Equivalent-Source Acoustic Holography for Projecting Measured Ultrasound Fields Through Complex Media

Treeby, Bradley E.; Lucka, Felix; Martin, Eleanor; Cox, Ben

doi:10.1109/tuffc.2018.2861895

Cited by 12 publications

(7 citation statements)

References 31 publications

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“…The field projected using the angular spectrum approach agrees with k-Wave with a difference in peak focal pressure of 1.4%. This level of agreement is similar to that shown previously with measured data [30] and is within the expected variation on measurements made with the same hydrophone established in our previous work [33]. Both the input plane and the validation measurements were made with the same hydrophone, and since the field is linear, the effect of uncertainty in the hydrophone frequency response should be limited (the short pulse has some bandwidth).…”

Section: A Free-field Validationsupporting

confidence: 90%

“…We also investigated the expected variation in measurements to quantify how closely we could reasonably expect measurements and models to agree. In terms of the simulations, the way in which the source is defined in k-Wave was modified to reduce errors arising from the use of Dirichlet boundary conditions in pseudospectral time domain solvers [30]. A correction was also implemented to reduce error in time-varying sources [29], and other minor bug fixes have been implemented in new k-Wave releases.…”

Section: Discussionmentioning

confidence: 99%

“…II-B. The measured signals were downsampled to the temporal resolution required for the simulations and input to a gradient-based optimisation that calculates an equivalent interior mass source that minimises the difference between the k-Wave forward model and the measured data [30]. The resulting source plane was then upsampled using Fourier interpolation to the required simulation spatial resolution.…”

Section: A Overviewmentioning

confidence: 99%

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Experimental Validation of k-Wave: Nonlinear Wave Propagation in Layered, Absorbing Fluid Media

Martin

Jaroš

Treeby

2020

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

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Models of ultrasound propagation in biologically relevant media have applications in planning and verification of ultrasound therapies and computational dosimetry. To be effective, the models must be able to accurately predict both the spatial distribution and amplitude of the acoustic pressure. This requires that the models are validated in absolute terms, which for arbitrarily heterogeneous media should be performed by comparison with measurements of the acoustic field. In this study, simulations performed using the open-source k-Wave acoustics toolbox, with a measurement-based source definition, were quantitatively validated against measurements of acoustic pressure in water and layered absorbing fluid media. In water, the measured and simulated spatial peak pressures agreed to within 3% under linear conditions and 7% under non-linear conditions. After propagation through a planar or wedge shaped glycerolfilled phantom, the difference in spatial peak pressure was 8.5% and 10.7%, respectively. These differences are within or close to the expected uncertainty of the acoustic pressure measurement. The -6 dB width and length of the focus agreed to within 4% in all cases, and the focal positions were within 0.7 mm for the planar phantom and 1.2 mm for the wedge shaped phantom. These results demonstrate that when the acoustic medium properties and geometry are well known, accurate quantitative predictions of the acoustic field can be made using k-Wave.

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Section: A Free-field Validationsupporting

confidence: 90%

Section: Discussionmentioning

confidence: 99%

Section: A Overviewmentioning

confidence: 99%

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Experimental Validation of k-Wave: Nonlinear Wave Propagation in Layered, Absorbing Fluid Media

Martin

Jaroš

Treeby

2020

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

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“…A recent work [43] proposed an alternative way of constructing an ultrasound source model, based on holographic projections. Briefly, this method allows the derivation of an equivalent source model from pressure measurements in a plane parallel to the transducer face by iterative optimization of the pressure distribution on the surface of the equivalent source.…”

Section: Discussionmentioning

confidence: 99%

Transducer modeling for accurate acoustic simulations of transcranial focused ultrasound stimulation

Pasquinelli¹,

Montanaro²,

Lee³

et al. 2020

J. Neural Eng.

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Objective: Low-intensity transcranial ultrasound stimulation (TUS) is emerging as noninvasive brain stimulation technique with superior spatial resolution and the ability to reach deep brain areas. Medical image-based computational modeling could be an important tool for individualized TUS dose control and targeting optimization, but requires further validation. This study aims to assess the impact of the transducer model on the accuracy of the simulations.Approach: Using hydrophone measurements, the acoustic beam of a single-element focused transducer (SEFT) with a flat piezoelectric disc and an acoustic lens was characterized. The acoustic beam was assessed in a homogeneous water bath and after transmission through obstacles (3D-printed shapes and skull samples). The acoustic simulations employed the finite-difference time-domain method and were informed by computed tomography (CT) images of the obstacles. Transducer models of varying complexity were tested, representing the SEFT either as a surface boundary condition with variable curvature, or also accounting for its internal geometry. In addition, a back-propagated pressure distribution from the first measurement plane was used as source model. The simulations and measurements were quantitatively compared using key metrics for peak location, focus size, intensity and spatial distribution.Main results: While a surface boundary with an adapted, 'effective' curvature radius based on the specifications given by the manufacturer could reproduce the measured focus location and size in a homogeneous water bath, it regularly failed to accurately predict the beam after obstacle transmission. In contrast, models that were based on a one-time 1 calibration to the homogeneous water bath measurements performed substantially better in all cases with obstacles. For one of the 3D-printed obstacles, the simulated intensities deviated substantially from the measured ones, irrespective of the transducer model. We attribute this finding to a standing wave effect, and further studies should clarify its relevance for accurate simulations of skull transmission.Significance: Validated transducer models are important to ensure accurate simulations of the acoustic beam of SEFTs, in particular in the presence of obstacles such as the skull.

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“…On the other hand, a number of methods exist to estimate transducer IRs in transmission and reception, with deconvolution-based methods [8], [9] and backpropagation [10], [11], [12], [13] among the most used ones. Deconvolution-based methods assume that the transducer behaves like a baffled piston and calculate an IR by deconvolving the expected infinite-bandwidth response of the transducer and its experimentally measured response.…”

Section: Introductionmentioning

confidence: 99%

Spatial response identification enables robust experimental ultrasound computed tomography

Cueto,

Guasch,

Cudeiro

et al. 2021

Preprint

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Ultrasoundcomputed tomography techniques have the potential to provide clinicians with 3D, quantitative and high-resolution information of both soft and hard tissues such as the breast or the adult human brain. Their practical application requires accurate modelling of the acquisition setup: the spatial location, orientation, and impulse response of each ultrasound transducer. However, existing calibration methods fail to accurately characterise these transducers unless their size can be considered negligible when compared to the dominant wavelength, which reduces signal-to-noise ratios below usable levels in the presence of high-contrast tissues such as the skull. In this paper, we introduce a methodology that can simultaneously estimate the location, orientation, and impulse response of the ultrasound transducers in a single calibration. We do this by extending spatial response identification, an algorithm that we have recently proposed to estimate transducer impulse responses. Our proposed methodology replaces the transducers in the acquisition device with a surrogate model whose effective response matches the experimental data by fitting a numerical model of wave propagation. This results in a flexible and robust calibration procedure that can accurately predict the behaviour of the ultrasound acquisition device without ever having to know where the real transducers are or their individual impulse response. Experimental results using a ring acquisition system show that spatial response identification produces calibrations of significantly higher quality than standard methodologies across all transducers, both in transmission and in reception. Experimental fullwaveform inversion reconstructions of a tissue-mimicking phantom demonstrate that spatial response identification generates more accurate reconstructions than those produced with standard calibration techniques.

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Equivalent-Source Acoustic Holography for Projecting Measured Ultrasound Fields Through Complex Media

Cited by 12 publications

References 31 publications

Experimental Validation of k-Wave: Nonlinear Wave Propagation in Layered, Absorbing Fluid Media

Experimental Validation of k-Wave: Nonlinear Wave Propagation in Layered, Absorbing Fluid Media

Transducer modeling for accurate acoustic simulations of transcranial focused ultrasound stimulation

Spatial response identification enables robust experimental ultrasound computed tomography

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