Pulse centroid echo method and apparatus for enhanced sound velocity estimation in vivo

Claim 1

I. A method of enhancing the accuracy of in vivo sound velocity estimation in organic tissue along a transducer generated tracked ultrasound beam, characterized by the steps of: (a) applying ultrasound transducers to the outer skin of a body containing said organic tissue; (b) partitioning said tracked beam into a plurality of contiguous segments, each segment having an estimated average velocity substantially different from its adjacent neighbor segments; (c) intersecting said tracked beam with a plurality of transducer generated tracking ultrasound beams, said tracking beams being substantially parallel, an angle of incidence between said tracked beam and a line normal to said tracking beams being varied through a plurality of values; (d) employing a means for measuring the energy and time duration of pulses produced by said ultrasound transducers; (e) determining the location of the centroids of the pulses produced by said ultrasound transducers; (f) measuring a first travel time for a pulse of ultrasound energy to travel between the ultrasound transducer producing the first tracking beam and the ultrasound transducer producing the tracked beam, based upon the baseline-to-centroid distance, on a time scale, of the pulses produced by said transducers; (g) measuring a second travel time for a pulse of ultrasound energy to travel between the ultrasound transducer producing the second tracking beam and the ultrasound transducer producing the tracked beam, based upon the baseline-to-centroid distance, on a time scale, of the pulses produced by said transducers; (h) computing the difference between said first and second travel :'mes; (i) repeating steps (a) through (h) for each of a plurality of preselected values for the angle of incidence; and (j) fitting the plurality of data pairs so derived to the equation:

Claim 2

A method of enhancing the accuracy of in vivo sound velocity estimation in organic tissue along a transducer generated tracked ultrasound beam, characterized by the steps of: (a) applying ultrasound transducers to the outer skin of a body containing said organic tissue; (b) partitioning said tracked beam into a plurality of contiguous segments, each segment having an estimated average velocity substantially different from its adjacent neighbor segments; (c) intersecting said tracked beam with a plurality of transducer generated tracking ultrasound beams, said tracking beams being substantially parallel, an angle of incidence between said tracked beam and a line normal to said tracking beams being varied through a plurality of values; (d) employing a means for measuring the energy and time duration of pulses produced by said ultrasound transducers; (e) determining the location of the centroids of the pulses produced by said ultrasound transducers; (f) measuring a first travel time for a pulse of ultrasound energy to travel between the ultrasound transducer producing the first tracking beam and the ultrasound transducer producing the tracked beam, based upon the baseline-to-centroid distance, on a time scale, of the pulses produced by said transducers; (g) measuring a second travel time for a pulse of ultrasound energy to travel between the ultrasound transducer producing the second tracking beam and the ultrasound transducer producing the tracked beam, based upon the baseline-to-centroid distance, on a time scale, of the pulses produced by said transducers; (h) computing the difference between said first and second travel times; (i) repeating steps (a) through (h) for each of a plurality of preselected values for the angle of incidence; (j) computing the average of said travel time differences; (k) recording the average of said travel time differences together with the value of said angle of incidents to form a data pair; (I) repeating steps (a) through (k) for a plurality of values of said angle of incidence; and (m) fitting the plurality of data pairs to the equation:

Claim 6

A method of enhancing the accuracy of in vivo sound velocity estimations in organic tissue along a transducer generated tracked ultrasound beam, characterized by the steps of: (a) measuring a time required for an ultrasound pulse to travel a distance along said tracked beam, based upon the baseline-to-centroid distance, on a time scale, of pulses produced by said tracking beam transducer and said tracked beam transducer; (b) recording said time together with said distance travelled to form a data pair; (c) repeating steps (a) and (b) whereby a plurality of data pairs are recorded; (d) plotting said data pairs; (e) determining the number of stair steps present in said plot; and (f) estimating the number of scatterers in the tissue from the number of stair steps.

Claim 12

A method of enhancing the accuracy of in vivo sound velocity estimation in organic tissue along a transducer generated tracked ultrasound beam, characterized by the steps of: (a) applying ultrasound transducers to the outer skin of a body containing said organic tissue; (b) partitioning said tracked beam into a plurality of contiguous segments, each segment having an estimated average velocity substantially different from its adjacent neighbor segments; (c) intersecting said tracked beam with a plurality of transducer generated tracking ultrasound beams, said tracking beams being substantially parallel, an angle of incidence between said tracked beam and a line normal to said tracking beams being varied through a plurality of values; (d) employing a means for measuring the energy and time duration of pulses produced by said ultrasound transducers; (e) determining the location of the centroids of the pulses produced by said ultrasound transducers; (f) measuring a first travel time for a pulse of ultrasound energy to travel between the ultrasound transducer producing the first tracking beam and the ultrasound transducer producing the tracked beam, based upon the baseline-to-centroid distance, on a time scale, of the pulses produced by said transducers; (g) measuring an undistorted apparent thickness of a tissue layer in a region of said tissue from an ultrasound image of said region; (h) injecting an acoustical contrast fluid into said region; (i) measuring a distorted apparent thickness of said tissue layer from the ultrasound image of said region; and (j) deriving the volumetric concentration of said acoustical contrast fluid using the equation:

Claim 17

A method of enhancing the accuracy of in vivo sound velocity estimation in organic tissue along a transducer generated tracked ultrasound beam, characterized by the steps of: (a) measuring the velocity of sound within a tissue region in the absence of acoustical contrast fluid, based upon the baseline-to-centroid distance, on a time scale, of the pulses produced by beam generating transducers; (b) injecting said region with an acoustical contrast liquid that is nontoxic to said tissue and in which the speed of sound is substantially known; (c) measuring the velocity of sound in said region based upon the baseline-to-centroid distance, on a time scale, of the pulses produced by said transducers; and (d) deriving the volumetric concentration of said acoustical contrast fluid using the equation:

Claim 18

An apparatus for estimating the velocity of sound in a region of interest in organic tissue, characterized by: (a) an electronic pulse generator adapted to produce an output of electronic pulses of a duration of between about 0.25 microseconds to about 5 microseconds; (b) an array of transmitting ultrasound transducers adapted to transmit pulses of ultrasound to a plurality of reflection points in said region, said array of transmitting ultrasound transducers having a plurality of transducer elements; (c) transmitting switching means adapted to connect a selected transducer element of the array of transmitting ultrasound transducers to the output of the electronic pulse generator; (d) an array of receiving ultrasound transducers adapted to receive ultrasound energy scattered from said reflection points responsive to pulses of ultrasound energy transmitted to said reflection points by said array of transmitting transducers, said array of receiving ultrasound transducers having a plurality of transducer elements, each transducer element of said array of said receiving ultrasound transducers having an electronic output; (e) receiving switching means adapted to select the output of one of the transducer elements of said array of receiving ultrasound transducers; (f) observing means adapted to observe the output of the transducer element of said array of receiving ultrasound transducers selected by said receiving switching means, said observing means further adapted to observing the output of the electronic pulse generator; (g) positioning means adapted to position said arrays, said electronic pulse generator emitting an electronic pulse to the transducers element selected by said transmitting switching means, said selected transducer element transmitting a pulse of ultrasound energy to a reflection point on said straight segment, the ultrasound energy scattered from said reflection point arriving at the transducer element selected by said receiving switching means whereby an electronic pulse is produced at the output of said transducer element selected by said receiving switching means, said observing means adapted to display the time interval represented by the baseline-to-centroid distance of said pulses; and (h) a means of determining the centroids of said electronic pulses.