US Patent 10342996 Online angle selection in rotational imaging and tracking systems

A radiation therapy apparatus determines a set of angles that have a tracking quality metric value that satisfies a tracking quality metric criterion. During an alignment phase or a treatment phase for a treatment stage of a target by the radiation therapy apparatus, the radiation therapy apparatus performs selects at least a first angle and a second angle from the set of angles for a first rotation of the gantry. The radiation therapy apparatus generates, using an imaging device mounted to the gantry, a first tracking image of the target from the first angle during the first rotation of the gantry. The radiation therapy apparatus generates, using the imaging device, a second tracking image of the target from the second angle during the first rotation of the gantry. The radiation therapy apparatus performs the target tracking based on the first tracking image and the second tracking image.