Absolute measurement of ultrasonic backscatter from single microbubbles

Sboros, Vassilis; Pye, S. D.; MacDonald, C.A.; Gomatam, Jagannathan; Moran, Carmel M.; McDicken, W.N.

doi:10.1016/j.ultrasmedbio.2005.04.018

Cited by 46 publications

(42 citation statements)

References 25 publications

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“…Additionally, the reference scattered pressure could be simulated instead of measured with scaling based on hydrophone measurements of the incident wavefield at the sphere location, similar to a method used to calibrate phased array transducers. 7 Another recently investigated PCD calibration approach is a pitch-catch substitution method that also utilizes three transducers: a focused PCD, a reference hydrophone, and a focused source aligned confocally and coaxially. 6 Because the PCD and hydrophone directly measure the transmit beam of the source, the acquired signals provide relatively high signal-to-noise ratio (SNR) over a broad frequency range, limited mainly by the combined bandwidth of the transmit-receive transducer pair.…”

Section: Discussionmentioning

confidence: 99%

“…Normalized sphere sizes of ka s up to 15 were investigated, corresponding approximately to frequencies in the megahertz range and scattering spheres of micron-scaled radii, consistent with previous calibration measurements using scattering techniques. 5,7 For both scatterer types, simulations of the spatially averaged PCD-measured and corresponding hydrophone-measured pressures were compared to test the equivalence of these measurements, and thus the achievable accuracy of calibrations using bistatic scattering substitution methods, as a function of frequency, PCD geometry, and scatterer type and size. Figure 2 illustrates the far-field scattered waves from silica and polystyrene spheres as a function of ka s and scattering angle h. Shown in Figs.…”

Section: Methodsmentioning

confidence: 99%

“…In receive calibrations using scattering, a wave scattered by a small sphere has been measured by the uncalibrated receiver and the scattered signal amplitude compared to a calculated 7 or measured 5 reference pressure. A bistatic substitution technique, schematically shown in Fig.…”

Section: Introductionmentioning

confidence: 99%

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Accuracy of a bistatic scattering substitution technique for calibration of focused receivers

Rich

Mast

2015

The Journal of the Acoustical Society of America

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A recent method for calibrating single-element, focused passive cavitation detectors (PCD) compares bistatic scattering measurements by the PCD and a reference hydrophone. Here, effects of scatterer properties and PCD size on frequency-dependent receive calibration accuracy are investigated. Simulated scattering from silica and polystyrene spheres was compared for small hydrophone and spherically focused PCD receivers to assess the achievable calibration accuracy as a function of frequency, scatterer size, and PCD size. Good agreement between measurements was found when the scatterer diameter was sufficiently smaller than the focal beamwidth of the PCD; this relationship was dependent on the scatterer material. For conditions that result in significant disagreement between measurements, the numerical methods described here can be used to correct experimental calibrations.

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Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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Accuracy of a bistatic scattering substitution technique for calibration of focused receivers

Rich

Mast

2015

The Journal of the Acoustical Society of America

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“…Previously reported work has included optical studies [1][2][3][4] and acoustical observations [5][6][7][8], and these techniques are integrated in this new instrument. The use of simultaneous optical and acoustical recording techniques facilitates the analysis of microbubble response to high time-bandwidth transmitted pulses.…”

Section: Discussionmentioning

confidence: 99%

“…Optical studies have been used to record the oscillation of contrast agents and investigate destructive mechanisms [1][2][3][4]. Acoustical observations of single microbubbles have been used to design new detection and imaging strategies [5][6][7][8], however, a system which records optical and acoustical observations simultaneously has not previously been reported and was the subject of this study.…”

Section: Introductionmentioning

confidence: 99%

Observation of contrast agent response to chirp insonation with a simultaneous optical-acoustical system

Sun¹,

Zhao²,

Dayton³

et al. 2006

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

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Rayleigh-Plesset analysis, ultra-high speed photography, and single bubble acoustical recordings have previously been applied independently to characterize the radial oscillation and resulting echoes from a microbubble in response to an ultrasonic pulse. In addition, high speed photography has shown that microbubbles are destroyed over a single pulse or pulse train by diffusion and fragmentation. In order to develop a single model to characterize microbubble echoes based on oscillatory and destructive characteristics, an optical-acoustical system was developed to simultaneously record the optical image and backscattered echo from each microbubble. Combined observation provides the opportunity to compare predictions for oscillation and echoes with experimental results and identify discrepancies due to diffusion or fragmentation. Optimization of agents and insonating pulse parameters may be facilitated with this system. The mean correlation of the predicted and experimental radius-time curves and echoes exceeds 0.7 for the parameters studied here. An important application of this new system is to record and analyze microbubble response to a long pulse where diffusion is shown to occur over the pulse duration. The microbubble response to an increasing or decreasing chirp is evaluated using this new tool. For chirp insonation beginning with the lower center frequency, low frequency modulation of the oscillation envelope was obvious. However, low frequency modulation was not observed in the radial oscillation produced by decreasing chirp insonation. Comparison of the echoes from similar sized microbubbles following increasing and decreasing chirp insonation demonstrated that the echoes were not time-reversed replicas. Using a transmission pressure of 620 kPa, the −6 dB echo length was 0.9 and 1.1 μs for increasing and decreasing chirp insonation, respectively (P = 0.02). The mean power in the low frequency portion of the echoes was 8 (mV) 2 and 13 (mV) 2 for increasing and decreasing chirp insonation, respectively, (P = 0.01).

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Encapsulated microbubbles and echogenic liposomes for contrast ultrasound imaging and targeted drug delivery

et al. 2014

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Micron- to nanometer-sized ultrasound agents, like encapsulated microbubbles and echogenic liposomes, are being developed for diagnostic imaging and ultrasound mediated drug/gene delivery. This review provides an overview of the current state of the art of the mathematical models of the acoustic behavior of ultrasound contrast microbubbles. We also present a review of the in vitro experimental characterization of the acoustic properties of microbubble based contrast agents undertaken in our laboratory. The hierarchical two-pronged approach of modeling contrast agents we developed is demonstrated for a lipid coated (Sonazoid™) and a polymer shelled (poly D-L-lactic acid) contrast microbubbles. The acoustic and drug release properties of the newly developed echogenic liposomes are discussed for their use as simultaneous imaging and drug/gene delivery agents. Although echogenicity is conclusively demonstrated in experiments, its physical mechanisms remain uncertain. Addressing questions raised here will accelerate further development and eventual clinical approval of these novel technologies.

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Absolute measurement of ultrasonic backscatter from single microbubbles

Cited by 46 publications

References 25 publications

Accuracy of a bistatic scattering substitution technique for calibration of focused receivers

Accuracy of a bistatic scattering substitution technique for calibration of focused receivers

Observation of contrast agent response to chirp insonation with a simultaneous optical-acoustical system

Encapsulated microbubbles and echogenic liposomes for contrast ultrasound imaging and targeted drug delivery

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