Patent ID: 8520800

Claim:
A radiation therapy system for delivering radiation to a human patient comprising: a radiation therapy source for delivering radiation to a target in said human patient; a scanning beam x-ray source for providing x-ray photons directed to said target; an x-ray detector for measuring a number of said x-ray photons passing through said target and striking said detector; an image reconstruction processor coupled to said x-ray detector for producing an image based on said number of said x-ray photons passing through said target and striking said detector; a detector shield assembly for shielding said x-ray detector from said radiation from said radiation therapy source, configured to have a first position outside of all beam paths between said scanning beam x-ray source and active surface of said x-ray detector and a second position occluding all of said beam paths between said scanning beam x-ray source and said active surface of said x-ray detector; and a mechanical actuator coupled to said detector shield assembly for moving said detector shield assembly between said first position and said second position in less than 0.3 seconds.