Method and imaging system for determining a reference radiograph for a later use in radiation therapy

1. A method for determining a reference radiograph, comprising the steps of:

providing a Four-Dimensional Cone Beam Computed Tomography (4D-CBCT) apparatus, comprising a source and a detector configured to be selectively positioned at different angular positions around a patient, the 4D-CBCT apparatus generating a plurality of CBCT images corresponding to different times;

providing a radiographic apparatus comprising a radiographic source and a radiographic detector, the radiographic apparatus being configured to generate a sequence of radiographs corresponding to different times;

positioning a patient for generating CBCT images of the patient with the 4D-CBCT apparatus and radiographs of the patient with the radiographic apparatus;

performing a 4D-CBCT scanning sequence with the 4D-CBCT apparatus to generate a plurality of CBCT images of a portion of the patient's body, the CBCT images corresponding to different temporal phases associated with the patient;

performing a radiographic sequence with the radiographic apparatus so as to generate a plurality of first radiographs of patient, the first radiographs corresponding to different temporal phases associated with the patient;

providing a synchronization device configured to correlate a CBCT image corresponding to a given temporal phase with a radiograph corresponding to an equivalent temporal phase;

generating a correlated radiograph by correlating, with the synchronization device, one of the first radiographs with a designated one of the CBCT images, the designated CBCT image corresponding to a designated temporal phase; and

identifying the correlated radiograph as the reference radiograph.

2. A method according to claim 1 , wherein the radiographic sequence is performed during at least a portion of the 4D-CBCT scanning sequence.

3. A method according to claim 1 , wherein the temporal phases correspond to respiratory phases of a respiratory cycle.

4. A method according to claim 1 , wherein each of the CBCT images corresponds to a CT image generated previously by a CT apparatus.

5. A method according to claim 1 , wherein correlating with the synchronization device comprises correlating the first radiographs with the CBCT images in multiple reference radiographs, wherein each of the multiple reference radiographs corresponds to a given designated temporal phase.

6. A method according to claim 5 , wherein comprising the step of generating at least ten CBCT images corresponding to at least ten temporal phases from the 4D-CBCT scanning sequence.

7. A method according to claim 1 , comprising the step of generating, from the radiographic sequence, at least ten radiographs for at least ten temporal phases from the radiographic sequence.

8. A method according to claim 1 , further comprising the steps of:

positioning a target volume of the patient's body between the radiographic source and the radiographic detector;

generating a second radiograph of the target volume with the radiographic apparatus;

comparing the second radiograph with the reference radiograph to generate a comparison result;

determining, based on the comparison result, whether the second radiograph matches the reference radiograph; and

when the second radiograph matches the reference radiograph, determining a position of a tissue of the patient from the CBCT image correlated with the reference radiograph.

9. A method according to claim 1 , wherein when the reference radiograph corresponds to a given temporal phase in order to send the treatment beam, the method further comprises the steps of:

configuring the radiographic apparatus to generate an image of a patient's body during treatment;

positioning a target volume of the patient's body in a treatment position;

generating a second radiograph of the target volume with the radiographic apparatus;

generating a comparison result by comparing the second radiograph with the reference radiograph;

determining, based on the comparison result, whether the second radiograph matches the reference radiograph; and

sending the treatment beam to the patient if the second radiograph matches the reference radiograph.

10. An imaging system for identifying a reference radiograph for use in radiation therapy, the imaging system comprising:

a 4D-CBCT apparatus comprising a source and a detector configured to be selectively positioned at different angular positions around a patient, the 4D-CBCT apparatus generating a plurality of CBCT images corresponding to different times;

a radiographic apparatus, including a radiographic source and a radiographic detector, the radiographic apparatus being configured to generate a sequence of radiographs corresponding to different times; and

a synchronization device configured to generate a reference radiograph by correlating a CBCT image corresponding to a given temporal phase with a radiograph corresponding to an equivalent temporal phase.

11. An imaging system according to claim 10 , wherein:

generating the CBCT images comprises generating the CBCT images as three dimensional images;

generating the radiographs comprises generating the radiographs as two dimensional images.

12. An imaging system according to claim 10 , wherein the temporal phase corresponds to a respiratory phase of a respiratory cycle.

13. An imaging system according to claim 10 , wherein the synchronization device comprises a controller configured to control the radiographic apparatus to generate the reference radiograph.

14. An imaging system according to claim 13 , wherein the controller is further configured to generate the radiograph by controlling the radiographic apparatus to perform a radiographic sequence during at least a portion of a 4D-CBCT scanning sequence the radiograph.

15. An imaging system according to claim 10 , wherein the synchronization device is configured to determine a temporal phase of a CBCT image.