A radiation treatment and imaging system for emitting a radiation treatment beam and X-ray imaging beams towards an object. The system includes an x-ray source and a collimator, first and second detectors, and a linear accelerator that delivers radiation beams to an object. The linear accelerator includes a radiation source positioned between the first and second detectors and emitting a therapy radiation beam in-line with the x-ray beams received by the first and second detectors. The system also includes a data processing device in communication with the first and second detectors. The data processing device receives imaging signals from the first and second detectors and reconstructs a three-dimensional tetrahedron beam computed tomography (TBCT) image from the received imaging signals. The system also includes a display in communication with the data processing device and for displaying the TBCT image.
