New piezoelectric transducers for therapeutic ultrasound

Chapelon, Jean Yves; Cathignol, D.; Cain, Charles A.; Ebbini, E.S.; Kluiwstra, J.-U.; Sapozhnikov, Oleg A.; Fleury, Gilles; Berriet, R.; Chupin, Laurent; Guey, J.-L.

doi:10.1016/s0301-5629(99)00120-9

Cited by 96 publications

(64 citation statements)

References 23 publications

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“…1). Histotripsy pulses were generated by an 18-element piezocomposite (1-3 composite [32]) spherical shell therapeutic array (Imasonic, S.A., Besançon, France) with a center frequency of 750 kHz and a geometric focal length of 100 mm. The therapeutic array has an annular configuration with outer and inner diameters of 145 and 68 mm, respectively.…”

Section: B Ultrasound Generation and Calibrationmentioning

confidence: 99%

High Speed Imaging of Bubble Clouds Generated in Pulsed Ultrasound Cavitational Therapy - Histotripsy

Raghavan

Hall

et al. 2007

IEEE Trans. Ultrason., Ferroelect., Freq. Contr.

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Our recent studies have demonstrated that mechanical fractionation of tissue structure with sharply demarcated boundaries can be achieved using short (<20 μs), high intensity ultrasound pulses delivered at low duty cycles. We have called this technique histotripsy. Histotripsy has potential clinical applications where noninvasive tissue fractionation and/or tissue removal are desired. The primary mechanism of histotripsy is thought to be acoustic cavitation, which is supported by a temporally changing acoustic backscatter observed during the histotripsy process. In this paper, a fast-gated digital camera was used to image the hypothesized cavitating bubble cloud generated by histotripsy pulses. The bubble cloud was produced at a tissue-water interface and inside an optically transparent gelatin phantom which mimics bulk tissue. The imaging shows the following: 1) Initiation of a temporally changing acoustic backscatter was due to the formation of a bubble cloud; 2) The pressure threshold to generate a bubble cloud was lower at a tissue-fluid interface than inside bulk tissue; and 3) at higher pulse pressure, the bubble cloud lasted longer and grew larger. The results add further support to the hypothesis that the histotripsy process is due to a cavitating bubble cloud and may provide insight into the sharp boundaries of histotripsy lesions.

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Section: B Ultrasound Generation and Calibrationmentioning

confidence: 99%

High Speed Imaging of Bubble Clouds Generated in Pulsed Ultrasound Cavitational Therapy - Histotripsy

Raghavan

Hall

et al. 2007

IEEE Trans. Ultrason., Ferroelect., Freq. Contr.

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“…8,9 However, the high power performance of 1-3 composites is generally lower than that of monolithic ceramics due to the inherently low mechanical quality factors and low thermal conductivity of the polymer fillers. [10][11][12][13] Approaches to improve the high power performance of composite transducers are, thus, to minimize the losses of the composite and/or to improve the thermal conductivity of the polymer matrix. Previous studies have shown that composites filled with a low loss polymer showed promising high power characteristics, exhibiting improved mechanical quality factor, consequently enhancing mechanical dynamic strain for a given drive field.…”

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confidence: 99%

Electroacoustic response of 1-3 piezocomposite transducers for high power applications

Lee

Zhang

Geng

et al. 2012

Applied Physics Letters

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The electroacoustic performance of 1-3 piezoelectric composite transducers with low loss polymer filler was studied and compared to monolithic Pb(Zr,Ti)O 3 (PZT) piezoelectric transducers. The 1-3 composite transducers exhibited significantly high electromechanical coupling factor (k t $ 0.64) when compared to monolithic counterparts (k t $ 0.5), leading to the improved bandwidth and loop sensitivity, being on the order of 67% and À24.0 dB versus 44% and À24.8 dB, respectively. In addition, the acoustic output power and transmit efficiency ($50%) were found to be comparable to the monolithic PZT transducers, demonstrating potential for broad bandwidth, high power ultrasonic transducer applications. V C 2012 American Institute of Physics.[http://dx.doi.org/10.1063/1.4772482] Piezoelectric transducers are widely employed in a range of medical applications, including ultrasound diagnostic imaging and ultrasound therapy. Ultrasound imaging is one of the most widely used imaging modalities due to the capability of a non-invasive visualization of interior tissues in real time with high resolution.1 Recently, ultrasound has attracted attention for therapeutic applications, specifically ultrasound guided high intensity focused ultrasound (HIFU) therapy, as it allows for thermal ablation of malignant and benign tumors without open surgery. 2-5The main differences between ultrasound imaging and therapeutic applications are operating frequency and power level. Megahertz or above ultrasound is usually used for diagnostic imaging as the image resolution is proportional to operating frequency. The acoustic power and intensity levels are relatively low, being on the order of 0.05 W and 1-2 W/cm 2 , respectively, in order to prevent the tissue damage. In contrast, the acoustic power and intensity levels of therapeutic ultrasound, such as HIFU, are several orders of magnitude greater, typically being on the order of 10-300 W and 1000 to 20,000 W/cm 2 , with operating frequencies in the range of 0.8 MHz to 2 MHz. General characteristics of the ultrasound used for different therapeutic applications, such as frequency and acoustic intensity, are summarized in Fig. 1. 6 For the generation of high power ultrasound, high electromechanical coupling k ij and mechanical quality factor Q m of piezoelectric transducers are desired, where the high electromechanical coupling factor permits effective energy conversion from electrical energy to mechanical energy, while the high mechanical quality factor reduces heat generation under high power operation. The electroacoustic power efficiency is also improved with increasing vibration velocity (v) of a piezoelectric material, which is related to the acoustic output power, and proportional to the product of electromechanical coupling and mechanical quality factor. 7Piezoelectric/polymer composites with 1-3 connectivity offer several advantages over monolithic ceramics for medical ultrasonic transducers, with high electromechanical coupling (k ij ), low spurious modes, and flexibility in terms o...

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“…Compared to quartz crystals, piezoelectric materials are easily formed into spherical shapes, which allow mechanical focusing and eliminate coupling through a lens [27]. Since the 1950's, many research groups have been optimizing and customizing compound piezoelectricbased materials for high power applications [28], [29]. Using these materials, both single-element, unfocused [30], [31] and mechanically-focused [27], [32] piezoelectric transducers have been used for therapeutics in the heart, liver, and kidney, to name a few.…”

Section: Introductionmentioning

confidence: 99%

Feasibility of MR-temperature mapping of ultrasonic heating from a CMUT

Wong

Watkins

Kupnik

et al. 2008

IEEE Trans. Ultrason., Ferroelect., Freq. Contr.

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In the last decade, high intensity focused ultrasound (HIFU) has gained popularity as a minimallyinvasive and non-invasive therapeutic tool for treatment of cancers, arrhythmias, and other medical conditions. HIFU therapy is often guided by magnetic resonance imaging (MRI), which provides anatomical images for therapeutic device placement, temperature maps for treatment guidance, and post-operative evaluation of the region of interest. While piezoelectric transducers are dominantly used for MR-guided HIFU, capacitive micromachined ultrasonic transducers (CMUTs) show competitive advantages such as ease of fabrication, integration with electronics, improved efficiency, and reduction of self-heating. In this paper, we will show our first results of an unfocused CMUT transducer monitored by MR-temperature maps. This 2.51 mm by 2.32 mm, unfocused CMUT heated a HIFU phantom by 14°C in 2.5 min. This temperature rise was successfully monitored by MR thermometry in a 3.0 T General Electric scanner. Index Terms

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New piezoelectric transducers for therapeutic ultrasound

Cited by 96 publications

References 23 publications

High Speed Imaging of Bubble Clouds Generated in Pulsed Ultrasound Cavitational Therapy - Histotripsy

High Speed Imaging of Bubble Clouds Generated in Pulsed Ultrasound Cavitational Therapy - Histotripsy

Electroacoustic response of 1-3 piezocomposite transducers for high power applications

Feasibility of MR-temperature mapping of ultrasonic heating from a CMUT

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