Method, computer program and system for dose calculation in radiotherapy

1. A method of dose calculation for radiotherapy, comprising:

a. providing a planning image of a portion of a body to be subjected to radiotherapy;

b. providing a fraction image of the portion of the body, the fraction image and the planning image taken at different times;

c. registering the planning image with the fraction image to produce a deformation field for the planning image, and using the deformation field to obtain a first basis for calculation comprising first location information and first material property information related to the portion;

d. obtaining a second basis for calculation based on the fraction image, comprising second location information and second material property information related to the portion; and

e. performing dose calculation using both the first basis for calculation and the second basis for calculation and using material property information from the first and the second basis for calculation.

2. The method according to claim 1 , wherein the dose calculation is performed using the first material property information from the first basis for calculation in at least a first region of the portion of the body and the second material property information from the second basis for calculation in at least a second region of the portion of the body.

3. The method according to claim 1 , wherein the step of performing dose calculation comprises:

f. producing a composite basis for calculation, based on the first basis for calculation and the second basis for calculation, the producing comprising:

g. determining at least a first area of the composite basis for calculation that is to incorporate the second material property information based on the second basis for calculation; and

h. producing the composite basis for calculation comprising the second material property information based on the second basis for calculation in the first area and the first material property information based on the first basis for calculation in at least a second area.

4. The method according to claim 3 , wherein the step of producing the composite basis for calculation is performed using material property information from both the fraction image and the planning image in the first area.

5. The method according to claim 3 , wherein third material property information in the first area is calculated in at least one voxel using combined second material property information and first material property information from the fraction image and the planning image, respectively.

6. The method according to claim 3 , wherein the first area includes at least part of one of the following: stomach, bowel, urinary bladder, uterus, lung, and tongue.

7. The method according to claim 1 , wherein the registration is performed using a deformable registration method.

8. The method according to claim 1 , wherein the material property information includes density or atomic structure of a region of interest.

9. The method according to claim 1 , wherein the planning image is acquired using fan beam CT.

10. The method according to claim 1 , wherein the fraction image is acquired using cone beam CT.

11. A non-transient computer readable medium containing program instructions which, when run in a computer will cause the computer to perform the method according to claim 1 .

12. A carrier comprising the non-transient computer readable medium of claim 11 .

13. A computer system for performing dose calculations for radiotherapy, the system comprising processing means for performing registration of images, said computer system having a memory having stored therein program instructions which, when executed, controls the processing means according to the method of claim 1 .