Image-guided radiation therapy

A treatment system for delivering an image-guided radiation therapy treatment to a moving structure included in a region of a patient body based on a treatment plan, the treatment system comprising:

• a receiving unit for receiving a series of first images of the region of the patient body in different phases of a motion of the moving structure, the series of first images being associated with a series of second images of the patient body in same phases of the motion of the moving structure as the series of first images,
• wherein the first images are acquired from a planning imaging unit in accordance with a first imaging mode and the second images are acquired from the planning imaging unit in a second imaging mode differing from the first imaging mode, wherein the first imaging mode is a 3 dimensional (3D) imaging mode and the second imaging mode is one of a 2 dimensional (2D) imaging mode or a 1 dimensional (1D) imaging mode, wherein the first images are 3D images, wherein the second images are 2D images when the second imaging mode is the 2D imaging mode, and wherein the second images are 1D images when the second imaging mode is the 1D imaging mode,
• wherein the first images and the second images are acquired using a same imaging modality as each other,
• wherein each second image is associated with a corresponding first image among the series of first images, wherein each second image and the corresponding first image pertain to a same phase of the motion of the moving structure as each other,
• a therapy imaging unit controllable to acquire a third image of the patient using the second imaging mode during the radiation therapy treatment, wherein the third image is a 2D image when the second imaging mode is the 2D imaging mode, and wherein the third image is a 1D image when the second imaging mode is the 1D imaging mode, and
• an evaluation unit configured to plan a continuation of the radiation therapy treatment upon the acquisition of the third image,
• wherein the evaluation unit is configured to compare the third image of the patient acquired using the second imaging mode during the radiation therapy treatment, with the second images which are associated with the first images, and is further configured to select a selected one of the first images based on the comparison between the third image and the second images which are associated with the first images, and is further configured to plan the continuation of the radiation therapy treatment based on data relating to the selected one of the first images.