Higher harmonics dynamic focalization in single-element ring transducers using biaxial driving

Delgado, Sagid; Curiel, Laura; Li, Siyun; Pichardo, Samuel

doi:10.1016/j.ultras.2023.107051

Cited by 2 publications

(5 citation statements)

References 30 publications

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“…We note that the single-element biaxial driving transducer was fabricated to have a similar center frequency and a casing of similar size as the spherical transducer to facilitate its mounting and use within the small-animal stereotactic navigation unit (RK50, FUS Instruments), but that other biaxial driving transducers have been characterized and tested in silico and in vitro 2017,2021,2023). Importantly, biaxial driving has also been found to reduce side lobes compared to conventional driving (Delgado et al 2023), and no significant side lobes were detected here (figure 5). It is further worth emphasizing that the biaxial transducer used here has an outer ring diameter of 40% of the aperture size of the highly focused (F# = 0.7) spherical transducer yet produced a smaller opening volume.…”

Section: Discussionmentioning

confidence: 58%

“…Theoretical predictions of the effects of biaxial driving on a ring-shaped PZT transducer of the dimensions used in this study (13.75 mm outer diameter, 10 mm inner diameter, 2.95 mm height) were made using finite element analysis (FEA, COMSOL 6.0, COMSOL Inc.) 2D-axisymmetric simulations, as done in Delgado et al (2023). Table A1 provides a comparison of simulated and experimentally determined −6 dB focal metrics for the smalland large-focus modes of the biaxial ring transducer fabricated for this study.…”

Section: Data Availability Statementmentioning

confidence: 99%

“…This differs from traditional steering, accomplished with phased arrays by applying delays to elements based on time-of-flight to modify where the beam will converge (Hynynen and Jones 2016). A recent study demonstrated that biaxial driving is especially well-suited for a ring-shaped transducer configuration, given its axisymmetric configuration (Delgado et al 2023). It was observed that for a lead zirconate titanate (PZT) transducer with an inner diameter of 9.75 mm and a width of 2.0 mm, the biaxial driving produced controllable focusing with the ring transducer at its fundamental resonant frequency (482 kHz), as well as at its 3rd (1.362 MHz) and 5th (2.62 MHz) harmonics.…”

Section: Introductionmentioning

confidence: 99%

“…In the case of ring-shaped transducers, the focus could be steered along the propagation axis (referred to in the present work as 'axial refocusing'). By adjusting the phase difference and power between P-and L-electrodes, the focal spot size could be reduced significantly; from 31.6 mm 2 when using only P-electrodes to 3.4 mm 2 when using biaxial driving at 482 kHz (Delgado et al 2023). The focal spot position can also be controlled (to the detriment of focal spot size) by applying different sets of power and phase between the electrodes (figure 1(B)).…”

Section: Introductionmentioning

confidence: 99%

“…The focal spot position can also be controlled (to the detriment of focal spot size) by applying different sets of power and phase between the electrodes (figure 1(B)). In essence, different phases produce a shift of the acoustic energy from being concentrated close to the transducer surface to moving farther away from it, while higher power supplied to the L-electrodes relative to the P-electrodes can reduce the focal area at the cost of reducing focal distance (figure 1(C)) (Delgado et al 2023). This ring-type biaxial transducer presents opportunities for addressing steering and efficiency issues with a smaller footprint for a new generation of fully steerable phased arrays.…”

Section: Introductionmentioning

confidence: 99%

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Biaxial ultrasound driving technique for small animal blood–brain barrier opening

Pellow,

Li,

Delgado

et al. 2023

Phys. Med. Biol.

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Biaxial driving can more efficiently convert electrical power to forward acoustic power in piezoelectric materials, and the interaction between the orthogonal electric fields can produce a combination of extensional and shear deformations as a function of the phase difference between them to allow dynamic steering of the beam with a single-element. In this study, we demonstrate for the first time the application of a single-element biaxially driven ring transducer in vivo for blood–brain barrier opening in mice, and compare it to that achieved with a conventional single-element highly focused (F# = 0.7) spherical transducer operating at a similar frequency. Transcranial focused ultrasound (0.45 MPa, 10 ms pulse length, 1 Hz repetition frequency, 30 s duration) was applied bilaterally to mice with a 40 μl/kg bolus of DefinityTM microbubbles, employing either a single-element biaxial ring (1.482 MHz, 10 mm inner diameter, 13.75 mm outer diameter) or spherical (1.5 MHz, 35 mm diameter, F# = 0.7; RK50, FUS Instruments) transducer on each side. Follow-up MRI scans (T1 pre- and post- 0.2 mmol/kg Gd injection, T2) were acquired to assess blood–brain barrier opening volume and potential damage. Compared to blood–brain barrier opening achieved with a conventional single-element spherical focused transducer, the opening volume achieved with a single-element biaxial ring transducer was 35% smaller (p = 0.002) with a device of a ring diameter of 40% the aperture size. Axial refocusing was further demonstrated with the single-element biaxial ring transducer, yielding a 1.63 mm deeper, five-fold larger opening volume (p = 0.048) relative to its small-focus mode. The biaxial ring transducer achieved a more localized opening compared to the spherical focused transducer under the same parameters, and further enabled dynamic axial refocusing with a single-element transducer with a smaller fabrication footprint.

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Section: Discussionmentioning

confidence: 58%

Section: Data Availability Statementmentioning

confidence: 99%