Quadrature excitation and fresnel focusing of row-column transducer arrays

A system for generating focused ultrasound, the system comprising:

• a row-column ultrasound transducer comprising:
• a two-dimensional array of ultrasound elements arranged in a diamond pattern defining a set of rows and columns, such that for a given transducer element, a row associated with the given transducer element extends along a first axis connecting a first pair of opposing vertices of the given transducer element, and a column associated with the given transducer element extends along a second axis connecting a second pair of opposing vertices of the given transducer element, each ultrasound element being capable of acoustic transduction when a bias is applied thereto, such that a phase of ultrasound waves emitted therefrom is dependent on a polarity of the bias;
• a set of signal conductive paths, each signal conductive path extending along a respective column of the two-dimensional array and being in electrical communication with signal electrodes of ultrasound elements of the respective column, said set of signal conductive paths comprising a set of odd signal conductive paths and a set of even signal conductive paths, wherein each even signal conductive path extends along a respective even column of the diamond pattern and each odd signal conductive path extends along a respective odd column of the diamond pattern;
• and
• a set of bias conductive paths, each bias conductive path extending along a respective row of the two-dimensional array and being in electrical communication with bias electrodes of ultrasound elements of the respective row, said set of bias conductive paths comprising a set of odd bias conductive paths and a set of even bias conductive paths, wherein each even bias conductive path extends along a respective even row of the diamond pattern and each odd bias conductive path extends along a respective odd row of the diamond pattern;
• and
• control and processing circuitry operatively coupled to said set of signal conductive paths and said set of bias conductive paths, said control and processing circuitry comprising at least one processor and associated memory, said memory comprising instructions executable by said processor to perform a transmit operation comprising:
• applying a first bias aperture to said set of odd bias conductive paths and a second bias aperture to said set of even bias conductive paths, the first bias aperture comprising a set of first bias values and the second bias aperture comprising a corresponding set of second bias values;
• and
• while applying the first bias aperture and the second bias aperture, delivering, to said set of odd signal conductive paths and said set of even signal conductive paths, a set of transmit signals defined according to a time-delay aperture, wherein set of transmit signals are provided to said set of even signal conductive paths in quadrature;
• the set of first bias values and the corresponding set of second bias values being configured such that the transmit operation results in the generation of a synthetic Fresnel aperture.

A system for generating focused ultrasound, the system comprising:

• a row-column ultrasound transducer comprising:
• a two-dimensional array of ultrasound elements arranged along a plurality of rows and columns;
• within each row, each ultrasound element comprising a first sub-element and a second sub-element residing laterally adjacent to one another, each sub-element being capable of acoustic transduction when a bias is applied thereto, such that a phase of ultrasound waves emitted therefrom is dependent on a polarity of the bias, such that each column of the two-dimensional array comprises a first sub-column of first sub-elements and a second sub-column column of second sub-elements;
• a set of signal conductive paths, each signal conductive path being in electrical communication with signal electrodes of ultrasound elements residing along a respective sub-column of the two-dimensional array, such that the first sub-column and second sub-column within a given column are separately addressable by respective first and second signal conductive paths;
• and
• a set of bias conductive path pairs, each bias conductive path pair comprising a first bias conductive path and a second bias conductive path that both extend along or adjacent to a given row of the two-dimensional array such that said first bias conductive path is configured to apply a respective bias to the first sub-elements with the given row and said second bias conductive path is configured to apply a respective bias to the second sub-elements within the given row;
• and
• control and processing circuitry operatively coupled to said signal conductive paths and said set of bias conductive path pairs, said control and processing circuitry comprising at least one processor and associated memory, said memory comprising instructions executable by said processor to perform a transmit operation comprising:
• applying a first bias aperture to said first bias conductive paths and a second bias aperture to said second bias conductive paths, the first bias aperture comprising a set of first bias values and the second bias aperture comprising a corresponding set of second bias values;
• and
• while applying the first bias aperture and the second bias aperture, delivering a set of transmit signals to said signal conductive paths according to a time-delay aperture, such that the time-delay aperture defines transmit beamforming time delays associated with each column of the two-dimensional array, and such that for a given column having a respective beamforming time delay associated therewith, the transmit signal delivered to the first sub-column and the second sub-column have a common temporal envelope temporally delayed according to the beamforming delay, and wherein a waveform phase of the second sub-column is shifted, relative to that of the first sub-column, by pi/2, the first sub-column and the second sub-column of a given column thereby being delivered beamformed transmit signals in quadrature;
• the set of first bias values and the corresponding set of second bias values being configured such that the transmit operation results in the generation of a Fresnel aperture.

A method of performing ultrasound imaging, the method comprising:

• providing a row-column ultrasound transducer comprising:
• a two-dimensional array of ultrasound elements arranged along a plurality of rows and columns, each ultrasound element being capable of acoustic transduction when a bias is applied thereto, such that a phase of ultrasound waves emitted therefrom is dependent on a polarity of the bias;
• a set of signal conductive paths, each signal conductive path being in electrical communication with signal electrodes of ultrasound elements residing along a respective column of the two-dimensional array;
• and
• a set of bias conductive paths, each bias conductive path being in electrical communication with bias electrodes of ultrasound elements residing along a respective row of the two-dimensional array;
• and
• performing, in a selected temporal order, a set of synthetic transmit and receive operations comprising:
• a first transmit operation and first receive operation performed by:
• while applying a first transmit bias aperture to said bias conductive paths, delivering a first set of transmit signals to said signal conductive paths;
• and
• while applying a first receive bias aperture to said bias conductive paths, receiving a first set of receive signals from said signal conductive paths;
• a second transmit operation and second receive operation performed by:
• while applying the first transmit bias aperture to said bias conductive paths, delivering a second set of transmit signals to said signal conductive paths, the second set of transmit signals being generated according to a driving waveform that is in phase with a corresponding driving waveform employed to generate the first set of transmit signals;
• while applying a second receive bias aperture to said bias conductive paths, receiving a second set of receive signals from said signal conductive paths;
• and
• applying a time delay to the second set of received signals, the time delay corresponding to a phase delay of pi/2
• a third transmit operation and third receive operation performed by:
• while applying a second transmit bias aperture to said bias conductive paths, delivering a third set of transmit signals to said signal conductive paths, the third set of transmit signals being generated according to a driving waveform that is phase shifted, relative to a corresponding driving waveform employed to generate the first set of transmit signals, by pi/2;
• and
• while applying the first receive bias aperture to said bias conductive paths, receiving a third set of receive signals from said signal conductive paths;
• and
• a fourth transmit operation and fourth receive operation performed by:
• while applying the second transmit bias aperture to said bias conductive paths, delivering a fourth set of transmit signals to said signal conductive paths, the fourth set of transmit signals being generated according to a driving waveform that is phase shifted, relative to a corresponding driving waveform employed to generate the first set of transmit signals, by pi/2;
• while applying the second receive bias aperture to said bias conductive paths, receiving a fourth set of receive signals from said signal conductive paths;
• and
• applying a time delay to the fourth set of received signals, the time delay corresponding to a phase delay of pi/2;
• summing the first, second, third and fourth sets of receive signals to obtain a summed set of receive signals;
• and
• beamforming the summed set of receive signals in the azimuth dimension to generate an image;
• wherein the first set of transmit signals, the second set of transmit signals, the third set of transmit signals and the fourth set of transmit signals are selected such that the resulting plurality of ultrasound pulses generated therefrom spatially overlap with each other in a far field region;
• wherein the first transmit bias aperture and the second transmit bias aperture are configured to generate a synthetic transmit Fresnel aperture when the set of synthetic transmit and receive operations are compounded;
• and
• wherein the first receive bias aperture and the second receive bias aperture are configured to generate a synthetic receive Fresnel aperture when the set of synthetic transmit and receive operations are compounded.

A method of generating focused ultrasound, the method comprising:

• providing a row-column ultrasound transducer comprising:
• a two-dimensional array of ultrasound elements arranged in a diamond pattern defining a set of rows and columns, such that for a given transducer element, a row associated with the given transducer element extends along a first axis connecting a first pair of opposing vertices of the given transducer element, and a column associated with the given transducer element extends along a second axis connecting a second pair of opposing vertices of the given transducer element, each ultrasound element being capable of acoustic transduction when a bias is applied thereto, such that a phase of ultrasound waves emitted therefrom is dependent on a polarity of the bias;
• a set of signal conductive paths, each signal conductive path extending along a respective column of the two-dimensional array and being in electrical communication with signal electrodes of ultrasound elements of the respective column, said set of signal conductive paths comprising a set of odd signal conductive paths and a set of even signal conductive paths, wherein each even signal conductive path extends along a respective even column of the diamond pattern and each odd signal conductive path extends along a respective odd column of the diamond pattern;
• and
• a set of bias conductive paths, each bias conductive path extending along a respective row of the two-dimensional array and being in electrical communication with bias electrodes of ultrasound elements of the respective row, said set of bias conductive paths comprising a set of odd bias conductive paths and a set of even bias conductive paths, wherein each even bias conductive path extends along a respective even row of the diamond pattern and each odd bias conductive path extends along a respective odd row of the diamond pattern;
• and
• applying a first bias aperture to said set of odd bias conductive paths and a second bias aperture to said set of even bias conductive paths, the first bias aperture comprising a set of first bias values and the second bias aperture comprising a corresponding set of second bias values;
• and
• while applying the first bias aperture and the second bias aperture, delivering, to said set of odd signal conductive paths and said set of even signal conductive paths, a set of transmit signals defined according to a time-delay aperture, wherein set of transmit signals are provided to said set of even signal conductive paths in quadrature;
• wherein the set of first bias values and the corresponding set of second bias values are configured such that the transmit operation results in the generation of a synthetic Fresnel aperture.

A method of generating focused ultrasound, the method comprising:

• providing a row-column ultrasound transducer comprising:
• a two-dimensional array of ultrasound elements arranged along a plurality of rows and columns;
• within each row, each ultrasound element comprising a first sub-element and a second sub-element residing laterally adjacent to one another, each sub-element being capable of acoustic transduction when a bias is applied thereto, such that a phase of ultrasound waves emitted therefrom is dependent on a polarity of the bias, such that each column of the two-dimensional array comprises a first sub-column of first sub-elements and a second sub-column column of second sub-elements;
• a set of signal conductive paths, each signal conductive path being in electrical communication with signal electrodes of ultrasound elements residing along a respective sub-column of the two-dimensional array, such that the first sub-column and second sub-column within a given column are separately addressable by respective first and second signal conductive paths;
• and
• a set of bias conductive path pairs, each bias conductive path pair comprising a first bias conductive path and a second bias conductive path that both extend along or adjacent to a given row of the two-dimensional array such that said first bias conductive path is configured to apply a respective bias to the first sub-elements with the given row and said second bias conductive path is configured to apply a respective bias to the second sub-elements within the given row;
• and
• applying a first bias aperture to said first bias conductive paths and a second bias aperture to said second bias conductive paths, the first bias aperture comprising a set of first bias values and the second bias aperture comprising a corresponding set of second bias values;
• and
• while applying the first bias aperture and the second bias aperture, delivering a set of transmit signals to said signal conductive paths according to a time-delay aperture, such that the time-delay aperture defines transmit beamforming time delays associated with each column of the two-dimensional array, and such that for a given column having a respective beamforming time delay associated therewith, the transmit signal delivered to the first sub-column and the second sub-column have a common temporal envelope temporally delayed according to the beamforming delay, and wherein a waveform phase of the second sub-column is shifted, relative to that of the first sub-column, by pi/2, the first sub-column and the second sub-column of a given column thereby being delivered beamformed transmit signals in quadrature;
• wherein the set of first bias values and the corresponding set of second bias values are configured such that the transmit operation results in the generation of a Fresnel aperture.