Inexpensive acoustoelectric hydrophone for mapping high intensity ultrasonic fields

Witte, Russell S.; Hall, Tim; Olafsson, Ragnar; Huang, Sheng Wen; O’Donnell, Matthew

doi:10.1063/1.2974622

Cited by 11 publications

(16 citation statements)

References 9 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…2(c)), consistent with theory and previous studies. [4][5][6][7][8][9][10] Also, a gradual decrease in the AE signal was observed on distant recording electrodes ( Fig. 2(d)) relative to the ground reference.…”

mentioning

confidence: 99%

“…3 Ultrasound current source density imaging (UCSDI) has been proposed as a complement and possible alternative to traditional mapping of electrophysiological signals. [4][5][6][7][8][9][10][11] UCSDI exploits the acoustoelectric effect (AE), an interaction between pressure and current, to map electric field distributions while scanning a focused ultrasound beam. A previous study in the rabbit heart demonstrated that UCSDI has sufficient sensitivity to map the cardiac activation wave.…”

mentioning

confidence: 99%

See 1 more Smart Citation

Four-dimensional ultrasound current source density imaging of a dipole field

Wang

Olafsson

Ingram

et al. 2011

Applied Physics Letters

View full text Add to dashboard Cite

Ultrasound current source density imaging (UCSDI) potentially transforms conventional electrical mapping of excitable organs, such as the brain and heart. For this study, we demonstrate volume imaging of a time-varying current field by scanning a focused ultrasound beam and detecting the acoustoelectric (AE) interaction signal. A pair of electrodes produced an alternating current distribution in a special imaging chamber filled with a 0.9% NaCl solution. A pulsed 1 MHz ultrasound beam was scanned near the source and sink, while the AE signal was detected on remote recording electrodes, resulting in time-lapsed volume movies of the alternating current distribution. Electrical mapping helps identify abnormal electric pathways in the heart (i.e., arrhythmias) and brain (i.e., epileptic seizures) during treatment.1,2 This invasive procedure requires assumptions for reconstructing the current distribution, has limited spatial resolution, and is sensitive to registration errors.3 Ultrasound current source density imaging (UCSDI) has been proposed as a complement and possible alternative to traditional mapping of electrophysiological signals.4-11 UCSDI exploits the acoustoelectric effect (AE), an interaction between pressure and current, to map electric field distributions while scanning a focused ultrasound beam. A previous study in the rabbit heart demonstrated that UCSDI has sufficient sensitivity to map the cardiac activation wave. 4 Potential advantages of UCSDI include 1) remote detection of current with a spatial resolution determined by the size of the ultrasound focus (<5 mm 3 ); 2) volume images of current flow and biopotentials with as few as one electrode and ground without major assumptions regarding conductivity; 3) automatic coregistration of UCSDI with pulse echo (PE) ultrasound for simultaneously portraying current flow with anatomy. This study demonstrates volume imaging of a timevarying current field produced by scanning an ultrasound beam and detecting the generated AE signal.UCSDI is based on reciprocal theory. 4,6,11 In an electric field produced from a distributed current source J I ¼ J I (x, y, z; t s ) changing in physiologic time t s , the voltage V i measured by lead i at coordinate x 0 , y 0 , z 0 can be expressed in four dimensions under the assumption of far field detection of the AE signal. If an ultrasound beam is centered at C(x 0 , y 0 , z 0 ), then any point (x, y, z) in the pressure field can be represented in the electric field as (x þ x 0 , y þ y 0 , z þ z 0 ). The induced AE voltage (V AE ) detected by two distant electrodes can be represented bywith pressure pulse amplitude P 0 , interaction constant K I , resistivity q 0 , current distribution of detector J i L (x, y, z), ultrasound beam pattern b(x, y, z) defined with the transducer at the origin, speed of sound c, ultrasound pulse waveform a(t-z/c), and fast ultrasound time t. The instantaneous local field potential is reconstructed by demodulating (or basebanding) the AE signal. The current density J I of the dipole is modele...

show abstract

mentioning

confidence: 99%

mentioning

confidence: 99%

Four-dimensional ultrasound current source density imaging of a dipole field

Wang

Olafsson

Ingram

et al. 2011

Applied Physics Letters

View full text Add to dashboard Cite

show abstract

“…In figure 3(b), the current density is highest at the center and electrode areas, and decreases quickly away these areas. To avoid the interference of noise, the AE signal at (x 0 , y 0 , z 0 ) is applied band-pass filter with the same center frequency of transducer ( [2], [5]). In figure 4, if the center of beam pattern points at C(x 0 , y 0 , z 0 ), then any point P in the ultrasound pressure field (x, y, z) can be described in the electric field as (x+x 0 , y+y 0 , z+z 0 ).…”

Section: Simulationmentioning

confidence: 99%

“…As an alternative to conventional hydrophones, a new design based on the AE effect has attractive attributes not typically observed in other hydrophones: simple construction, low cost, decent sensitivity, resilience to damage at high intensity ultrasound field, and potentially wider bandwidth and improved sensitivity. The acousto-electric hydrophone [5] can use practically any conductive material. As a result, they are not limited to piezomaterials, possibly leading to novel designs at low cost.…”

Section: Introductionmentioning

confidence: 99%

Simulation-based optimization of the acoustoelectric hydrophone for mapping an ultrasound beam

et al. 2010

Self Cite

View full text Add to dashboard Cite

Most single element hydrophones depend on a piezoelectric material that converts pressure changes to electricity. These devices, however, can be expensive, susceptible to damage at high pressure, and/or have limited bandwidth and sensitivity. The acousto-electric (AE) hydrophone is based on the AE effect, an interaction between electrical current and acoustic pressure generated when acoustic waves travel through a conducting material. As we have demonstrated previously, an AE hydrophone requires only a conductive material and can be constructed out of common laboratory supplies to generate images of an ultrasound beam pattern consistent with more expensive hydrophones. The sensitivity is controlled by the injected bias current, hydrophone shape, thickness and width.In this report we describe simulations aimed at optimizing the design of the AE hydrophone with experimental validation using new devices composed of a resistive element of indium tin oxide (ITO). Several shapes (e.g., bowtie and dumbbell) and resistivities were considered. The AE hydrophone with a dumbbell configuration achieved the best beam pattern of a 2.25MHz ultrasound transducer with lateral and axial resolutions consistent with images generated from a commercial hydrophone (Onda Inc.). The sensitivity of this device was ~2 nV/Pa. Our simulations and experimental results both indicate that designs using a combination of ITO and gold (ratio of resistivities = ~18) produce the best results. We hope that design optimization will lead to new devices for monitoring ultrasonic fields for biomedical imaging and therapy, including lithotripsy and focused ultrasound surgery.

show abstract

“…We have previously described a type of inexpensive hydrophone that exploits the AE effect [17]. The AE hydrophone has attractive attributes not typically observed in other hydrophones: simple construction, low cost, high sensitivity, resistance to damage from high-intensity ultrasound fields, and potentially wide bandwidth with an improved design.…”

Section: Introductionmentioning

confidence: 99%

Design considerations and performance of MEMS acoustoelectric ultrasound detectors

Wang

Ingram

Greenlee

et al. 2013

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

Self Cite

View full text Add to dashboard Cite

Most single-element hydrophones depend on a piezoelectric material that converts pressure changes to electricity. These devices, however, can be expensive, susceptible to damage at high pressure, and/or have limited bandwidth and sensitivity. We have previously described the acoustoelectric (AE) hydrophone as an inexpensive alternative for mapping an ultrasound beam and monitoring acoustic exposure. The device exploits the AE effect, an interaction between electrical current flowing through a material and a propagating pressure wave. Previous designs required imprecise fabrication methods using common laboratory supplies, making it difficult to control basic features such as shape and size. This study describes a different approach based on microelectromechanical systems (MEMS) processing that allows for much finer control of several design features. In an effort to improve the performance of the AE hydrophone, we combine simulations with bench-top testing to evaluate key design features, such as thickness, shape, and conductivity of the active and passive elements. The devices were evaluated in terms of sensitivity, frequency response, and accuracy for reproducing the beam pattern. Our simulations and experimental results both indicated that designs using a combination of indium tin oxide (ITO) for the active element and gold for the passive electrodes (conductivity ratio = ~20) produced the best result for mapping the beam of a 2.25-MHz ultrasound transducer. Also, the AE hydrophone with a rectangular dumbbell configuration achieved a better beam pattern than other shape configurations. Lateral and axial resolutions were consistent with images generated from a commercial capsule hydrophone. Sensitivity of the best-performing device was 1.52 nV/Pa at 500 kPa using a bias voltage of 20 V. We expect a thicker AE hydrophone closer to half the acoustic wavelength to produce even better sensitivity, while maintaining high spectral bandwidth for characterizing medical ultrasound transducers. AE ultrasound detectors may also be useful for monitoring acoustic exposure during therapy or as receivers for photoacoustic imaging.

show abstract

Inexpensive acoustoelectric hydrophone for mapping high intensity ultrasonic fields

Cited by 11 publications

References 9 publications

Four-dimensional ultrasound current source density imaging of a dipole field

Four-dimensional ultrasound current source density imaging of a dipole field

Simulation-based optimization of the acoustoelectric hydrophone for mapping an ultrasound beam

Design considerations and performance of MEMS acoustoelectric ultrasound detectors

Contact Info

Product

Resources

About