Extended view ultrasound imaging system

• US 6,540,681 B1
• Filed: 11/24/2000
• Issued: 04/01/2003
• Est. Priority Date: 11/24/2000
• Status: Expired due to Term

• Current Assignee: U-System Inc. (General Electric Company)
• Original Assignee: U-System Inc. (General Electric Company)
• Inventors: Cheng, Xiangyong, Lin, Shengtz
• Primary Examiner(s): Lateef, Marvin M.
• Assistant Examiner(s): Jain, Ruby
• Application Number:
  US09/721,645
• Time in Patent Office: 858 Days
• Field of Search: 600/443, 128/916, 345/589, 382/162
• US Class Current: 600/443
• CPC Class Codes: A61B 8/0866 involving foetal diagnosis; pre-natal or peri-natal diagnosis of the baby
• CPC Class Codes: A61B 8/4245 involving determining the position of the probe, e.g. with respect to an external reference frame or to the patient
• CPC Class Codes: A61B 8/4254 using sensors mounted on the probe
• CPC Class Codes: G01S 5/18 using ultrasonic, sonic, or infrasonic waves
• CPC Class Codes: G01S 7/52065 Compound scan display, e.g. panoramic imaging

Abstract

An extended view ultrasound imaging system in which a position sensor is used to detect the location and orientation of a ultrasound transducer for each scan frame as the ultrasound transducer is swept across the surface of a target. The contents of the successive scan frames, together with their location and orientation information, are processed to generate an extended view ultrasound image of the target region. An output array representing the extended view image is first initialized, and then successively updated as each scan frame is received. In a preferred embodiment, an alpha-blending algorithm is used to combine the information in the current scan frame with previous output array values to generate the current output array values. Because the content of the successive image frames is not relied upon to piece them together, system processing requirements are substantially reduced and the output image is robust against increased transducer speed, bumps in the transducer path, and departures of the transducer from a common plane. In an additional preferred embodiment, the alpha-blending weighting factor can be user-adjustable and/or can be dynamically adjusted on a per-location basis based on acoustic reflectivity, edge motion, or other factors. Also in an additional preferred embodiment, the amount of departure from a common plane during the movement of the transducer across the target can be displayed to the user for assistance in interpreting the extended view image.

Claims

1. A method for generating an extended view ultrasound image, comprising the steps of:

generating a plurality of scan frames as a transducer is moved across a target;

detecting transducer position information corresponding to each of said scan frames, said position information including location and orientation information; and

using said transducer position information to form an extended view image from said scan frames;

initializing an output array; and

sequentially processing said scan frames and updating said output array as each scan frame is processed;

wherein said extended view image comprises at least a portion of said output array;

said scan frames being at least partially overlapping, wherein a blending algorithm is used at each overlapping location to update said output array based on a current scan frame value at that location and at least one previous scan frame value at that location;

said blending algorithm comprising the steps of;

weighting the current scan frame value at that location by a first weighting factor to produce a first intermediate result;

weighting the previous output array value at that location by a second weighting factor to produce a second intermediate result; and

setting the current value of the output array at that location to a sum of said first and second intermediate results;

wherein said first weighting factor is equal to a value α

, and wherein said second weighting factor is equal to (1−

α

); and

wherein α

is a predetermined fixed value greater than or equal to 0.4 and less than or equal to 0.9.

2. A method for generating an extended view ultrasound image, comprising the steps of:

generating a plurality of scan frames as a transducer is moved across a target;

detecting transducer position information corresponding to each of said scan frames, said position information including location and orientation information; and

using said transducer position information to form an extended view image from said scan frames;

initializing an output array; and

sequentially processing said scan frames and updating said output array as each scan frame is processed;

wherein said extended view image comprises at least a portion of said output array;

said scan frames being at least partially overlapping, wherein a blending algorithm is used at each overlapping location to update said output array based on a current scan frame value at that location and at least one previous scan frame value at that location;

said blending algorithm comprising the steps of;

weighting the current scan frame value at that location by a first weighting factor to produce a first intermediate result;

weighting the previous output array value at that location by a second weighting factor to produce a second intermediate result; and

setting the current value of the output array at that location to a sum of said first and second intermediate results;

wherein said first weighting factor is equal to a value α

, and wherein said second weighting factor is equal to (1−

α

); and

wherein α

is a user-adjustable value, whereby α

may be set closer to 1.0 than to 0.0 for increased temporal resolution, and whereby α

may be set closer to 0.0 than to 1.0 for decreased speckle and increased signal to noise performance.

3. A method for generating an extended view ultrasound image, comprising the steps of:

generating a plurality of scan frames as a transducer is moved across a target;

detecting transducer position information corresponding to each of said scan frames, said position information including location and orientation information; and

using said transducer position information to form an extended view image from said scan frames;

initializing an output array; and

sequentially processing said scan frames and updating said output array as each scan frame is processed;

wherein said extended view image comprises at least a portion of said output array;

said scan frames being at least partially overlapping, wherein a blending algorithm is used at each overlapping location to update said output array based on a current scan frame value at that location and at least one previous scan frame value at that location;

said blending algorithm comprising the steps of;

weighting the current scan frame value at that location by a first weighting factor to produce a first intermediate result;

weighting the previous output array value at that location by a second weighting factor to produce a second intermediate result; and

setting the current value of the output array at that location to a sum of said first and second intermediate results;

wherein said first weighting factor is equal to a value α

, and wherein said second weighting factor is equal to (1−

α

); and

wherein α

is automatically and dynamically adjusted on a per location basis, wherein α

is increased for locations of high ultrasound reflectivity, and wherein α

is decreased for locations of low ultrasound reflectivity.

4. A method for generating an extended view ultrasound image, comprising the steps of:

generating a plurality of scan frames as a transducer is moved across a target;

detecting transducer position information corresponding to each of said scan frames, said position information including location and orientation information; and

using said transducer position information to form an extended view image from said scan frames;

initializing an output array; and

sequentially processing said scan frames and updating said output array as each scan frame is processed;

wherein said extended view image comprises at least a portion of said output array;

said step of sequentially processing and updating comprising the steps of;

mapping each location in the current scan frame to a corresponding location of said output array;

if the previous output array value at that location is equal to its initialized value, setting the current value of the output array at that location to the current scan frame value;

if the previous output array value at that location is not equal to its initialized value, performing the steps of;

weighting the current scan frame value at that location by a first weighting factor to produce a first intermediate result;

weighting the previous output array value at that location by a second weighting factor to produce a second intermediate result; and

setting the current value of the output array at that location to a sum of said first and second intermediate results.

5. The method of claim 4, wherein said first weighting factor is equal to a value α

, and wherein said second weighting factor is equal to (1−

α

).

6. The method of claim 5, said transducer comprising a linear array of elements used in defining a scan frame area, said scan frame area comprising a plurality of scan lines, wherein said scan frames are generated only from scan lines that are within a predetermined distance of a center line of said scan frame area.

7. The method of claim 6, wherein said predetermined distance is less than 25% of a width of the scan frame area.

8. The method of claim 5, wherein said scan frames are of a type selected from a group consisting of:

B-mode, color Doppler mode, and power Doppler mode.

9. A method for generating an extended view ultrasound image, comprising the steps of:

generating a plurality of scan frames as a transducer is moved across a target;

detecting transducer position information corresponding to each of said scan frames, said position information including location and orientation information; and

using said transducer position information to form an extended view image from said scan frames;

initializing an output array; and

sequentially processing said scan frames and updating said output array as each scan frame is processed;

wherein said extended view image comprises at least a portion of said output array;

said scan frames being at least partially overlapping, wherein a blending algorithm is used at each overlapping location to update said output array based on a current scan frame value at that location and at least one previous scan frame value at that location;

establishing an intended target plane based on at least one transducer position as the transducer is moved across the target;

for each scan frame, using its corresponding transducer position information to compute a departure metric between said intended target plane and the plane of the scan frame and; and

for each scan frame, superimposing information related to said departure metric onto corresponding locations of said extended view image;

wherein said step of superimposing information comprises the steps of;

determining, for a plurality of locations in each scan frame, a linear distance between said location and said intended target plane; and

coloring the corresponding location in said extended view image with a color representative of said linear distance;

wherein said step of superimposing information comprises the step of displaying a separate trace near said extended view image that communicates a magnitude of said departure metric for corresponding groups of extended view image locations.

10. An extended view ultrasound imaging system, comprising:

an ultrasound transducer, said ultrasound transducer being capable of generating scan frames while being swept across a target surface, said scan frames defining a ribbon-like path through the target as the ultrasound transducer is swept across the target surface;

a sensor for detecting ultrasound transducer position information corresponding to each scan frame, said position information including location and orientation information;

a processor for receiving the scan frames and corresponding position information and generating therefrom an output array comprising acoustic reflectivity data for each location along said ribbon-like path; and

an output device for displaying said output array to a user;

said processor being adapted to perform the steps of;

initializing the output array to null values;

mapping each location in a current scan frame to a corresponding location of the output array; and

updating the output array based on a previous value of the output array at that location and the value of the current scan frame at that location.

11. The system of claim 10, said processor being further adapted to perform the steps of:

establishing a reference plane based on at least one ultrasound transducer position as said ultrasound transducer is moved across the target;

using the ultrasound transducer position information associated with each scan frame to determine a departure amount between the ribbon-like path and the reference plane for each location in the scan frame;

converting said departure amount into a user perceivable representation for transfer to said output device.

12. The system of claim 11, said departure amount comprising a linear distance between the ribbon-like path and the reference plane for each location in the scan frame.

13. The system of claim 12, said departure amount comprising an angular distance between a plane of the ultrasound transducer and said reference plane for each location in the scan frame.

14. The system of claim 13, said step of converting said departure amount into a user perceivable representation comprising the step of creating a pixel color representative of said linear distance.

15. The system of claim 10, wherein for each location in the current scan frame said processor is further adapted to perform the steps of:

if the previous output array value is equal to a null value, setting the current value of the output array equal to the current scan frame value;

if the previous output array value is not equal to a null value, performing the steps of;

weighting the current scan frame value by a first weighting factor to produce a first intermediate result;

weighting the previous output array value by a second weighting factor to produce a second intermediate result; and

setting the current value of the output array to a sum of said first and second intermediate results.

16. The system of claim 15, wherein said first weighting factor is equal to a value α

, and where in said second weighting factor is equal to (1−

α

).

17. The system of claim 16, said ultrasound transducer comprising a linear array of elements used in defining a scan frame area, said scan frame area comprising a plurality of scan lines, wherein said scan frames are generated only from scan lines that are within a predetermined distance of a center line of said scan frame area.

18. The method of claim 17, wherein said predetermined distance is less than 25% of a width of the scan frame area.

19. The system of claim 17, wherein α

is a predetermined fixed value greater than or equal to 0.4 and less than or equal to 0.9.

20. The system of claim 17, wherein α

is a user-adjustable value, whereby α

may be set closer to 1.0 than to 0.0 for increased temporal resolution, and whereby a may be set closer to 0.0 than to 1.0 for decreased speckle and increased signal to noise performance.

21. The system of claim 17, wherein α

is automatically and dynamically adjusted on a per location basis, wherein α

is increased for locations of high ultrasound reflectivity, and wherein α

is decreased for locations of low ultrasound reflectivity.

22. The system of claim 17, wherein said processor is adapted to detect tissue motion in the target using information from the successive scan frames, wherein α

is automatically and dynamically adjusted on a per location or per segment basis, wherein α

is increased for locations of faster tissue movement for increased temporal resolution, and wherein α

is decreased for locations of slower tissue movement for decreased speckle and increased signal to noise performance.

23. The system of claim 17, wherein said processor is adapted to receive, for each scan frame, information relating that scan frame to a systolic or diastolic cycle, wherein α

is automatically and dynamically adjusted on a per scan frame basis, wherein α

is increased for scan frames during the systolic cycle for increased temporal resolution, and wherein α

is decreased for scan frames during the diastolic cycle for decreased speckle and increased signal to noise performance.