Systems, methods, and related computer program products for image-guided radiation treatment (IGRT) are described. For one preferred embodiment, an IGRT apparatus is provided comprising a ring gantry having a central opening and a radiation treatment head coupled to the ring gantry that is rotatable around the central opening in at least a 180 degree arc. For one preferred embodiment, the apparatus further comprises a gantry translation mechanism configured to translate the ring gantry in a direction of a longitudinal axis extending through the central opening. Noncoplanar radiation treatment delivery can thereby be achieved without requiring movement of the patient. For another preferred embodiment, an independently translatable 3D imaging device distinct from the ring gantry is provided for further achieving at least one of pre-treatment imaging and setup imaging of the target tissue volume without requiring movement of the patient.
