A system including a diagnostic-quality CT scanner for imaging a patient, the diagnostic-quality CT scanner having an imaging isocenter and a radiation therapy device positioned adjacent the diagnostic-quality CT scanner, the radiation therapy device including a gantry carrying a radiation therapy beam source and having a radiation therapy isocenter separate from the imaging isocenter of the diagnostic-quality CT scanner. The system including a couch configured to position the patient for imaging and for radiation therapy by translating the patient between the diagnostic quality CT scanner and the radiation therapy device.