1. Chunlei Han Turku PET centre March 31, 2005
Application of Gradient Vector Flow (GVF) Active Contour in Searching Heart Surface
Chunlei Han
Turku PET centre
March 31, 2005

2. Contains Active Contour Gradient Vector Flow (GVF)
Results and Demonstration

3. Active Contour Models Names: Snake, Active Contour, Deformable Model
First introduced in 1987 by Kass et al, and gained popularity since then.
Kass et al: Snakes: active contour models. International Journal of Computer Vision, , 1987
The contour is atracted to image boundares
controlled by two forces (energies)
Internal force (itself)
external force (image)
Initial line
target

4. Definition of active contour energy
A contour is definded as a parameter curve
Internal energy
External energy
is defined based o image information, such image intensity, edge ect.

5. Internal energy
Elastic Energy is treated as an elastic rubber band possessing elastic potential energy. Responsible for shrinking of the contour
Rigid Energy is considered to behave like a thin metal strip giving rise to bending energy. Bending energy is minimum for a circle.

6. Solution of Active Contour (Snake)

7. External energy
Xu & Price: Snakes, Shape and Gradient Vector Flow. Processing Image on Transactions IEEE
1998, March,

8. Gradient Vector Flow (GVF)
Why need GVF
The original active contour can not move in many cases, such as
concavities
initial line is far away from object
initial line acrosses with object (has points inside and outside of object)

10. GVF field is defined as the equilibrium solution to
the following diffusion equation
Xu & Prince: Snake, shape and gradient vector flow. IEEE trans image processing
1998, 7:

11. Result and Demostration

12. Conclusion
GVF active contour is a useful method in heart surface searching