Cone beam computed tomography with a flat panel imager

A process for on-line cone beam computed tomography guidance of radiation therapy procedures that involves:

• 1) a cone beam computed tomography image system that includes a flat panel imager and a keV x-ray source that generates x-ray beams in a cone-beam form towards the flat panel imager and 2) a radiation therapy source system comprising:
• a radiation therapy source that generates therapeutic radiation, a collimating structure and an imager that is located opposite said radiation therapy source that generates therapeutic radiation, the process comprising:
• performing an off-line treatment process comprising:
• providing a planning image on which contours of a target volume of an object to be treated and surrounding structures are defined;
• performing inverse planning according to a given protocol for radiation therapy of said object so as to generate a reference plan;
• generating a plurality of additional plans as a function of various translations and/or rotations of said target volume;
• performing an on-line treatment process comprising:
• positioning said object on a treatment table;
• acquiring cone beam computed tomography images of said object on said treatment table;
• delineating said target volume and surrounding structures in said cone beam computed tomography images so as to identify translations and/or rotations of said target volume relative to a position and orientation in said planning image;
• correcting translation of said object observed in said cone beam computed tomography images relative to said planning image by translation of said object on said treatment table in y and/or z directions, and/or by rotation about an x axis;
• and
• correcting orientation of said target volume by selecting from said reference plan and said plurality of additional plans a modified radiation therapy treatment plan that most closely corresponds to a measured rotation of said target volume.