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Liu J.,University of California at Davis | Foiret J.,University of California at Davis | Stephens D.N.,University of California at Davis | Le Baron O.,Imasonic | Ferrara K.W.,University of California at Davis
Physics in Medicine and Biology | Year: 2016

A 1.5 MHz prolate spheroidal therapeutic array with 128 circular elements was designed to accommodate standard imaging arrays for ultrasonic image-guided hyperthermia. The implementation of this dual-array system integrates real-time therapeutic and imaging functions with a single ultrasound system (Vantage 256, Verasonics). To facilitate applications involving small animal imaging and therapy the array was designed to have a beam depth of field smaller than 3.5 mm and to electronically steer over distances greater than 1 cm in both the axial and lateral directions. In order to achieve the required f number of 0.69, 1-3 piezocomposite modules were mated within the transducer housing. The performance of the prototype array was experimentally evaluated with excellent agreement with numerical simulation. A focal volume (2.70 mm (axial)x 0.65 mm (transverse)x 0.35 mm (transverse)) defined by the -6 dB focal intensity was obtained to address the dimensions needed for small animal therapy. An electronic beam steering range defined by the -3 dB focal peak intensity (17 mm (axial)x 14 mm (transverse)x 12 mm (transverse)) and -8 dB lateral grating lobes (24 mm (axial)x 18 mm (transverse)x 16 mm (transverse)) was achieved. The combined testing of imaging and therapeutic functions confirmed well-controlled local heating generation and imaging in a tissue mimicking phantom. This dual-array implementation offers a practical means to achieve hyperthermia and ablation in small animal models and can be incorporated within protocols for ultrasound-mediated drug delivery. © 2016 Institute of Physics and Engineering in Medicine.

Bouchoux G.,French Institute of Health and Medical Research | Bouchoux G.,University Claude Bernard Lyon 1 | Owen N.R.,University of Washington | Chavrier F.,French Institute of Health and Medical Research | And 7 more authors.
IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control | Year: 2010

Interstitial ultrasound applicators can be a minimally invasive alternative for treating targets that are unresectable or are inaccessible by extracorporeal methods. Dualmode transducers for ultrasound imaging and therapy were developed to address the constraints of a miniaturized applicator and real-time treatment monitoring. We propose an original treatment strategy that combines ultrasound imaging and therapy using a dual-mode transducer rotating at 8 revolutions per second. Real-time B-mode imaging was interrupted to emit high-intensity ultrasound over a selected therapy aperture. A full 360 image was taken every 8th rotation to image the therapy aperture. Numerical simulations were performed to study the effect of rotation on tissue heating, and to study the effect of the treatment sequence on transducer temperature. With the time-averaged transducer surface intensity held at 12 W/ cm2 to maintain transducer temperature below 66°C, higher field intensities and deeper lesions were produced by narrower therapy apertures. A prototype system was built and tested using in vitro samples of porcine liver. Lesions up to 8 mm were produced using a time-averaged transducer surface intensity of 12 W/cm2 applied for a period of 240 s over a therapy aperture of 40°. Apparent strain imaging of the therapy aperture improved the contrast between treated and spared tissues, which could not be differentiated on B-mode images. With appropriate limits on the transducer output, real-time imaging and deep thermal ablation are feasible and sustainable using a rotating dual-mode transducer. © 2010 IEEE.

Owen N.R.,University of Washington | Owen N.R.,French Institute of Health and Medical Research | Bouchoux G.,University of Lyon | Seket B.,University of Washington | And 13 more authors.
IEEE Transactions on Biomedical Engineering | Year: 2010

Unresectable liver tumors are often treated with interstitial probes that modify tissue temperature, and efficacious treatment relies on image guidance for tissue targeting and assessment. Here, we report the in vivo evaluation of an interstitial applicator with a mechanically oscillating five-element dual-mode transducer. After thoroughly characterizing the transducer, tissue response to high-intensity ultrasound was numerically calculated to select parameters for experimentation in vivo. Using perfused porcine liver, B-mode sector images were formed before and after a 120-s therapy period, and M-mode imaging monitored the therapy axis during therapy. The time-averaged transducer surface intensity was 21 or 27 W/cm2. Electroacoustic conversion efficiency was maximally 72 ± 3% and impulse response length was 295 ± 1.0 ns at -6 dB. The depth of thermal damage measured by gross histology ranged from 10 to 25 mm for 13 insertion sites. For six sites, M-mode data exhibited a reduction in gray-scale intensity that was interpreted as the temporal variation of coagulation necrosis. Contrast ratio analysis indicated that the gray-scale intensity dropped by 7.8 ± 3.3 dB, and estimated the final lesion depth to an accuracy of 2.3 ± 2.4 mm. This paper verified that the applicator could induce coagulation necrosis in perfused liver and demonstrated the feasibility of real-time monitoring. © 2009 IEEE.

Fleury G.,IMASONIC | Berriet R.,IMASONIC | Chupin L.,IMASONIC | Guey J.-L.,IMASONIC | And 3 more authors.
Proceedings - IEEE Ultrasonics Symposium | Year: 2010

Potential applications of High Intensity Therapeutic Ultrasound (HITU) are numerous. Some commercial devices already exist to treat for instance prostate cancers or uterine fibroids. Strong technical and clinical research effort is also being made to validate systems and treatment procedures for various organs: for instance, breast, liver, kidney, thyroid and even brain. Many other applications are under investigation or to be explored in the future. This diversity of applications leads to requirements for the transducer which are specific to each application and significantly different from one case to another. In this paper, specifications of HITU transducers are discussed in relation to different conditions of use. The first criterion that determines the design of the transducer is the way chosen to reach the organ to be treated: treatment can be performed from outside the body, through a natural cavity or by interstitial means. The size and geometry of the radiating surface, the acoustic power level and the operation frequency are then specified for each configuration. Starting from these requirements, a dedicated transducer is designed. Different technological solutions are available including piezocomposite technologies widely used in current HITU transducer design. An important point to take into account at this stage is the imaging method used for locating the area to be treated, positioning the transducer and finally monitoring the treatment. Ultrasound Imaging or Magnetic Resonance Imaging is generally chosen in HITU procedures. The HITU transducer has to be compatible with the specified imaging environment. After manufacture, the performance of the transducer is evaluated with respect to expected characteristics. Specific methods have been developed for this purpose such as, for instance, the radiation force balance with a liquid target to evaluate the total output power or acoustic holography to estimate acoustic field parameters. All recent developments in HITU transducer design and characterisation are driven by the needs of HITU procedures to provide a better medical service: quicker treatment, less expensive total procedure including hospitalisation time, safety for the patient, and efficiency evaluated with respect to alternative methods. These developments will be reinforced by the availability of dedicated imaging methods allowing better monitoring of the treatment, but also by the elaboration of standards currently under preparation concerning the characterisation of HITU systems from the acoustic and safety point of view. © 2010 IEEE.

Imasonic | Date: 2012-11-20

Scientific other than medical apparatus and instruments, making it possible to exploit the uses of vibrations, sounds and ultrasound, namely, ultrasound transducers, ultrasound probes, ultrasound emitters, ultrasound receivers and ultrasound sensors; apparatus and instruments for measuring biophysical parameters, namely, ultrasound transducers and ultrasound probes; ultrasound transducers, probes, emitters, receivers and sensors; software and computer programs, namely, software and computer programs for simulating, measuring and displaying ultrasound fields and designing, measuring and reporting the characteristics of ultrasound probes and ultrasound transducers for use in the field of transducers, probes and other components emitting and/or receiving vibrations, sounds and ultrasound. Arranging and conducting conferences, congresses, seminars, symposiums and exhibitions for cultural or educational purposes; arranging and conducting of professional workshops; publication of texts, other than publicity texts; all these services being in connection with the field of transducers, probes and other components emitting and/or receiving vibrations, sounds and ultrasound. Engineering services including providing evaluations, estimates and research in the scientific and technological fields provided by engineers in the field of transducers, probes and other components emitting and/or receiving vibrations, sounds and ultrasound; research and development for others in the field of transducers, probes and other components emitting and/or receiving vibrations, sounds and ultrasound; technical project studies, namely, scientific study and research in the field of transducers, probes and other components emitting and/or receiving vibrations, sounds and ultrasound; scientific and technical consultancy services in the field of transducers, probes and other components emitting and/or receiving vibrations, sounds and ultrasound; engineering, industrial research including analysis and technical control in the field of transducers, probes and other components emitting and/or receiving vibrations, sounds and ultrasound.

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