Method and apparatus for applying synthetic aperture focusing techniques to a catheter based system for high frequency ultrasound imaging of small vessels
First Claim
1. A method of acquiring a plurality of pulse/echo signals obtained from a corresponding plurality of ultrasound transducer elements for imaging thereof comprising:
- disposing said elements in an array around a catheter for intravascular placement;
providing a pulse capable of exciting said elements;
sequentially sampling said plurality of elements in order to fully multiplex an incrementally stepped contiguous subset thereof operating as a transceiver subarray on each consecutive excitation pulse;
fully multiplexing signals transmitted and received from each sequential transceiver subarray in a parallel manner on each consecutive excitation pulse;
maintaining a consecutively equivalent subarray by incrementally sampling array elements on each excitation pulse; and
dynamically focusing said multiplexed signals by characterizing said transceiver subarray as a subset of a synthetic aperture array;
wherein respective echo signals derived from each excitation pulse are retrospectively time delayed, demodulated into respective complex components, respectively component weighted by complex filtering according to range and summed over said synthetic aperture array.
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Abstract
A catheter based ultrasound imaging system is disclosed which is capable of providing images of coronary vessels at frequencies near 50 MHz. The catheter based system implements a Synthetic Aperture Focusing Technique (SAFT) by scanning through a miniature ultrasound transducer array to sequentially select and fully multiplex a subset of array elements to operate as a sub-aperture of the total synthetic aperture on each firing; thus reducing the number of required catheter interconnections. Each synthetic aperture array is dynamically and retrospectively focused to accommodate precision imaging at high frequency without conventional signal to noise losses.
226 Citations
14 Claims
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1. A method of acquiring a plurality of pulse/echo signals obtained from a corresponding plurality of ultrasound transducer elements for imaging thereof comprising:
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disposing said elements in an array around a catheter for intravascular placement; providing a pulse capable of exciting said elements; sequentially sampling said plurality of elements in order to fully multiplex an incrementally stepped contiguous subset thereof operating as a transceiver subarray on each consecutive excitation pulse; fully multiplexing signals transmitted and received from each sequential transceiver subarray in a parallel manner on each consecutive excitation pulse; maintaining a consecutively equivalent subarray by incrementally sampling array elements on each excitation pulse; and dynamically focusing said multiplexed signals by characterizing said transceiver subarray as a subset of a synthetic aperture array;
wherein respective echo signals derived from each excitation pulse are retrospectively time delayed, demodulated into respective complex components, respectively component weighted by complex filtering according to range and summed over said synthetic aperture array. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. Apparatus for catheter based ultrasound imaging of coronary vessels comprising:
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a plurality of ultrasound transducers disposed about a catheter; a multiplexor disposed in said catheter being controlled by a single cable in order to make parallel connection to a subset of said array elements operating as a transceiver subarray of a synthetic aperture transducer array on each excitation pulse; a controller disposed external to said catheter being coupled to said multiplexor in order to electronically control sampling of said transducer array to selectively connect said subarray thereof for full signal multiplexing said multiplexor being coupled to a transmit/receive switch which amplifies signals on receive only; a summing circuit disposed within said catheter and coupled between said multiplexor and said transmit/receive switch; and imaging electronics disposed external to said catheter. - View Dependent Claims (9, 10, 11, 12, 13, 14)
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Specification