Abstract: A calibration sheet is located at a first position where its surface substantially corresponds to the expected position of a patient surface lying on a mechanical couch during treatment. Images of the calibration sheet are obtained and processed to ascertain relative locations and orientations of the image detectors obtaining the images and optical distortion parameters indicative of optical distortions present in the obtained images of the calibration sheet. The calibration sheet is then re-located to a known position relative to the iso-centre of the treatment apparatus and images of the re-located calibration sheet are obtained and processed to determine a transform corresponding to the relocation of the calibration sheet from the first position to the iso-centre of the treatment apparatus. Data indicative of optical distortions present in the images and data indicative of the locations and orientations of the image detectors relative to the iso-centre of the treatment apparatus are stored.

Abstract: A patient monitoring system for monitoring a patient undergoing radiotherapy comprising a projector operable to project a pattern of light onto a patient undergoing radiation treatment, a patient restraint operable to restrain the patient relative to a treatment apparatus, an image detector operable to obtain images of the patient, and a model generation module operable to process images of the patient obtained by the image detector to generate a model of the surface of a portion of the patient, wherein at least a portion of the patient restraint is colored and the model generation module is inhibited from generating a model of the colored portion of the patient restraint.