Method and apparatus for elastographic measurement and imaging
First Claim
1. A method for taking elastographic measurements of a heterogeneous target body comprising the steps of:
- (a) sonically coupling an ultrasonic source to the surface of a target body;
(b) emitting a first pulse of ultrasonic energy from the source along a radiation axis in the target body;
(c) recording the arrival time of the first echo sequence having at least one echo segment arriving in response to said first pulse of ultrasonic energy;
(d) displacing the surface of the target body a known displacement, Δ
X, along a force axis so as to compress the target body;
(e) emitting a next pulse of ultrasonic energy from the source along said radiation axis in the target body following said movement;
(f) recording the arrival time of a next echo sequence arriving in response to said next pulse of ultrasonic energy, said echo sequence having at least one echo segment that is congruent with at least one said echo segment that arrived in response to the preceding pulse;
(g) measuring the differential displacement from at least one congruent echo segment of the two most recent pulses of ultrasonic energy;
(h) calculating the strain from the differential displacement data obtained in step (g);
(i) storing strain data that meets a predetermined quality standard in a retrievable medium;
(j) normalizing the calculated strain data stored in step (i) using the formula;
NSn =CSn /n where;
NSn =normalized strain at displacement interval nCSn =calculated strain at displacement interval n; and
(k) repeating steps (d)-(j) until enough strain data has been stored to produce an image of the tissue body region under interrogation.
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Abstract
An improved ultrasonic pulse-echo method and apparatus that has particular application in making precision measurements of compressibility in any backscattering material, in particular organic tissue, is disclosed. The method employs a standard transducer or transducer containing device which is translated transaxially, thereby compressing or displacing a proximal region of a target body in small known increments. At each increment, a pulse is emitted and an echo sequence (A-line) is detected from regions within the target along the sonic travel path or beam of the transducer. Resulting time shifts in echo segments corresponding to features in the target, corrected for regions of varying sonic speed along the sonic path, provide relative and quantitative information concerning the strain caused by the compressions. The stress imparted by the transducer and containing device is also determined, corrected for depth along the sonic path. The appropriate values for stress are divided into the respective values for strain along each path to yield an elastogram, or array of compressibility values, of the target.
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Citations
20 Claims
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1. A method for taking elastographic measurements of a heterogeneous target body comprising the steps of:
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(a) sonically coupling an ultrasonic source to the surface of a target body; (b) emitting a first pulse of ultrasonic energy from the source along a radiation axis in the target body; (c) recording the arrival time of the first echo sequence having at least one echo segment arriving in response to said first pulse of ultrasonic energy; (d) displacing the surface of the target body a known displacement, Δ
X, along a force axis so as to compress the target body;(e) emitting a next pulse of ultrasonic energy from the source along said radiation axis in the target body following said movement; (f) recording the arrival time of a next echo sequence arriving in response to said next pulse of ultrasonic energy, said echo sequence having at least one echo segment that is congruent with at least one said echo segment that arrived in response to the preceding pulse; (g) measuring the differential displacement from at least one congruent echo segment of the two most recent pulses of ultrasonic energy; (h) calculating the strain from the differential displacement data obtained in step (g); (i) storing strain data that meets a predetermined quality standard in a retrievable medium; (j) normalizing the calculated strain data stored in step (i) using the formula; NSn =CSn /n where; NSn =normalized strain at displacement interval n CSn =calculated strain at displacement interval n; and (k) repeating steps (d)-(j) until enough strain data has been stored to produce an image of the tissue body region under interrogation. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. A method for taking elastographic measurements of a heterogeneous target body comprising the steps of:
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(a) sonically coupling an ultrasonic source to a target body; (b) emitting a first pulse of ultrasonic energy from the source along a radiation axis in the target body; (c) recording the arrival time of the first echo sequence having at least one echo segment arriving in response to said first pulse of ultrasonic energy; (d) moving the ultrasonic source a known displacement, Δ
X, along a force axis so as to compress the target body;(e) emitting a next pulse of ultrasonic energy from the source along the radiation axis in the target body following said movement; (f) recording the arrival time of a next echo sequence arriving in response to said next pulse of ultrasonic energy, said echo sequence having at least one echo segment that is congruent with at least one said echo segment that arrived in response to the preceding pulse; (g) measuring the differential displacement from at least one congruent echo segment of the first pulse and most recent pulse of ultrasonic energy; (h) calculating the strain from the differential displacement data obtained in step (g); (i) storing strain data that meets a predetermined quality standard in a retrievable medium; (j) normalizing the calculated strain data stored in step (i) using the formula; NSn =CSn /n where; NSn =normalized strain at displacement interval n CSn =calculated strain at displacement interval n; and (k) repeating steps (d)-(j) until the ultrasonic source has traveled a desired compression distance; (l) moving the ultrasonic source a known displacement, Δ
X, along the force axis so as to decompress the target body;(m) emitting a next pulse of ultrasonic energy from the source along the radiation axis in the target body following said movement; (n) recording the arrival time of a next echo sequence arriving in response to said next pulse of ultrasonic energy, said echo sequence having at least one echo segment that is congruent with at least one said echo segment that arrived in response to the preceding pulse; (o) measuring the strain from at least one congruent echo segment of the first pulse and most recent pulse of ultrasonic energy; (p) calculating the strain from the differential displacement data obtained in step (o); (q) storing strain data that meets a predetermined quality standard in a retrievable medium; (r) normalizing the calculated strain data stored in step (q) using the formula; NSn =CSn /n where; NSn =normalized strain at displacement interval n CSn =calculated strain at displacement interval n; and (s) repeating steps (l)-(r) until the ultrasonic source has traveled a desired decompression distance. - View Dependent Claims (16, 17, 18, 19, 20)
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Specification