A process for the preparation of beads including a biocompatible hydrophobic polymer, a perfluorocarbon, polyvinylalcohol and optionally a metal compound, including the steps of: adding the perfluorocarbon and optionally the metal compound to a solution of the biocompatible hydrophobic polymer in a polar solvent to provide a first liquid mixture, adding the first liquid mixture to an aqueous solution of a biocompatible surfactant including polyvinylalcohol under sonication to obtain a second liquid mixture, a) maintaining the sonication of the second liquid mixture while cooling, b) evaporating the polar solvent from the second liquid mixture to obtain a suspension of beads including the biocompatible hydrophobic polymer, the perfluorocarbon and optionally the metal compound, c) separating the beads from the suspension and preparing a water suspension of the beads and d) freeze-drying the water suspension to obtain the beads, wherein the addition of the first liquid mixture to the biocompatible surfactant in step b) is performed within a period of at most 10 seconds, wherein the sonication in step b) and the sonication in step c) are performed directly into the liquid mixtures by for example a probe or flow sonicator at an amplitude of at least 120 μm for 0.01-10 minutes and wherein the weight ratio of the biocompatible surfactant to the biocompatible hydrophobic polymer is at least 3:1. Beads having close F—H2O interactions, which are suitable for imaging purposes.

Method for ultrasonic characterization of a medium, including generating a series of incident ultrasonic waves, generating an experimental reflection matrix R.sub.ui(t) defined between the emission basis (i) as input and a reception basis (u) as output, and determining a focused reflection matrix RFoc(r.sub.in, r.sub.out, δt) of the medium between an input virtual transducer (TV.sub.in) calculated based on a focusing as input to the experimental reflection matrix and an output virtual transducer (TV.sub.out) calculated based on a focusing as output from the experimental reflection matrix, the responses of the output virtual transducer (TV.sub.out) being obtained at a time instant that is shifted by an additional delay Ot relative to a time instant of the responses of the input virtual transducer (TV.sub.in).

Method for ultrasonic characterization of a medium, comprising generating a series of incident ultrasonic waves, generating an experimental reflection matrix R.sub.ui(t) defined between the emission basis (i) as input and a reception basis (u) as output, determining a focused reflection matrix RFoc(r.sub.in, r.sub.out, δt) of the medium between an input virtual transducer (TV.sub.in) calculated based on a focusing as input to the experimental reflection matrix and an output virtual transducer (TV.sub.out) calculated based on a focusing as output from the experimental reflection matrix, the responses of the output virtual transducer (TV.sub.out) being obtained at a time instant that is shifted by an additional delay δt relative to a time instant of the responses of the input virtual transducer (TV.sub.in).

Method for ultrasonic characterization of a medium, comprising generating a series of incident ultrasonic waves, generating an experimental reflection matrix R.sub.ui(t) defined between the emission basis (i) as input and a reception basis (u) as output, and determining a focused reflection matrix RFoc(r.sub.in, r.sub.out, δt) of the medium between an input virtual transducer (TV.sub.in) calculated based on a focusing as input to the experimental reflection matrix and an output virtual transducer (TV.sub.out) calculated based on a focusing as output from the experimental reflection matrix, the responses of the output virtual transducer (TV.sub.out) being obtained at a time instant that is shifted by an additional delay δt relative to a time instant of the responses of the input virtual transducer (TV.sub.in).

An imaging device includes a transducer that includes an array of piezoelectric elements formed on a substrate. Each piezoelectric element includes at least one membrane suspended from the substrate, at least one bottom electrode disposed on the membrane, at least one piezoelectric layer disposed on the bottom electrode, and at least one top electrode disposed on the at least one piezoelectric layer. Adjacent piezoelectric elements are configured to be isolated acoustically from each other. The device is utilized to measure flow or flow along with imaging anatomy.

Aspects of the technology described herein relate to built-in self-testing (BIST) of circuitry (e.g., a pulser or receive circuitry) and/or transducers in an ultrasound device. A BIST circuit may include a transconductance amplifier coupled between a pulser and receive circuitry, a capacitor network coupled between a pulser and receive circuitry, and/or a current source couplable to the input terminal of receive circuitry to which a transducer is also couplable. The collapse voltages of transducers may be characterized using BIST circuitry, and a bias voltage may be applied to the membranes of the transducers based at least in part on their collapse voltages. The capacitances of transducers may also be measured using BIST circuitry and a notification may be generated based on the sets of measurements.

Aspects of the technology described herein relate to built-in self-testing (BIST) of circuitry (e.g., a pulser or receive circuitry) and/or transducers in an ultrasound device. A BIST circuit may include a transconductance amplifier coupled between a pulser and receive circuitry, a capacitor network coupled between a pulser and receive circuitry, and/or a current source couplable to the input terminal of receive circuitry to which a transducer is also couplable. The collapse voltages of transducers may be characterized using BIST circuitry, and a bias voltage may be applied to the membranes of the transducers based at least in part on their collapse voltages. The capacitances of transducers may also be measured using BIST circuitry and a notification may be generated based on the sets of measurements.

Described herein are methods and apparatuses for packaging an ultrasound-on-a-chip. An ultrasound-on-a-chip may be coupled to a redistribution layer and to an interposer layer. Encapsulation may encapsulate the ultrasound-on-a-chip device and first metal pillars may extend through the encapsulation and electrically couple to the redistribution layer. Second metal pillars may extend through the interposer layer. The interposer layer may include aluminum nitride. The first metal pillars may be electrically coupled to the second metal pillars. A printed circuit board may be coupled to the interposer layer.

Systems and methods for performing shear wave elastography using push and/or detection ultrasound beams that are generated by subsets of the available number of transducer elements in an ultrasound transducer. These techniques provide several advantages over currently available approaches to shear wave elastography, including the ability to use a standard, low frame rate ultrasound imaging system and the ability to measure shear wave speed throughout the entire field-of-view rather than only those regions where the push beams are not generated.

The subject disclosure presents systems and computer-implemented methods for determining an acoustic time-of-flight (TOF) of sound waves through a sample material with greater accuracy and in a more repeatable fashion, by invoking one or more of an envelope generation for an error function, fitting a non-linear curve to an ultrasound frequency sweep, or performing a clustered piece-wise linear regression on individual linear parts of the ultrasonic frequency sweep. The systems and methods are useful for, among other things, monitoring diffusion of fluids through porous materials, such as tissue samples.