Method for generating time independent images of moving objects

• US 6,909,914 B2
• Filed: 06/13/2003
• Issued: 06/21/2005
• Est. Priority Date: 06/13/2003
• Status: Expired due to Term

• Current Assignee: AMID SRL, Esaote SpA
• Original Assignee: AMID SRL, Esaote SpA
• Inventors: Pedrizzetti, Gianni, Tonti, Giovanni, Marchese, Emidio
• Primary Examiner(s): Casler, Brian L.
• Assistant Examiner(s): JUNG, WILLIAM C
• Application Number:
  US10/461,120
• Publication Number:
  US 20040254440A1
• Time in Patent Office: 739 Days
• Field of Search: 600407-482, 382/162, 382/254, 382/255, 382260-308, 128920-925, 250/455, 348/453
• US Class Current: 600/407
• CPC Class Codes: A61B 5/055 involving electronic [EMR] or nuclear [NMR] magnetic resonance, e.g. magnetic resonance imaging
• CPC Class Codes: A61B 6/503 for diagnosis of the heart
• CPC Class Codes: A61B 8/06 Measuring blood flow measuring volume flow in general G01F, e.g. G01F1/66, G01F1/72; measuring speed of fluids in general G01P5/00
• CPC Class Codes: A61B 8/08 Detecting organic movements or changes, e.g. tumours, cysts, swellings A61B8/02 - A61B8/06 take precedence
• CPC Class Codes: A61B 8/0883 for diagnosis of the heart
• CPC Class Codes: A61B 8/14 Echo-tomography
• CPC Class Codes: A61B 8/488 involving Doppler signals
• CPC Class Codes: G01R 33/563 of moving material, e.g. flow contrast angiography
• CPC Class Codes: G06T 2207/30048 Heart; Cardiac
• CPC Class Codes: G06T 7/20 Analysis of motion motion estimation for coding, decoding, compressing or decompressing digital video signals H04N19/43, H04N19/51
• CPC Class Codes: Y10S 128/923 by comparison of patient data to other data
• CPC Class Codes: Y10S 128/925 Neural network

Abstract

A method for generating time independent images of moving objects with the image information being related to properties of the moving objects represented by sequences of digital images. The images are transformed into a series of space-time representations of the image data. A function is derived from the space-time representation images that approximates the object motion and is used to create time independent images of the moving objects.

Claims

1. A method for generating time independent images of moving objects comprising the following steps:

providing a sequence of digital images of the moving part of an object;

transforming image information of said sequence into a series of space-time images comprised of pixels or groups of pixels on a series of adjacent line-segments, said line-segments being positioned in such a way as to cross the said moving part of said object and being distributed in such a way as to completely cover said moving part of the said object;

aligning said space-time images of each of said line-segments related to different images of said sequence in order to compensate for motion of said moving part of said object along said line-segments by shifting said images of said sequence taken at different times along a given line-segment for a distance corresponding to the displacement of said moving part of said object;

defining an evaluation function having at least one parameter and calculating for each pixel or group of pixels the value of the said parameter for best fitting said evaluation function with a curve representing the values of said pixel or group of pixels obtained from said aligned space-time images; and

constructing a time independent image of said moving object by defining a pixel appearance scale univocally correlated to said at least one parameter and using said evaluation function.

2. The method according to claim 1 characterised in that the pixel values comprise the brightness of a black and white digital image or one or more of variables of a color image.

3. The method according claim 1 characterised in that said alignment of said images along said segment at different times for freezing said motion of said object is carried out in accordance with a statistical algorithm.

4. The method according to claim 1, characterised in that said alignment of said images along said segment at different times for freezing said motion of said object is carried out by means of edge or contour recognition algorithms.

5. The method according to claim 1, characterised in that said alignment of said images along said segment at different times for freezing said motion of said object is carried out by determining the barycentre line between upper and lower edges of said image along each of said segments and calculating parameters of each of said segments relative to the distance of said pixels on said segment from an origin.

6. The method according to claim 1, characterised in that said estimation function is of the form y(t)=A(1−

e<sup>−

Bt</sup>), where y(t) is the pixel value depending from time, t is the time at which the pixel value has been determined in the image and A and B are parameters giving the best fit of said estimation function.

7. The method of claim 6, characterised in that said parameters can be imaged in a two-dimensional or a three-dimensional image, or in any known representation of a function of one, two, or more variables.

8. The method according claim 6, characterised in that said pixel appearance scale for imaging different values of said is a color scale.

9. The method according to claim 1, characterised in that an interpolation algorithm is used for defining pixel values for pixels lying between two adjacent segments by interpolating the pixel values along each of said two adjacent segments.

10. The method according to claim 1, characterised in that said image sequences are formed by echographic images.

11. The method according to claim 1, characterised in that said image sequence is formed by MRI images.

12. The method according to claim 1, characterised in that said image sequence is formed by images acquired by analogic acquisition methods.

13. The method according to claim 12, wherein said analogic acquisition methods comprise photographic and radiographic methods.

14. The method according to claim 1, characterised in that said pixel data comprises the brightness of said pixels of said image sequence.

15. The method according to claim 1, characterised in that said pixel data is obtained by imaging modes comprising Doppler, power Doppler, B-mode, and Harmonic imaging.

16. The method according to claim 1, characterised in that said moving object is the myocardium of the heart.

17. The method according to claim 1, characterised in that said pixel data is related to the presence of a contrast agent in the tissue of the myocardium.

18. The method according to claim 1, characterised in that said pixel data is a measurement of the contrast agent perfusion in a biologic tissue.

19. A method for generating time-independent images of moving objects, comprising the steps:

acquiring a sequence of a plurality of digital images of a region of interest of an object which has at least one part performing a cyclic or oscillatory or non oscillatory motion;

defining at least one segment of a line oriented in such a way as to cross the moving part of said object, said segment having a starting point and ending point which lie outside said images of said moving part of said object;

defining a certain number of pixels or groups of pixels along said segment;

generating a first image of each pixel or group of pixels along said segment such that a plurality of images are presented in the correct time sequence so as to form a two-dimensional image defined by two axes, where one axis is the distance position of each pixel or group of pixels along said segment and the other axis is time;

compensating the motion of said moving part of said object by aligning relative to time adjacent images of said pixels or group of pixels along said segment by shifting relative to the distance axis said position of said pixels or group of pixels along said segment for at least part of each image along said segment taken at different times;

retrieving pixel data from said digital image of each of said pixels or groups of pixels along said segment and representing said pixel data in a two-dimensional image defined by two axes, where one axis is said pixel data and the other axis is time;

defining an estimation function of said pixel data as a function of time, where said function has at least one parameter;

calculating said parameter of said estimation function leading to the best fit of said estimation function with said pixel data;

defining a plurality of additional segments which are placed side by side in order to cover at least a portion of said moving part of said object;

repeating said preceding steps with respect to each pixel or group of pixels along each of said additional segments;

defining a scale of pixel appearance which is univocally related to the values of said at least one parameter and which defines different appearances of said pixels or groups of pixels; and

reconstructing an image representative of said moving part of said object in which each of said pixels or groups of pixels is positioned on a segment in a time-independent position and where each of said pixels or groups of pixels has an appearance corresponding to the value calculated for said at least one parameter with respect to said pixel or group of pixels.

20. The method according to claim 19, characterised in that said pixel data comprises the brightness of a black and white digital image or one or more of variables of a color image.

21. The method according claim 19, characterised in that said compensation of said motion is carried out in accordance with a statistical algorithm.

22. The method according to claim 19, characterised in that said compensation of said motion is carried out by means of edge or contour recognition algorithms.

23. The method according to claim 19, characterised in that said compensation of said motion is carried out by determining the barycentre line between upper and lower edges of said image along each of said segments and calculating parameters of each of said segments relative to the distance of said pixels on said segment from an origin.

24. The method according to claim 19, characterised in that said estimation function is of the form y(t)=A(1−

e<sup>−

Bt</sup>), where y(t) is the pixel value depending from time, t is the time at which the pixel value has been determined in the image and A and B are parameters giving the best fit of said estimation function.

25. The method of claim 24, characterised in that said parameters can be imaged in a two-dimensional or a three-dimensional image, or in any known representation of a function of one, two, or more variables.

26. The method according claim 24, characterised in that said pixel appearance scale for imaging different values of said is a color scale.

27. The method according to claim 19, characterised in that an interpolation algorithm is used for defining pixel values for pixels lying between two adjacent segments by interpolating the pixel values along each of said two adjacent segments.

28. The method according to claim 19, characterised in that said image sequences are formed by echographic images.

29. The method according to claim 19, characterised in that said image sequence is formed by MRI images.

30. The method according to claim 19, characterised in that said image sequence is formed by images acquired by analogic acquisition methods.

31. The method according to claim 30, wherein said analogic acquisition methods comprise photographic and radiographic methods.

32. The method according to claim 19, characterised in that said pixel data comprises the brightness of said pixels of said image sequence.

33. The method according to claim 19, characterised in that said pixel data is obtained by imaging modes comprising Doppler, power Doppler, B-mode, and Harmonic imaging.

34. The method according to claim 19, characterised in that said moving object is the myocardium of the heart.

35. The method according to claim 19, characterised in that said pixel data is related to the presence of a contrast agent in the tissue of the myocardium.

36. The method according to claim 19, characterised in that said pixel data is a measurement of the contrast agent perfusion in a biologic tissue.