Ultrasound phased arrays for noninvasive myocardial ablation: initial studies

Kluiwstra, J.-U.; Zhang, Y.; VanBaren, P.; Strickberg, S.A.; Ebbini, E.S.; Cain, Charles A.

doi:10.1109/ultsym.1995.495862

Cited by 14 publications

(11 citation statements)

References 5 publications

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“…That is, phased arrays continue to offer the promise of noninvasive treatment of tumors and other target tissues previously considered inaccessible to other focusing systems, e.g., lens-focused and shell transducers. The results shown here and experimentally obtained elsewhere [15] demonstrate the potential for large-aperture ultrasound arrays for tissue targets in the liver and the heart. It is interesting to note that Fig.…”

Section: Discussionsupporting

confidence: 65%

“…5 indicates that the synthesis procedure utilizes the full aperture of the array, including elements that do not have a direct path to the focus, since they are shadowed by the scattering obstacles. In contrast, previously proposed methods relying strictly on ray tracing (see [15] for an example) utilize only a fraction of the array aperture. This could severely limit the array gain and, consequently, limit our ability to generate useful heating patterns.…”

Section: Discussionmentioning

confidence: 99%

“…To do so, we need to express (10) in matrix form and to accomplish this, we rewrite φ total (r) as (15) where (16) In this form, h tot (k, r) can be identified as the contribution of all subapertures at the field point due to the kth line source. Equations (15) and (16) can be tested at M points to obtain the matrix system (17) where u is the complex excitation vector of length K with its kth element equal to v k e jθ k and H is the total matrix response (of size M × K) where its elements are given by (16).…”

Section: Pseudo Inverse Solutionmentioning

confidence: 99%

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A hybrid computational model for ultrasound phased-array heating in presence of strongly scattering obstacles

Botros

Volakis

VanBaren

et al. 1997

IEEE Trans. Biomed. Eng.

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A computationally efficient hybrid ray-physical optics (HRPO) model is presented for the analysis and synthesis of multiple-focus ultrasound heating patterns through the human rib cage. In particular, a ray method is used to propagate the ultrasound fields from the source to the frontal plane of the rib cage. The physical-optics integration method is then employed to obtain the intensity pattern inside the rib cage. The solution of the matrix system is carried out by using the pseudo inverse technique to synthesize the desired heating pattern. The proposed technique guides the fields through the intercostal spacings between the solid ribs and, thus, minimal intensity levels are observed over the solid ribs. This simulation model allows for the design and optimization of large-aperture phasedarray applicator systems for noninvasive ablative thermal surgery in the heart and liver through the rib cage.

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Section: Discussionsupporting

confidence: 65%

Section: Discussionmentioning

confidence: 99%

Section: Pseudo Inverse Solutionmentioning

confidence: 99%

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A hybrid computational model for ultrasound phased-array heating in presence of strongly scattering obstacles

Botros

Volakis

VanBaren

et al. 1997

IEEE Trans. Biomed. Eng.

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“…6 Phased-array systems may be suitable for noninvasive cardiac ablation because of the ability to control for the position of the target site by switching between different beam patterns at electronic speed, to correct for aberrations due to complex inhomogeneous intervening tissue, such as the ribs and lungs, and the ability to change the effective aperture dimensions during treatment by adjusting the driving signals. 6,24,25 Previous Studies Using High-Intensity Ultrasound…”

Section: Comparison With Transcatheter Ultrasound Ablationmentioning

confidence: 99%

“…24 In addition, many parameters, such as frequency, the ratio between the aperture size and focal depth, and duration of energy application, can affect lesion size and volume. These factors need to be more completely understood to optimize lesion formation.…”

Section: Technological Limitations Of Ultrasound Ablationmentioning

confidence: 99%

Extracardiac Ablation of the Canine Atrioventricular Junction by Use of High-Intensity Focused Ultrasound

et al. 1999

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Background-High-intensity focused ultrasound has been applied to internal organs from outside the body to ablate tissue.No published study has assessed the feasibility of ablating cardiac tissue within the beating heart by use of this type of therapeutic ultrasound. The purpose of this study was to determine whether high-intensity focused ultrasound can be used to ablate the atrioventricular (AV) junction within the beating heart. Methods and Results-Ten dogs were anesthetized and underwent a thoracotomy. The heart was covered with a polyvinyl chloride membrane. The thorax above the membrane was perfused with degassed water, which functioned as a coupling medium for the ultrasound. A 7.0-MHz diagnostic ultrasound probe was affixed to a spherically focused 1.4-MHz high-intensity focused ultrasound transducer with a 1.1ϫ8.3-mm focal zone 63.5 mm from the ablation transducer. The diagnostic ultrasound probe was calibrated such that the location of the focal zone of the ablation transducer was identifiable on the 2-dimensional ultrasound image. Target sites were identified with the diagnostic ultrasound. The maximum ultrasound intensity for ablation (2.8 kW/cm 2 ) was delivered to the AV junction only during electrical diastole and for a total of 30 seconds. Complete AV block was achieved in each of the 10 dogs with 6.5Ϯ5.6 (range, 3 to 21) 30-second applications of therapeutic ultrasound. Gross inspection showed that the mean lesion volume was 124Ϯ143 mm 3 , with a depth of 6.7Ϯ3.6 mm, a length of 5.7Ϯ2.5 mm, and a width of 4.7Ϯ1.8 mm. Four hours after the dogs were killed, histopathological study demonstrated a well-demarcated area of necrosis and early inflammation. Conclusions-High-intensity focused ultrasound produces well-demarcated lesions and appears to be a feasible energy source to create complete AV block within the beating heart without damaging the overlying or underlying cardiac tissue. This energy source may allow for a noninvasive approach to ablation of cardiac arrhythmias. (Circulation. 1999;100:203-208.)

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Ultrasonic Biophysics

Frizzell

2003

Digital Encyclopedia of Applied Physics

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Ultrasound phased arrays for noninvasive myocardial ablation: initial studies

Cited by 14 publications

References 5 publications

A hybrid computational model for ultrasound phased-array heating in presence of strongly scattering obstacles

A hybrid computational model for ultrasound phased-array heating in presence of strongly scattering obstacles

Extracardiac Ablation of the Canine Atrioventricular Junction by Use of High-Intensity Focused Ultrasound

Ultrasonic Biophysics

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