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Peek AT, Thomas GPL, Leotta DF, Yuldashev PV, Khokhlova VA, Khokhlova TD. Robust and durable aberrative and absorptive phantom for therapeutic ultrasound applications. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2022; 151:3007. [PMID: 35649925 PMCID: PMC9071501 DOI: 10.1121/10.0010369] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Phase aberration induced by soft tissue inhomogeneities often complicates high-intensity focused ultrasound (HIFU) therapies by distorting the field and, previously, we designed and fabricated a bilayer gel phantom to reproducibly mimic that effect. A surface pattern containing size scales relevant to inhomogeneities of a porcine body wall was introduced between gel materials with fat- and muscle-like acoustic properties-ballistic and polyvinyl alcohol gels. Here, the phantom design was refined to achieve relevant values of ultrasound absorption and scattering and make it more robust, facilitating frequent handling and use in various experimental arrangements. The fidelity of the interfacial surface of the fabricated phantom to the design was confirmed by three-dimensional ultrasound imaging. The HIFU field distortions-displacement of the focus, enlargement of the focal region, and reduction of focal pressure-produced by the phantom were characterized using hydrophone measurements with a 1.5 MHz 256-element HIFU array and found to be similar to those induced by an ex vivo porcine body wall. A phase correction approach was used to mitigate the aberration effect on nonlinear focal waveforms and enable boiling histotripsy treatments through the phantom or body wall. The refined phantom represents a practical tool to explore HIFU therapy systems capabilities.
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Affiliation(s)
- Alex T Peek
- Center for Industrial and Medical Ultrasound, Applied Physics Laboratory, University of Washington, 1013 NE 40th Street, Seattle, Washington 98105, USA
| | - Gilles P L Thomas
- Center for Industrial and Medical Ultrasound, Applied Physics Laboratory, University of Washington, 1013 NE 40th Street, Seattle, Washington 98105, USA
| | - Daniel F Leotta
- Center for Industrial and Medical Ultrasound, Applied Physics Laboratory, University of Washington, 1013 NE 40th Street, Seattle, Washington 98105, USA
| | | | - Vera A Khokhlova
- Center for Industrial and Medical Ultrasound, Applied Physics Laboratory, University of Washington, 1013 NE 40th Street, Seattle, Washington 98105, USA
| | - Tatiana D Khokhlova
- Division of Gastroenterology, Department of Medicine, University of Washington, Seattle, Washington 98125, USA
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Peek AT, Hunter C, Kreider W, Khokhlova TD, Rosnitskiy PB, Yuldashev PV, Sapozhnikov OA, Khokhlova VA. Bilayer aberration-inducing gel phantom for high intensity focused ultrasound applications. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2020; 148:3569. [PMID: 33379925 PMCID: PMC8097711 DOI: 10.1121/10.0002877] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/24/2020] [Revised: 11/04/2020] [Accepted: 11/15/2020] [Indexed: 05/19/2023]
Abstract
Aberrations induced by soft tissue inhomogeneities often complicate high-intensity focused ultrasound (HIFU) therapies. In this work, a bilayer phantom made from polyvinyl alcohol hydrogel and ballistic gel was built to mimic alternating layers of water-based and lipid tissues characteristic of an abdominal body wall and to reproducibly distort HIFU fields. The density, sound speed, and attenuation coefficient of each material were measured using a homogeneous gel layer. A surface with random topographical features was designed as an interface between gel layers using a 2D Fourier spectrum approach and replicating different spatial scales of tissue inhomogeneities. Distortion of the field of a 256-element 1.5 MHz HIFU array by the phantom was characterized through hydrophone measurements for linear and nonlinear beam focusing and compared to the corresponding distortion induced by an ex vivo porcine body wall of the same thickness. Both spatial shift and widening of the focal lobe were observed, as well as dramatic reduction in focal pressures caused by aberrations. The results suggest that the phantom produced levels of aberration that are similar to a real body wall and can serve as a research tool for studying HIFU effects as well as for developing algorithms for aberration correction.
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Affiliation(s)
- Alex T Peek
- Center for Industrial and Medical Ultrasound, Applied Physics Laboratory, University of Washington, 1013 NE 40th Street, Seattle, Washington 98105, USA
| | - Christopher Hunter
- Center for Industrial and Medical Ultrasound, Applied Physics Laboratory, University of Washington, 1013 NE 40th Street, Seattle, Washington 98105, USA
| | - Wayne Kreider
- Center for Industrial and Medical Ultrasound, Applied Physics Laboratory, University of Washington, 1013 NE 40th Street, Seattle, Washington 98105, USA
| | - Tatiana D Khokhlova
- Division of Gastroenterology, Department of Medicine, University of Washington, 1959 NE Pacific Street, Seattle, Washington 98195, USA
| | - Pavel B Rosnitskiy
- Department of Acoustics, Physics Faculty, Moscow State University, Leninskie Gory, Moscow 119991, Russia
| | - Petr V Yuldashev
- Department of Acoustics, Physics Faculty, Moscow State University, Leninskie Gory, Moscow 119991, Russia
| | - Oleg A Sapozhnikov
- Department of Acoustics, Physics Faculty, Moscow State University, Leninskie Gory, Moscow 119991, Russia
| | - Vera A Khokhlova
- Department of Acoustics, Physics Faculty, Moscow State University, Leninskie Gory, Moscow 119991, Russia
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Bigelow TA, Thomas CL, Wu H. Scan Parameter Optimization for Histotripsy Treatment of S. Aureus Biofilms on Surgical Mesh. IEEE TRANSACTIONS ON ULTRASONICS, FERROELECTRICS, AND FREQUENCY CONTROL 2020; 67:341-349. [PMID: 31634828 PMCID: PMC7039400 DOI: 10.1109/tuffc.2019.2948305] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
There is a critical need to develop new noninvasive therapies to treat bacteria biofilms. Previous studies have demonstrated the effectiveness of cavitation-based ultrasound histotripsy to destroy these biofilms. In this study, the dependence of biofilm destruction on multiple scan parameters was assessed by conducting exposures at different scan speeds (0.3-1.4 beamwidths/s), step sizes (0.25-0.5 beamwidths), and the number of passes of the focus across the mesh (2-6). For each of the exposure conditions, the number of colony-forming units (CFUs) remaining on the mesh was quantified. A regression analysis was then conducted, revealing that the scan speed was the most critical parameter for biofilm destruction. Reducing the number of passes and the scan speed should allow for more efficient biofilm destruction in the future, reducing the treatment time.
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Macoskey JJ, Zhang X, Hall TL, Shi J, Beig SA, Johnsen E, Lee FT, Cain CA, Xu Z. Bubble-Induced Color Doppler Feedback Correlates with Histotripsy-Induced Destruction of Structural Components in Liver Tissue. ULTRASOUND IN MEDICINE & BIOLOGY 2018; 44:602-612. [PMID: 29329687 PMCID: PMC5801099 DOI: 10.1016/j.ultrasmedbio.2017.11.012] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/22/2017] [Revised: 11/09/2017] [Accepted: 11/20/2017] [Indexed: 06/01/2023]
Abstract
Bubble-induced color Doppler (BCD) is a histotripsy-therapy monitoring technique that uses Doppler ultrasound to track the motion of residual cavitation nuclei that persist after the collapse of the histotripsy bubble cloud. In this study, BCD is used to monitor tissue fractionation during histotripsy tissue therapy, and the BCD signal is correlated with the destruction of structural and non-structural components identified histologically to further understand how BCD monitors the extent of treatment. A 500-kHz, 112-element phased histotripsy array is used to generate approximately 6- × 6- × 7-mm lesions within ex vivo bovine liver tissue by scanning more than 219 locations with 30-1000 pulses per location. A 128-element L7-4 imaging probe is used to acquire BCD signals during all treatments. The BCD signal is then quantitatively analyzed using the time-to-peak rebound velocity (tprv) metric. Using the Pearson correlation coefficient, the tprv is compared with histologic analytics of lesions generated by various numbers of pulses using a significance level of 0.001. Histologic analytics in this study include viable cell count, reticulin-stained type III collagen area and trichrome-stained type I collagen area. It is found that the tprv metric has a statistically significant correlation with the change in reticulin-stained type III collagen area with a Pearson correlation coefficient of -0.94 (p <0.001), indicating that changes in BCD are more likely because of destruction of the structural components of tissue.
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Affiliation(s)
- Jonathan J Macoskey
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA.
| | - Xi Zhang
- 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
| | - Jiaqi Shi
- Department of Pathology, University of Michigan, Ann Arbor, MI, USA
| | | | - Eric Johnsen
- Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI, USA
| | - Fred T Lee
- Department of Radiology, University of Wisconsin, Madison, WI, USA
| | - Charles A Cain
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA; Department of Electrical Engineering & Computer Science, University of Michigan, Ann Arbor, MI, USA
| | - Zhen Xu
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA
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Villemain O, Kwiecinski W, Bel A, Robin J, Bruneval P, Arnal B, Tanter M, Pernot M, Messas E. Pulsed cavitational ultrasound for non-invasive chordal cutting guided by real-time 3D echocardiography. Eur Heart J Cardiovasc Imaging 2016; 17:1101-7. [DOI: 10.1093/ehjci/jew145] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/20/2016] [Accepted: 04/10/2016] [Indexed: 01/12/2023] Open
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Ghorbani M, Oral O, Ekici S, Gozuacik D, Kosar A. Review on Lithotripsy and Cavitation in Urinary Stone Therapy. IEEE Rev Biomed Eng 2016; 9:264-83. [PMID: 27249837 DOI: 10.1109/rbme.2016.2573381] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Cavitation is the sudden formation of vapor bubbles or voids in liquid media and occurs after rapid changes in pressure as a consequence of mechanical forces. It is mostly an undesirable phenomenon. Although the elimination of cavitation is a major topic in the study of fluid dynamics, its destructive nature could be exploited for therapeutic applications. Ultrasonic and hydrodynamic sources are two main origins for generating cavitation. The purpose of this review is to give the reader a general idea about the formation of cavitation phenomenon and existing biomedical applications of ultrasonic and hydrodynamic cavitation. Because of the high number of the studies on ultrasound cavitation in the literature, the main focus of this review is placed on the lithotripsy techniques, which have been widely used for the treatment of urinary stones. Accordingly, cavitation phenomenon and its basic concepts are presented in Section II. The significance of the ultrasound cavitation in the urinary stone treatment is discussed in Section III in detail and hydrodynamic cavitation as an important alternative for the ultrasound cavitation is included in Section IV. Finally, side effects of using both ultrasound and hydrodynamic cavitation in biomedical applications are presented in Section V.
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Lin KW, Hall TL, Xu Z, Cain CA. Histotripsy Lesion Formation Using an Ultrasound Imaging Probe Enabled by a Low-Frequency Pump Transducer. ULTRASOUND IN MEDICINE & BIOLOGY 2015; 41:2148-60. [PMID: 25929995 PMCID: PMC4466130 DOI: 10.1016/j.ultrasmedbio.2015.03.026] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/01/2014] [Revised: 03/11/2015] [Accepted: 03/27/2015] [Indexed: 05/11/2023]
Abstract
When histotripsy pulses shorter than 2 cycles are applied, the formation of a dense bubble cloud relies only on the applied peak negative pressure (p-) exceeding the "intrinsic threshold" of the medium (absolute value of 26-30 MPa in most soft tissues). It has been found that a sub-threshold high-frequency probe pulse (3 MHz) can be enabled by a sub-threshold low-frequency pump pulse (500 kHz) where the sum exceeds the intrinsic threshold, thus generating lesion-producing dense bubble clouds ("dual-beam histotripsy"). Here, the feasibility of using an imaging transducer to provide the high-frequency probe pulse in the dual-beam histotripsy approach is investigated. More specifically, an ATL L7-4 imaging transducer (Philips Healthcare, Andover, MA, USA), pulsed by a V-1 Data Acquisition System (Verasonics, Redmond, WA, USA), was used to generate the high-frequency probe pulses. The low-frequency pump pulses were generated by a 20-element 345-kHz array transducer, driven by a custom high-voltage pulser. These dual-beam histotripsy pulses were applied to red blood cell tissue-mimicking phantoms at a pulse repetition frequency of 1 Hz, and optical imaging was used to visualize bubble clouds and lesions generated in the red blood cell phantoms. The results indicated that dense bubble clouds (and resulting lesions) were generated when the p- of the sub-threshold pump and probe pulses combined constructively to exceed the intrinsic threshold. The average size of the smallest reproducible lesions using the imaging probe pulse enabled by the sub-threshold pump pulse was 0.7 × 1.7 mm, whereas that using the supra-threshold pump pulse alone was 1.4 × 3.7 mm. When the imaging transducer was steered laterally, bubble clouds and lesions were steered correspondingly until the combined p- no longer exceeded the intrinsic threshold. These results were also validated with ex vivo porcine liver experiments. Using an imaging transducer for dual-beam histotripsy can have two advantages: (i) lesion steering can be achieved using the steering of the imaging transducer (implemented with the beamformer of the accompanying programmable ultrasound system), and (ii) treatment can be simultaneously monitored when the imaging transducer is used in conjunction with an ultrasound imaging system.
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Affiliation(s)
- Kuang-Wei Lin
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan, USA.
| | - Timothy L Hall
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan, USA
| | - Zhen Xu
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan, USA
| | - Charles A Cain
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan, USA
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Liu Z, Guo X, Tu J, Zhang D. Variations in temperature distribution and tissue lesion formation induced by tissue inhomogeneity for therapeutic ultrasound. ULTRASOUND IN MEDICINE & BIOLOGY 2014; 40:1857-1868. [PMID: 24768487 DOI: 10.1016/j.ultrasmedbio.2014.02.004] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/18/2013] [Revised: 01/29/2014] [Accepted: 02/03/2014] [Indexed: 06/03/2023]
Abstract
Tissue inhomogeneity might have an important effect on the treatment accuracy of therapeutic ultrasound. Both computer simulation and measurement were performed to study the influence of tissue inhomogeneity on the temperature distribution and tissue lesion formation induced by focused ultrasound. The inhomogeneous tissue is considered a combination of a homogeneous medium and a phase aberration screen in this article. Temperature distributions and lesion dimensions were predicted using the combination of acoustic non-linear and bio-heat transfer equations. To verify the theoretical predictions, polyethylene plates with phase distributions of different correlation lengths and standard deviations were made to mimic inhomogeneous tissues such as human abdominal tissue, and a series of experiments were performed, including acoustic and thermal measurements. The results indicate that the tissue inhomogeneity caused phase aberration of the ultrasound beam. With increasing standard deviation and correlation length of phase aberration, the scattering level of the acoustic field increased, while ultrasound-induced peak temperature and lesion size decreased. This study provides a theoretical and experimental basis for future development of accurate treatment plans for high-intensity focused ultrasound.
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Affiliation(s)
- Zhenbo Liu
- Key Laboratory of Modern Acoustics (Nanjing University), Ministry of Education, Nanjing, China; Nanjing Normal University, Nanjing, China
| | - Xiasheng Guo
- Key Laboratory of Modern Acoustics (Nanjing University), Ministry of Education, Nanjing, China
| | - Juan Tu
- Key Laboratory of Modern Acoustics (Nanjing University), Ministry of Education, Nanjing, China.
| | - Dong Zhang
- Key Laboratory of Modern Acoustics (Nanjing University), Ministry of Education, Nanjing, China; State Key Laboratory of Acoustics, Institute of Acoustics, Chinese Academy of Sciences, Beijing, China.
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Lin KW, Hall TL, McGough RJ, Xu Z, Cain CA. Synthesis of monopolar ultrasound pulses for therapy: the frequency-compounding transducer. IEEE TRANSACTIONS ON ULTRASONICS, FERROELECTRICS, AND FREQUENCY CONTROL 2014; 61:1123-1136. [PMID: 24960702 DOI: 10.1109/tuffc.2014.3012] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
In diagnostic ultrasound, broadband transducers capable of short acoustic pulse emission and reception can improve axial resolution and provide sufficient bandwidth for harmonic imaging and multi-frequency excitation techniques. In histotripsy, a cavitation-based ultrasound therapy, short acoustic pulses (<2 cycles) can produce precise tissue ablation wherein lesion formation only occurs when the applied peak negative pressure exceeds an intrinsic threshold of the medium. This paper investigates a frequency compounding technique to synthesize nearly monopolar (half-cycle) ultrasound pulses. More specifically, these pulses were generated using a custom transducer composed of 23 individual relatively-broadband piezoceramic elements with various resonant frequencies (0.5, 1, 1.5, 2, and 3 MHz). Each frequency component of the transducer was capable of generating 1.5-cycle pulses with only one high-amplitude negative half-cycle using a custom 23-channel high-voltage pulser. By varying time delays of individual frequency components to allow their principal peak negative peaks to arrive at the focus of the transducer constructively, destructive interference occurs elsewhere in time and space, resulting in a monopolar pulse approximation with a dominant negative phase (with measured peak negative pressure [P-]: peak positive pressure [P+] = 4.68: 1). By inverting the excitation pulses to individual elements, monopolar pulses with a dominant positive phase can also be generated (with measured P+: P- = 4.74: 1). Experiments in RBC phantoms indicated that monopolar pulses with a dominant negative phase were able to produce very precise histotripsy-type lesions using the intrinsic threshold mechanism. Monopolar pulses with a dominant negative phase can inhibit shock scattering during histotripsy, leading to more predictable lesion formation using the intrinsic threshold mechanism, while greatly reducing any constructive interference, and potential hot-spots elsewhere. Moreover, these monopolar pulses could have many potential benefits in ultrasound imaging, including axial resolution improvement, speckle reduction, and contrast enhancement in pulse inversion imaging.
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Lin KW, Kim Y, Maxwell AD, Wang TY, Hall TL, Xu Z, Fowlkes JB, Cain CA. Histotripsy beyond the intrinsic cavitation threshold using very short ultrasound pulses: microtripsy. IEEE TRANSACTIONS ON ULTRASONICS, FERROELECTRICS, AND FREQUENCY CONTROL 2014; 61:251-65. [PMID: 24474132 PMCID: PMC3966303 DOI: 10.1109/tuffc.2014.6722611] [Citation(s) in RCA: 103] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Histotripsy produces tissue fractionation through dense energetic bubble clouds generated by short, high-pressure, ultrasound pulses. Conventional histotripsy treatments have used longer pulses from 3 to 10 cycles, wherein the lesion-producing bubble cloud generation depends on the pressure-release scattering of very high peak positive shock fronts from previously initiated, sparsely distributed bubbles (the shock-scattering mechanism). In our recent work, the peak negative pressure (P-) for generation of dense bubble clouds directly by a single negative half cycle, the intrinsic threshold, was measured. In this paper, the dense bubble clouds and resulting lesions (in red blood cell phantoms and canine tissues) generated by these supra-intrinsic threshold pulses were studied. A 32-element, PZT-8, 500-kHz therapy transducer was used to generate very short (<2 cycles) histotripsy pulses at a pulse repetition frequency (PRF) of 1 Hz and P- from 24.5 to 80.7 MPa. The results showed that the spatial extent of the histotripsy-induced lesions increased as the applied P- increased, and the sizes of these lesions corresponded well to the estimates of the focal regions above the intrinsic cavitation threshold, at least in the lower pressure regime (P- = 26 to 35 MPa). The average sizes for the smallest reproducible lesions were approximately 0.9 × 1.7 mm (lateral × axial), significantly smaller than the -6-dB beamwidth of the transducer (1.8 × 4.0 mm). These results suggest that, using the intrinsic threshold mechanism, well-confined and microscopic lesions can be precisely generated and their spatial extent can be estimated based on the fraction of the focal region exceeding the intrinsic cavitation threshold. Because the supra-threshold portion of the negative half cycle can be precisely controlled, lesions considerably less than a wavelength are easily produced, hence the term microtripsy.
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Lin KW, Duryea AP, Kim Y, Hall TL, Xu Z, Cain CA. Dual-beam histotripsy: a low-frequency pump enabling a high-frequency probe for precise lesion formation. IEEE TRANSACTIONS ON ULTRASONICS, FERROELECTRICS, AND FREQUENCY CONTROL 2014; 61:325-40. [PMID: 24474138 PMCID: PMC3971546 DOI: 10.1109/tuffc.2014.6722617] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Histotripsy produces tissue fractionation through dense energetic bubble clouds generated by short, high-pressure, ultrasound pulses. When using pulses shorter than 2 cycles, the generation of these energetic bubble clouds only depends on where the peak negative pressure (P-) exceeds the intrinsic threshold of the medium (26 to 30 MPa in soft tissue with high water content). This paper investigates a strategic method for precise lesion generation in which a low-frequency pump pulse is applied to enable a sub-threshold high-frequency probe pulse to exceed the intrinsic threshold. This pump-probe method of controlling a supra-threshold volume can be called dual-beam histotripsy. A 20-element dual-frequency (500-kHz and 3-MHz elements confocally aligned) array transducer was used to generate dual-beam histotripsy pulses in red blood cell phantoms and porcine hepatic tissue specimens. The results showed that when sub-intrinsic-threshold pump (500-kHz) and probe (3-MHz) pulses were applied together, dense bubble clouds (and resulting lesions) were only generated when their peak negative pressures combined constructively to exceed the intrinsic threshold. The smallest reproducible lesion varied with the relative amplitude between the pump and probe pulses, and, with a higher proportion of the probe pulse, smaller lesions could be generated. When the propagation direction of the probe pulse relative to the pump pulse was altered, the shape of the produced lesion changed based on the region that exceeded intrinsic threshold. Because the low-frequency pump pulse is more immune to attenuation and aberrations, and the high-frequency probe pulse can provide precision in lesion formation, this dual-beam histotripsy approach would be very useful in situations in which precise lesion formation is required through a highly attenuative and aberrative medium, such as transcranial therapy. This is particularly true if a small low-attenuation acoustic window is available for the high-frequency probe transducer.
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Fan T, Liu Z, Chen T, Li F, Zhang D. A modeling approach to predict acoustic nonlinear field generated by a transmitter with an aluminum lens. Med Phys 2011; 38:5033-9. [PMID: 21978047 DOI: 10.1118/1.3622602] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE In this work, the authors propose a modeling approach to compute the nonlinear acoustic field generated by a flat piston transmitter with an attached aluminum lens. METHODS In this approach, the geometrical parameters (radius and focal length) of a virtual source are initially determined by Snell's refraction law and then adjusted based on the Rayleigh integral result in the linear case. Then, this virtual source is used with the nonlinear spheroidal beam equation (SBE) model to predict the nonlinear acoustic field in the focal region. RESULTS To examine the validity of this approach, the calculated nonlinear result is compared with those from the Westervelt and (Khokhlov-Zabolotskaya-Kuznetsov) KZK equations for a focal intensity of 7 kW/cm(2). Results indicate that this approach could accurately describe the nonlinear acoustic field in the focal region with less computation time. CONCLUSIONS The proposed modeling approach is shown to accurately describe the nonlinear acoustic field in the focal region. Compared with the Westervelt equation, the computation time of this approach is significantly reduced. It might also be applicable for the widely used concave focused transmitter with a large aperture angle.
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Affiliation(s)
- Tingbo Fan
- Institute of Acoustics, Key Laboratory of Modern Acoustics, MOE, Nanjing University, Nanjing 210093, China
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Fan T, Liu Z, Zhang D, Tang M. Comparative study of lesions created by high-intensity focused ultrasound using sequential discrete and continuous scanning strategies. IEEE Trans Biomed Eng 2011; 60:763-9. [PMID: 21914564 DOI: 10.1109/tbme.2011.2167719] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Lesion formation and temperature distribution induced by high-intensity focused ultrasound (HIFU) were investigated both numerically and experimentally via two energy-delivering strategies, i.e., sequential discrete and continuous scanning modes. Simulations were presented based on the combination of Khokhlov-Zabolotskaya-Kuznetsov (KZK) equation and bioheat equation. Measurements were performed on tissue-mimicking phantoms sonicated by a 1.12-MHz single-element focused transducer working at an acoustic power of 75 W. Both the simulated and experimental results show that, in the sequential discrete mode, obvious saw-tooth-like contours could be observed for the peak temperature distribution and the lesion boundaries, with the increasing interval space between two adjacent exposure points. In the continuous scanning mode, more uniform peak temperature distributions and lesion boundaries would be produced, and the peak temperature values would decrease significantly with the increasing scanning speed. In addition, compared to the sequential discrete mode, the continuous scanning mode could achieve higher treatment efficiency (lesion area generated per second) with a lower peak temperature. The present studies suggest that the peak temperature and tissue lesion resulting from the HIFU exposure could be controlled by adjusting the transducer scanning speed, which is important for improving the HIFU treatment efficiency.
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Affiliation(s)
- Tingbo Fan
- Institute of Acoustics, Key Laboratory of Modern Acoustics, Ministry of Education, Nanjing University, Nanjing 210093, China.
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Carvell KJ, Bigelow TA. Dependence of optimal seed bubble size on pressure amplitude at therapeutic pressure levels. ULTRASONICS 2011; 51:115-122. [PMID: 20656313 DOI: 10.1016/j.ultras.2010.06.005] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/07/2010] [Revised: 06/22/2010] [Accepted: 06/28/2010] [Indexed: 05/29/2023]
Abstract
Medical ultrasound has shown great potential as a minimally invasive therapy technique. It can be used in areas such as histotripsy, thermal ablation, and administering medication. The success of these therapies is improved by the cavitation of small microbubbles, and often it is useful to know which bubbles might provide the most effective therapy. When using therapies based on stable cavitation, the optimal bubble size is approximately given by R(0)≅3MHzμm/f(0)(lin). However, a similar expression is not available for therapies involving inertial cavitation. Therefore, the goal of our study was to develop an approximate expression relating the initial size of the bubble that resulted in the maximum response to the ultrasound operating frequency and pressure of the ultrasound wave when inertial cavitation is expected. The study was conducted by simulating the response of air bubbles in water to linearly propagating sine waves using the Gilmore-Akulichev formulation to solve for the bubble response. The frequency of the sine wave varied from 0.5 to 5MHz while the amplitude of the sine wave varied from 0.0001 to 5MPa. The optimal initial size for a particular frequency of excitation and amplitude, which is normally only established for stable cavitation, was defined in the study as the initial bubble size that resulted in the maximum bubble expansion prior to bubble radius dropping below its initial radius. A fit over pressure and frequency then yielded that the optimal size was approximately given by R(optimal)=(0.0327f(2)+0.0679f+16.5P(2))(-0.5) where R(optimal) is in μm, f is the frequency of the ultrasound wave in MHz, and P the pressure amplitude of the ultrasound wave in MPa.
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Affiliation(s)
- Kelsey J Carvell
- Department of Electrical and Computer Engineering, Iowa State University, Ames, IA 50011, USA
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Dogra VS, Zhang M, Bhatt S. High-Intensity Focused Ultrasound (HIFU) Therapy Applications. ACTA ACUST UNITED AC 2009. [DOI: 10.1016/j.cult.2009.10.005] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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Bigelow TA, Northagen T, Hill TM, Sailer FC. The destruction of Escherichia coli biofilms using high-intensity focused ultrasound. ULTRASOUND IN MEDICINE & BIOLOGY 2009; 35:1026-1031. [PMID: 19171416 DOI: 10.1016/j.ultrasmedbio.2008.12.001] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/11/2008] [Revised: 11/26/2008] [Accepted: 12/02/2008] [Indexed: 05/27/2023]
Abstract
High-intensity focused ultrasound (HIFU) has shown great potential for replacing surgery in many applications. In this work, HIFU was used to destroy Escherichia coli (E. coli) biofilms that had been grown on chambered microscope slides. Biofilms are central to the pathogenesis and persistence of nosocomial (hospital-acquired) infections associated with indwelling medical devices. The slides were exposed to 9.1 mus pulses at a pulse repetition frequency of 1000 Hz. The pulses were generated by a 1.1 MHz spherically focused source with a focal length of 6.3 cm and an active diameter of 7 cm. The peak rarefactional pressure for the pulses was varied as 3.1, 4.1, 5.2, 6.2 and 7.6 MPa in addition to a sham where the biofilms were not exposed. The effectiveness of the treatment was assessed by determining the number of colony forming units (CFU) remaining following exposure of the bacteria to HIFU. Most of the biofilms treated at the higher exposures of 6.2 and 7.6 MPa had no detectable CFU, indicating that bacteria in the biofilm were killed by the treatment or that treatment disrupted the biofilm and released bacteria from the slide. However, the ability of some bacteria to survive at the higher exposure settings needs to be resolved prior to implementing the treatment clinically.
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Affiliation(s)
- Timothy A Bigelow
- Department of Electrical Engineering, School of Engineering and Mines, University of North Dakota, Grand Forks, ND, USA.
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Bigelow TA, Northagen T, Hill TM, Sailer FC. Ultrasound histotripsy and the destruction of Escherichia coli biofilms. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2009; 2008:4467-70. [PMID: 19163706 DOI: 10.1109/iembs.2008.4650203] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Ultrasound histotripsy has shown great potential for replacing surgery in many applications. In this work, a modification of ultrasound histotripsy was used to destroy Escherichia coli (E. coli) biofilms that had been grown on chambered microscope slides. Biofilms are central to the pathogenesis and persistence of nosocomial (hospital-acquired) infections associated with indwelling medical devices. The slides were exposed to 9.1 micros pulses at a pulse repetition frequency of 1000 Hz. The pulses were generated by a 1.1 MHz spherically focused source with a focal length of 6.3 cm and an active diameter of 7 cm. The peak rarefactional pressure for the pulses was varied as 3.1, 4.1, 5.2, 6.2, and 7.6 MPa in addition to a sham where the biofilms were not exposed. The effectiveness of the treatment was assessed by determining the viable number of colony forming units (CFU) remaining in the biofilm. Most of the biofilms treated at the higher exposures of 6.2 and 7.6 MPa had no remaining CFU indicating that the biofilm was completely destroyed. However, the persistence of some CFU for some of the biofioms at the higher exposure settings needs to be resolved prior to implementing the treatment clinically.
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Yu T, Hu D, Xu C. Microbubbles improve the ablation efficiency of extracorporeal high intensity focused ultrasound against kidney tissues. World J Urol 2008; 26:631-6. [DOI: 10.1007/s00345-008-0290-z] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2007] [Accepted: 05/27/2008] [Indexed: 12/11/2022] Open
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Wu CC, Chen WS, Ho MC, Huang KW, Chen CN, Yen JY, Lee PH. Minimizing abdominal wall damage during high-intensity focused ultrasound ablation by inducing artificial ascites. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2008; 124:674-679. [PMID: 18647009 DOI: 10.1121/1.2839907] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
High-intensity focused ultrasound (HIFU) is becoming an important tool for tumor treatment [especially hepatocellular carcinoma (HCC)] in Asian countries. A HIFU system provides unique advantages of low invasiveness and absence of nonradiation. However, if the target HCC is close to the proximal surface of the liver, HIFU may overheat diaphragm, abdominal wall or skin. To avoid this complication, a method using artificial ascites in the abdominal cavity to separate the liver from the peritoneum, and to serve as a heat sink to cool overlying structures and thereby avoid inducing permanent damage was proposed. Target tissue that was 10 mm below the liver surface was ablated in 12 New Zealand white rabbits: 6 in the experimental group and 6 in the control group. Artificial ascites was established in the experimental group by injecting normal saline into the abdominal cavity until the pressure reached 150 mm H2O. Artificial ascites not only reduced the probability and extent of thermal damage to intervening structures, but also had no adverse affect on the efficacy of HIFU ablation.
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Affiliation(s)
- Chih-Ching Wu
- Department of Mechanical Engineering, National Taiwan University, Taipei, Taiwan
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Wu CC, Chen CN, Ho MC, Chen WS, Lee PH. Using the acoustic interference pattern to locate the focus of a high-intensity focused ultrasound (HIFU) transducer. ULTRASOUND IN MEDICINE & BIOLOGY 2008; 34:137-46. [PMID: 17720300 DOI: 10.1016/j.ultrasmedbio.2007.07.001] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/25/2006] [Revised: 06/04/2007] [Accepted: 07/02/2007] [Indexed: 05/16/2023]
Abstract
One of the main problems encountered when using conventional B-mode ultrasound (US) for targeting and monitoring purposes during ablation therapies employing high-intensity focused US (HIFU) is the appearance of strong interference in the obtained diagnostic US images. In this study, instead of avoiding the interference noise, we demonstrate how we used it to locate the focus of the HIFU transducer in both in vitro tissue-mimicking phantoms and an ex vivo tissue block. We found that when the B-mode image plane coincided with the HIFU focal plane, the interference noise was maximally converged and enhanced compared with the off-focus situations. Stronger interference noise was recorded when the angle (alpha) between the US image plane and the HIFU axis was less than or equal to 90 degrees. By intentionally creating a target (group of bubbles) at the 3.5-MHz HIFU focus (7.1 mm in length and 0.7 mm in diameter), the position of the maximal noise convergence coincided well with the target. The difference between the predicted focus and the actual one (bubbles) on x and z axes (axes perpendicular to the HIFU central axis, Fig. 1) were both about 0.9 mm. For y axis (HIFU central axis), the precision was within 1.0 mm. For tissue block ablation, the interference noise concentrated at the position of maximal heating of the HIFU-induced lesions. The proposed method can also be used to predict the position of the HIFU focus by using a low intensity output scheme before permanent changes in the target tissue were made.
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Affiliation(s)
- Chih-Ching Wu
- Department of Mechanical Engineering, National Taiwan University, Taipei, Taiwan
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Abstract
PURPOSE OF REVIEW Solid renal tumours with a diameter 4 cm or less are frequently found during routine radiologic investigations. Since a significant number of patients are elderly and frail, there is a growing interest in effectively treating these patients by minimally invasive energy-ablative surgery. RECENT FINDINGS Such tumours may be treated by either freezing (cryoablation) or by heat (radio-frequency ablation or high-intensity focused ultrasound). In addition, percutaneous methods are available, but percutaneous focused ultrasound is not feasible as yet with the technique available. All percutaneous techniques lack effective monitoring of ablation, however, and oncological follow-up commonly relies on radiologic measurements only. Not surprisingly, the effectiveness of all percutaneous procedures is significantly lower, with a high recurrence and re-treatment rate as compared with open or laparoscopic procedures. Long-term results in larger series are missing, but it seems that laparoscopic cryoablation is most effective in respect to oncological results, but requires more technical efforts and surgical skills as compared with radio-frequency ablation or focused ultrasound. SUMMARY There is currently no ideal energy-ablative energy source on the horizon, but cryoablation seems to produce the most durable result. Focused ultrasound, however, may have the greatest potential for further developments.
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