Polyacrylamide gel as an acoustic coupling medium for focused ultrasound therapy

Prokop, Adrian F.; Vaezy, Shahram; Noble, Misty L.; Kaczkowski, Peter J.; Martin, Roy W.; Crum, Lawrence A.

doi:10.1016/s0301-5629(03)00979-7

Cited by 92 publications

(69 citation statements)

References 12 publications

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“…The thermal diffusivity (K) was also independently measured for the phantom samples using the transient hot-wire technique (Carslaw and Jaeger 1959;Prokop et al 2003), a standard method reported in the heat transfer literature for measuring the thermal properties of solids. The estimates obtained by this method were compared with those obtained using the noninvasive ultrasound-based estimation procedure.…”

Section: Phantom Experimentsmentioning

confidence: 99%

Noninvasive Measurement of Local Thermal Diffusivity Using Backscattered Ultrasound and Focused Ultrasound Heating

Anand

Kaczkowski

2008

Ultrasound in Medicine & Biology

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Previously, noninvasive methods of estimating local tissue thermal and acoustic properties using backscattered ultrasound have been proposed in the literature. In this article, a noninvasive method of estimating local thermal diffusivity in situ during focused ultrasound heating using beamformed acoustic backscatter data and applying novel signal processing techniques is developed. A high intensity focused ultrasound (HIFU) transducer operating at subablative intensities is employed to create a brief local temperature rise of no more than 10°C. Beamformed radio-frequency (RF) data are collected during heating and cooling using a clinical ultrasound scanner. Measurements of the time-varying "acoustic strain", that is, spatiotemporal variations in the RF echo shifts induced by the temperature related sound speed changes, are related to a solution of the heat transfer equation to estimate the thermal diffusivity in the heated zone. Numerical simulations and experiments performed in vitro in tissue mimicking phantoms and excised turkey breast muscle tissue demonstrate agreement between the ultrasound derived thermal diffusivity estimates and independent estimates made by a traditional hot-wire technique. The new noninvasive ultrasonic method has potential applications in thermal therapy planning and monitoring, physiological monitoring and as a means of noninvasive tissue characterization.

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Section: Phantom Experimentsmentioning

confidence: 99%

Noninvasive Measurement of Local Thermal Diffusivity Using Backscattered Ultrasound and Focused Ultrasound Heating

Anand

Kaczkowski

2008

Ultrasound in Medicine & Biology

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“…In the front part, a protective layer is found, where the coupling medium is used (gel or oil) to maintain adequate acoustic impedance between the oscillator and the tissue [7].…”

Section: Figure 1 Us Transducermentioning

confidence: 99%

Application of ultrasound in medicine part ii: the ultrasonic transducer and its associated electronics

2013

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This paper introduces the reader to a review and analysis of various ultrasound (us) applications in the medical field. First, the transducer is shown, along with a diagram of the basic electronics that it uses to generate and receive signals that allow the reconstruction of images, for medical purposes. Also, us practical uses in medical therapy is shown. This subject is addressed by combining the physical principles involved in the us application, with the implemented technology and the modes of operation for non-invasive studies of pathologies related to brain, heart, and eyes such as injuries, tumors and hematomas. The methodology used in this article also suggests an analysis method for the us scientific and technological research principles combined for their implementation in medical applications.Keywords: ultrasonic transducer, piezoelectric, transmitter, receiver, converter, modes ResumenEn este trabajo se presenta al lector una revisión y análisis de diferentes aplicaciones del ultrasonido (us) en el campo médico. Inicialmente se muestra el transductor y un esquema de su electrónica básica asociada usada para emitir y adquirir las señales que permiten la reconstrucción de las imágenes, para efectos médicos y también la aplicación del us para terapia; la temática se aborda conjugando los principios físicos asociados a la aplicación del us con la tecnología implementada y sus modos de operación, para estudios no invasivos de patologías relacionadas con el cerebro, el corazón, los ojos y lesiones tales como tumores y hematomas. La metodología implementada en este artículo sugiere también un método de análisis de los principios científicos del us e investigación tecnológica asociadas para su concreción en las aplicaciones médicas.

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“…Our experimental tests on various materials (data not shown) indicated that sonicating a plasticised semi-flexible PVC (PVC-P) tube (Tubclair, Tricoflex, Rueil Malmaison, France) can mimic the temperature elevation around an ex vivo rib positioned in the HIFU near field. A segment of PVC-P tube of inner diameter 12 mm and wall thickness 2 mm was embedded in a 3-cm thick layer of 15% polymethylmethacrylate (PMMA) gel [35]. Once the polymerisation of the PMMA gel had finished, the tube was filled with degassed water and placed in the pre-focal zone (approximately 5 cm below the focus), then sonicated (180 W, 36 s) in order to observe the thermal build-up around the obstacle.…”

Section: Preliminary In Vitro Studymentioning

confidence: 99%

Spatio-temporal quantitative thermography of pre-focal interactions between high intensity focused ultrasound and the rib cage

Petrusca

Salomir

Manasseh

et al. 2015

International Journal of Hyperthermia

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Objective: The aim of this paper is to quantitatively investigate the thermal effects generated by the pre-focal interactions of a HIFU beam with a rib cage, in the context of minimally invasive transcostal therapy of liver malignancies. Materials and methods: HIFU sonications were produced by a phased-array MR-compatible transducer on Turkey muscle placed on a sheep thoracic cage specimen. The thoracic wall was positioned in the pre-focal zone 3.5 to 6.5 cm below the focus. Thermal monitoring was simultaneously performed using fluoroptic sensors inserted into the medullar cavity of the ribs and high resolution MR-thermometry (voxel: 1 Â 1 Â 5 mm 3 , four multi-planar slices). Results: MR-thermometry data indicated nearly isotropic distribution of the thermal energy at the ribs' surface. The temperature elevation at the focus was comparable with the pericostal temperature elevation around unprotected ribs, while being systematically inferior, by more than a factor of four on average, to the intra-medullar values. The spatial profiles of the pericostal and intra-medullar thermal build-up measurements could be smoothly connected using a Gaussian function. The dynamics of the post-sonication thermal relaxation as determined by fluoroptic measurements was demonstrated to be theoretically coherent with the experimental observations. Conclusion: The experimental findings motivate further efforts for the transfer towards clinical routine of effective rib-sparing strategies for hepatic HIFU.

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Polyacrylamide gel as an acoustic coupling medium for focused ultrasound therapy

Cited by 92 publications

References 12 publications

Noninvasive Measurement of Local Thermal Diffusivity Using Backscattered Ultrasound and Focused Ultrasound Heating

Noninvasive Measurement of Local Thermal Diffusivity Using Backscattered Ultrasound and Focused Ultrasound Heating

Application of ultrasound in medicine part ii: the ultrasonic transducer and its associated electronics

Spatio-temporal quantitative thermography of pre-focal interactions between high intensity focused ultrasound and the rib cage

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