1
|
Pellow C, Li S, Delgado S, Pike GB, Curiel L, Pichardo S. Biaxial ultrasound driving technique for small animal blood-brain barrier opening. Phys Med Biol 2023; 68:195006. [PMID: 37607563 DOI: 10.1088/1361-6560/acf2e3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2023] [Accepted: 08/22/2023] [Indexed: 08/24/2023]
Abstract
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 transducerin vivofor 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 40μl/kg bolus of DefinityTMmicrobubbles, 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.
Collapse
Affiliation(s)
- Carly Pellow
- Department of Radiology, Cumming School of Medicine, University of Calgary, Alberta, Canada
- Hotchkiss Brain Institute, University of Calgary, Alberta, Canada
| | - Siyun Li
- Department of Radiology, Cumming School of Medicine, University of Calgary, Alberta, Canada
| | - Sagid Delgado
- Department of Radiology, Cumming School of Medicine, University of Calgary, Alberta, Canada
| | - G Bruce Pike
- Department of Radiology, Cumming School of Medicine, University of Calgary, Alberta, Canada
- Hotchkiss Brain Institute, University of Calgary, Alberta, Canada
- Department of Clinical Neurosciences, Cumming School of Medicine, University of Calgary, Alberta, Canada
| | - Laura Curiel
- Hotchkiss Brain Institute, University of Calgary, Alberta, Canada
- Department of Biomedical Engineering, Schulich School of Engineering, University of Calgary, Alberta, Canada
| | - Samuel Pichardo
- Department of Radiology, Cumming School of Medicine, University of Calgary, Alberta, Canada
- Hotchkiss Brain Institute, University of Calgary, Alberta, Canada
- Department of Clinical Neurosciences, Cumming School of Medicine, University of Calgary, Alberta, Canada
| |
Collapse
|
2
|
Delgado S, Curiel L, Li S, Pichardo S. Higher harmonics dynamic focalization in single-element ring transducers using biaxial driving. ULTRASONICS 2023; 133:107051. [PMID: 37276698 DOI: 10.1016/j.ultras.2023.107051] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/14/2023] [Revised: 05/15/2023] [Accepted: 05/22/2023] [Indexed: 06/07/2023]
Abstract
Biaxial driving is a new driving technique that allows the steering of the ultrasound field generated by a single-element piezoceramic transducer. Because of their natural axisymmetric geometry, ultrasound generation with ring transducers can take advantage of the biaxial driving to change the focus of the beam generated by this type of transducer using only two driving signals. In this study, we applied the biaxial driving technique into a single-element PZT ring transducer operating at 500 kHz to produce a change in size and position of the focal spot while using the 1st (482 kHz), 3rd (1.362 MHz) and 5th (2.62 MHz) harmonic excitation. The transducer had a thickness of 2.85 mm, an inner diameter of 9.75 mm and a ring width of 2.0 mm, and two pairs of electrodes as required for biaxial driving. Simulation and experimental results showed that both the focal area and the distance at which the focal area centre was located changed as a function of the phase and power difference between the two driving signals. Experimental results showed that the focal area could be reduced from 31.6 mm2 (conventional driving) to 3.4 mm2 (89 % reduction) when using the first harmonic excitation. For the third harmonic, the focal area could be reduced from 4.0 mm2 (conventional driving) to 3.3 mm2 (17.5 % reduction). For the fifth harmonic, the focal area could be reduced from 1.7 mm2 (conventional driving) to 1 mm2 (41.7 % reduction). Results also demonstrated the centre of the focus could be displaced between 3.0 mm and 9.3 mm from the surface of the transducer when using the first harmonic, between 7.3 mm and 8.4 mm at the third harmonic, and between 4.9 mm and 8.2 mm at the fifth harmonic. The reduction in the focus area, as well as the possibility to displace the focus dynamically will be advantageous for preclinical applications of focused ultrasound, especially on drug delivery and neuromodulation studies in small rodents.
Collapse
Affiliation(s)
- Sagid Delgado
- Department of Radiology, University of Calgary, Calgary, Canada.
| | - Laura Curiel
- Department of Biomedical Engineering, University of Calgary, Calgary, Canada.
| | - Siyun Li
- Department of Radiology, University of Calgary, Calgary, Canada.
| | - Samuel Pichardo
- Department of Radiology, University of Calgary, Calgary, Canada; Department of Clinical Neurosciences, University of Calgary, Calgary, Canada.
| |
Collapse
|
3
|
Delgado S, Curiel L, Pichardo S. Steering single-element lead zirconate titanate ultrasound transducers using biaxial driving. ULTRASONICS 2021; 110:106241. [PMID: 32916381 DOI: 10.1016/j.ultras.2020.106241] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/11/2020] [Revised: 08/09/2020] [Accepted: 08/27/2020] [Indexed: 06/11/2023]
Abstract
Previous work has shown that biaxial driving using two phase-offset orthogonal electric fields (propagation and lateral) improves the efficiency of ferroelectric materials by reducing coercivity and, hence, energy dissipation. In the current investigation, we demonstrated the capability of the biaxial method to steer ultrasound waves in single-element piezoceramic transducers made of prismatic lead zirconate titanate (PZT). We conducted finite element analysis simulations for 133 kHz (model 1) and 470 kHz biaxial (model 2) transducers models. We performed experimental validation with biaxially driven single-element transducers (n = 3) operating at an average frequency of 131 kHz with the same characteristics as model 1. For both models, we found non-symmetric steering that was a function of both the phase and power of the second electric field. At a constant electrical power (1 W) on the propagation electrodes, simulations for the 133 kHz model predicted maximal steering of 10.3°, 22.6°, and 30.9° for lateral electrode powers of 0.1 W, 0.5 W, and 1.0 W, respectively. Experimentally, for model 1, the maximal steering was 11.7° ± 1.9°, 23.5° ± 3.5°, and 30.2° ± 4.4° for the lateral electrode powers of 0.1 W, 0.5 W, and 1.0 W, respectively. Simulations for the 470 kHz model predicted maximal steering of 8.8°, 16.1°, and 27° for lateral electrode powers of 0.1 W, 0.5 W, and 1.0 W, respectively. Simulations showed that the cause of the steering asymmetry was a non-uniform shear deformation associated with the slightly off-resonance lateral electric field driving frequency. This is the first demonstration of ultrasound steering using a single-element transducer, which can have important applications for ultrasound focusing with phased arrays.
Collapse
Affiliation(s)
- Sagid Delgado
- Department of Electrical and Computer Engineering, Lakehead University, Canada.
| | - Laura Curiel
- Department of Electrical and Computer Engineering, University of Calgary, Canada.
| | - Samuel Pichardo
- Departments of Radiology and Clinical Neurosciences, University of Calgary, Canada.
| |
Collapse
|