Methods and systems for color flow dynamic frame persistence

1. An image processing method for calculating blood vessel direction of a flow velocity image comprising a plurality of point-regions, each point-region associated with a central point, the method comprising:

distinguishing each of the point-regions in the flow velocity image as point-regions in a flow region and point-regions in a background region;

estimating a rough direction of a computing point-region by:

setting a plurality of directions and respectively calculating the number of point-regions in the flow region connecting with the computing point-region in each direction; and

taking the direction with the maximum number of point-regions as the rough direction of the computing point-region;

determining middle point-regions on the direction perpendicular to the rough direction in a neighborhood;

determining a line connecting the central points of the middle point-regions as a median line of the blood vessel in the neighborhood, wherein the neighborhood is centered on the computing point-region and includes a plurality of point-regions in the flow region in the rough direction; and

calculating the direction of the blood vessel on the computing point-region according to the determined median line of the blood vessel,

wherein calculating comprises applying a linear fitting or Hough Transform to the determined median line of the blood vessel.

2. The method of claim 1 , wherein distinguishing comprises binarizing the image by marking the point-regions whose values are smaller than a predefined threshold as zero and the remaining point-regions as one, thereby distinguishing the point-regions in the flow region and the point-regions in the background region.

3. The method of claim 1 wherein the plurality of directions is selected from the group consisting of two directions, or four directions, and eight directions.

4. The method of claim 3 , wherein the plurality of directions is selected from the group consisting of a set of directions comprising horizontal and vertical directions, and a set of directions comprising 0°, 45°, 90° and 135°.

5. A system for calculating blood vessel direction of a flow velocity image comprising a plurality of point-regions, each point-region associated with a central point, the system comprising:

a processor;

a distinguishing module configured to distinguish each of the point-regions in the blood flow velocity image as point-regions in a flow region and point-regions in a background region;

an estimation module configured to set a plurality of directions and respectively calculate the number of the point-regions in the flow region connecting with a computing point-region each direction, and take the direction with the maximum number as the rough direction of the computing point-region;

a determination module configured to determine middle point-regions on the direction perpendicular to the rough direction in a neighborhood;

determining a line connecting the central points of the middle point-regions as a median line of the blood vessel in the neighborhood, wherein the neighborhood takes the computing point-region as a center point-regions and comprises a plurality of point-regions in the flow region in the rough direction; and

a computation module configured to calculate the direction of the blood vessel on the computing point-region according to the determined median line of the blood vessel,

wherein the computation module is configured to applying a linear fitting or Hough Transform to the determined median line of the blood vessel.

6. The system of claim 5 , wherein the first distinguishing module is configured to binarize the image by marking the point-regions whose values are smaller than a predefined threshold as zero and the remaining point-regions as 1, thereby distinguishing the point-regions in the flow region and the point-regions in the background region.

7. The system of claim 5 , wherein the plurality of directions comprises two directions, or four directions, or eight directions.

8. A non-transitory computer-readable medium comprising program code that causes a processor to perform operations for calculating blood vessel direction of a flow velocity image comprising a plurality of point-regions, each point-region associated with a central point, the operations comprising:

distinguishing each of the point-regions in the flow velocity image as point-regions in a flow region and point-regions in a background region;

estimating a rough direction of a computing point-region by setting a plurality of directions and respectively calculating the number of point-regions in the flow region connecting with the computing point-region in each direction, and taking the direction with the maximum number of point-regions as the rough direction of the computing point-region;

determining middle point-regions on the direction perpendicular to the rough direction in a neighborhood;

determining a line connecting the central points of the middle point-regions as a median line of the blood vessel in the neighborhood, wherein the neighborhood is centered around the computing point-region and includes a plurality of point-regions in the flow region in the rough direction; and

calculating the direction of the blood vessel on the computing point-region according to the determined median line of the blood vessel,

wherein calculating comprises applying a linear fitting or Hough Transform to the determined median line of the blood vessel.