Intravascular ultrasonic analysis using active contour method and system

• US 6,381,350 B1
• Filed: 07/02/1999
• Issued: 04/30/2002
• Est. Priority Date: 07/02/1999
• Status: Expired due to Term

• Current Assignee: Cleveland Clinic Foundation
• Original Assignee: Cleveland Clinic Foundation
• Inventors: Klingensmith, Jon D., Shekhar, Raj, Vince, David Geoffrey
• Primary Examiner(s): Mehta, Bhavesh
• Assistant Examiner(s): TABATABAI, ABOLFAZL
• Application Number:
  US09/347,209
• Time in Patent Office: 1,033 Days
• Field of Search: 382/128, 382/27, 382/256, 382/129, 382/130, 382/131, 382/132, 128/672, 128/922, 424/101, 600/443, 600/485
• US Class Current: 382/128
• CPC Class Codes: A61B 5/02007 Evaluating blood vessel condition, e.g. elasticity, compliance
• CPC Class Codes: A61B 5/1076 for measuring dimensions inside body cavities, e.g. using catheters A61B3/1005 takes precedence
• CPC Class Codes: A61B 8/0833 involving detecting or locating foreign bodies or organic structures
• CPC Class Codes: A61B 8/0858 involving measuring tissue layers, e.g. skin, interfaces
• CPC Class Codes: A61B 8/12 in body cavities or body tracts, e.g. by using catheters catheters per se A61M25/00
• CPC Class Codes: A61B 8/4461 Features of the scanning mechanism, e.g. for moving the transducer within the housing of the probe
• CPC Class Codes: A61B 8/463 characterised by displaying multiple images or images and diagnostic data on one display composite display in devices for short-range imaging with acoustic waves G01S7/52074
• CPC Class Codes: G06T 2207/10132 Ultrasound image
• CPC Class Codes: G06T 2207/20101 Interactive definition of point of interest, landmark or seed
• CPC Class Codes: G06T 2207/30101 Blood vessel; Artery; Vein; Vascular
• CPC Class Codes: G06T 7/12 Edge-based segmentation
• CPC Class Codes: G06T 7/149 involving deformable models, e.g. active contour models
• CPC Class Codes: G06V 10/755 Deformable models or variational models, e.g. snakes or active contours

Abstract

An intravascular ultrasound (IVUS) analysis system and method is provided which determines luminal and medial-adventitial boundaries of a blood vessel. Ultrasonic data is acquired by a rotating transducer mounted to a tip of a catheter which is inserted into the blood vessel. An intravascular image is reconstructed from the ultrasound data. To determine the luminal boundary of a vessel, a user selects boundary points on the image believed to be locations of the luminal boundary. A boundary contour is generated based on the boundary points. The boundary contour is then optimized by adjusting the boundary points based on a radially determined edge of the luminal boundary performed on the image in polar format. Once the final luminal boundary contour is generated, the process is repeated to determine the medial-adventitial boundary contour. With the contour data, properties of the blood vessel are analyzed including determining the area of the lumen and percent of occlusion caused by plaque.

Claims

1. A method of determining a boundary contour of a blood vessel from an intravascular ultrasound image where the ultrasound image is generated from data acquired radially within the blood vessel by an ultrasonic device, the method comprising the steps of:

displaying the ultrasound image, the ultrasound image being a cross-sectional view of a blood vessel and being a Cartesian image, the ultrasound image including a representation of a boundary of the blood vessel;

selecting control points along the boundary of the blood vessel from the Cartesian image;

interpolating between the control points to generate a boundary contour from the Cartesian image; and

optimizing the boundary contour from the Cartesian image by adjusting each of the control points based on a gradient polar image which includes a distinguished boundary of the blood vessel, the gradient polar image being determined from the ultrasound image.

2. The method of determining a boundary contour as set forth in claim 1 further including determining the distinguished boundary by radially analyzing pixel values of the ultrasound image.

3. The method of determining a boundary contour as set forth in claim 1 wherein the gradient image is formed by:

converting the ultrasound image to a polar image, the polar image having a plurality of radial scan lines which include a plurality of pixels;

radially determining an edge of the boundary along each of the radial scan lines by applying a gradient filter to each of the plurality of pixels, the gradient filter distinguishing pixels which likely form the edge of the boundary, the distinguished pixels defining the distinguished boundary; and

converting the polar image of the ultrasound image to a Cartesian format to obtain the gradient image in Cartesian format including the distinguished boundary.

4. The method of determining a boundary contour as set forth in claim 1 wherein the optimizing further includes adjusting each of the control points based on a point spacing constraint and a curvature constraint maintain continuity in the boundary contour.

5. The method of determining a boundary contour as set forth in claim 4 further including iteratively performing the optimizing step for each of the control points.

6. The method of determining a boundary contour as set forth in claim 1 wherein:

the displaying further includes displaying a plurality of ultrasound images being a sequential sequence of images of the blood vessel, the ultrasound image being a starting image;

the selecting further includes selecting control points along the boundary on an ending image from the plurality of ultrasound images such that at least one intermediate image is between the starting and ending images; and

the interpolating further includes interpolating between the control points of the starting and ending images to automatically generate a boundary contour on the at least one intermediate image.

7. The method of determining a boundary contour as set forth in claim 6 further including:

optimizing the boundary contour on the starting image, the at least one intermediate image and the ending image by adjusting each of the control points based on a gradient image which includes a distinguished boundary determined from the ultrasound image of the starting image, the at least one intermediate image and the ending image.

8. A method of intravascular analysis of an intravascular image, the intravascular image being generated from data acquired by an ultrasonic device which radially scans a vascular object internally, the method comprising the steps of:

converting the intravascular image to a Cartesian format, the intravascular image representing a boundary of the vascular object;

selecting a plurality of boundary points on the intravascular image in a vicinity of the boundary;

generating a first boundary contour based on the plurality of boundary points;

generating a second boundary contour based on a radial boundary determination performed on a polar image of the intravascular image; and

adjusting the first boundary contour by an influence from the second boundary contour to obtain an optimized boundary contour.

9. The method of intravascular analysis as set forth in claim 8 wherein the generating the first boundary contour includes linearly interpolating between the plurality of boundary points.

10. The method of intravascular analysis as set forth in claim 8 wherein the generating the second boundary contour includes applying a gradient filter to the polar image.

11. The method of intravascular analysis as set forth in claim 10 wherein the radial boundary determination includes applying the gradient filter in a radial direction on the polar image, the gradient filter distinguishing areas of the polar image in the vicinity of the boundary of the vascular object.

12. The method of intravascular analysis as set forth in claim 8 wherein the generating the second boundary contour includes:

converting the intravascular image into the polar image having a plurality of scan lines;

forming a gradient image of the polar image by radially applying a gradient filter across each of the plurality of scan lines to distinguish the boundary of the vascular object; and

converting the gradient image to a Cartesian format, the distinguished boundary defining the second boundary contour.

13. The method of intravascular analysis as set forth in claim 8 wherein the adjusting further includes adjusting each of the plurality of boundary points in accordance with a spacing function with restricts a location of a boundary point based on an average distance between each of the plurality of boundary points.

14. The method of intravascular analysis as set forth in claim 13 wherein the adjusting further includes adjusting each of the plurality of boundary points in accordance with a curvature function which restricts a location of a boundary point based on a curvature of the first boundary contour.

15. The method of intravascular analysis as set forth in claim 8 wherein each of the plurality of boundary points has a location on the intravascular image and, the adjusting includes adjusting the location of each of the plurality of boundary points based on a corresponding location on the second boundary contour.

16. The method of intravascular analysis as set forth in claim 8 wherein the boundary is a luminal boundary of the vascular object.

17. The method of intravascular analysis as set forth in claim 8 wherein the boundary is a medial adventitial boundary of the vascular object.

18. A method of intravascular ultrasound image analysis where an intravascular image is generated from ultrasonic data acquired radially from an ultrasonic device from within a vascular object, the improvement comprising:

determining a boundary of the vascular object in accordance with a user defined boundary from image data having a first coordinate format and a polar image of the intravascular image having a second coordinate format different from the first coordinate format.

19. The method as set forth in claim 18 further includes:

applying a gradient to the polar image, the gradient generating a distinguished edge within the polar image which represents the boundary of the vascular object; and

adjusting the user defined boundary based on the distinguished edge within the polar image to obtain the boundary of the vascular object.

20. The method as set forth in claim 18 wherein the improvement further includes:

selecting a group of ultrasonic images from the ultrasonic data acquired from a segment of the vascular object, the group of ultrasonic images being defined by a starting image and an ending image which have intermediate images therebetween;

generating a starting boundary contour on the starting image representative of the boundary of the vascular object;

generating an ending boundary contour on the ending image representative of the boundary of the vascular object; and

generating a boundary contour on each of the intermediate images representative of the boundary of the vascular object based on the starting and ending boundary contours.

21. The method as set forth in claim 20 wherein the generating a starting and ending boundary contours further includes:

selecting the boundary of the vascular object with a plurality of boundary points on both the starting image and the ending image; and

interpolating the plurality of boundary points on the starting image to obtain the starting boundary contour; and

interpolating the plurality of boundary points on the ending image to obtain the ending boundary contour.

22. The method as set forth in claim 21 wherein the generating a boundary contour on each of the intermediate images includes interpolating the starting boundary contour and the ending boundary contour across the intermediate images.

23. The method as set forth in claim 22 further including:

generating a corresponding polar image for each of the starting, intermediate and ending images; and

adjusting the starting, intermediate and ending boundary contours based on the corresponding polar image.

27. The method as set forth in claim 18 wherein the first coordinate format is in Cartesian coordinates and the second coordinate format is in polar coordinates.

24. A method of determining a boundary contour of a blood vessel from a series of intravascular ultrasound images which are generated from data acquired radially within the blood vessel by an ultrasonic device, the method comprising the steps of:

selecting a starting image and an ending image from the series of intravascular ultrasound images which define a group of images having intermediate images therebetween;

selecting boundary points on the starting and ending images which are in a vicinity of and partially outline a boundary of the blood vessel;

generating a starting contour outlining the boundary of the blood vessel based on the boundary points of the starting image and generating an ending contour outlining the boundary of the blood vessel based on the boundary points of the ending image;

generating intermediate contours outlining the boundary of the blood vessel for each of the intermediate images based on the starting and ending contours; and

determining a boundary contour of the blood vessel in three dimensions based on the starting, intermediate and ending contours.

25. The method of determining a boundary contour of a blood vessel as set forth in claim 24 further including optimizing the starting contour, the intermediate contours, and the ending contour by adjusting each contour based on a polar image generated from the corresponding ultrasound image.

26. The method of determining a boundary contour of a blood vessel as set forth in claim 25 further including adjusting the polar image to distinguish pixel values around a boundary in the polar image.