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Huang W, Jiao Y, Li J, He Y, Shao W, Cui Y. Evaluation of Dual-Frequency Switching HIFU for Optimizing Superficial Ablation. ULTRASOUND IN MEDICINE & BIOLOGY 2024; 50:908-919. [PMID: 38548527 DOI: 10.1016/j.ultrasmedbio.2024.02.016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/06/2023] [Revised: 01/21/2024] [Accepted: 02/23/2024] [Indexed: 05/01/2024]
Abstract
OBJECTIVE Dual-frequency high-intensity focused ultrasound (HIFU) thermal ablation is an exceptionally promising technique for treating tumors due to its precision and effectiveness. However, there are still a few studies on improving the accuracy and efficiency of HIFU in superficial ablation applications. This study proposes a method utilizing dual frequency switching ultrasound (DFSU) to enhance the efficiency and precision of superficial treatments. METHODS A dual-frequency HIFU transducer operating at 4.5 MHz and 13.7 MHz was designed, and a dual-frequency impedance matching network was designed to optimize electro-acoustic conversion efficiency. Phantom and ex vivo tests were conducted to measure and compare thermal lesion areas and temperature rises caused by single-frequency ultrasound (SFU) and DFSU. RESULTS In both phantom and ex vivo tests, the utilization of DFSU resulted in larger lesion areas compared to SFU. Moreover, DFSU provided improved control and versatility, enabling precise and efficient ablation. CONCLUSION DFSU exhibits the ability to generate larger ablation areas in superficial tissue compared to SFU, and DFSU allows flexible control over the ablation area and temperature rise rate. The acoustic power deposition of HIFU can be optimized to achieve precise ablation.
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Affiliation(s)
- Wenchang Huang
- School of Biomedical Engineering (Suzhou), Division of Life Sciences and Medicine, University of Science and Technology of China, Suzhou, Jiangsu, China; Suzhou Institute of Biomedical Engineering and Technology, Chinese Academy of Sciences, Suzhou, Jiangsu, China
| | - Yang Jiao
- Suzhou Institute of Biomedical Engineering and Technology, Chinese Academy of Sciences, Suzhou, Jiangsu, China
| | - Jiaqi Li
- School of Biomedical Engineering (Suzhou), Division of Life Sciences and Medicine, University of Science and Technology of China, Suzhou, Jiangsu, China; Suzhou Institute of Biomedical Engineering and Technology, Chinese Academy of Sciences, Suzhou, Jiangsu, China
| | - Yan He
- School of Biomedical Engineering (Suzhou), Division of Life Sciences and Medicine, University of Science and Technology of China, Suzhou, Jiangsu, China; Suzhou Institute of Biomedical Engineering and Technology, Chinese Academy of Sciences, Suzhou, Jiangsu, China
| | - Weiwei Shao
- Suzhou Institute of Biomedical Engineering and Technology, Chinese Academy of Sciences, Suzhou, Jiangsu, China
| | - Yaoyao Cui
- Suzhou Institute of Biomedical Engineering and Technology, Chinese Academy of Sciences, Suzhou, Jiangsu, China.
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Dillon CR, Farrer A, McLean H, Almquist S, Christensen D, Payne A. Experimental assessment of phase aberration correction for breast MRgFUS therapy. Int J Hyperthermia 2017; 34:731-743. [PMID: 29278946 DOI: 10.1080/02656736.2017.1422029] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
PURPOSE This study validates that phase aberrations in breast magnetic resonance-guided focussed ultrasound (MRgFUS) therapies can be corrected in a clinically relevant time frame to generate more intense, smaller and more spatially accurate foci. MATERIALS AND METHODS Hybrid angular spectrum (HAS) ultrasound calculations in an magnetic resonance imaging (MRI)-based tissue model, were used to compute phase aberration corrections for improved experimental MRgFUS heating in four heterogeneous breast-mimicking phantoms (n = 18 total locations). Magnetic resonance(MR) temperature imaging was used to evaluate the maximum temperature rise, focus volume and focus accuracy for uncorrected and phase aberration-corrected sonications. Thermal simulations assessed the effectiveness of the phase aberration correction implementation. RESULTS In 13 of 18 locations, the maximum temperature rise increased by an average of 30%, focus volume was reduced by 40% and focus accuracy improved from 4.6 to 3.6 mm. Mixed results were observed in five of the 18 locations, with focus accuracy improving from 6.1 to 2.5 mm and the maximum temperature rise decreasing by 8% and focus volume increasing by 10%. Overall, the study demonstrated significant improvements (p < 0.005) in maximum temperature rise, focus volume and focus accuracy. Simulations predicted greater improvements than observed experimentally, suggesting potential for improvement in implementing the technique. The complete phase aberration correction procedure, including model generation, segmentation and phase aberration computations, required less than 45 min per sonication location. CONCLUSION The significant improvements demonstrated in this study i.e., focus intensity, size and accuracy from phase aberration correction have the potential to improve the efficacy, time-efficiency and safety of breast MRgFUS therapies.
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Affiliation(s)
- Christopher R Dillon
- a Department of Radiology and Imaging Sciences , University of Utah , Salt Lake City , UT , USA
| | - Alexis Farrer
- b Department of Bioengineering , University of Utah , Salt Lake City , UT , USA
| | - Hailey McLean
- a Department of Radiology and Imaging Sciences , University of Utah , Salt Lake City , UT , USA
| | - Scott Almquist
- c School of Computing , University of Utah , Salt Lake City , UT , USA
| | - Douglas Christensen
- b Department of Bioengineering , University of Utah , Salt Lake City , UT , USA.,d Department of Electrical and Computer Engineering , University of Utah , Salt Lake City , UT , USA
| | - Allison Payne
- a Department of Radiology and Imaging Sciences , University of Utah , Salt Lake City , UT , USA
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Grisey A, Yon S, Letort V, Lafitte P. Simulation of high-intensity focused ultrasound lesions in presence of boiling. J Ther Ultrasound 2016; 4:11. [PMID: 27034778 PMCID: PMC4815116 DOI: 10.1186/s40349-016-0056-9] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2015] [Accepted: 03/17/2016] [Indexed: 01/18/2023] Open
Abstract
Background The lesions induced by high-intensity focused ultrasound (HIFU) thermal ablations are particularly difficult to simulate due to the complexity of the involved phenomena. In particular, boiling has a strong influence on the lesion shape. Thus, it must be accounted for if it happens during the pulses to be modeled. However, no acoustic model enables the simulation of the resulting wave scattering. Therefore, we propose an equivalent model for the heat deposition pattern in the presence of boiling. Methods Firstly, the acoustic field is simulated with k-Wave and the heat source term is calculated. Then, a thermal model is designed, including the equivalent model for boiling. It is rigorously calibrated and validated through the use of diversified ex vivo and in vivo data, including usually unexploited data types related to the bubble clouds. Results The proposed model enabled to efficiently simulate unitary pulses properties, including the sizes of the lesions, their morphology, the boiling onset time, and the influence of the boiling onset time on the lesions sizes. Conclusions In this article, the whole procedure of model design, calibration, and validation is discussed. In addition to depicting the creative use of data, our modeling approach focuses on the understanding of the mechanisms influencing the shape of the lesion. Further work is required to study the influence of the remaining bubble clouds in the context of pulse groups.
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Affiliation(s)
- Anthony Grisey
- Theraclion, 102 Rue Etienne Dolet, Malakoff, 92240 France ; CentraleSupélec, Mathematics in Interaction with Computer Science, Grande voie des vignes, Châtenay-Malabry, 92295 France
| | - Sylvain Yon
- Theraclion, 102 Rue Etienne Dolet, Malakoff, 92240 France
| | - Véronique Letort
- CentraleSupélec, Mathematics in Interaction with Computer Science, Grande voie des vignes, Châtenay-Malabry, 92295 France
| | - Pauline Lafitte
- CentraleSupélec, Mathematics in Interaction with Computer Science, Grande voie des vignes, Châtenay-Malabry, 92295 France
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Chen J, Hou GY, Marquet F, Han Y, Camarena F, Konofagou E. Radiation-force-based estimation of acoustic attenuation using harmonic motion imaging (HMI) in phantoms and in vitro livers before and after HIFU ablation. Phys Med Biol 2015; 60:7499-512. [PMID: 26371501 DOI: 10.1088/0031-9155/60/19/7499] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Acoustic attenuation represents the energy loss of the propagating wave through biological tissues and plays a significant role in both therapeutic and diagnostic ultrasound applications. Estimation of acoustic attenuation remains challenging but critical for tissue characterization. In this study, an attenuation estimation approach was developed using the radiation-force-based method of harmonic motion imaging (HMI). 2D tissue displacement maps were acquired by moving the transducer in a raster-scan format. A linear regression model was applied on the logarithm of the HMI displacements at different depths in order to estimate the acoustic attenuation. Commercially available phantoms with known attenuations (n = 5) and in vitro canine livers (n = 3) were tested, as well as HIFU lesions in in vitro canine livers (n = 5). Results demonstrated that attenuations obtained from the phantoms showed a good correlation (R² = 0.976) with the independently obtained values reported by the manufacturer with an estimation error (compared to the values independently measured) varying within the range of 15-35%. The estimated attenuation in the in vitro canine livers was equal to 0.32 ± 0.03 dB cm(-1) MHz(-1), which is in good agreement with the existing literature. The attenuation in HIFU lesions was found to be higher (0.58 ± 0.06 dB cm(-1) MHz(-1)) than that in normal tissues, also in agreement with the results from previous publications. Future potential applications of the proposed method include estimation of attenuation in pathological tissues before and after thermal ablation.
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Affiliation(s)
- Jiangang Chen
- Department of Biomedical Engineering, Columbia University, New York, NY 10027, USA
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Chen WS, Liu HL, Tung YS, Wang JC, Ding YH, Jan CK. Reducing lesion aberration by dual-frequency focused ultrasound ablations. Int J Hyperthermia 2011; 27:637-47. [DOI: 10.3109/02656736.2011.594850] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
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Morris H, Rivens I, Shaw A, Haar GT. Investigation of the viscous heating artefact arising from the use of thermocouples in a focused ultrasound field. Phys Med Biol 2008; 53:4759-76. [PMID: 18701773 DOI: 10.1088/0031-9155/53/17/020] [Citation(s) in RCA: 97] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Accurate temperature measurements in therapeutic ultrasound fields are necessary for understanding damage mechanisms, verification of thermal modelling and calibration of non-invasive clinical thermometry. However, artefactual heating, primarily due to viscous forces which result from motion relative to the surrounding tissue, occurs when metal thermocouples are used in an ultrasound field. The magnitude and time dependence of this artefact has been characterized by comparison with novel thin-film thermocouples (TFTs) at 1-2 cm focal depths in fresh degassed ex vivo bovine liver. High-intensity focused ultrasound exposures (1.7 MHz; free-field spatial-peak temporal-average intensities 40-600 W cm(-2)) were used. Subtraction of the TFT data from that obtained for other thermocouples yielded the time dependence of the viscous heating artefact. This was found to be intensity independent up to 600 W cm(-2) (below the threshold for cavitation and lesion formation) and remained significant at radial distances out to the first side lobe in the focal plane. The contribution of viscous heating to cooling was also found to be significant for at least 5 s after the end of insonation. The ratio of viscous artefact to absorptive heating after 5 s was: 1.76 +/- 0.07 for a fine-wire, 0.45 +/- 0.07 and 1.93 +/- 0.07 for two different sheathed-wires and 0.24 +/- 0.07 for a needle thermocouple.
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Affiliation(s)
- Hugh Morris
- Joint Department of Physics, Institute of Cancer Research, Royal Marsden NHS Trust, Sutton, Surrey SM2 5PT, UK
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Wear KA. The effect of phase cancellation on estimates of broadband ultrasound attenuation and backscatter coefficient in human calcaneus in vitro. IEEE TRANSACTIONS ON ULTRASONICS, FERROELECTRICS, AND FREQUENCY CONTROL 2008; 55:384-90. [PMID: 18334344 PMCID: PMC6931155 DOI: 10.1109/tuffc.2008.656] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
Broadband ultrasound attenuation (BUA) is a clinically proven indicator of osteoporotic fracture risk. BUA measurements are typically performed in throughtransmission with single-element phase sensitive (PS) receivers and therefore can be compromised by phase cancellation artifact. Phase-insensitive (PI) receivers suppress phase cancellation artifact. To study the effect of phase cancellation on BUA measurements, through-transmission measurements were performed on 16 human calcaneus samples in vitro using a two-dimensional receiver array that enabled PS and PI BUA estimation. The means plus or minus standard deviations for BUA measurements were 22.1 +/- 15.8 dB/MHz (PS) and 17.6 +/- 7.2 dB/MHz (PI), suggesting that, on the average, approximately 20% of PS BUA values in vitro can be attributed to phase cancellation artifact. Therefore, although cortical plates are often regarded as the primary source of phase cancellation artifact, the heterogeneity of cancellous bone in the calcaneal interior may also be a significant source. Backscatter coefficient estimates in human calcaneus that are based on PS attenuation compensation overestimate 1) average magnitude of backscatter coefficient at 500 kHz by a factor of about 1.6 +/- 0.3 and 2) average exponent (n) of frequency dependence by about 0.34 +/- 0.12 (where backscatter coefficient is fit to a power law form proportional to frequency to the nth power).
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Affiliation(s)
- Keith A Wear
- US Food and Drug Administration, Silver Spring, MD 20993-0002, USA.
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Wear KA. The effect of phase cancellation on estimates of calcaneal broadband ultrasound attenuation in vivo. IEEE TRANSACTIONS ON ULTRASONICS, FERROELECTRICS, AND FREQUENCY CONTROL 2007; 54:1352-9. [PMID: 17718324 PMCID: PMC6935505 DOI: 10.1109/tuffc.2007.395] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
Broadband ultrasonic attenuation (BUA) is a clinically-accepted measurement for prediction of osteoporotic fracture risk. Typical clinical BUA measurements are performed with phase-sensitive receivers and, therefore, can be affected by phase cancellation. In order to separate the effects of conventional attenuation (absorption plus scattering) from phase cancellation, BUA was measured on phantoms with acrylic wedge phase aberrators and on 73 women using both phase sensitive (PS) and phase insensitive (PI) reception. A clinical bone sonometer with a two-dimensional (2-D) receiver array was used. PI BUA measurements on phantoms with acrylic wedge phase aberrators were found to be far more resistant to phase cancellation than PS BUA measurements. In data from 73 women, means and standard deviations for BUA measurements were 81.4 +/- 21.4 dB/MHz (PS) and 67.2 +/- 9.7 dB/MHz (PI). The magnitude of the discrepancy between PS BUA and PI BUA tended to increase with bone mineral density (BMD).
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Affiliation(s)
- Keith A Wear
- US Food and Drug Administration, Center for Devices and Radiological Health, Rockville, MD 20852, USA.
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9
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Bailey MR, Couret LN, Sapozhnikov OA, Khokhlova VA, ter Haar G, Vaezy S, Shi X, Martin R, Crum LA. Use of overpressure to assess the role of bubbles in focused ultrasound lesion shape in vitro. ULTRASOUND IN MEDICINE & BIOLOGY 2001; 27:695-708. [PMID: 11397534 DOI: 10.1016/s0301-5629(01)00342-8] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Overpressure--elevated hydrostatic pressure--was used to assess the role of gas or vapor bubbles in distorting the shape and position of a high-intensity focused ultrasound (HIFU) lesion in tissue. The shift from a cigar-shaped lesion to a tadpole-shaped lesion can mean that the wrong area is treated. Overpressure minimizes bubbles and bubble activity by dissolving gas bubbles, restricting bubble oscillation and raising the boiling temperature. Therefore, comparison with and without overpressure is a tool to assess the role of bubbles. Dissolution rates, bubble dynamics and boiling temperatures were determined as functions of pressure. Experiments were made first in a low-overpressure chamber (0.7 MPa maximum) that permitted imaging by B-mode ultrasound (US). Pieces of excised beef liver (8 cm thick) were treated in the chamber with 3.5 MHz for 1 to 7 s (50% duty cycle). In situ intensities (I(SP)) were 600 to 3000 W/cm(2). B-mode US imaging detected a hyperechoic region at the HIFU treatment site. The dissipation of this hyperechoic region following HIFU cessation corresponded well with calculated bubble dissolution rates; thus, suggesting that bubbles were present. Lesion shape was then tested in a high-pressure chamber. Intensities were 1300 and 1750 W/cm(2) ( +/- 20%) at 1 MHz for 30 s. Hydrostatic pressures were 0.1 or 5.6 MPa. At 1300 W/cm(2), lesions were cigar-shaped, and no difference was observed between lesions formed with or without overpressure. At 1750 W/cm(2), lesions formed with no overpressure were tadpole-shaped, but lesions formed with high overpressure (5.6 MPa) remained cigar-shaped. Data support the hypothesis that bubbles contribute to the lesion distortion.
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Affiliation(s)
- M R Bailey
- Applied Physics Laboratory, University of Washington, Seattle, WA 98105, USA.
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Szabo TL, Wu J. A model for longitudinal and shear wave propagation in viscoelastic media. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2000; 107:2437-46. [PMID: 10830366 DOI: 10.1121/1.428630] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Relaxation models fail to predict and explain loss characteristics of many viscoelastic materials which follow a frequency power law. A model based on a time-domain statement of causality is presented that describes observed power-law behavior of many viscoelastic materials. A Hooke's law is derived from power-law loss characteristics; it reduces to the Hooke's law for the Voigt model for the specific case of quadratic frequency loss. Broadband loss and velocity data for both longitudinal and shear elastic types of waves agree well with predictions. These acoustic loss models are compared to theories for loss mechanisms in dielectrics based on isolated polar molecules and cooperative interactions.
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Affiliation(s)
- TL Szabo
- Agilent Technologies, Andover, Massachusetts 01810, USA.
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Foster FS, Pavlin CJ, Harasiewicz KA, Christopher DA, Turnbull DH. Advances in ultrasound biomicroscopy. ULTRASOUND IN MEDICINE & BIOLOGY 2000; 26:1-27. [PMID: 10687788 DOI: 10.1016/s0301-5629(99)00096-4] [Citation(s) in RCA: 392] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
The visualisation of living tissues at microscopic resolution is attracting attention in several fields. In medicine, the goals are to image healthy and diseased tissue with the aim of providing information previously only available from biopsy samples. In basic biology, the goal may be to image biological models of human disease or to conduct longitudinal studies of small-animal development. High-frequency ultrasonic imaging (ultrasound biomicroscopy) offers unique advantages for these applications. In this paper, the development of ultrasound biomicroscopy is reviewed. Aspects of transducer development, systems design and tissue properties are presented to provide a foundation for medical and biological applications. The majority of applications appear to be developing in the 40-60-MHz frequency range, where resolution on the order of 50 microm can be achieved. Doppler processing in this frequency range is beginning to emerge and some examples of current achievements will be highlighted. The current state of the art is reviewed for medical applications in ophthalmology, intravascular ultrasound, dermatology, and cartilage imaging. Ultrasound biomicroscopic studies of mouse embryonic development and tumour biology are presented. Speculation on the continuing evolution of ultrasound biomicroscopy will be discussed.
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Affiliation(s)
- F S Foster
- Sunnybrook Health Science Centre and Department of Medical Biophysics, University of Toronto, Ontario, Canada.
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Pan L, Zan L, Foster FS. Ultrasonic and viscoelastic properties of skin under transverse mechanical stress in vitro. ULTRASOUND IN MEDICINE & BIOLOGY 1998; 24:995-1007. [PMID: 9809634 DOI: 10.1016/s0301-5629(98)00071-4] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Ultrasound properties of rabbit and human skin tissues under transverse stress have been studied in vitro over the frequency range from 15 MHz to 40 MHz. B-scan images show significant increases in average dermal grey-scale levels for increasing strain. Quantitative measurements show that ultrasound attenuation coefficients decrease significantly with increasing strain. A linear decrease of 0.109 dB/mm/strain% in rabbit skin and 0.069 dB/mm/strain% in human breast reduction skin was observed at 30 MHz. Experimental results show that backscattering coefficients only exhibit minor variation with strain. The speed of sound in human skin appears to be age-dependent. The viscoelastic and mechanical properties of skin, including stress relaxation, creep and Young's modulus as a function of strain were also studied.
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Affiliation(s)
- L Pan
- Department of Medical Biophysics, University of Toronto, Sunnybrook Health Science Centre, Ontario, Canada
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Watkin NA, ter Haar GR, Rivens I. The intensity dependence of the site of maximal energy deposition in focused ultrasound surgery. ULTRASOUND IN MEDICINE & BIOLOGY 1996; 22:483-91. [PMID: 8795175 DOI: 10.1016/0301-5629(95)02062-4] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
The relationship between spatial peak intensity and the position of ultrasound induced tissue damage was studied in in vitro tissue models, using a 1.69 MHz spherical bowl transducer. The models corresponded to the transabdominal route to the bladder and prostate, which are potential target sites for focused ultrasound surgery. The results confirm that there is a relationship between lesion position and intensity, with lesions forming, under some exposure conditions, ahead of the geometric focus. Forward growth of lesions appears to be due to changes in the absorption characteristics of the tissue in the beam path. Using a computer model, we have demonstrated that the absorption coefficient of the tissue must increase significantly in front of the focus to enable lesions to form ahead of the predicted position. A possible mechanism for this is bubble formation as a result of acoustic cavitation. The effect of nonlinear propagation in the tissue, at the intensities studied, is shown to be relatively small.
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Affiliation(s)
- N A Watkin
- Joint Department of Physics, Royal Marsden Hospital, Sutton, Surrey, U.K
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Embree PM, O'Brien WD. Pulsed Doppler accuracy assessment due to frequency-dependent attenuation and Rayleigh scattering error sources. IEEE Trans Biomed Eng 1990; 37:322-6. [PMID: 2184122 DOI: 10.1109/10.52334] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
All engineering measurements are subject to inaccurate and imprecise estimates, including the estimate of blood flow velocity. An assessment of specific error sources can minimize such uncertainties. Frequency-dependent attenuation and Rayleigh scattering are significant error sources for pulsed Doppler ultrasound because the transmitted ultrasonic signal has a finite width spectrum. The former causes a frequency downshift and the latter a frequency upshift, both of which are independent of the actual Doppler frequency shift. This communication evaluates these error sources through computer stimulation and compares the computed error to experimental data.
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Affiliation(s)
- P M Embree
- Department of Electrical and Computer Engineering, University of Illinois, Urbana 61801
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Riederer-Henderson MA, Olerud JE, O'Brien WD, Forster FK, Steiger DL, Ketterer DJ, Odland GF. Biochemical and acoustical parameters of normal canine skin. IEEE Trans Biomed Eng 1988; 35:967-72. [PMID: 3198142 DOI: 10.1109/10.8678] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
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Tervola K, Foster S, O'Brien W. Attenuation Coefficient Measurement Technique at 100 MHz with the Scanning Laser Acoustic Microscope. ACTA ACUST UNITED AC 1985. [DOI: 10.1109/t-su.1985.31592] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Abstract
Scattering of ultrasound by biological tissues (continuous-inhomogeneous media) is discussed. An analytical expression for the attenuation due to scattering (alpha Tsc) and backscatter coefficients (sigma T) of tissues are obtained. The results explain the variation of alpha Tsc and sigma T with frequency for a number of tissues. The study also provides two statistical parameters, velocity fluctuation coefficient and correlation length, in terms of which the scattering of tissues can be defined quantitatively.
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Nyborg WL, Steele RB. Temperature elevation in a beam of ultrasound. ULTRASOUND IN MEDICINE & BIOLOGY 1983; 9:611-620. [PMID: 6670146 DOI: 10.1016/0301-5629(83)90006-6] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Computations are made of the temperature elevation expected at points along the axis of an unfocussed beam of ultrasound in a homogeneous absorbing medium. A simplified model is used in which the intensity is assumed uniform over a cross section. Heat conduction is taken into account, but not convection or perfusion. Results are presented for frequencies from 1 to 10 MHz and beam diameters from 0.2 to 2.4 cm. The results include limiting temperatures, reached at infinite time, as well as temperature vs time characteristics. As an example for certain conditions (transducer diameter 1.2 cm, frequency 4 MHz, intensity at the transducer 0.1 W/cm2, tissue acoustically similar to liver, transducer thermal conductivity similar to that of tissue) the temperature elevation produced at a distance 2 cm from the transducer is calculated to be 0.61 degrees C after 253 s; it then increases more and more slowly, approaching, but never exceeding 1.46 degrees C.
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