Position verification and correction for radiation therapy using nonorthogonal on-board imaging

A radiation treatment system comprising:

• a gantry;
• an X-ray imaging system mounted on the gantry;
• and
• a processor configured to perform:
• acquiring a first X-ray image of a region of patient anatomy while the region of patient anatomy is in a first location relative to an isocenter of the radiation therapy system, the gantry is in a first imaging position, and a center axis of an imaging beam passes through the isocenter of the radiation therapy system along a first imaging path;
• acquiring a second X-ray image of the region of patient anatomy while the region of patient anatomy is in the first location, the gantry is in a second imaging position, and the center axis of the imaging beam passes through the isocenter of the radiation therapy system along a second imaging path, wherein an angle between the first imaging path and the second imaging path is a non-orthogonal angle;
• and
• based on a three-dimensional image of the region reconstructed from the first X-ray image, the second X-ray image, and a three-dimensional treatment planning image of the region, determining an offset between a planning location for the region and the first location of the region.

A computer-implemented method for a radiation therapy system that includes a gantry and an X-ray imaging system mounted on the gantry, the method comprising:

• acquiring a first X-ray image of a region of patient anatomy while the region of patient anatomy is in a first location relative to an isocenter of the radiation therapy system, the gantry is in a first imaging position, and a center axis of an imaging beam passes through the isocenter of the radiation therapy system along a first imaging path;
• after acquiring the first X-ray image of the region, causing the gantry to rotate from the first imaging position to a second imaging position;
• acquiring one or more additional X-ray images while the gantry rotates from the first imaging position to the second imaging position;
• acquiring a second X-ray image of the region of patient anatomy while the region of patient anatomy is in the first location, the gantry is in the second imaging position, and the center axis of the imaging beam passes through the isocenter of the radiation therapy system along a second imaging path, wherein an angle between the first imaging path and the second imaging path is a non-orthogonal angle;
• and
• generating a three-dimensional image of the region based on the first X-ray image, the second X-ray image, and the one or more additional X-ray images for determining an offset between a planning location for the region and the first location of the region.