Several linear accelerator vendors have systems with single x-ray imager. A single x-ray imager presents a challenge to estimate 3D positioning. A method to estimate the 3D position using a single x-ray imager with prior information has been developed by Stanford researchers.
Real-time internal target position estimation is of high interest in radiotherapy, particularly with the recent development of robotic, linear accelerator, DMLC and couch-based systems which can continuously align the radiation beam with the target.