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Sleiman N, Pflieger R, Hallez L, Nikitenko SI, Hihn JY. Magnesium and magnesium alloy dissolution by high intensity focused ultrasound: erosion/cavitation vs. Wave propagation. ULTRASONICS SONOCHEMISTRY 2024; 104:106836. [PMID: 38430906 PMCID: PMC10912864 DOI: 10.1016/j.ultsonch.2024.106836] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/26/2023] [Revised: 02/07/2024] [Accepted: 02/27/2024] [Indexed: 03/05/2024]
Abstract
The dissolution of metals, influenced by mechanical and chemical factors, plays a crucial role in various applications. Ultrasonic irradiation has been explored for its ability to enhance dissolution rates and modify surface characteristics. In this study, we investigate the dissolution of magnesium (Mg) and magnesium alloys under high-intensity focused ultrasound (HIFU) conditions with frequency sweeping (wobbling). Our findings reveal distinct effects of cavitation and acoustic streaming on the dissolution process. For pure magnesium, ultrasonic treatment significantly increases dissolution rates compared to silent conditions. Negative frequency sweeps result in the highest dissolution rates, linked to increased cavitation activity, while positive sweeps reduce dissolution rates but maintain acoustic streaming effects. The removal of surface oxides is accelerated in all sonication conditions. Macro- and micro-roughness patterns on the surface correspond to the wobbling frequency range, with wavelengths matching the average ultrasonic frequency. However, dissolution is not uniform across the sample, and preferential attack occurs at the focal point during negative frequency sweeps. In contrast, magnesium alloys exhibit lower dissolution rates than pure Mg. The alloy's mechanical properties make it less susceptible to cavitation erosion but more sensitive to acoustic streaming-induced dissolution. Grain boundaries are preferentially attacked, revealing differences between ductile pure Mg and the harder, more cavitation-resistant, alloy. This study highlights the complex interplay between cavitation and acoustic streaming in the dissolution of magnesium and its alloys under HIFU conditions, shedding light on the limits and potential applications of this technique, particularly in microstructure analysis.
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Affiliation(s)
- Noura Sleiman
- Université de Franche-Comté, CNRS, Institut UTINAM UMR 6213, F-25000 Besançon, France; ICSM UMR 5257 - CEA, Univ Montpellier, CNRS, ENSCM, Bagnols-sur-Cèze, France; IRT M2P, Metz, France
| | - Rachel Pflieger
- ICSM UMR 5257 - CEA, Univ Montpellier, CNRS, ENSCM, Bagnols-sur-Cèze, France
| | - Loïc Hallez
- Université de Franche-Comté, CNRS, Institut UTINAM UMR 6213, F-25000 Besançon, France
| | - Sergey I Nikitenko
- ICSM UMR 5257 - CEA, Univ Montpellier, CNRS, ENSCM, Bagnols-sur-Cèze, France
| | - Jean-Yves Hihn
- Université de Franche-Comté, CNRS, Institut UTINAM UMR 6213, F-25000 Besançon, France; IRT M2P, Metz, France.
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Lorton O, Guillemin PC, Peloso A, M’Rad Y, Crowe LA, Koessler T, Poletti PA, Boudabbous S, Ricoeur A, Salomir R. In Vivo Thermal Ablation of Deep Intrahepatic Targets Using a Super-Convergent MRgHIFU Applicator and a Pseudo-Tumor Model. Cancers (Basel) 2023; 15:3961. [PMID: 37568777 PMCID: PMC10417404 DOI: 10.3390/cancers15153961] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2023] [Revised: 07/28/2023] [Accepted: 08/01/2023] [Indexed: 08/13/2023] Open
Abstract
BACKGROUND HIFU ablation of liver malignancies is particularly challenging due to respiratory motion, high tissue perfusion and the presence of the rib cage. Based on our previous development of a super-convergent phased-array transducer, we aimed to further investigate, in vivo, its applicability to deep intrahepatic targets. METHODS In a series of six pigs, a pseudo-tumor model was used as target, visible both on intra-operatory MRI and post-mortem gross pathology. The transcostal MRgHIFU ablation was prescribed coplanar with the pseudo-tumor, either axial or sagittal, but deliberately shifted 7 to 18 mm to the side. No specific means of protection of the ribs were implemented. Post-treatment MRI follow-up was performed at D7, followed by animal necropsy and gross pathology of the liver. RESULTS The pseudo-tumor was clearly identified on T1w MR imaging and subsequently allowed the MRgHIFU planning. The peak temperature at the focal point ranged from 58-87 °C. Gross pathology confirmed the presence of the pseudo-tumor and the well-delineated MRgHIFU ablation at the expected locations. CONCLUSIONS The specific design of the transducer enabled a reliable workflow. It demonstrated a good safety profile for in vivo transcostal MRgHIFU ablation of deep-liver targets, graded as challenging for standard surgery.
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Affiliation(s)
- Orane Lorton
- Image Guided Interventions Laboratory (GR-949), Faculty of Medicine, University of Geneva, 1211 Geneva, Switzerland
| | - Pauline Coralie Guillemin
- Image Guided Interventions Laboratory (GR-949), Faculty of Medicine, University of Geneva, 1211 Geneva, Switzerland
| | - Andrea Peloso
- Visceral Surgery Division, University Hospitals of Geneva, 1205 Geneva, Switzerland
| | - Yacine M’Rad
- Image Guided Interventions Laboratory (GR-949), Faculty of Medicine, University of Geneva, 1211 Geneva, Switzerland
| | | | - Thibaud Koessler
- Oncology Department, University Hospitals of Geneva, 1205 Geneva, Switzerland
| | | | - Sana Boudabbous
- Image Guided Interventions Laboratory (GR-949), Faculty of Medicine, University of Geneva, 1211 Geneva, Switzerland
- Radiology Division, University Hospitals of Geneva, 1205 Geneva, Switzerland
| | - Alexis Ricoeur
- Image Guided Interventions Laboratory (GR-949), Faculty of Medicine, University of Geneva, 1211 Geneva, Switzerland
- Radiology Division, University Hospitals of Geneva, 1205 Geneva, Switzerland
| | - Rares Salomir
- Image Guided Interventions Laboratory (GR-949), Faculty of Medicine, University of Geneva, 1211 Geneva, Switzerland
- Radiology Division, University Hospitals of Geneva, 1205 Geneva, Switzerland
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Lorton O, Guillemin PC, M’Rad Y, Peloso A, Boudabbous S, Charbonnier C, Holman R, Crowe LA, Gui L, Poletti PA, Ricoeur A, Terraz S, Salomir R. A Novel Concept of a Phased-Array HIFU Transducer Optimized for MR-Guided Hepatic Ablation: Embodiment and First In-Vivo Studies. Front Oncol 2022; 12:899440. [PMID: 35769711 PMCID: PMC9235567 DOI: 10.3389/fonc.2022.899440] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2022] [Accepted: 04/27/2022] [Indexed: 11/28/2022] Open
Abstract
Purpose High-intensity focused ultrasound (HIFU) is challenging in the liver due to the respiratory motion and risks of near-/far-field burns, particularly on the ribs. We implemented a novel design of a HIFU phased-array transducer, dedicated to transcostal hepatic thermo-ablation. Due to its large acoustic window and strong focusing, the transducer should perform safely for this application. Material and Methods The new HIFU transducer is composed of 256 elements distributed on 5 concentric segments of a specific radius (either 100, 111, or 125 mm). It has been optimally shaped to fit the abdominal wall. The shape and size of the acoustic elements were optimized for the largest emitting surface and the lowest symmetry. Calibration tests have been conducted on tissue-mimicking gels under 3-T magnetic resonance (MR) guidance. In-vivo MR-guided HIFU treatment was conducted in two pigs, aiming to create thermal ablation deep in the liver without significant side effects. Imaging follow-up was performed at D0 and D7. Sacrifice and post-mortem macroscopic examination occurred at D7, with the ablated tissue being fixed for pathology. Results The device showed −3-dB focusing capacities in a volume of 27 × 46 × 50 mm3 as compared with the numerical simulation volume of 18 × 48 × 60 mm3. The shape of the focal area was in millimeter-range agreement with the numerical simulations. No interference was detected between the HIFU sonication and the MR acquisition. In vivo, the temperature elevation in perivascular liver parenchyma reached 28°C above physiological temperature, within one breath-hold. The lesion was visible on Gd contrast-enhanced MRI sequences and post-mortem examination. The non-perfused volume was found in pig #1 and pig #2 of 8/11, 6/8, and 7/7 mm along the LR, AP, and HF directions, respectively. No rib burns or other near-field side effects were visually observed on post-mortem gross examination. High-resolution contrast-enhanced 3D MRI indicated a minor lesion on the sternum. Conclusion The performance of this new HIFU transducer has been demonstrated in vitro and in vivo. The transducer meets the requirement to perform thermal lesions in deep tissues, without the need for rib-sparing means.
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Affiliation(s)
- Orane Lorton
- Image Guided Interventions Laboratory (GR-949), Faculty of Medicine, University of Geneva, Geneva, Switzerland
- *Correspondence: Orane Lorton,
| | - Pauline C. Guillemin
- Image Guided Interventions Laboratory (GR-949), Faculty of Medicine, University of Geneva, Geneva, Switzerland
| | - Yacine M’Rad
- Image Guided Interventions Laboratory (GR-949), Faculty of Medicine, University of Geneva, Geneva, Switzerland
| | - Andrea Peloso
- Visceral Surgery Division, University Hospitals of Geneva, Geneva, Switzerland
| | - Sana Boudabbous
- Image Guided Interventions Laboratory (GR-949), Faculty of Medicine, University of Geneva, Geneva, Switzerland
- Radiology Division, University Hospitals of Geneva, Geneva, Switzerland
| | - Caecilia Charbonnier
- Image Guided Interventions Laboratory (GR-949), Faculty of Medicine, University of Geneva, Geneva, Switzerland
- Medical Research Department, Artanim Foundation, Geneva, Switzerland
| | - Ryan Holman
- Image Guided Interventions Laboratory (GR-949), Faculty of Medicine, University of Geneva, Geneva, Switzerland
| | - Lindsey A. Crowe
- Radiology Division, University Hospitals of Geneva, Geneva, Switzerland
| | - Laura Gui
- Image Guided Interventions Laboratory (GR-949), Faculty of Medicine, University of Geneva, Geneva, Switzerland
| | | | - Alexis Ricoeur
- Radiology Division, University Hospitals of Geneva, Geneva, Switzerland
| | - Sylvain Terraz
- Image Guided Interventions Laboratory (GR-949), Faculty of Medicine, University of Geneva, Geneva, Switzerland
- Radiology Division, University Hospitals of Geneva, Geneva, Switzerland
| | - Rares Salomir
- Image Guided Interventions Laboratory (GR-949), Faculty of Medicine, University of Geneva, Geneva, Switzerland
- Radiology Division, University Hospitals of Geneva, Geneva, Switzerland
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Sleiman N, Hallez L, Pflieger R, Nikitenko SI, Hihn JY. Sonoluminescence emission spectra of a 3.6 MHz HIFU in sweeping mode. ULTRASONICS SONOCHEMISTRY 2022; 83:105939. [PMID: 35123254 PMCID: PMC8927739 DOI: 10.1016/j.ultsonch.2022.105939] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/20/2021] [Revised: 01/26/2022] [Accepted: 01/28/2022] [Indexed: 06/14/2023]
Abstract
Use of sweeping mode with a 3.6 MHz High Intensity Focused Ultrasound (HIFU) allows cavitation activity to be controlled. This is especially true in the pre-focal zone where the high concentration of bubbles acts as an acoustic reflector and quenches cavitation above this area. Previous studies attributed the enhancement of cavitation activity under negative sweep to the activation of more bubble nuclei, requiring deeper investigations. After mapping this activity with SCL measurements, cavitation noise spectra were recorded. The behavior of the acoustic broadband noise follows the sonochemical one i.e., showing the same attenuation (positive scan) or intensification (negative scan) of cavitational activity. In 1 M NaCl 3.7 mM 2-propanol solution saturated by a mixture of Ar-15.5%O2-2.2%N2, intensities of SL spectra are high enough to allow detection of several molecular emissions (OH, NH, C2, Na) under negative frequency sweeps. This is the first report of molecular emissions at such high frequency. Their intensities are low, and they are very broad, following the trend obtained at fixed frequency up to 1 MHz. Under optimized conditions, CN emission chosen as a spectroscopic probe is strong enough to be simulated, which is reported for the first time at such high frequency. The resulting characteristics of the plasma do not show any spectral difference, so bubble nature is the same in the pre-and post-focal zone under different sweeping parameters. Consequently, SL and SCL intensification was not related to a change in plasma nature inside the bubbles but to the number of cavitation bubbles.
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Affiliation(s)
- Noura Sleiman
- UTINAM UMR 6213, Univ Bourgogne-Franche-Comté/CNRS, Besançon, France; ICSM UMR 5257 - CEA, Univ Montpellier, CNRS, ENSCM, Bagnols-sur-Cèze, France; IRT M2P, Metz, France
| | - Loïc Hallez
- UTINAM UMR 6213, Univ Bourgogne-Franche-Comté/CNRS, Besançon, France
| | - Rachel Pflieger
- ICSM UMR 5257 - CEA, Univ Montpellier, CNRS, ENSCM, Bagnols-sur-Cèze, France
| | - Sergey I Nikitenko
- ICSM UMR 5257 - CEA, Univ Montpellier, CNRS, ENSCM, Bagnols-sur-Cèze, France
| | - Jean-Yves Hihn
- UTINAM UMR 6213, Univ Bourgogne-Franche-Comté/CNRS, Besançon, France; IRT M2P, Metz, France.
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Haqshenas SR, Gélat P, van 't Wout E, Betcke T, Saffari N. A fast full-wave solver for calculating ultrasound propagation in the body. ULTRASONICS 2021; 110:106240. [PMID: 32950757 DOI: 10.1016/j.ultras.2020.106240] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/25/2020] [Revised: 08/20/2020] [Accepted: 08/25/2020] [Indexed: 05/23/2023]
Abstract
Therapeutic ultrasound is a promising non-invasive method for inducing various beneficial biological effects in the human body. In cancer treatment applications, high-power ultrasound is focused at a target tissue volume to ablate the malignant tumour. The success of the procedure depends on the ability to accurately focus ultrasound and destroy the target tissue volume through coagulative necrosis whilst preserving the surrounding healthy tissue. Patient-specific treatment planning strategies are therefore being developed to increase the efficacy of such therapies, while reducing any damage to healthy tissue. These strategies require to use high-performance computing methods to solve ultrasound wave propagation in the body quickly and accurately. For realistic clinical scenarios, all numerical methods which employ volumetric meshes require several hours or days to solve the full-wave propagation on a computer cluster. The boundary element method (BEM) is an efficient approach for modelling the wave field because only the boundaries of the hard and soft tissue regions require discretisation. This paper presents a multiple-domain BEM formulation with a novel preconditioner for solving the Helmholtz transmission problem (HTP). This new formulation is efficient at high-frequencies and where high-contrast materials are present. Numerical experiments are performed to solve the HTP in multiple domains comprising: (i) human ribs, an idealised abdominal fat layer and liver tissue, (ii) a human kidney with a perinephric fat layer, exposed to the acoustic field generated by a high-intensity focused ultrasound (HIFU) array transducer. The time required to solve the equations associated with these problems on a single workstation is of the order of minutes. These results demonstrate the great potential of this new BEM formulation for accurately and quickly solving ultrasound wave propagation problems in large anatomical domains which is essential for developing treatment planning strategies.
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Affiliation(s)
- S R Haqshenas
- Department of Mechanical Engineering, University College London, London WC1E 7JE, UK; Department of Mathematics, University College London, London WC1H 0AY, UK.
| | - P Gélat
- Department of Mechanical Engineering, University College London, London WC1E 7JE, UK
| | - E van 't Wout
- Institute for Mathematical and Computational Engineering, School of Engineering and Faculty of Mathematics, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - T Betcke
- Department of Mathematics, University College London, London WC1H 0AY, UK
| | - N Saffari
- Department of Mechanical Engineering, University College London, London WC1E 7JE, UK
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Jiang L, Yang Y, Chen Y, Zhou Q. Ultrasound-Induced Wireless Energy Harvesting: From Materials Strategies to Functional Applications. NANO ENERGY 2020; 77:105131. [PMID: 32905454 PMCID: PMC7469949 DOI: 10.1016/j.nanoen.2020.105131] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
Wireless energy harvesting represents an emerging technology that can be integrated into a variety of systems for biomedical, physical, and chemical functions. The miniaturization and ease of implementation are the main challenges for the development of wireless energy harvesting systems. Unlike most reported wireless energy harvesting technologies represented by electromagnetic coupling, the new generation of ultrasound-induced wireless energy harvesting (UWEH) that use propagating ultrasound waves to carry the available energy provides a strategy with higher resolution, deeper penetration, and more security, especially in nanodevices and implantable medical systems where a long-term stable power is required. Recently, advances in nanotechnologies, microelectronics, and biomedical systems are revolutionizing UWEH. In this article, an overview of recent developments in UWEH technologies that use a variety of material strategies and system designs based on the piezoelectric and capacitive energy harvesting mechanisms is provided. Practical applications are also presented, including wireless power for bio-implantable devices, direct cell/tissue electrical stimulations, wireless recording and communication in nervous systems, ultrasonic modulated drug delivery, self-powered acoustic sensors, and ultrasound-induced piezoelectric catalysis. Finally, perspectives and opportunities are also highlighted.
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Affiliation(s)
- Laiming Jiang
- Roski Eye Institute, Keck School of Medicine, University of Southern California, Los Angeles, CA 90033 USA
- Epstein Department of Industrial and Systems Engineering, Department of Aerospace and Mechanical Engineering, Viterbi School of Engineering, University of Southern California, Los Angeles, CA 90089 USA
| | - Yang Yang
- Department of Mechanical Engineering, San Diego State University, 5500 Campanile Drive, San Diego, CA 92182 USA
| | - Yong Chen
- Epstein Department of Industrial and Systems Engineering, Department of Aerospace and Mechanical Engineering, Viterbi School of Engineering, University of Southern California, Los Angeles, CA 90089 USA
| | - Qifa Zhou
- Roski Eye Institute, Keck School of Medicine, University of Southern California, Los Angeles, CA 90033 USA
- Department of Biomedical Engineering, Viterbi School of Engineering, University of Southern California, Los Angeles, CA 90089 USA
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Cao R, Huang Z, Nabi G, Melzer A. Patient-Specific 3-Dimensional Model for High-Intensity Focused Ultrasound Treatment Through the Rib Cage: A Preliminary Study. JOURNAL OF ULTRASOUND IN MEDICINE : OFFICIAL JOURNAL OF THE AMERICAN INSTITUTE OF ULTRASOUND IN MEDICINE 2020; 39:883-899. [PMID: 31721248 DOI: 10.1002/jum.15170] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/13/2019] [Revised: 09/12/2019] [Accepted: 10/16/2019] [Indexed: 06/10/2023]
Abstract
OBJECTIVES The purpose of this study was to develop a patient-specific 3-dimensional model for high-intensity focused ultrasound (HIFU) treatment through the rib cage using patient data. METHODS Experimental testing to derive parameters used in defining the amount of energy and alteration needed in treatment protocols for upper abdominal disorders under the rib cage was performed. Reconstructed rib cage models based on patient data, tissue-mimicking material phantoms, and magnetic resonance imaging-guided HIFU using a multielement phased array transducer were used in the experiments. Changes in the focal temperature, acoustic power, and acoustic pressure distribution were investigated with and without the presence of the rib cage model. An ExAblate system (InSightec Ltd, Tirat Carmel, Israel) was used to sonicate phantoms by varying the target phantom or rib cage model location. RESULTS The effect of the rib cage on the acoustic pressure distribution and acoustic power was closely related to the anatomic structures of the ribs. Thermometry revealed that heating at the focus could be controlled by changing either the power or duration of HIFU application to improve the focal temperature change. The focal temperature change was found to be related to the distance between the rib cage model and focus and the shadow area on the transducer elements covered by the rib cage model in the beam path. CONCLUSIONS Experimental results suggest that the rib cage model is a valuable and useful tool that can provide realistic human anatomic structures and properties for evaluating the effects of the rib cage on ultrasound propagation.
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Affiliation(s)
- Rui Cao
- Tianjin Key Laboratory of Integrated Design and On-line Monitoring for Light Industry & Food Machinery and Equipment, College of Mechanical Engineering, Tianjin University of Science and Technology, Tianjin, China
| | - Zhihong Huang
- School of Science and Engineering, University of Dundee, Dundee, UK
| | - Ghulam Nabi
- School of Medicine, Ninewells Hospital, Dundee, UK
| | - Andreas Melzer
- Institute for Medical Science and Technology, Dundee, UK
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Ma Y, Hsu G, Zhang F. The applicability and efficacy of magnetic resonance-guided high intensity focused ultrasound system in the treatment of primary trigeminal neuralgia. Med Hypotheses 2020; 139:109688. [PMID: 32240878 DOI: 10.1016/j.mehy.2020.109688] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2020] [Accepted: 03/23/2020] [Indexed: 12/27/2022]
Abstract
Primary trigeminal neuralgia is a common clinical refractory neuralgia characterized by an onset of excruciating pain that can severely affect patients' quality of life. Long-term suffering from this pain may lead to depression, anxiety, and suicide. Current treatments, however, are associated with high recurrent rates and severe complications. We hypothesize that both the applicability and efficacy of magnetic resonance-guided high intensity focused ultrasound (MR-HIFU) treatment in primary trigeminal neuralgia can be achieved under the following conditions: a specific target focus and incident channel, a temperature measurement system that does not incur damage to surrounding tissues, and an optimal radiation dose. Successful non-invasive treatment of primary trigeminal neuralgia by MR-HIFU systems could represent a breakthrough of this technology applied to the oral and maxillofacial region.
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Affiliation(s)
- Yaping Ma
- Chongqing Key Laboratory of Oral Diseases and Biomedical Sciences, Stomatological Hospital of Chongqing Medical University, Chongqing 401147, China; Department of Oral and Maxillofacial Surgery, Stomatological Hospital of Chongqing Medical University, Chongqing 401147, China
| | - Grace Hsu
- Department of Oral and Maxillofacial Surgery, Massachusetts General Hospital, Boston, MA 02114, USA
| | - Fugui Zhang
- Department of Oral and Maxillofacial Surgery, Stomatological Hospital of Chongqing Medical University, Chongqing 401147, China; Department of Oral and Maxillofacial Surgery, Massachusetts General Hospital, Boston, MA 02114, USA.
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Almekkawy M, Ebbini ES. The Optimization of Transcostal Phased Array Refocusing Using the Semidefinite Relaxation Method. IEEE TRANSACTIONS ON ULTRASONICS, FERROELECTRICS, AND FREQUENCY CONTROL 2020; 67:318-328. [PMID: 31567081 PMCID: PMC8651278 DOI: 10.1109/tuffc.2019.2944434] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Tumors in organs partially obscured by the rib cage represent a challenge for high-intensity focused ultrasound (HIFU) therapy. The ribs distort the HIFU beams in a manner that reduces the focusing gain at the target, which could result in treatment-limiting collateral damage. In fact, skin burns are a common complication during the ablation of hepatic tumors. This problem can be addressed by employing optimal refocusing algorithms that are designed to achieve a specified focusing gain at the target while controlling the exposure to the ribs in the path of the HIFU beam. However, previously proposed optimal refocusing algorithms did not allow for the controlled transmission through the ribs. In this article, we introduce a new approach for refocusing that can more efficiently steer power toward the target while limiting the power deposition on the ribs. The approach utilizes the semidefinite relaxation (SDR) technique to approximate the original (nonconvex) optimization problem. An important advantage of the SDR-based method over previously proposed optimization methods is the control of the side lobes in the focal plane. The method also allows for specifying an acceptable level of exposure to the ribs. Simulation results using a 1-MHz spherical concave phased array focused on an inhomogeneous medium are presented to demonstrate the performance of the SDR refocusing approach. A finite-difference time-domain propagation model was used to model the propagation in the inhomogeneous tissues, including the ribs. Temperature simulations based on the inhomogeneous transient bioheat transfer equation (tBHTE) demonstrate the significance of the improvements in the focusing gain when using the limited power deposition (LPD) method. The results also demonstrate that the LPD method yields well-behaved array excitation vectors, realizable by currently existing drivers.
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Xu R, O'Reilly MA. A Spine-Specific Phased Array for Transvertebral Ultrasound Therapy: Design and Simulation. IEEE Trans Biomed Eng 2020; 67:256-267. [DOI: 10.1109/tbme.2019.2912146] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Khan W, Jia Y, Madi F, Weber A, Ghovanloo M, Li W. Inductively coupled, mm-sized, single channel optical neuro-stimulator with intensity enhancer. MICROSYSTEMS & NANOENGINEERING 2019; 5:23. [PMID: 31231537 PMCID: PMC6545326 DOI: 10.1038/s41378-019-0061-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/16/2018] [Revised: 03/13/2019] [Accepted: 03/14/2019] [Indexed: 05/06/2023]
Abstract
We introduce a single channel neuro-stimulator consisting of a reflector-coupled microscale light emitting diode (µLED) with an integrated mm-sized wireless receiver (Rx) coil for free-floating, battery-free, untethered optogenetics neuromodulation. The system utilizes a two-coil inductive link to deliver instantaneous power at a low operating frequency (<100 MHz) for continuous optical stimulation with minimized invasiveness and tissue exposure to electromagnetic radiation. Coupling a microscale reflector to the µLED provides significant light intensity enhancement compared to a bare µLED. Our activated stimulators have an operational temperature increase of <1 °C, well below the safety limit of biomedical implants. In vivo experiment and histological analysis verify the efficacy of wireless optical stimulation in the primary visual cortex of rats, using c-Fos biomarker as a reporter of light-evoked neuronal activity.
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Affiliation(s)
- Wasif Khan
- Department of Electrical and Computer Engineering, Michigan State University, East Lansing, MI USA
| | - Yaoyao Jia
- School of Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta, GA USA
| | - Fatma Madi
- Department of Physiology, Michigan State University, East Lansing, MI USA
| | - Arthur Weber
- Department of Physiology, Michigan State University, East Lansing, MI USA
| | - Maysam Ghovanloo
- School of Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta, GA USA
| | - Wen Li
- Department of Electrical and Computer Engineering, Michigan State University, East Lansing, MI USA
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Chang TC, Weber MJ, Charthad J, Baltsavias S, Arbabian A. End-to-End Design of Efficient Ultrasonic Power Links for Scaling Towards Submillimeter Implantable Receivers. IEEE TRANSACTIONS ON BIOMEDICAL CIRCUITS AND SYSTEMS 2018; 12:1100-1111. [PMID: 30235147 PMCID: PMC6269189 DOI: 10.1109/tbcas.2018.2871470] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
We present an analytical framework for optimizing the efficiency of ultrasonic wireless power links for implantable devices scaled down to sub-mm dimensions. Key design insights and tradeoffs are considered for various parameters including the operating frequency, the transmission depth, the size of the transmitter, the impedance and the aperture efficiency of the miniaturized receiver, and the interface between the receiver and the power recovery chain on the implant. The performance of spherically focused transducers as ultrasonic transmitters is analyzed to study the limits and the tradeoffs. Two optimization methods are presented: "Focal Peak" sets the focus of transducers at target depths, and "Global Maximum" maximizes the efficiency globally with off-focus operation. The results are also compared to phased array implementations. To investigate the efficiency of implants, miniaturized receivers made from single crystalline piezoelectric material, PMN-PT, are used as they have resonances in the derived optimal carrier frequency range (∼1-2 MHz). A methodology to achieve an efficient interface to the power electronics is then provided using an optogenetic stimulator as an example platform. The analytical results are verified through both simulations and measurements. Finally, an example ultrasonic link using a spherical transmitter with a radius of 2 cm is demonstrated; link efficiencies of 1.93-0.23% are obtained at 6-10 cm depths with sub-mm receivers for the optogenetic application.
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Robin J, Simon A, Arnal B, Tanter M, Pernot M. Self-adaptive ultrasonic beam amplifiers: application to transcostal shock wave therapy. Phys Med Biol 2018; 63:175014. [PMID: 30101750 DOI: 10.1088/1361-6560/aad9b5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Ultrasound shock wave therapy is increasingly used for non-invasive surgery. It requires the focusing of very high pressure amplitude in precisely controlled focal spots. In transcostal therapy of the heart or the liver, the high impedance mismatch between the bones and surrounding tissues gives rise to strong aberrations and attenuation of the therapeutic wavefront, with potential risks of injury at the tissue-bone interface. An adaptive propagation of the ultrasonic beam through the intercostal spaces would be required. Several solutions have been developed so far, but they require a prior knowledge of the patient's anatomy or an invasive calibration process, not applicable in clinic. Here, we develop a non-invasive adaptive focusing method for ultrasound therapy through the ribcage using a time reversal cavity (TRC) acting as an ultrasonic beam amplifier. This method is based on ribcage imaging through the TRC and a projection orthogonally to the strongest identified reflectors. The focal pressure of our device was improved by up to 30% using such self-adaptive processing, without degrading the focal spots size and shape. This improvement allowed lesion formation in an Ultracal® phantom through a ribcage without invasive calibration of the device. This adaptive method could be particularly interesting to improve the efficiency and the safety of pulsed cavitational therapy of the heart or the liver.
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Affiliation(s)
- J Robin
- Institut Langevin, ESPCI Paris, Inserm U979, CNRS UMR 7587, Université Paris Diderot, PSL Research University, Paris, France
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14
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Charthad J, Chang TC, Liu Z, Sawaby A, Weber MJ, Baker S, Gore F, Felt SA, Arbabian A. A mm-Sized Wireless Implantable Device for Electrical Stimulation of Peripheral Nerves. IEEE TRANSACTIONS ON BIOMEDICAL CIRCUITS AND SYSTEMS 2018; 12:257-270. [PMID: 29578414 DOI: 10.1109/tbcas.2018.2799623] [Citation(s) in RCA: 84] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
A wireless electrical stimulation implant for peripheral nerves, achieving >10× improvement over state of the art in the depth/volume figure of merit, is presented. The fully integrated implant measures just 2 mm × 3 mm × 6.5 mm (39 mm3, 78 mg), and operates at a large depth of 10.5 cm in a tissue phantom. The implant is powered using ultrasound and includes a miniaturized piezoelectric receiver (piezo), an IC designed in 180 nm HV BCD process, an off-chip energy storage capacitor, and platinum stimulation electrodes. The package also includes an optional blue light-emitting diode for potential applications in optogenetic stimulation in the future. A system-level design strategy for complete operation of the implant during the charging transient of the storage capacitor, as well as a unique downlink command/data transfer protocol, is presented. The implant enables externally programmable current-controlled stimulation of peripheral nerves, with a wide range of stimulation parameters, both for electrical (22 to 5000 μA amplitude, ∼14 to 470 μs pulse-width, 0 to 60 Hz repetition rate) and optical (up to 23 mW/mm2 optical intensity) stimulation. Additionally, the implant achieves 15 V compliance voltage for chronic applications. Full integration of the implant components, end-to-end in vitro system characterizations, and results for the electrical stimulation of a sciatic nerve, demonstrate the feasibility and efficacy of the proposed stimulator for peripheral nerves.
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15
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Almekkawy M, McMahon D, Alqarni H. Optimization of transcostal phased-array refocusing using sparse semidefinite relaxation method. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2017; 2017:1449-1452. [PMID: 29060151 DOI: 10.1109/embc.2017.8037107] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Treating tumors in organs shadowed by the ribs is a challenge for high intensity focused ultrasound (HIFU). The ribs absorb energy from the ultrasound beams causing their temperature to rise, while also distorting the beams, and limiting the target heat deposition. Accordingly, it is necessary to devise focusing methods that address the difficulties presented by the ribs. In this paper, a new approach that reduces total power deposition on the region of interest (ROI) by removing transducer elements is introduced. The method builds on the limited power deposition (LPD) method, which took advantage of the semidefinite relaxation (SDR) method to relax nonconvex constraints into convex form. The method introduced in this paper induces sparsity using the one-norm squared. The results of using this method to focus a 1-MHz spherical phased array on a target in an inhomogeneous medium are presented and compared to the ray tracing (shadowing) approach [1]. A finite-difference time domain propagation model was used to model the wave propagation to the target. Temperature simulations that utilized the inhomogeneous bioheat transfer equation (BHTE) illustrate the advantages of the induced sparsity LPD method. Together, these simulation results illustrate the advantages of using optimization based on sparsity inducing techniques over the shadowing approach.
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16
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Ramaekers P, de Greef M, Berriet R, Moonen CTW, Ries M. Evaluation of a novel therapeutic focused ultrasound transducer based on Fermat’s spiral. Phys Med Biol 2017; 62:5021-5045. [DOI: 10.1088/1361-6560/aa716c] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
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17
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Ramaekers P, Ries M, Moonen CT, de Greef M. Improved intercostal HIFU ablation using a phased array transducer based on Fermat's spiral and Voronoi tessellation: A numerical evaluation. Med Phys 2017; 44:1071-1088. [DOI: 10.1002/mp.12082] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2016] [Revised: 11/22/2016] [Accepted: 12/25/2016] [Indexed: 01/25/2023] Open
Affiliation(s)
- Pascal Ramaekers
- Imaging Division; University Medical Center Utrecht; 3508 GA Utrecht The Netherlands
| | - Mario Ries
- Imaging Division; University Medical Center Utrecht; 3508 GA Utrecht The Netherlands
| | - Chrit T.W. Moonen
- Imaging Division; University Medical Center Utrecht; 3508 GA Utrecht The Netherlands
| | - Martijn de Greef
- Imaging Division; University Medical Center Utrecht; 3508 GA Utrecht The Netherlands
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Chang TC, Weber MJ, Wang ML, Charthad J, Khuri-Yakub BPT, Arbabian A. Design of Tunable Ultrasonic Receivers for Efficient Powering of Implantable Medical Devices With Reconfigurable Power Loads. IEEE TRANSACTIONS ON ULTRASONICS, FERROELECTRICS, AND FREQUENCY CONTROL 2016; 63:1554-1562. [PMID: 27623580 DOI: 10.1109/tuffc.2016.2606655] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
Miniaturized ultrasonic receivers are designed for efficient powering of implantable medical devices with reconfigurable power loads. Design parameters that affect the efficiency of these receivers under highly variable load conditions, including piezoelectric material, geometry, and operation frequency, are investigated. Measurements were performed to characterize electrical impedance and acoustic-to-electrical efficiency of ultrasonic receivers for off-resonance operation. Finally, we propose, analyze, and demonstrate adaptive matching and frequency tuning techniques using two different reconfigurable matching networks for typical implant loads from 10 [Formula: see text] to 1 mW. Both simulations and measurements show a significant increase in total implant efficiency (up to 50 percentage points) over this load power range when operating off-resonance with the proposed matching networks.
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Hallez L, Touyeras F, Hihn JY, Bailly Y. Characterization of HIFU transducers designed for sonochemistry application: Acoustic streaming. ULTRASONICS SONOCHEMISTRY 2016; 29:420-427. [PMID: 26585023 DOI: 10.1016/j.ultsonch.2015.10.019] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/08/2014] [Revised: 10/05/2015] [Accepted: 10/27/2015] [Indexed: 06/05/2023]
Abstract
Cavitation distribution in a High Intensity Focused Ultrasound sonoreactors (HIFU) has been extensively described in the recent literature, including quantification by an optical method (Sonochemiluminescence SCL). The present paper provides complementary measurements through the study of acoustic streaming generated by the same kind of HIFU transducers. To this end, results of mass transfer measurements (electrodiffusional method) were compared to optical method ones (Particle Image Velocimetry). This last one was used in various configurations: with or without an electrode in the acoustic field in order to have the same perturbation of the wave propagation. Results show that the maximum velocity is not located at the focal but shifted near the transducer, and that this shift is greater for high powers. The two cavitation modes (stationary and moving bubbles) are greatly affect the hydrodynamic behavior of our sonoreactors: acoustic streaming and the fluid generated by bubble motion. The results obtained by electrochemical measurements show the same low hydrodynamic activity in the transducer vicinity, the same shift of the active focal toward the transducer, and the same absence of activity in the post-focal axial zone. The comparison with theoretical Eckart's velocities (acoustic streaming in non-cavitating media) confirms a very high activity at the "sonochemical focal", accounted for by wave distortion, which induced greater absorption coefficients. Moreover, the equivalent liquid velocities are one order of magnitude larger than the ones measured by PIV, confirming the enhancement of mass transfer by bubbles oscillation and collapse close to the surface, rather than from a pure streaming effect.
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Affiliation(s)
- L Hallez
- Institut UTINAM/SRS, UMR 6213, CNRS, University of Bourgogne Franche-Comté, Besançon, France
| | - F Touyeras
- Institut UTINAM/SRS, UMR 6213, CNRS, University of Bourgogne Franche-Comté, Besançon, France
| | - J-Y Hihn
- Institut UTINAM/SRS, UMR 6213, CNRS, University of Bourgogne Franche-Comté, Besançon, France.
| | - Y Bailly
- Institut FEMTO-ST/ENISYS, UMR 6174, CNRS, University of Bourgogne Franche-Comté, ENSMM, UTBM, Belfort, France
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20
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MRI-Guided HIFU Methods for the Ablation of Liver and Renal Cancers. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2016; 880:43-63. [DOI: 10.1007/978-3-319-22536-4_3] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
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21
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van 't Wout E, Gélat P, Betcke T, Arridge S. A fast boundary element method for the scattering analysis of high-intensity focused ultrasound. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2015; 138:2726-37. [PMID: 26627749 DOI: 10.1121/1.4932166] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
High-intensity focused ultrasound (HIFU) techniques are promising modalities for the non-invasive treatment of cancer. For HIFU therapies of, e.g., liver cancer, one of the main challenges is the accurate focusing of the acoustic field inside a ribcage. Computational methods can play an important role in the patient-specific planning of these transcostal HIFU treatments. This requires the accurate modeling of acoustic scattering at ribcages. The use of a boundary element method (BEM) is an effective approach for this purpose because only the boundaries of the ribs have to be discretized instead of the standard approach to model the entire volume around the ribcage. This paper combines fast algorithms that improve the efficiency of BEM specifically for the high-frequency range necessary for transcostal HIFU applications. That is, a Galerkin discretized Burton-Miller formulation is used in combination with preconditioning and matrix compression techniques. In particular, quick convergence is achieved with the operator preconditioner that has been designed with on-surface radiation conditions for the high-frequency approximation of the Neumann-to-Dirichlet map. Realistic computations of acoustic scattering at 1 MHz on a human ribcage model demonstrate the effectiveness of this dedicated BEM algorithm for HIFU scattering analysis.
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Affiliation(s)
- Elwin van 't Wout
- Department of Computer Science, University College London, London, United Kingdom
| | - Pierre Gélat
- Department of Mechanical Engineering, University College London, London, United Kingdom
| | - Timo Betcke
- Department of Mathematics, University College London, London, United Kingdom
| | - Simon Arridge
- Department of Computer Science, University College London, London, United Kingdom
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22
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de Greef M, Schubert G, Wijlemans JW, Koskela J, Bartels LW, Moonen CTW, Ries M. Intercostal high intensity focused ultrasound for liver ablation: The influence of beam shaping on sonication efficacy and near-field risks. Med Phys 2015; 42:4685-97. [DOI: 10.1118/1.4925056] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
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23
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Chao YT, Hsu CJ, Yu YL, Yen JY, Ho MC, Chen YY, Chang HC, Lian FL. A novel sound-blocking structure based on the muffler principle for rib-sparing transcostal high-intensity focused ultrasound treatment. Int J Hyperthermia 2015; 31:507-27. [DOI: 10.3109/02656736.2015.1028483] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Affiliation(s)
- Yu-Tin Chao
- Department of Mechanical Engineering, National Taiwan University, Taipei,
| | - Che-Jung Hsu
- Department of Mechanical Engineering, National Taiwan University, Taipei,
| | - Ya-Lin Yu
- Department of Mechanical Engineering, National Taiwan University, Taipei,
| | - Jia-Yush Yen
- Department of Mechanical Engineering, National Taiwan University, Taipei,
| | - Ming-Chih Ho
- Department of Surgery, National Taiwan University Hospital and College of Medicine, Taipei, and
| | - Yung-Yaw Chen
- Department of Electrical Engineering, National Taiwan University, Taipei, Taiwan, Republic of China
| | - Hung-Cheng Chang
- Department of Mechanical Engineering, National Taiwan University, Taipei,
| | - Feng-Li Lian
- Department of Electrical Engineering, National Taiwan University, Taipei, Taiwan, Republic of China
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24
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Gélat P, Ter Haar G, Saffari N. An assessment of the DORT method on simple scatterers using boundary element modelling. Phys Med Biol 2015; 60:3715-30. [DOI: 10.1088/0031-9155/60/9/3715] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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25
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Gélat P, Ter Haar G, Saffari N. A comparison of methods for focusing the field of a HIFU array transducer through human ribs. Phys Med Biol 2014; 59:3139-71. [PMID: 24861888 DOI: 10.1088/0031-9155/59/12/3139] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
A forward model, which predicts the scattering by human ribs of a multi-element high-intensity focused ultrasound transducer, was used to investigate the efficacy of a range of focusing approaches described in the literature. This forward model is based on the boundary element method and was described by Gélat et al (2011 Phys. Med. Biol. 56 5553-81; 2012 Phys. Med. Biol. 57 8471-97). The model has since been improved and features a complex surface impedance condition at the surface of the ribs. The inverse problem of focusing through the ribs was implemented on six transducer array-rib topologies and five methods of focusing were investigated, including spherical focusing, binarized apodization based on geometric ray tracing, phase conjugation and the decomposition of the time-reversal operator method. The excitation frequency was 1 MHz and the array was of spherical-section type. Both human and idealized rib topologies were considered. The merit of each method of focusing was examined. It was concluded that the constrained optimization approach offers greater potential than the other focusing methods in terms of maximizing the ratio of acoustic pressure magnitudes at the focus to those on the surface of the ribs whilst taking full advantage of the dynamic range of the phased array.
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Affiliation(s)
- P Gélat
- National Physical Laboratory, Hampton Road, Teddington TW11 0LW, UK. Department of Mechanical Engineering, University College London, Torrington Place, London WC1E 7JE, UK
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26
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Lin J, Liu X, Gong X, Ping Z, Wu J. Computational study on the propagation of strongly focused nonlinear ultrasound in tissue with rib-like structures. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2013; 134:1702-1714. [PMID: 23927211 DOI: 10.1121/1.4812897] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
The presence of a rib cage is a significant hindrance to the potential applications of focused ultrasound as a noninvasive extracorporeal surgery modality for various internal organs. Here the influence of ribs on the propagation of strongly focused high-intensity nonlinear ultrasound beam inside the body is studied. Based on the spheroidal beam equation, a three-dimensional numerical algorithm is developed to solve the nonlinear acoustic field generated by a focused ultrasonic transducer with a large aperture angle. Idealized ribs, of rectangular cross sectional, with high absorption and impedance, and various dimensions, are used to simulate human anatomical configurations. The changes in the spatial distribution of acoustic intensity and the reduction of the acoustic pressure amplitude and heat deposition rate due to the presence of "ribs" are investigated. It is somewhat surprising that in some cases, the axial peak positions shift less than 2 mm and more than 80% of the sound energy can propagate through the space of the rib cage in the strongly focused sound field. This study also includes quantitative analyses of the effects of different rib configurations and transducers of various f-numbers. The results can be used as reference information for further study and clinical applications.
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Affiliation(s)
- Jiexing Lin
- Key Lab of Modern Acoustics, Institute of Acoustics, Nanjing University, Nanjing 210093, People's Republic of China
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