagittal direction and 8 to 4.4 mm in the axial direction, compared to 1.5 and 3 mm in the absence of aberration. After performing AC, lesions with diameters ranging from 0.24 to 1.35 mm were generated using electronic steering over a mm grid in a tissue-mimicking phantom. An average volume of 4.07 ± 0.91 mL was liquefied and drained after using electronic steering to treat a 4.2-mL spherical volume in in vitro bovine clots through the skullcap.
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25
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Enhanced Energy Localization in Hyperthermia Treatment Based on Hybrid Electromagnetic and Ultrasonic System: Proof of Concept with Numerical Simulations. BIOMED RESEARCH INTERNATIONAL 2017; 2017:5787484. [PMID: 28840125 PMCID: PMC5559980 DOI: 10.1155/2017/5787484] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/24/2017] [Revised: 05/17/2017] [Accepted: 06/18/2017] [Indexed: 12/31/2022]
Abstract
This paper proposes a hybrid hyperthermia treatment system, utilizing two noninvasive modalities for treating brain tumors. The proposed system depends on focusing electromagnetic (EM) and ultrasound (US) energies. The EM hyperthermia subsystem enhances energy localization by incorporating a multichannel wideband setting and coherent-phased-array technique. A genetic algorithm based optimization tool is developed to enhance the specific absorption rate (SAR) distribution by reducing hotspots and maximizing energy deposition at tumor regions. The treatment performance is also enhanced by augmenting an ultrasonic subsystem to allow focused energy deposition into deep tumors. The therapeutic faculty of ultrasonic energy is assessed by examining the control of mechanical alignment of transducer array elements. A time reversal (TR) approach is then investigated to address challenges in energy focus in both subsystems. Simulation results of the synergetic effect of both modalities assuming a simplified model of human head phantom demonstrate the feasibility of the proposed hybrid technique as a noninvasive tool for thermal treatment of brain tumors.
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26
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Marsac L, Chauvet D, La Greca R, Boch AL, Chaumoitre K, Tanter M, Aubry JF. Ex vivo optimisation of a heterogeneous speed of sound model of the human skull for non-invasive transcranial focused ultrasound at 1 MHz. Int J Hyperthermia 2017; 33:635-645. [PMID: 28540778 DOI: 10.1080/02656736.2017.1295322] [Citation(s) in RCA: 50] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022] Open
Abstract
Transcranial brain therapy has recently emerged as a non-invasive strategy for the treatment of various neurological diseases, such as essential tremor or neurogenic pain. However, treatments require millimetre-scale accuracy. The use of high frequencies (typically ≥1 MHz) decreases the ultrasonic wavelength to the millimetre scale, thereby increasing the clinical accuracy and lowering the probability of cavitation, which improves the safety of the technique compared with the use of low-frequency devices that operate at 220 kHz. Nevertheless, the skull produces greater distortions of high-frequency waves relative to low-frequency waves. High-frequency waves require high-performance adaptive focusing techniques, based on modelling the wave propagation through the skull. This study sought to optimise the acoustical modelling of the skull based on computed tomography (CT) for a 1 MHz clinical brain therapy system. The best model tested in this article corresponded to a maximum speed of sound of 4000 m.s-1 in the skull bone, and it restored 86% of the optimal pressure amplitude on average in a collection of six human skulls. Compared with uncorrected focusing, the optimised non-invasive correction led to an average increase of 99% in the maximum pressure amplitude around the target and an average decrease of 48% in the distance between the peak pressure and the selected target. The attenuation through the skulls was also assessed within the bandwidth of the transducers, and it was found to vary in the range of 10 ± 3 dB at 800 kHz and 16 ± 3 dB at 1.3 MHz.
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Affiliation(s)
- L Marsac
- a INSERM U979, Institut Langevin , Paris , France.,b ESPCI Paris, PSL Research University, Institut Langevin , Paris , France.,c CNRS UMR 7587 , Paris , France.,d SuperSonic Imagine, Aix en Provence , France
| | - D Chauvet
- e Service de Neurochirurgie, Hôpital de la Pitié-Salpêtrière, Assistance Publique - Hôpitaux de Paris , Paris Cedex 13 , France.,f Neurosurgery Department, Fondation A Rothschild , Paris Cedex 19 , France
| | - R La Greca
- d SuperSonic Imagine, Aix en Provence , France
| | - A-L Boch
- e Service de Neurochirurgie, Hôpital de la Pitié-Salpêtrière, Assistance Publique - Hôpitaux de Paris , Paris Cedex 13 , France.,g Centre de Recherche de l?Institut du Cerveau et de la Moelle Épinière, INSERM - UMRS 975, CNRS 7225, Hôpital de la Pitié-Salpêtrière , Paris Cedex 13 , France
| | - K Chaumoitre
- h Imaging Department , North Hospital, Aix Marseille Université , Marseille , France
| | - M Tanter
- a INSERM U979, Institut Langevin , Paris , France.,b ESPCI Paris, PSL Research University, Institut Langevin , Paris , France.,c CNRS UMR 7587 , Paris , France
| | - J-F Aubry
- a INSERM U979, Institut Langevin , Paris , France.,b ESPCI Paris, PSL Research University, Institut Langevin , Paris , France.,c CNRS UMR 7587 , Paris , France
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27
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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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28
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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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29
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Wang Q, Howell M, Shimizu S, James S, Smiley A, Clement GT. Investigation of the correlation between diffuse infrared and ultrasound for transcranial ultrasound. Biomed Phys Eng Express 2016; 2. [PMID: 27298731 DOI: 10.1088/2057-1976/2/3/035016] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Over the past two decades the feasibility for using transcranial ultrasound as both a therapeutic and diagnostic tool has been established. Various aberration-correction techniques have been proposed to achieve transcranial focusing, including CT-derived model based corrections, ultrasound-derived model based corrections, magnetic resonance acoustic radiation force (MR-ARFI) techniques, and techniques involving the invasive introduction of an acoustic source or receiver into the brain. Here, we investigate the correlation between transcranial infrared light (IR) and transcranial ultrasound, where we examine whether IR could be an indicator of any of the key acoustic properties that affect transcranial transmission (signal attenuation, speed of sound, and bone density). Nine human skull samples were utilized in the study. The interior of each sample was illuminated over its inner surface using a diffuse light source. Light transmitted to the outer surface was detected by a 3-mm diameter 940-nm infrared sensor. Acoustic measurements were likewise obtained in a water tank using a 12.7-mm diameter 1-MHz source and a needle hydrophone receiver. Results reveal a positive correlation between the acoustic time-of-flight and optical intensity (the correlation coefficient is between 0.5 and 0.9). Subsequent investigation shows this correlation to hold independent of the presence or absence of dura mater on the samples. Poor correlation is observed between acoustic amplitude and optical intensity (the correlation coefficient is between 0.1 and 0.7).
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Affiliation(s)
- Qi Wang
- Department of Biomedical Engineering, Cleveland Clinic Lerner Research Institute, Cleveland, OH, USA
| | - Mark Howell
- Department of Biomedical Engineering, Cleveland Clinic Lerner Research Institute, Cleveland, OH, USA
| | - Shota Shimizu
- Department of Biomedical Engineering, Cleveland Clinic Lerner Research Institute, Cleveland, OH, USA
| | - Sheronica James
- Department of Biomedical Engineering, Cleveland Clinic Lerner Research Institute, Cleveland, OH, USA
| | - Aref Smiley
- Department of Biomedical Engineering, Cleveland Clinic Lerner Research Institute, Cleveland, OH, USA
| | - Gregory T Clement
- Department of Biomedical Engineering, Cleveland Clinic Lerner Research Institute, Cleveland, OH, USA
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Sukovich J, Xu Z, Kim Y, Cao H, Nguyen TS, Pandey A, Hall T, Cain C. Targeted Lesion Generation Through the Skull Without Aberration Correction Using Histotripsy. IEEE TRANSACTIONS ON ULTRASONICS, FERROELECTRICS, AND FREQUENCY CONTROL 2016; 63:671-682. [PMID: 26890732 PMCID: PMC7371448 DOI: 10.1109/tuffc.2016.2531504] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
This study demonstrates the ability of histotripsy to generate targeted lesions through the skullcap without using aberration correction. Histotripsy therapy was delivered using a 500 kHz, 256-element hemispherical transducer with an aperture diameter of 30 cm and a focal distance of 15 cm fabricated in our lab. This transducer is theoretically capable of producing peak rarefactional pressures, based on linear estimation, (p-)LE, in the free field in excess of 200MPa with pulse durations 2 acoustic cycles. Three excised human skullcaps were used displaying attenuations of 73-81% of the acoustic pressure without aberration correction. Through all three skullcaps, compact lesions with radii less than 1mm were generated in red blood cell (RBC) agarose tissue phantoms without aberration correction, using estimated (p-)LE of 28-39MPa, a pulse repetition frequency of 1Hz, and a total number of 300 pulses. Lesion generation was consistently observed at the geometric focus of the transducer as the position of the skullcap with respect to the transducer was varied, and multiple patterned lesions were generated transcranially by mechanically adjusting the position of the skullcap with respect to the transducer to target different regions within. These results show that compact, targeted lesions with sharp boundaries can be generated through intact skullcaps using histotripsy with very short pulses without using aberration correction. Such capability has the potential to greatly simplify transcranial ultrasound therapy for non-invasive transcranial applications, as current ultrasound transcranial therapy techniques all require sophisticated aberration correction.
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Jones RM, Hynynen K. Comparison of analytical and numerical approaches for CT-based aberration correction in transcranial passive acoustic imaging. Phys Med Biol 2016; 61:23-36. [PMID: 26605827 PMCID: PMC5022767 DOI: 10.1088/0031-9155/61/1/23] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Computed tomography (CT)-based aberration corrections are employed in transcranial ultrasound both for therapy and imaging. In this study, analytical and numerical approaches for calculating aberration corrections based on CT data were compared, with a particular focus on their application to transcranial passive imaging. Two models were investigated: a three-dimensional full-wave numerical model (Connor and Hynynen 2004 IEEE Trans. Biomed. Eng. 51 1693-706) based on the Westervelt equation, and an analytical method (Clement and Hynynen 2002 Ultrasound Med. Biol. 28 617-24) similar to that currently employed by commercial brain therapy systems. Trans-skull time delay corrections calculated from each model were applied to data acquired by a sparse hemispherical (30 cm diameter) receiver array (128 piezoceramic discs: 2.5 mm diameter, 612 kHz center frequency) passively listening through ex vivo human skullcaps (n = 4) to emissions from a narrow-band, fixed source emitter (1 mm diameter, 516 kHz center frequency). Measurements were taken at various locations within the cranial cavity by moving the source around the field using a three-axis positioning system. Images generated through passive beamforming using CT-based skull corrections were compared with those obtained through an invasive source-based approach, as well as images formed without skull corrections, using the main lobe volume, positional shift, peak sidelobe ratio, and image signal-to-noise ratio as metrics for image quality. For each CT-based model, corrections achieved by allowing for heterogeneous skull acoustical parameters in simulation outperformed the corresponding case where homogeneous parameters were assumed. Of the CT-based methods investigated, the full-wave model provided the best imaging results at the cost of computational complexity. These results highlight the importance of accurately modeling trans-skull propagation when calculating CT-based aberration corrections. Although presented in an imaging context, our results may also be applicable to the problem of transmit focusing through the skull.
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Affiliation(s)
- Ryan M. Jones
- Physical Sciences Platform, Sunnybrook Research Institute, Toronto, Canada
- Department of Medical Biophysics, University of Toronto, Toronto, Canada
| | - 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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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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Eames MDC, Farnum M, Khaled M, Elias WJ, Hananel A, Snell JW, Kassell NF, Aubry JF. Head phantoms for transcranial focused ultrasound. Med Phys 2015; 42:1518-27. [PMID: 25832042 DOI: 10.1118/1.4907959] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
PURPOSE In the ongoing endeavor of fine-tuning, the clinical application of transcranial MR-guided focused ultrasound (tcMRgFUS), ex-vivo studies wlkiith whole human skulls are of great use in improving the underlying technology guiding the accurate and precise thermal ablation of clinically relevant targets in the human skull. Described here are the designs, methods for fabrication, and notes on utility of three different ultrasound phantoms to be used for brain focused ultrasound research. METHODS Three different models of phantoms are developed and tested to be accurate, repeatable experimental options to provide means to further this research. The three models are a cadaver, a gel-filled skull, and a head mold containing a skull and filled with gel that mimics the brain and the skin. Each was positioned in a clinical tcMRgFUS system and sonicated at 1100 W (acoustic) for 12 s at different locations. Maximum temperature rise as measured by MR thermometry was recorded and compared against clinical data for a similar neurosurgical target. Results are presented as heating efficiency in units (°C/kW/s) for direct comparison to available clinical data. The procedure for casting thermal phantom material is presented. The utility of each phantom model is discussed in the context of various tcMRgFUS research areas. RESULTS The cadaveric phantom model, gel-filled skull model, and full head phantom model had heating efficiencies of 5.3, 4.0, and 3.9 °C/(kW/s), respectively, compared to a sample clinical heating efficiency of 2.6 °C/(kW/s). In the seven research categories considered, the cadaveric phantom model was the most versatile, though less practical compared to the ex-vivo skull-based phantoms. CONCLUSIONS Casting thermal phantom material was shown to be an effective way to prepare tissue-mimicking material for the phantoms presented. The phantom models presented are all useful in tcMRgFUS research, though some are better suited to a limited subset of applications depending on the researchers needs.
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Affiliation(s)
| | - Mercy Farnum
- Focused Ultrasound Foundation, Charlottesville, Virginia 22903
| | - Mohamad Khaled
- Department of Neurosurgery, University of Virginia, Charlottesville, Virginia 22908
| | - W Jeff Elias
- Department of Neurosurgery, University of Virginia, Charlottesville, Virginia 22908
| | - Arik Hananel
- Focused Ultrasound Foundation, Charlottesville, Virginia 22903 and Department of Radiation Oncology, University of Virginia, Charlottesville, Virginia 22908
| | - John W Snell
- Focused Ultrasound Foundation, Charlottesville, Virginia 22903 and Department of Neurosurgery, University of Virginia, Charlottesville, Virginia 22908
| | - Neal F Kassell
- Focused Ultrasound Foundation, Charlottesville, Virginia 22903 and Department of Neurosurgery, University of Virginia, Charlottesville, Virginia 22908
| | - Jean-Francois Aubry
- Department of Radiation Oncology, University of Virginia, Charlottesville, Virginia 22908 and Institut Langevin, ESPCI ParisTech, CNRS UMR 7587, INSERM U979, Paris 75005, France
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Bing C, Nofiele J, Staruch R, Ladouceur-Wodzak M, Chatzinoff Y, Ranjan A, Chopra R. Localised hyperthermia in rodent models using an MRI-compatible high-intensity focused ultrasound system. Int J Hyperthermia 2015; 31:813-22. [PMID: 26540488 DOI: 10.3109/02656736.2015.1094833] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
PURPOSE Localised hyperthermia in rodent studies is challenging due to the small target size. This study describes the development and characterisation of an MRI-compatible high-intensity focused ultrasound (HIFU) system to perform localised mild hyperthermia treatments in rodent models. MATERIAL AND METHODS The hyperthermia platform consisted of an MRI-compatible small animal HIFU system, focused transducers with sector-vortex lenses, a custom-made receive coil, and means to maintain systemic temperatures of rodents. The system was integrated into a 3T MR imager. Control software was developed to acquire images, process temperature maps, and adjust output power using a proportional-integral-derivative feedback control algorithm. Hyperthermia exposures were performed in tissue-mimicking phantoms and in a rodent model (n = 9). During heating, an ROI was assigned in the heated region for temperature control and the target temperature was 42 °C; 30 min mild hyperthermia treatment followed by a 10-min cooling procedure was performed on each animal. RESULTS 3D-printed sector-vortex lenses were successful at creating annular focal regions which enables customisation of the heating volume. Localised mild hyperthermia performed in rats produced a mean ROI temperature of 42.1 ± 0.3 °C. The T10 and T90 percentiles were 43.2 ± 0.4 °C and 41.0 ± 0.3 °C, respectively. For a 30-min treatment, the mean time duration between 41-45 °C was 31.1 min within the ROI. CONCLUSIONS The MRI-compatible HIFU system was successfully adapted to perform localised mild hyperthermia treatment in rodent models. A target temperature of 42 °C was well-maintained in a rat thigh model for 30 min.
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Affiliation(s)
- Chenchen Bing
- a Department of Radiology , University of Texas Southwestern Medical Center , Dallas , Texas
| | - Joris Nofiele
- a Department of Radiology , University of Texas Southwestern Medical Center , Dallas , Texas
| | - Robert Staruch
- a Department of Radiology , University of Texas Southwestern Medical Center , Dallas , Texas .,b Clinical Sites Research Program, Philips Research , Briarcliff Manor , New York
| | | | - Yonatan Chatzinoff
- c Applied Research Center, University of Texas at Dallas , Dallas , Texas
| | - Ashish Ranjan
- d Center of Veterinary Health Sciences, Oklahoma State University , Stillwater , Oklahoma , USA , and
| | - Rajiv Chopra
- a Department of Radiology , University of Texas Southwestern Medical Center , Dallas , Texas .,e Advanced Imaging Research Center, University of Texas Southwestern Medical Center , Dallas , Texas
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Maksimov AO, Polovinka YA. Time reversal technique for gas leakage detection. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2015; 137:2168-2179. [PMID: 25920866 DOI: 10.1121/1.4916693] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The acoustic remote sensing of subsea gas leakage traditionally uses sonars as active acoustic sensors and hydrophones picking up the sound generated by a leak as passive sensors. When gas leaks occur underwater, bubbles are produced and emit sound at frequencies intimately related to their sizes. The experimental implementation of an acoustic time-reversal mirror (TRM) is now well established in underwater acoustics. In the basic TRM experiment, a probe source emits a pulse that is received on an array of sensors, time reversed, and re-emitted. After time reversal, the resulting field focuses back at the probe position. In this study, a method for enhancing operation of the passive receiving system has been proposed by using it in the regime of TRM. Two factors, the local character of the acoustic emission signal caused by the leakage and a resonant nature of the bubble radiation at their birth, make particularly effective scattering with the conjugate wave (CW). Analytical calculations are performed for the scattering of CW wave on a single bubble when CW is formed by bubble birthing wail received on an array, time reversed, and re-emitted. The quality of leakage detection depends on the spatio-temporal distribution of ambient noise.
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Affiliation(s)
- A O Maksimov
- Pacific Oceanological Institute, Far Eastern Branch of the Russian Academy of Sciences, Vladivostok 690041, Russia
| | - Yu A Polovinka
- Pacific Oceanological Institute, Far Eastern Branch of the Russian Academy of Sciences, Vladivostok 690041, Russia
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Liu N, Liutkus A, Aubry JF, Marsac L, Tanter M, Daudet L. Random calibration for accelerating MR-ARFI guided ultrasonic focusing in transcranial therapy. Phys Med Biol 2015; 60:1069-85. [PMID: 25585885 DOI: 10.1088/0031-9155/60/3/1069] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Transcranial focused ultrasound is a promising therapeutic modality. It consists of placing transducers around the skull and emitting shaped ultrasound waves that propagate through the skull and then concentrate on one particular location within the brain. However, the skull bone is known to distort the ultrasound beam. In order to compensate for such distortions, a number of techniques have been proposed recently, for instance using Magnetic Resonance Imaging feedback. In order to fully determine the focusing distortion due to the skull, such methods usually require as many calibration signals as transducers, resulting in a lengthy calibration process. In this paper, we investigate how the number of calibration sequences can be significantly reduced, based on random measurements and optimization techniques. Experimental data with six human skulls demonstrate that the number of measurements can be up to three times lower than with the standard methods, while restoring 90% of the focusing efficiency.
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Affiliation(s)
- Na Liu
- Institut Langevin, UMR 7587, ESPCI ParisTech, CNRS, INSERM, Paris Diderot University, 1 rue Jussieu, F-75005, Paris, France
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Crake C, Victor MDS, Owen J, Coviello C, Collin J, Coussios CC, Stride E. Passive acoustic mapping of magnetic microbubbles for cavitation enhancement and localization. Phys Med Biol 2015; 60:785-806. [DOI: 10.1088/0031-9155/60/2/785] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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O'Reilly MA, Hynynen K. A super-resolution ultrasound method for brain vascular mapping. Med Phys 2014; 40:110701. [PMID: 24320408 DOI: 10.1118/1.4823762] [Citation(s) in RCA: 125] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
PURPOSE High-resolution vascular imaging has not been achieved in the brain due to limitations of current clinical imaging modalities. The authors present a method for transcranial ultrasound imaging of single micrometer-size bubbles within a tube phantom. METHODS Emissions from single bubbles within a tube phantom were mapped through an ex vivo human skull using a sparse hemispherical receiver array and a passive beamforming algorithm. Noninvasive phase and amplitude correction techniques were applied to compensate for the aberrating effects of the skull bone. The positions of the individual bubbles were estimated beyond the diffraction limit of ultrasound to produce a super-resolution image of the tube phantom, which was compared with microcomputed tomography (micro-CT). RESULTS The resulting super-resolution ultrasound image is comparable to results obtained via the micro-CT for small tissue specimen imaging. CONCLUSIONS This method provides superior resolution to deep-tissue contrast ultrasound and has the potential to be extended to provide complete vascular network imaging in the brain.
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Affiliation(s)
- Meaghan A O'Reilly
- Physical Sciences Platform, Sunnybrook Research Institute, Toronto, Ontario M4N 3M5, Canada
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Pulkkinen A, Werner B, Martin E, Hynynen K. Numerical simulations of clinical focused ultrasound functional neurosurgery. Phys Med Biol 2014; 59:1679-700. [PMID: 24619067 DOI: 10.1088/0031-9155/59/7/1679] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
A computational model utilizing grid and finite difference methods were developed to simulate focused ultrasound functional neurosurgery interventions. The model couples the propagation of ultrasound in fluids (soft tissues) and solids (skull) with acoustic and visco-elastic wave equations. The computational model was applied to simulate clinical focused ultrasound functional neurosurgery treatments performed in patients suffering from therapy resistant chronic neuropathic pain. Datasets of five patients were used to derive the treatment geometry. Eight sonications performed in the treatments were then simulated with the developed model. Computations were performed by driving the simulated phased array ultrasound transducer with the acoustic parameters used in the treatments. Resulting focal temperatures and size of the thermal foci were compared quantitatively, in addition to qualitative inspection of the simulated pressure and temperature fields. This study found that the computational model and the simulation parameters predicted an average of 24 ± 13% lower focal temperature elevations than observed in the treatments. The size of the simulated thermal focus was found to be 40 ± 13% smaller in the anterior-posterior direction and 22 ± 14% smaller in the inferior-superior direction than in the treatments. The location of the simulated thermal focus was off from the prescribed target by 0.3 ± 0.1 mm, while the peak focal temperature elevation observed in the measurements was off by 1.6 ± 0.6 mm. Although the results of the simulations suggest that there could be some inaccuracies in either the tissue parameters used, or in the simulation methods, the simulations were able to predict the focal spot locations and temperature elevations adequately for initial treatment planning performed to assess, for example, the feasibility of sonication. The accuracy of the simulations could be improved if more precise ultrasound tissue properties (especially of the skull bone) could be obtained.
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Affiliation(s)
- Aki Pulkkinen
- University of Eastern Finland, Kuopio Campus, PO Box 1627, FI-70211 Kuopio, Finland
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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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Chauvet D, Marsac L, Pernot M, Boch AL, Guillevin R, Salameh N, Souris L, Darrasse L, Fink M, Tanter M, Aubry JF. Targeting accuracy of transcranial magnetic resonance-guided high-intensity focused ultrasound brain therapy: a fresh cadaver model. J Neurosurg 2013; 118:1046-52. [PMID: 23451909 DOI: 10.3171/2013.1.jns12559] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
OBJECT This work aimed at evaluating the accuracy of MR-guided high-intensity focused ultrasound (MRgHIFU) brain therapy in human cadaver heads. METHODS Eighteen heads of fresh human cadavers were removed with a dedicated protocol preventing intracerebral air penetration. The MR images allowed determination of the ultrasonic target: a part of the thalamic nucleus ventralis intermedius implicated in essential tremor. Osseous aberrations were corrected with simulation-based time reversal by using CT data from the heads. The ultrasonic session was performed with a 512-element phased-array transducer system operating at 1 MHz under stereotactic conditions with thermometric real-time MR monitoring performed using a 1.5-T imager. RESULTS Dissection, imaging, targeting, and planning have validated the feasibility of this human cadaver model. The average temperature elevation measured by proton resonance frequency shift was 7.9°C ± 3°C. Based on MRI data, the accuracy of MRgHIFU is 0.4 ± 1 mm along the right/left axis, 0.7 ± 1.2 mm along the dorsal/ventral axis, and 0.5 ± 2.4 mm in the rostral/caudal axis. CONCLUSIONS Despite its limits (temperature, vascularization), the human cadaver model is effective for studying the accuracy of MRgHIFU brain therapy. With the 1-MHz system investigated here, there is millimetric accuracy.
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Affiliation(s)
- Dorian Chauvet
- Department of Neurosurgery, Groupe Hospitalier Pitié Salpêtrière, Paris, France
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Targeted drug delivery across the blood-brain barrier using ultrasound technique. Ther Deliv 2012; 1:819-48. [PMID: 21785679 DOI: 10.4155/tde.10.66] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Effective delivery of therapeutic agents into the brain can greatly improve the treatments of neurological and neurodegenerative diseases. Application of focused ultrasound facilitated by microbubbles has shown the potential to deliver drugs across the blood-brain barrier into targeted sites within the brain noninvasively. This review provides a summary of the technological background and principle, highlights of recent significant developments and research progress, as well as a critical commentary on the challenges and future directions in the field. This review also outlines and discusses the tasks that researchers face in order to successfully translate the technology into a clinical reality, including obtaining improved understanding of the mechanisms, demonstration of therapeutic efficacy and safety for specific applications, and development of methodology for rational design to achieve optimized and consistent outcomes.
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Marsac L, Chauvet D, Larrat B, Pernot M, Robert B, Fink M, Boch AL, Aubry JF, Tanter M. MR-guided adaptive focusing of therapeutic ultrasound beams in the human head. Med Phys 2012; 39:1141-9. [PMID: 22320825 DOI: 10.1118/1.3678988] [Citation(s) in RCA: 89] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE This study aims to demonstrate, using human cadavers the feasibility of energy-based adaptive focusing of ultrasonic waves using magnetic resonance acoustic radiation force imaging (MR-ARFI) in the framework of non-invasive transcranial high intensity focused ultrasound (HIFU) therapy. METHODS Energy-based adaptive focusing techniques were recently proposed in order to achieve aberration correction. The authors evaluate this method on a clinical brain HIFU system composed of 512 ultrasonic elements positioned inside a full body 1.5 T clinical magnetic resonance (MR) imaging system. Cadaver heads were mounted onto a clinical Leksell stereotactic frame. The ultrasonic wave intensity at the chosen location was indirectly estimated by the MR system measuring the local tissue displacement induced by the acoustic radiation force of the ultrasound (US) beams. For aberration correction, a set of spatially encoded ultrasonic waves was transmitted from the ultrasonic array and the resulting local displacements were estimated with the MR-ARFI sequence for each emitted beam. A noniterative inversion process was then performed in order to estimate the spatial phase aberrations induced by the cadaver skull. The procedure was first evaluated and optimized in a calf brain using a numerical aberrator mimicking human skull aberrations. The full method was then demonstrated using a fresh human cadaver head. RESULTS The corrected beam resulting from the direct inversion process was found to focus at the targeted location with an acoustic intensity 2.2 times higher than the conventional non corrected beam. In addition, this corrected beam was found to give an acoustic intensity 1.5 times higher than the focusing pattern obtained with an aberration correction using transcranial acoustic simulation-based on X-ray computed tomography (CT) scans. CONCLUSIONS The proposed technique achieved near optimal focusing in an intact human head for the first time. These findings confirm the strong potential of energy-based adaptive focusing of transcranial ultrasonic beams for clinical applications.
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Affiliation(s)
- L Marsac
- Université Paris 7, Paris, France.
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Jing Y, Meral FC, Clement GT. Time-reversal transcranial ultrasound beam focusing using a k-space method. Phys Med Biol 2012; 57:901-17. [PMID: 22290477 PMCID: PMC3366238 DOI: 10.1088/0031-9155/57/4/901] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
This paper proposes the use of a k-space method to obtain the correction for transcranial ultrasound beam focusing. Mirroring past approaches, a synthetic point source at the focal point is numerically excited, and propagated through the skull, using acoustic properties acquired from registered computed tomography of the skull being studied. The received data outside the skull contain the correction information and can be phase conjugated (time reversed) and then physically generated to achieve a tight focusing inside the skull, by assuming quasi-plane transmission where shear waves are not present or their contribution can be neglected. Compared with the conventional finite-difference time-domain method for wave propagation simulation, it will be shown that the k-space method is significantly more accurate even for a relatively coarse spatial resolution, leading to a dramatically reduced computation time. Both numerical simulations and experiments conducted on an ex vivo human skull demonstrate that precise focusing can be realized using the k-space method with a spatial resolution as low as only 2.56 grid points per wavelength, thus allowing treatment planning computation on the order of minutes.
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Affiliation(s)
- Yun Jing
- Department of Mechanical and Aerospace Engineering, North Carolina State University Raleigh, NC 27695, USA.
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Kenis AM, Grinfeld J, Zadicario E, Vitek S. Impact of propagating and standing waves on cavitation appearance. ULTRASOUND IN MEDICINE & BIOLOGY 2012; 38:99-108. [PMID: 22104538 DOI: 10.1016/j.ultrasmedbio.2011.08.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/27/2010] [Revised: 07/20/2011] [Accepted: 08/02/2011] [Indexed: 05/31/2023]
Abstract
Standing waves play a significant role in the appearance of cavitation phenomena. The goal of this study was to investigate the effect that the relation between standing and propagating waves in a focused field has on acoustic bubble cloud formation. Measurements of the cavitation signals were performed on five different configurations of a hemispheric phased array transducer (230 kHz) representing a wide range of relations between propagating and standing waves. The results show that configurations with a larger propagating component induce bubble clouds at lower pressures than configurations with a larger standing component.
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Gateau J, Aubry JF, Chauvet D, Boch AL, Fink M, Tanter M. In vivo bubble nucleation probability in sheep brain tissue. Phys Med Biol 2011; 56:7001-15. [PMID: 22015981 DOI: 10.1088/0031-9155/56/22/001] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Gas nuclei exist naturally in living bodies. Their activation initiates cavitation activity, and is possible using short ultrasonic excitations of high amplitude. However, little is known about the nuclei population in vivo, and therefore about the rarefaction pressure required to form bubbles in tissue. A novel method dedicated to in vivo investigations was used here that combines passive and active cavitation detection with a multi-element linear ultrasound probe (4-7 MHz). Experiments were performed in vivo on the brain of trepanated sheep. Bubble nucleation was induced using a focused single-element transducer (central frequency 660 kHz, f-number = 1) driven by a high power (up to 5 kW) electric burst of two cycles. Successive passive recording and ultrafast active imaging were shown to allow detection of a single nucleation event in brain tissue in vivo. Experiments carried out on eight sheep allowed statistical studies of the bubble nucleation process. The nucleation probability was evaluated as a function of the peak negative pressure. No nucleation event could be detected with a peak negative pressure weaker than -12.7 MPa, i.e. one order of magnitude higher than the recommendations based on the mechanical index. Below this threshold, bubble nucleation in vivo in brain tissues is a random phenomenon.
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Affiliation(s)
- J Gateau
- Institut Langevin, ESPCI ParisTech, CNRS UMR 7587, INSERM U979, Université Denis Diderot, Paris VII, 10 Rue Vauquelin, 75005 Paris, France.
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47
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Cochard E, Aubry JF, Tanter M, Prada C. Adaptive projection method applied to three-dimensional ultrasonic focusing and steering through the ribs. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2011; 130:716-723. [PMID: 21877786 DOI: 10.1121/1.3607419] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
An adaptive projection method for ultrasonic focusing through the rib cage, with minimal energy deposition on the ribs, was evaluated experimentally in 3D geometry. Adaptive projection is based on decomposition of the time-reversal operator (DORT method) and projection on the "noise" subspace. It is shown that 3D implementation of this method is straightforward, and not more time-consuming than 2D. Comparisons are made between adaptive projection, spherical focusing, and a previously proposed time-reversal focusing method, by measuring pressure fields in the focal plane and rib region using the three methods. The ratio of the specific absorption rate at the focus over the one at the ribs was found to be increased by a factor of up to eight, versus spherical emission. Beam steering out of geometric focus was also investigated. For all configurations projecting steered emissions were found to deposit less energy on the ribs than steering time-reversed emissions: thus the non-invasive method presented here is more efficient than state-of-the-art invasive techniques. In fact, this method could be used for real-time treatment, because a single acquisition of back-scattered echoes from the ribs is enough to treat a large volume around the focus, thanks to real time projection of the steered beams.
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Affiliation(s)
- E Cochard
- Laboratoire Ondes et Acoustique, Université Paris VII, Inserm, ESPCI, Paris, France
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48
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Pulkkinen A, Huang Y, Song J, Hynynen K. Simulations and measurements of transcranial low-frequency ultrasound therapy: skull-base heating and effective area of treatment. Phys Med Biol 2011; 56:4661-83. [PMID: 21734333 DOI: 10.1088/0031-9155/56/15/003] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Measurements of temperature elevations induced by sonications in a single intact cadaver skull filled with soft-tissue mimicking phantom material were performed using magnetic resonance thermometry. The sonications were done using a clinical transcranial ultrasound therapy device operating at 230 kHz and the measurements were compared with simulations done using a model incorporating both the longitudinal and shear wave propagation. Both the measurements and simulations showed that in some situations the temperature increase could be higher in the phantom material adjacent to the skull-base than at the focus, which could lead to undesired soft-tissue damage in treatment situations. On average the measurements of the sonicated locations, as well as the comparative simulations, showed 32 ± 64% and 49 ± 32% higher temperature elevations adjacent to the skull-base than at the focus, respectively. The simulation model was used to extend the measurements by simulating multiple sonications of brain tissue in five different skulls with and without correcting the aberrations caused by the skull on the ultrasound. Without aberration correction the closest sonications to the skulls that were treatable in any brain location without undesired tissue damage were at a distance of 19.1 ± 2.6 mm. None of the sonications beyond a distance of 41.2 ± 5.3 mm were found to cause undesired tissue damage. When using the aberration correction closest treatable, safe distances for sonications were found to be 16.0 ± 1.6 and 38.8 ± 3.8 mm, respectively. New active cooling of the skull-base through the nasal cavities was introduced and the treatment area was investigated. The closest treatable distance without aberration correction reduced to 17.4 ± 1.9 mm with the new cooling method. All sonications beyond a distance of 39.7 ± 6.6 mm were found treatable. With the aberration correction no difference in the closest treatable or the safety distance was found in comparison to sonications without nasal cavity cooling. To counteract undesired skull-base heating a new anti-focus within solid media was developed along with a new regularized phasing method. Mathematical bases for both the methods and simulations utilizing them were presented. It was found that utilizing the anti-focus in solid media and regularized phasing, the fraction of temperature increase of the brain tissue at the focus and the peak temperature increase adjacent to the skull-base can be increased from 1.00 to 1.95. This improves the efficiency of the sonication by reducing the energy transfer to the skull-base.
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Affiliation(s)
- Aki Pulkkinen
- Sunnybrook Research Institute, Sunnybrook Health Sciences Centre, 2075 Bayview Avenue, Toronto, ON, M4N 3M5, Canada.
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Lindsey BD, Light ED, Nicoletto HA, Bennett ER, Laskowitz DT, Smith SW. The ultrasound brain helmet: new transducers and volume registration for in vivo simultaneous multi-transducer 3-D transcranial imaging. IEEE TRANSACTIONS ON ULTRASONICS, FERROELECTRICS, AND FREQUENCY CONTROL 2011; 58:1189-202. [PMID: 21693401 PMCID: PMC3271736 DOI: 10.1109/tuffc.2011.1929] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Because stroke remains an important and time-sensitive health concern in developed nations, we present a system capable of fusing 3-D transcranial ultrasound volumes acquired from two sides of the head. This system uses custom sparse array transducers built on flexible multilayer circuits that can be positioned for simultaneous imaging through both temporal acoustic windows, allowing for potential registration of multiple real-time 3-D scans of cerebral vasculature. We examine hardware considerations for new matrix arrays-transducer design and interconnects-in this application. Specifically, it is proposed that SNR may be increased by reducing the length of probe cables. This claim is evaluated as part of the presented system through simulation, experimental data, and in vivo imaging. Ultimately, gains in SNR of 7 dB are realized by replacing a standard probe cable with a much shorter flex interconnect; higher gains may be possible using ribbon-based probe cables. In vivo images are presented, showing cerebral arteries with and without the use of microbubble contrast agent; they have been registered and fused using a simple algorithm which maximizes normalized cross-correlation.
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Affiliation(s)
- Brooks D Lindsey
- Department of Biomedical Engineering, Duke University, Durham, NC, USA.
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Gateau J, Aubry JF, Pernot M, Fink M, Tanter M. Combined passive detection and ultrafast active imaging of cavitation events induced by short pulses of high-intensity ultrasound. IEEE TRANSACTIONS ON ULTRASONICS, FERROELECTRICS, AND FREQUENCY CONTROL 2011; 58:517-32. [PMID: 21429844 PMCID: PMC3350371 DOI: 10.1109/tuffc.2011.1836] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
The activation of natural gas nuclei to induce larger bubbles is possible using short ultrasonic excitations of high amplitude, and is required for ultrasound cavitation therapies. However, little is known about the distribution of nuclei in tissues. Therefore, the acoustic pressure level necessary to generate bubbles in a targeted zone and their exact location are currently difficult to predict. To monitor the initiation of cavitation activity, a novel all-ultrasound technique sensitive to single nucleation events is presented here. It is based on combined passive detection and ultrafast active imaging over a large volume using the same multi-element probe. Bubble nucleation was induced using a focused transducer (660 kHz, f-number = 1) driven by a high-power electric burst (up to 300 W) of one to two cycles. Detection was performed with a linear array (4 to 7 MHz) aligned with the single-element focal point. In vitro experiments in gelatin gel and muscular tissue are presented. The synchronized passive detection enabled radio-frequency data to be recorded, comprising high-frequency coherent wave fronts as signatures of the acoustic emissions linked to the activation of the nuclei. Active change detection images were obtained by subtracting echoes collected in the unnucleated medium. These indicated the appearance of stable cavitating regions. Because of the ultrafast frame rate, active detection occurred as quickly as 330 μs after the high-amplitude excitation and the dynamics of the induced regions were studied individually.
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Affiliation(s)
- Jérôme Gateau
- Institut Langevin, Ecole Superieure de Physique et de Chimie Industrielles de la Ville de Paris (ESPCI) ParisTech, Centre National de la Recherche Scientifique (CNRS), UMR 7587, Paris, France.
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