Method and system for determining a sharp panoramic image constructed from a group of projection images

• US 7,860,300 B2
• Filed: 08/18/2005
• Issued: 12/28/2010
• Est. Priority Date: 08/18/2005
• Status: Expired due to Fees

• Current Assignee: Palodex Group Oy (Envista Holdings Corporation)
• Original Assignee: Palodex Group Oy (Envista Holdings Corporation)
• Inventors: Setälä, Henri, Suuronen, Esa, Kalke, Martti, Siltanen, Samuli
• Primary Examiner(s): Mariam; Daniel G
• Assistant Examiner(s): Woldemariam; Aklilu K
• Application Number:
  US11/207,165
• Publication Number:
  US 20070041489A1
• Time in Patent Office: 1,958 Days
• Field of Search: 382/154, 382/131, 382/132, 378/4, 378/40
• US Class Current: 382/154
• CPC Class Codes: A61B 6/51 for dentistry
• CPC Class Codes: G06T 2207/10116 X-ray image
• CPC Class Codes: G06T 2207/20221 Image fusion; Image merging
• CPC Class Codes: G06T 2207/30036 Dental; Teeth
• CPC Class Codes: G06T 3/4038 Image mosaicing, e.g. composing plane images from plane sub-images
• CPC Class Codes: G06T 5/50 using two or more images, e.g. averaging or subtraction

Abstract

The invention relates to a method and system for determining a sharp panoramic image constructed from a group of projection images, especially the invention relates to defining a structure of the panoramic X-ray image of an area of a dentition and of jaws. The structure of a panoramic image to be generated from a group of projection images is determined by at least two crucial parameters, namely parameters of the central surface S of the sharp layer and thickness t(s) of the sharp layer, using penalty function F(S,t), which is at least a penalty function F3(S,t) of low-frequency changes in the computed panoramic image corresponding to the choices S and t(S). After computing F3(S,t) the best center surface and thickness function (in other words the sharpest layer of the panoramic image) is obtained by minimizing said penalty function F(S,t) over parameter space.

Claims

1. A method for determining a sharp layer from a sharp panoramic image layer generated by limited angle tomography, the sharp panoramic image layer extending along a clinically relevant curvilinear anatomic structure including a structure of a dentition jaw or jaw bone, the sharp panoramic image layer constructed from projection image data, the method comprising:

operating an X-ray imaging device to obtain a plurality of projection images of the anatomic structure;

configuring a non-transient storage medium wherein a set of computer executable code is stored;

executing the set of computer executable code with a processor to carry out the following steps;

identifying a first plurality of control points of a first thickness value of the sharp panoramic image layer;

applying a penalty function to the first plurality of control points and the first thickness value;

selecting a control point from the first plurality of control points that has a lowest penalty function value;

identifying a second plurality of control points of a second thickness value of the sharp panoramic image layer;

applying the penalty function to the second plurality of control points and the second thickness value;

selecting a control point from the second plurality of control points that has a lowest penalty function value; and

selecting a center surface (S) from a plurality of predetermined center surfaces as the sharp layer, the sharp layer being the center surface (S) that best fits the selected control points from the first and second plurality of control points.

2. The method of claim 1, wherein the penalty function computes a panoramic image corresponding to a plurality of control points and a thickness value, and wherein the penalty function computes a penalty that is inversely related to a frequency of data in the computed panoramic image.

3. The method of claim 2, wherein the penalty function computes a first panoramic image corresponding to the first plurality of control points and the first thickness value and computes a second panoramic image corresponding to the second plurality of control points and the second thickness value.

4. The method of claim 2, wherein the penalty function further computes the penalty as inversely related to a rate of change in a surface defined by the plurality of control points.

5. The method of claim 2, wherein the penalty function further computes the penalty as inversely related to a rate of change in the first thickness value or the second thickness value.

6. The method of claim 1, wherein the penalty function is a summation of F1(S), F2(t), and F3(S,t), and the step of applying the penalty function to the first plurality of control points comprises:

calculating F1(S) as a value inversely related to a rate of change in the first plurality of control points;

calculating F2(t) as a value inversely related to a rate of change in the first thickness value;

calculating F3(S,t) as a value inversely related to a frequency of data in a first panoramic image constructed from the first plurality of control points and the first thickness value; and

calculating a summation of F1(S), F2(t), and F3(S,t) as a penalty function value.

7. The method of claim 6, wherein the step of applying the penalty function to the second plurality of control points comprises:

calculating F1(S) as a value inversely related to a rate of change in the second plurality of control points;

calculating F2(t) as a value inversely related to a rate of change in the second thickness value;

calculating F3(S,t) as a value inversely related to a frequency of data in a second panoramic image constructed from the second plurality of control points and the second thickness value; and

calculating a summation of F1(S), F2(t), and F3(S,t) as a penalty function value.

8. The method of claim 1, wherein the sharp panoramic image layer is an X-ray image of a dentition or jaw.

9. The method of claim 1, wherein the first thickness value and the second thickness value are each within a range of 2 mm to 30 mm.

10. The method of claim 1, wherein the first plurality of control points and the second plurality of control points are coordinates in three dimensional space.

11. The method of claim 10, wherein the center surface (S) is made up of spline functions passing through the selected control points from the first and second plurality of control points.

12. The method of claim 11, wherein the first plurality of control points and the second plurality of control points are bounded by a dimension of the curvilinear anatomic structure in the plurality of projection images.

13. The method of claim 2, wherein the step of selecting the center surface (S) further comprises using a Powell &

Brent or Gaussian method.

14. A system for determining a sharp layer from a sharp panoramic image layer generated by limited angle tomography, the sharp panoramic image layer extending along a clinically relevant curvilinear anatomic structure including a structure of a dentition jaw or jaw bone, the sharp panoramic image layer constructed from projection image data, the system comprising:

an X-ray imaging device configured to obtain a plurality of projection images of the anatomic structure;

a non-transient storage medium upon which a set of computer executable code is stored;

a processor communicatively connected to the non-transient storage medium;

wherein the processor performs the following steps upon execution of the set of computer executable code;

identifying a first plurality of control points of a first thickness value of the sharp panoramic image layer;

applying a penalty function to the first plurality of control points and the first thickness value;

selecting a control point from the first plurality of control points that has a lowest penalty function value;

identifying a second plurality of control points of a second thickness value of the sharp panoramic image layer;

applying the penalty function to the second plurality of control points and the second thickness value;

selecting a control point from the second plurality of control points that has a lowest penalty function value; and

selecting a center surface (S) from a plurality of predetermined center surfaces as the sharp layer, the sharp layer being the center surface (S) that best fits the selected control points from the first and second plurality of control points.

15. The system of claim 14, wherein the penalty function computes a panoramic image corresponding to a plurality of control points and a thickness value, and wherein the penalty function computes a penalty that is inversely related to a frequency of data in the computed panoramic image.

16. The system of claim 15, wherein the penalty function computes a first panoramic image corresponding to the first plurality of control points and the first thickness value and computes a second panoramic image corresponding to the second plurality of control points and the second thickness value.

17. The system of claim 15, wherein the penalty function further computes the penalty as inversely related to a rate of change in a surface defined by a plurality of control points.

18. The system of claim 15, wherein the penalty function further computes the penalty as inversely related to a rate of change in the first thickness value or the second thickness value.

19. The system of claim 14, wherein the penalty function is a summation of F1(S), F2(t), and F3(S,t), and the processor applying the penalty function to the first plurality of control points comprises:

calculating F1(S) as a value inversely related to a rate of change in the first plurality of control points;

calculating F2(t) as a value inversely related to a rate of change in the first thickness value;

calculating F3(S,t) as a value inversely related to a frequency of data in a first panoramic image constructed from the first plurality of control points and the first thickness value; and

calculating a summation of F1(S), F2(t), and F3(S,t) as a penalty function value.

20. The system of claim 19, wherein the processor applying the penalty function to the second plurality of control points comprises:

calculating F1(S) as a value inversely related to a rate of change in the second plurality of control points;

calculating F2(t) as a value inversely related to a rate of change in the second thickness value;

calculating F3(S,t) as a value inversely related to a frequency of data in a second panoramic image constructed from the second plurality of control points and of second thickness value; and

calculating a summation of F1(S), F2(t), and F3(S,t) as a penalty function value.

21. The system of claim 14, wherein the first plurality of control points and the second plurality of control points are coordinates in three dimensional space.

22. The system of claim 14, wherein the center surface (S) is made up of spline functions passing through the selected control points from the first and second plurality of control points.

23. The system of claim 14, wherein the plurality of first control points and the plurality of second control points are bounded by a dimension of the curvilinear anatomic structure in the plurality of projection images.

24. A non-transient computer readable medium embodying computer readable code for determining a sharp layer from a sharp panoramic image layer generated by limited angle tomography, the sharp panoramic image layer extending along a clinically relevant curvilinear anatomic structure including a structure of a detention jaw or jaw bone, the sharp panoramic image layer constructed from projection image data, wherein upon execution of the computer readable code, the processor:

receives a plurality of projection images of the anatomic structure;

identifies a first plurality of control points of a first thickness value of the sharp panoramic image layer;

applies a penalty function to the first plurality of control points and the first thickness value;

selects a control point from the first plurality of control points that has a lowest penalty function value;

identifies a second plurality of control points of a second thickness value of the sharp panoramic image layer;

applies the penalty function to the second plurality of control points and the second thickness value;

selects a control point from the second plurality of control points that has a lowest penalty function value; and

selects a center surface (S) from a plurality of predetermined center surfaces as the sharp layer, the sharp layer being the center surface (S) that best fits the selected control points from the first and second plurality of control points.

25. The computer readable medium of claim 24, wherein the penalty function computes a panoramic image corresponding to a plurality of control points and a thickness value, and wherein the penalty function computes a penalty that is inversely related to a frequency of data in the panoramic image.

26. The computer readable medium of claim 25, wherein the penalty function computes a first panoramic image corresponding to the first plurality of control points and the first thickness value and computes a second panoramic image corresponding to the second plurality of control points and the second thickness value.

27. The computer readable medium of claim 25, wherein the penalty function further computes the penalty as inversely related to a rate of change in a surface defined by the plurality of control points.

28. The computer readable medium of claim 25, wherein the penalty function further computes the penalty as inversely related to a rate of change in the first thickness value or the second thickness value.

29. The computer readable medium of claim 24, wherein the penalty function is a summation of F1(S), F2(t), and F3(S,t), and the execution of the computer readable code further causes the processor to:

calculate F1(S) as a value inversely related to a rate of change in the first plurality of control points;

calculate F2(t) as a value inversely related to a rate of change in the first thickness value;

calculate F3(S,t) as a value inversely related to a frequency of data in a first panoramic image constructed from the first plurality of control points and the first thickness value; and

calculate a summation of F1(S), F2(t), and F3(S,t) as a penalty function value.