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Abstract
The use of focused ultrasound to obtain diagnostically significant information about the eye goes back to the 1950s. This review describes the historical and technological development of ophthalmic ultrasound and its clinical application and impact. Ultrasound, like light, can be focused, which is crucial for formation of high-resolution, diagnostically useful images. Focused, single-element, mechanically scanned transducers are most common in ophthalmology. Specially designed transducers have been used to generate focused, high-intensity ultrasound that through thermal effects has been used to treat glaucoma (via ciliodestruction), tumors, and other pathologies. Linear and annular transducer arrays offer synthetic focusing in which precise timing of the excitation of independently addressable array elements allows formation of a converging wavefront to create a focus at one or more programmable depths. Most recently, linear array-based plane-wave ultrasound, in which the array emits an unfocused wavefront and focusing is performed solely on received data, has been demonstrated for imaging ocular anatomy and blood flow. While the history of ophthalmic ultrasound extends back over half-a-century, new and powerful technologic advances continue to be made, offering the prospect of novel diagnostic capabilities.
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Affiliation(s)
- Ronald H Silverman
- Department of Ophthalmology, Columbia University Medical Center
- F.L. Lizzi Center for Biomedical Engineering, Riverside Research, New York, NY, USA
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2
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Yin L, Gudur MSR, Hsiao YS, Kumon RE, Deng CX, Jiang H. Tomographic reconstruction of tissue properties and temperature increase for high-intensity focused ultrasound applications. ULTRASOUND IN MEDICINE & BIOLOGY 2013; 39:1760-70. [PMID: 23849388 PMCID: PMC3789063 DOI: 10.1016/j.ultrasmedbio.2013.04.009] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/25/2012] [Revised: 03/30/2013] [Accepted: 04/11/2013] [Indexed: 05/18/2023]
Abstract
The acoustic and thermal properties as well as the temperature change within a tissue volume during high-intensity focused ultrasound ablation are critically important for treatment planning and monitoring. Described in this article is a tomographic reconstruction method used to determine the tissue properties and increase in temperature in a 3-D volume. On the basis of the iterative finite-element solution to the bioheat equation coupled with Tikhonov regularization techniques, our reconstruction algorithm solves the inverse problem of bioheat transfer and uses the time-dependent temperature measured on a tissue surface to obtain the acoustic absorption coefficient, thermal diffusivity and temperature increase within the subsurface volume. Numerical simulations were performed to validate the reconstruction algorithm. The method was initially conducted in ex vivo experiments in which time-dependent temperature on a tissue surface was measured using high-resolution, non-invasive infrared thermography.
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Affiliation(s)
- Lu Yin
- Department of Biomedical Engineering, University of Florida, Gainesville, Florida, USA
| | | | - Yi-Sing Hsiao
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan, USA
| | - Ronald E. Kumon
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan, USA
| | - Cheri X. Deng
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan, USA
| | - Huabei Jiang
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan, USA
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3
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Wang S, Mahesh SP, Liu J, Geist C, Zderic V. Focused ultrasound facilitated thermo-chemotherapy for targeted retinoblastoma treatment: A modeling study. Exp Eye Res 2012; 100:17-25. [DOI: 10.1016/j.exer.2012.04.009] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2012] [Revised: 04/13/2012] [Accepted: 04/19/2012] [Indexed: 12/30/2022]
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4
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Abstract
Mathematical modeling has proven to be a viable alternative for investigating the temperature distribution inside the human eye. This is due to its ability to overcome the limitations infrared (IR) thermography; the leading method in ocular temperature measurement. A wide range of mathematical studies on the ocular temperature distribution during various conditions have been published in the literature. In this paper, we carry out an in-depth review of the various mathematical models of the eye that have been developed in the past. Various problems and the implications from the mathematical predictions of these studies are discussed. The future directions of studies in ocular temperature distribution are deliberated.
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Affiliation(s)
- E. H. OOI
- School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore
| | - E. Y. K. NG
- School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore
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5
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Bigelow T. Estimating the total ultrasound attenuation along the propagation path by applying multiple filters to backscattered echoes from a single spherically focused source. IEEE TRANSACTIONS ON ULTRASONICS, FERROELECTRICS, AND FREQUENCY CONTROL 2010; 57:900-7. [PMID: 20378452 PMCID: PMC3082479 DOI: 10.1109/tuffc.2010.1494] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Quantifying the correlation length of the tissue microstructure has shown potential for differentiating between benign and malignant tumors. To implement these advances in the clinic, the total frequency-dependent attenuation along the propagation path must be determined on a patient specific basis. Previously, an algorithm was developed to estimate this attenuation using echoes from multiple sources. In this study, the developed algorithm was extended to echoes from a single source by filtering the echoed signal into multiple frequency bands. This step was needed because it would be challenging to scan exactly the same tissue region using multiple sources in the clinic. Computer simulations and phantom experiments were conducted to verify the attenuation could be determined by filtering the echoes from a single source. The simulations utilized a spherically focused single-element source (5 cm focal length, f/4, 14 MHz center frequency, 50% bandwidth) exposing a homogeneous tissue region (Gaussian scattering structures with effective radii of 5 to 55 mum at a density of 250/mm(3), attenuation of 0.1 to 0.9 dB/cm.MHz). The phantom experiments utilized a spherically focused single-element source (5.08 cm focal length, f/4, 7.5 MHz center frequency) exposing a 0.5 dB/cm.MHz homogeneous glass bead phantom. The computer simulations and phantom experiment confirmed that the total attenuation along the propagation path can be determined by appropriately applying multiple filters to the backscattered echoes from a single source.
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Affiliation(s)
- Timothy Bigelow
- Department of Electrical and Computer Engineering, Iowa State University, Ames, IA, USA.
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6
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Bigelow TA. Improved heating efficiency with High-Intensity Focused Ultrasound using a new ultrasound source excitation. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2009; 2009:3393-6. [PMID: 19963801 DOI: 10.1109/iembs.2009.5332768] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
High-Intensity Focused Ultrasound (HIFU) is quickly becoming one of the best methods to thermally ablate tissue noninvasively. Unlike RF or Laser ablation, the tissue can be destroyed without inserting any probes into the body minimizing the risk of secondary complications such as infections. In this study, the heating efficiency of HIFU sources is improved by altering the excitation of the ultrasound source to take advantage of nonlinear propagation. For ultrasound, the phase velocity of the ultrasound wave depends on the amplitude of the wave resulting in the generation of higher harmonics. These higher harmonics are more efficiently converted into heat in the body due to the frequency dependence of the ultrasound absorption in tissue. In our study, the generation of the higher harmonics by nonlinear propagation is enhanced by transmitting an ultrasound wave with both the fundamental and a higher harmonic component included. Computer simulations demonstrated up to a 300% increase in temperature increase compared to transmitting at only the fundamental for the same acoustic power transmitted by the source.
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7
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Abstract
Computer simulations are being performed to model the temperature patterns produced during ultrasonically induced hyperthermia of ocular tumours. The software package for these simulations incorporates operator interaction and uses tissue geometry obtained from B-mode data. Previous studies used geometric approximations for the incident beams used for hyperthermia. In the current study, these beams were computed using diffraction analysis to obtain more realistic simulations of clinical exposures.
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Affiliation(s)
- F L Lizzi
- Riverside Research Institute, NYC, NY 10036
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8
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Bigelow TA. Ultrasound attenuation estimation using backscattered echoes from multiple sources. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2008; 124:1367-73. [PMID: 18681622 PMCID: PMC2680592 DOI: 10.1121/1.2949519] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
The objective of this study was to devise an algorithm that can accurately estimate the attenuation along the propagation path (i.e., the total attenuation) from backscattered echoes. It was shown that the downshift in the center frequency of the backscattered ultrasound echoes compared to echoes obtained in a water bath was calculated to have the form Deltaf=mf(o)+b after normalizing with respect to the source bandwidth where m depends on the correlation length, b depends on the total attenuation, and f(o) is the center frequency of the source as measured from a reference echo. Therefore, the total attenuation can be determined independent of the scatterer correlation length by measuring the downshift in center frequency from multiple sources (i.e., different f(o)) and fitting a line to the measured shifts versus f(o). The intercept of the line gives the total attenuation along the propagation path. The calculations were verified using computer simulations of five spherically focused sources with 50% bandwidths and center frequencies of 6, 8, 10, 12, and 14 MHz. The simulated tissue had Gaussian scattering structures with effective radii of 25 mum placed at a density of 250 mm(3). The attenuation of the tissue was varied from 0.1 to 0.9 dB / cm-MHz. The error in the attenuation along the propagation path ranged from -3.5+/-14.7% for a tissue attenuation of 0.1 dB / cm-MHz to -7.0+/-3.1% for a tissue attenuation of 0.9 dB / cm-MHz demonstrating that the attenuation along the propagation path could be accurately determined using backscattered echoes from multiple sources using the derived algorithm.
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Affiliation(s)
- Timothy A Bigelow
- Department of Electrical Engineering, University of North Dakota, PO Box 7165, Grand Forks, ND 58202, USA.
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9
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Bigelow TA, Miller RJ, Blue JP, O'Brien WD. Hemorrhage near fetal rat bone exposed to pulsed ultrasound. ULTRASOUND IN MEDICINE & BIOLOGY 2007; 33:311-7. [PMID: 17306701 DOI: 10.1016/j.ultrasmedbio.2006.08.015] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/09/2006] [Revised: 08/03/2006] [Accepted: 08/10/2006] [Indexed: 05/14/2023]
Abstract
Ultrasound-induced hemorrhage near the fetal rat skull was investigated to determine if the damage could be correlated with temporal-average intensity. A 0.92-MHz f/1 spherically focused transducer (5.1-cm focal length) was used to expose the skull of 18- to 19-day gestation exteriorized Sprague-Dawley rat fetuses (n = 197). There were four ultrasound-exposed groups (n = 36 each), one sham exposed group (n = 36) and one cage control group (n = 17). Three of the ultrasound-exposed groups had the same peak compressional (10 MPa)/peak rarefactional (6.7 MPa) pressure but different spatial-peak temporal-average intensities (I(TA)) of 1.9, 4.7 and 9.4 W/cm(2); the pulse repetition frequency (PRF) was varied (100, 250 and 500 Hz, respectively). The fourth ultrasound-exposed group had a peak compressional (6.7 MPa)/peak rarefactional (5.0 MPa) pressure and corresponding I(TA) of 4.6 W/cm(2); PRF was 500 Hz. Hemorrhage occurrence increased slightly with increasing I(TA), as well as peak rarefactional pressure and PRF, but the hemorrhage area did not correlate with any of the exposure parameters.
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Affiliation(s)
- Timothy A Bigelow
- Department of Electrical Engineering, University of North Dakota, Grand Forks, ND 58202, USA.
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10
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Abstract
This paper is based on material presented at the start of a Health Protection Agency meeting on ultrasound and infrasound. In answering the question 'what is ultrasound?', it shows that the simple description of a wave which transports mechanical energy through the local vibration of particles at frequencies of 20 kHz or more, with no net transport of the particles themselves, can in every respect be misleading or even incorrect. To explain the complexities responsible for this, the description of ultrasound is first built up from the fundamental properties of these local particle vibrations. This progresses through an exposition of the characteristics of linear waves, in order to explain the propensity for, and properties of, the nonlinear propagation which occurs in many practical ultrasonic fields. Given the Health Protection environment which framed the original presentation, explanation and examples are given of how these complexities affect issues of practical importance. These issues include the measurement and description of fields and exposures, and the ability of ultrasound to affect tissue (through microstreaming, streaming, cavitation, heating, etc.). It is noted that there are two very distinct regimes, in terms of wave characteristics and potential for bioeffect. The first concerns the use of ultrasound in liquids/solids, for measurement or material processing. For biomedical applications (where these two processes are termed diagnosis and therapy, respectively), the issue of hazard has been studied in depth, although this has not been done to such a degree for industrial uses of ultrasound in liquids/solids (sonar, non-destructive testing, ultrasonic processing etc.). However, in the second regime, that of the use of ultrasound in air, although the waves in question tend to be of much lower intensities than those used in liquids/solids, there is a greater mismatch between the extent to which hazard has been studied, and the growth in commercial applications for airborne ultrasound.
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Affiliation(s)
- Timothy G Leighton
- Institute of Sound and Vibration Research, Southampton University, Highfield, Southampton, SO17 1BJ, UK.
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11
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Sarvazyan A. Model-based imaging. ULTRASOUND IN MEDICINE & BIOLOGY 2006; 32:1713-20. [PMID: 17112957 DOI: 10.1016/j.ultrasmedbio.2006.05.016] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/03/2006] [Revised: 05/11/2006] [Accepted: 05/19/2006] [Indexed: 05/12/2023]
Abstract
The concept of model-based imaging provides a possibility of integration of both structural and functional information obtained by imaging and nonimaging sources of diagnostically relevant information. Merging information of different origin and nature in a simulated computer patient-specific three-dimensional (3-D) model is important for multimodal imaging approaches to medical diagnostics. The work of F. L. Lizzi on life-like imaging done nearly 20 years ago was the first successful attempt of patient-specific 3-D computer modeling using conventional ultrasonography data. He demonstrated the applications of such 3-D models, which incorporated acoustic, optical and thermal properties of imaged tissue, in physiologic studies, in planning and monitoring ultrasonic hyperthermia and ablation. However, numerous obstacles hinder the wide use of the model-based imaging concept. Using the example of model-based imaging of prostate, the advantages and limitation on the applicability of the concept are discussed. Attempts of implementing the model-based imaging concept in the mechanical imaging technology--imaging with the use of measurements of stress pattern on the surface of tissue--are described. It is shown that composing a patient-specific 3-D model requires well-defined and carefully validated algorithms for translating features of the object assessed by an imaging modality into the quantitative anatomic and histopathologic parameters.
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12
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Liu Y, Kon T, Li C, Zhong P. High intensity focused ultrasound-induced gene activation in sublethally injured tumor cells in vitro. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2005; 118:3328-36. [PMID: 16334906 PMCID: PMC1948881 DOI: 10.1121/1.2041247] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Cultured human cervical cancer (HeLa) and rat mammary carcinoma (R3230Ac) cells were transfected with vectors encoding green fluorescent protein (GFP) under the control of hsp70B promoter. Aliquots of 10-microl transfected cells (5 x 10(7) cells/ml) were placed in 0.2-ml thin-wall polymerase chain reaction tubes and exposed to 1.1-MHz high intensity focused ultrasound (HIFU) at a peak negative pressure P- = 2.68 MPa. By adjusting the duty cycle of the HIFU transducer, the cell suspensions were heated to a peak temperature from 50 to 70 degrees C in 1-10 s. Exposure dependent cell viability and gene activation were evaluated. For a 5-s HIFU exposure, cell viability dropped from 95% at 50 degrees C to 13% at 70 degrees C. Concomitantly, gene activation in sublethally injured tumor cells increased from 4% at 50 degrees C to 41% at 70 degrees C. A similar trend was observed at 60 degrees C peak temperature as the exposure time increased from 1 to 5 s. Further increase of exposure duration to 10 s led to significantly reduced cell viability and lower overall gene activation in exposed cells. Altogether, maximum HIFU-induced gene activation was achieved at 60 degrees C in 5 s. Under these experimental conditions, HIFU-induced gene activation was found to be produced primarily by thermal rather than mechanical stresses.
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Affiliation(s)
- Yunbo Liu
- Department of Mechanical Engineering and Materials Science, Duke University, Durham, North Carolina 27708
| | - Takashi Kon
- Department of Radiation Oncology, Duke University Medical Center, Durham, North Carolina 27708
| | - Chuanyuan Li
- Department of Radiation Oncology, Duke University Medical Center, Durham, North Carolina 27708
| | - Pei Zhong
- Author to whom correspondence should be addressed; electronic mail:
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13
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Cucevic V, Brown AS, Foster FS. Thermal assessment of 40-MHz pulsed Doppler ultrasound in human eye. ULTRASOUND IN MEDICINE & BIOLOGY 2005; 31:565-573. [PMID: 15831335 DOI: 10.1016/j.ultrasmedbio.2005.01.004] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/13/2004] [Revised: 12/22/2004] [Accepted: 01/06/2005] [Indexed: 05/24/2023]
Abstract
Tissue exposure to diagnostic pulsed Doppler ultrasound (US) can cause significant temperature rises. Temperature rise induced by US biomicroscopy (UBM) system (VS40, VisualSonics, Toronto, ON, Canada) was measured in ex vivo human and rabbit eyes with a 26-gauge K-type needle thermocouple. The operating frequency was 40 MHz with a free field I(SPTA) of 2.6 mW/cm(2) (B-mode) and 11.9 W/cm(2) (Doppler). Peak negative pressures were 5.22 MPa (B-mode) and 7.32 MPa (Doppler), resulting in MIs of 0.83 (B-mode) and 1.05 (Doppler mode). In Doppler mode, mean temperature rises of 2.27 degrees C and 1.93 degrees C were measured for the human lens and ciliary body after a 3-min insonation, vs. 2.66 degrees C for the rabbit lens. Our results indicate that US-induced temperature rise decreases with decreasing number of cycles, decreasing pulse-repetition frequency (PRF) or increased transmit attenuation, and is consistent with simple models of heating. To limit risk of temperature rises of 1 degrees C in human ciliary body, use of the maximum settings of 16 cycles (0.400 micros pulse duration), 20-kHz PRF should include 3-dB transmit attenuation, and exposure time should be limited. For insonation of the lens, exposure settings no higher than nine cycles (0.225-micros pulse duration) and 10-kHz PRF should be employed and exposure time limited to minimize risk of temperature increases of 1 degree C.
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Affiliation(s)
- Viviene Cucevic
- Imaging Research, Sunnybrook Health Sciences Centre, Toronto, ON M4N 3M5, Canada
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14
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Huang J, Holt RG, Cleveland RO, Roy RA. Experimental validation of a tractable numerical model for focused ultrasound heating in flow-through tissue phantoms. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2004; 116:2451-8. [PMID: 15532675 DOI: 10.1121/1.1787124] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Heating from high intensity focused ultrasound (HIFU) can be used to control bleeding, both from individual blood vessels as well as from gross damage to the capillary bed. The presence of vascularity can limit one's ability to elevate the temperature owing to convective heat transport. In an effort to better understand the heating process in tissues with vascular structure we have developed a numerical simulation that couples models for ultrasound propagation, acoustic streaming, ultrasound heating and blood cooling in a Newtonian viscous medium. The 3-D simulation allows for the study of complicated biological structures and insonation geometries. We have also undertaken a series of in vitro experiments employing non-uniform flow-through tissue phantoms and designed to provide verification of the model predictions. We show that blood flow of 2 cm/s (6.4 ml/min through a 2.6 mm 'vessel') can reduce peak temperature in a vessel wall by 25%. We also show that HIFU intensities of 6.5 x 10(5) W/m2 can induce acoustic streaming with peak velocities up to 5 cm/s and this can reduce heating near a vessel wall by more than 10%. These results demonstrate that convective cooling is important in HIFU and can be accounted for within simulation models.
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Affiliation(s)
- Jinlan Huang
- Boston University, Department of Aerospace and Mechanical Engineering, Boston, Massachusetts 02215, USA
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15
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Lizzi FL, Muratore R, Deng CX, Ketterling JA, Alam SK, Mikaelian S, Kalisz A. Radiation-force technique to monitor lesions during ultrasonic therapy. ULTRASOUND IN MEDICINE & BIOLOGY 2003; 29:1593-1605. [PMID: 14654155 DOI: 10.1016/s0301-5629(03)01052-4] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
This report describes a monitoring technique for high-intensity focused ultrasound (US), or HIFU, lesions, including protein-denaturing lesions (PDLs) and those made for noninvasive cardiac therapy and tumor treatment in the eye, liver and other organs. Designed to sense the increased stiffness of a HIFU lesion, this technique uniquely utilizes the radiation force of the therapeutic US beam as an elastographic push to detect relative stiffness changes. Feasibility was demonstrated with computer simulations (treating acoustically induced displacements, concomitant heating, and US displacement-estimation algorithms) and pilot in vitro experimental studies, which agree qualitatively in differentiating HIFU lesions from normal tissue. Detectable motion can be induced by a single 5 ms push with temperatures well below those needed to form a lesion. Conversely, because the characteristic heat diffusion time is much longer than the characteristic relaxation time following a push, properly timed multiple therapy pulses will form lesions while providing precise control during therapy.
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Affiliation(s)
- Frederic L Lizzi
- Biomedical Engineering Laboratories, Riverside Research Institute, New York, NY 10038, USA
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16
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Nyborg WL. Biological effects of ultrasound: development of safety guidelines. Part I: personal histories. ULTRASOUND IN MEDICINE & BIOLOGY 2000; 26:911-964. [PMID: 10996695 DOI: 10.1016/s0301-5629(00)00243-x] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
After the end of World War II, advances in ultrasound (US) technology brought improved possibilities for medical applications. The first major efforts in this direction were in the use of US to treat diseases. Medical studies were accompanied by experiments with laboratory animals and other model systems to investigate basic biological questions and to obtain better understanding of mechanisms. Also, improvements were made in methods for measuring and controlling acoustical quantities such as power, intensity and pressure. When diagnostic US became widely used, the scope of biological and physical studies was expanded to include conditions for addressing relevant safety matters. In this historical review, a major part of the story is told by 21 investigators who took part in it. Each was invited to prepare a brief personal account of his/her area(s) of research, emphasizing the "early days," but including later work, showing how late and early work are related, if possible, and including anecdotal material about mentors, colleagues, etc.
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Affiliation(s)
- W L Nyborg
- Physics Department, University of Vermont, Burlington, VT 05405, USA.
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17
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Meaney PM, Cahill MD, ter Haar GR. The intensity dependence of lesion position shift during focused ultrasound surgery. ULTRASOUND IN MEDICINE & BIOLOGY 2000; 26:441-50. [PMID: 10773375 DOI: 10.1016/s0301-5629(99)00161-1] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Knowledge of the spatial distribution of intensity loss from an ultrasonic beam is critical for predicting lesion formation in focused ultrasound (US) surgery (FUS). To date, most models have used linear propagation models to predict intensity profiles required to compute the temporally varying temperature distributions used to compute thermal dose contours. These are used to predict the extent of thermal damage. However, these simulations fail to describe adequately the abnormal lesion formation behaviour observed during ex vivo experiments in cases for which the transducer drive levels are varied over a wide range. In such experiments, the extent of thermal damage has been observed to move significantly closer to the transducer with increased transducer drive levels than would be predicted using linear-propagation models. The first set of simulations described herein use the KZK (Khokhlov-Zabolotskaya-Kuznetsov) nonlinear propagation model with the parabolic approximation for highly focused US waves to demonstrate that both the peak intensity and the lesion positions do, indeed, move closer to the transducer. This illustrates that, for accurate modelling of heating during FUS, nonlinear effects should be considered. Additionally, a first order approximation has been employed that attempts to account for the abnormal heat deposition distributions that accompany high transducer drive level FUS exposures where cavitation and boiling may be present. The results of these simulations are presented. It is suggested that this type of approach may be a useful tool in understanding thermal damage mechanisms.
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Affiliation(s)
- P M Meaney
- Thayer School of Engineering, Dartmouth College, Hanover, NH, USA
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18
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Lizzi FL, Deng CX, Lee P, Rosado A, Silverman RH, Coleman DJ. A comparison of ultrasonic beams for thermal treatment of ocular tumors. EUROPEAN JOURNAL OF ULTRASOUND : OFFICIAL JOURNAL OF THE EUROPEAN FEDERATION OF SOCIETIES FOR ULTRASOUND IN MEDICINE AND BIOLOGY 1999; 9:71-8. [PMID: 10099168 DOI: 10.1016/s0929-8266(99)00011-7] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
OBJECTIVE This study examined the relative merits of different ultrasonic beams and exposure modalities for treating ocular melanomas. METHODS Simulations were conducted to evaluate temperature patterns and lesion shapes induced by intense-ultrasound treatment of ocular tumors. In-vitro insonification experiments were conducted in bovine lenses. RESULTS Simulated hyperthermia exposures did not effectively treat tumor margins because of thermal conduction into nearby fluid-like media. Standard high-intensity focused beams produced narrow lesions during 2-s exposures. A high-intensity, multi-lobed beam, produced by a transducer with strip electrodes, generated asymmetric lesions with a single large dimension; this lesion shape could expedite the production of lesion matrices within large tumors. In-vitro cataract shapes were consistent with simulation results for focused high-intensity beams. CONCLUSIONS Thermal conduction and perfusion can cause underheating of tumor margins during hyperthermia unless special beam designs are used. The strip-electrode transducer configuration promises to expedite treatment of extended tumor volumes.
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Affiliation(s)
- F L Lizzi
- Biomedical Engineering Laboratories, Riverside Research Institute, 330 West 42nd Street, New York, NY 10036, USA.
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19
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Sun Z, Ying H. A multi-gate time-of-flight technique for estimation of temperature distribution in heated tissue: theory and computer simulation. ULTRASONICS 1999; 37:107-122. [PMID: 10209554 DOI: 10.1016/s0041-624x(98)00055-9] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Non-invasive determination of temperature distribution in biological media is important in many heating-related studies, such as thermal treatment. In this paper, we present an in vitro ultrasound technique for estimation of temperature distribution in heated tissue. Our technique consists of two major steps: (1) using multiple time gates to track echo signals scattered from tissue regions at different depths; (2) estimating temperature distribution based on heating-induced changes of arrival times of echo signals scattered from the targeted tissue regions. We use the conventional cross-correlation approach to track echoes. For temperature estimation, we have developed an iterative method that takes into account the influences of thermal expansion and heating-induced change in the speed of sound on the time of flight. We have introduced a concept of thermal sensitivity of the time of flight and used it to derive a theoretical formula that relates the achievable accuracy on the estimation of tissue temperature to seven parameters. The seven parameters are tissue thermal sensitivity of the time of flight, signal-to-noise ratio, bandwidth and center frequency of the signal, degree of signal decorrelation induced by changes in tissue physical properties during tissue heating, and widths and spacing of the time gates. We tested our technique by computer simulation, using a random discrete scatterer model and temperature distribution data acquired in our laser heating experiments on prostate tissue of live dog. Simulation results showed that our technique could accurately estimate the temperature distribution in the heated tissue. Our technique is fast in terms of computation and could be used as a research tool for in vitro real-time monitoring of temperature distribution in tissue under hyperthermal heating.
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Affiliation(s)
- Z Sun
- Biomedical Engineering Center, University of Texas Medical Branch, Galveston 77555-0456, USA
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Meaney PM, Clarke RL, ter Haar GR, Rivens IH. A 3-D finite-element model for computation of temperature profiles and regions of thermal damage during focused ultrasound surgery exposures. ULTRASOUND IN MEDICINE & BIOLOGY 1998; 24:1489-1499. [PMID: 10385970 DOI: 10.1016/s0301-5629(98)00102-1] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Although there have been numerous models implemented for modeling thermal diffusion effects during focused ultrasound surgery (FUS), most have limited themselves to representing simple situations for which analytical solutions and the use of cylindrical geometries sufficed. For modeling single lesion formation and the heating patterns from a single exposure, good results were achieved in comparison with experimental results for predicting lesion size, shape and location. However, these types of approaches are insufficient when considering the heating of multiple sites with FUS exposures when the time interval between exposures is short. In such cases, the heat dissipation patterns from initial exposures in the lesion array formation can play a significant role in the heating patterns for later exposures. Understanding the effects of adjacent lesion formation, such as this, requires a three-dimensional (3-D) representation of the bioheat equation. Thus, we have developed a 3-D finite-element representation for modeling the thermal diffusion effects during FUS exposures in clinically relevant tissue volumes. The strength of this approach over past methods is its ability to represent arbitrarily shaped 3-D situations. Initial simulations have allowed calculation of the temperature distribution as a function of time for adjacent FUS exposures in excised bovine liver, with the individually computed point temperatures comparing favorably with published measurements. In addition to modeling these temperature distributions, the model was implemented in conjunction with an algorithm for calculating the thermal dose as a way of predicting lesion shape. Although used extensively in conventional hyperthermia applications, this thermal dose criterion has only been applied in a limited number of simulations in FUS for comparison with experimental measurements. In this study, simulations were run for focal depths 2 and 3 cm below the surface of pig's liver, using multiple intensity levels and exposure times. The results also compare favorably to published in vitro experimental measurements, which bodes well for future application to more complex problems, such as the modeling of multiple lesion arrays within complex anatomical geometries.
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Affiliation(s)
- P M Meaney
- Thayer School of Engineering, Dartmouth College, Hanover, NH, USA
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Thijssen JM. The history of ultrasound techniques in ophthalmology. ULTRASOUND IN MEDICINE & BIOLOGY 1993; 19:599-618. [PMID: 8134966 DOI: 10.1016/0301-5629(93)90068-y] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
The history of 50 years of applications of ultrasound in ophthalmology is described. This period started in 1938 with a study of the possible effects of high intensity ultrasound on eyes. The measurement of biological effects for the assessment of potential hazards characterizes the first decades. More recently, the therapeutic use of ultrasound by hyperthermia has gained much interest in ophthalmology. Further topics are: the measurement of acoustic characteristics of ocular tissues; the biometry of the eye ball, the results of which are used to calculate the optical power of artificial lens implants; the development of diagnostic instruments in various parts of the world; and ultrasonic tissue characterization for the differential diagnosis of pathology. The final topic is concerned with some recent developments which present a look into the future.
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Affiliation(s)
- J M Thijssen
- Biophysics Laboratory, University Hospital St. Radboud, Nijmegen, The Netherlands
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