System and method for patient positioning for radiotherapy in the presence of respiratory motion

1. A method for positioning a patient for radiotherapy, comprising:

acquiring a first x-ray image sequence of a target inside the patient by projecting a radiation beam from a linear accelerator positioned at a first angle;

acquiring first respiratory signals of the patient while acquiring the first x-ray image sequence;

acquiring a second x-ray image sequence of the target by projecting a radiation beam from the linear accelerator positioned at a second angle;

acquiring second respiratory signals of the patient while acquiring the second x-ray image sequence, wherein the second x-ray image sequence and second respiratory signals are acquired after the first x-ray image sequence and first respiratory signals;

retrospectively synchronizing the first and second respiratory signals with each other to form synchronized first and second x-ray image sequences;

identifying the target in the synchronized first and second x-ray image sequences; and

determining three-dimensional (3D) positions of the target through time in the synchronized first and second x-ray image sequences.

2. The method of claim 1 , wherein the first and second x-ray image sequences are two-dimensional (2D) image sequences.

3. The method of claim 1 , wherein the first angle is 0 degrees and the second angle is 90 degrees.

4. The method of claim 1 , wherein the step of synchronizing the first and second respiratory signals, comprises:

resolving a time delay between the first and second respiratory signals.

5. The method of claim 1 , wherein the synchronized first and second x-ray image sequences represent the first and second x-ray image sequences if they were acquired at the same time.

6. The method of claim 1 , wherein the step of identifying the target in the synchronized first and second x-ray image sequences, comprises:

selecting the target from one image of the synchronized first and second x-ray image sequences; and

tracking the target in the remaining images of the synchronized first and second x-ray image sequences.

7. The method of claim 1 , wherein the step of determining the 3D position of the target through time, comprises:

extracting the target from the synchronized first and second x-ray image sequences; and

performing a triangulation using the first and second angles.

8. The method of claim 1 , further comprising:

matching the 3D positions of the target from the synchronized first and second x-ray image sequences with four-dimensional (4D) positions of the target acquired from a computed tomography (CT) scan of the patient.

9. The method of claim 8 , further comprising:

generating a graphical user interface (GUI) having a first window for displaying the 3D positions of the target that match the 4D positions of the target.

10. The method of claim 9 , wherein the GUI includes a second window for displaying a metric representing a difference between the 3D positions of the target and the 4D positions of the target.

11. The method of claim 8 , further comprising:

generating a first x-ray image sequence of the 3D positions of the target and a first digitally reconstructed radiograph (DRR) illustrating the 4D positions of the target.

12. The method of claim 11 , further comprising:

overlaying the first x-ray image sequence of the 3D positions of the target and the first DRR to determine one of matching and non-matching 3D positions of the target and 4D positions of the target.

13. The method of claim 8 , further comprising:

positioning the patient and performing radiotherapy in accordance with the matched 3D and 4D positions of the target.

14. The method of claim 1 , further comprising:

tracking internal markers while acquiring the first and second x-ray image sequences.

15. The method of claim 1 , wherein the first and second x-ray image sequences are acquired using a trigger signal having a predetermined frequency and the first and second respiratory signals are digitized using the trigger signal.

16. A system for positioning a patient for radiotherapy, comprising:

a memory device for storing a program,

a processor in communication with the memory device, the processor operative with the program to:

acquire a first x-ray image sequence of a target inside the patient by projecting a radiation beam from a linear accelerator positioned at a first angle;

acquire first respiratory signals of the patient while acquiring the first x-ray image sequence;

acquire a second x-ray image sequence of the target by projecting a radiation beam from the linear accelerator positioned at a second angle;

acquire second respiratory signals of the patient while acquiring the second x-ray image sequence, wherein the second x-ray image sequence and second respiratory signals are acquired after the first x-ray image sequence and first respiratory signals;

retrospectively synchronize the first and second respiratory signals with each other to form synchronized first and second x-ray image sequences;

identify the target in the synchronized first and second x-ray image sequences; and

determine three-dimensional (3D) positions of the target through time in the synchronized first and second x-ray image sequences.

17. The system of claim 16 , wherein the radiation beams are kilo-electron volt (KeV) or mega-electron volt (MeV) beams.

18. The system of claim 16 , wherein the first and second respiratory signals are acquired using one of a respiratory monitoring belt and an optical tracking device.

19. The system of claim 16 , wherein the processor is further operative with the program to:

match the 3D positions of the target from the synchronized first and second x-ray image sequences with four-dimensional (4D) positions of the target acquired from a computed tomography (CT) scan of the patient.

20. The system of claim 19 , wherein the CT data is acquired by using one of a CT, helical CT, positron emission tomographic (PET), fluoroscopic, ultrasound and magnetic resonance (MR) imaging device.

21. The system of claim 16 , wherein the processor is further operative with the program to:

track internal markers while acquiring the first and second x-ray image sequences.

22. The system of claim 21 , wherein the internal markers are gold balls.

23. The system of claim 16 , wherein the processor is further operative with the program to:

perform radiotherapy in accordance with the matched 3D and 4D positions of the target.

24. A method for positioning a patient for image guided radiation therapy (IGRT), comprising:

acquiring image data associated with a cancerous target inside the patient using a computed tomography (CT) imaging technique;

acquiring a first x-ray image sequence of the target by projecting a radiation beam from a linear accelerator positioned at a first angle and simultaneously acquiring first respiratory signals of the patient;

acquiring a second x-ray image sequence of the target by projecting a radiation beam from the linear accelerator positioned at a second angle and simultaneously acquiring second respiratory signals of the patient, wherein the second x-ray image sequence and second respiratory signals are acquired after the first x-ray image sequence and first respiratory signals;

synchronizing the first and second respiratory signals with each other after the first and second x-ray image sequences have been acquired to form synchronized first and second x-ray image sequences;

selecting the target from one image of the synchronized first and second x-ray image sequences and tracking the target in the remaining images of the synchronized first and second x-ray image sequences; and

extracting the target from the synchronized first and second x-ray image sequences and performing a triangulation using the first and second angles to determine 3D positions of the target through time in the synchronized first and second x-ray image sequences.

25. The method of claim 24 , wherein the first angle and the second angle are orthogonal to each other.

26. The method of claim 24 , further comprising:

matching the 3D positions of the target from the synchronized first and second x-ray image sequences with four-dimensional (4D) positions of the target acquired from a computed tomography (CT) scan of the patient.

27. The method of claim 26 , further comprising:

positioning the patient and performing the IGRT in accordance with the matched 3D and 4D positions of the target.