Ultrasonic blood vessel measurement apparatus and method
First Claim
1. A method for characterizing a blood vessel, having adventitia, media, and intima regions surrounding a lumen, by measuring the apparent intima-media thickness, the method comprising:
- providing an image of a blood vessel, the image having a longitudinal direction substantially corresponding to an axial direction of a blood vessel, a lateral direction substantially orthogonal thereto, and comprising pixels each having an intensity associated therewith;
selecting a series of longitudinal positions and finding for each longitudinal position thereof the brightest pixel, having the greatest value of intensity with respect to other pixels positioned laterally therefrom;
defining an adventitia datum by fitting a first curve to the lateral positions of the brightest pixels over a domain of the longitudinal positions;
defining a lumen datum by fitting a second curve to lateral locations of the lumen substantially closest toward the adventitia and corresponding to the longitudinal positions;
defining a media datum by fitting a third curve to pixels, a plurality of which correspond to the location of local minima distributed in a longitudinal direction and positioned between the lumen datum and the adventitia datum;
locating the lumen-intima boundary, extending along the longitudinal direction, as the lateral location of local steepest ascent of intensity in a traverse from the lumen datum toward the media datum;
locating the media-adventitia boundary, extending along the longitudinal direction, as the lateral location of local steepest ascent in intensity in a traverse from the media datum toward the adventitia datum; and
calculating the intima-media thickness as the lateral distance between the lumen-intima boundary and the media-adventitia boundary.
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Abstract
An apparatus and method for determining the apparent intima-media thickness (IMT) of arteries through acquisition and analysis of ultrasound images comprising an array of pixel intensities. An acquired image may be referenced, determining threshold values relating to the intensity of pixels forming images of portions of an artery wall, particularly the lumen, media, and adventitia. A datum, or datums, may be established across multiple columns of pixels bounding the portion of the image containing either the lumen/intima boundary, the media/adventitia boundary, or both. The datums may be approximate the shape of one more of the lumen, intima, media, and adventitia. Within a bounded portion of the image, a method may search for intensity gradients having characteristics indicating the gradients represent probable locations of the lumen/intima and media/adventitia boundaries. A valid gradient may be identified by its proximity to a characteristic point on a graph of pixel intensities or to a datum line, by an intensity above or below a threshold, or both. An IMT measurement is calculated based on the location of the lumen/intima and media/adventitia boundaries. An IMT measurement may be adjusted for sloping or tapering of an artery wall. Taper adjustment may be accomplished by normalizing an IMT measurement based on a compiled database of IMT measurements relating the amount of taper with respect to location to characteristic IMT values.
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Citations
41 Claims
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1. A method for characterizing a blood vessel, having adventitia, media, and intima regions surrounding a lumen, by measuring the apparent intima-media thickness, the method comprising:
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providing an image of a blood vessel, the image having a longitudinal direction substantially corresponding to an axial direction of a blood vessel, a lateral direction substantially orthogonal thereto, and comprising pixels each having an intensity associated therewith;
selecting a series of longitudinal positions and finding for each longitudinal position thereof the brightest pixel, having the greatest value of intensity with respect to other pixels positioned laterally therefrom;
defining an adventitia datum by fitting a first curve to the lateral positions of the brightest pixels over a domain of the longitudinal positions;
defining a lumen datum by fitting a second curve to lateral locations of the lumen substantially closest toward the adventitia and corresponding to the longitudinal positions;
defining a media datum by fitting a third curve to pixels, a plurality of which correspond to the location of local minima distributed in a longitudinal direction and positioned between the lumen datum and the adventitia datum;
locating the lumen-intima boundary, extending along the longitudinal direction, as the lateral location of local steepest ascent of intensity in a traverse from the lumen datum toward the media datum;
locating the media-adventitia boundary, extending along the longitudinal direction, as the lateral location of local steepest ascent in intensity in a traverse from the media datum toward the adventitia datum; and
calculating the intima-media thickness as the lateral distance between the lumen-intima boundary and the media-adventitia boundary. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28)
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29. A method for finding an intima-media thickness associated with a blood vessel, the method comprising:
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providing an image having a longitudinal direction substantially corresponding to an axial direction of a blood vessel and a lateral direction across the axial direction;
the image further comprising locations distributed longitudinally and laterally, each location having an intensity associated therewith and positioned at a unique combination of lateral and longitudinal locations;
selecting a series of longitudinal positions along the longitudinal direction and determining for each such longitudinal position a lateral position at which the image has the greatest intensity;
defining an adventitia datum by fitting a first curve to a range of the lateral positions and a domain of the longitudinal positions;
determining the lateral location of the lumen by identifying for at least one of the longitudinal positions a position corresponding to the lumen;
locating the lumen-intima boundary, extending along the longitudinal direction, as the lateral location of local steepest ascent in intensity, proximate the lateral location of the lumen, in a traverse from the lateral location of the lumen toward the adventitia datum;
locating the media-adventitia boundary, at a plurality of the series of longitudinal positions, as the lateral location of local steepest ascent in intensity, proximate the adventitia datum, in a traverse from the lateral location of the lumen toward the adventitia datum;
calculating the intima-media thickness as the lateral distance between the lumen-intima boundary and the media-adventitia boundary. - View Dependent Claims (30, 31, 32, 33, 34, 35, 36, 37, 38, 39)
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40. A method for finding an intima-media thickness associated with a blood vessel, the method comprising:
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providing an image having a longitudinal direction substantially corresponding to an axial direction of a blood vessel and a lateral direction across the axial direction, and comprising locations, distributed longitudinally and laterally, uniquely positioned, and each having an intensity associated therewith;
selecting a series of longitudinal positions along the longitudinal direction and determining for each such longitudinal position a lateral position at which the image has the greatest intensity;
defining an adventitia datum by fitting a first curve to a range of the lateral positions and a domain of the longitudinal positions;
determining the lateral location of the lumen with respect to the adventitia datum;
defining a lumen-intima boundary, and a media-adventitia boundary between the adventitia datum and the lumen;
calculating the intima-media thickness as the lateral distance between the lumen-intima boundary and the media-adventitia boundary.
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41. A method for measuring the apparent intima-media thickness of an artery, the method comprising:
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Providing an image of an artery wall having lumen, intima, media, and adventitia layers, the image comprising an array of pixels each having an intensity associated therewith and defining rows and columns of pixels with each column defining a longitudinal position and extending across lumen, intima, media, and adventitia layers and with each row defining a lateral position;
identifying an adventitia datum corresponding a curve fit to the lateral position of high intensity pixels in a plurality of columns;
identifying a bounding location, with portions of the lumen, intima, media bounded laterally between the bounding location and the adventitia datum;
identifying a first relatively large intensity gradient proximate the adventitia datum, in a plurality of columns, between the adventitia datum and the bounding location;
identifying a second relatively large intensity gradient proximate the bounding location, in a plurality of columns, between the adventitia datum and the bounding location;
calculating for each of a plurality of columns the lateral distance between the two intensity gradients; and
deriving from the lateral distances a value reflecting an intima-media thickness measurement.
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Specification