A radiotherapy apparatus to generate electron beam and CBCT (Cone Beam Computed Tomography) image wherein the apparatus comprises: a. a ring gantry having a central opening to accommodate the body of a patient positioned along the longitudinal axis and extending there through; b. at least two KV sources (102a and 102b) in the ring gantry, wherein the two KV sources (102a and 102b) are used for generating a beam of imaging radiation directed towards the patient's table used for stereotactic imaging; c. at least two movable detectors (103 and 104) arranged on the ring gantry and mounted iso-centrically on the ring gantry and separated by an angle of 90 degrees to detect the beam of imaging radiation after it has passed through the patient table; and d. the two movable detectors (103 and 104) are a first movable detector and a second movable detector, i. the first movable detector configured to be placed far from the patient plane to accommodate wider bore/ central opening and further configured to move closer to the patient's plane and to capture a full fan mode of X ray beam of imaging radiation with a FOV of at least 250 X 250 mm; ii. the second movable detector configured to be placed far from the patient plane to accommodate wider bore/ central opening and further configured to move further towards the iso-center of the ring gantry to capture a half fan mode of X-ray beam of imaging radiation with a greater FOV of 250 X 450 mm a. a ring gantry having a central opening to accommodate the body of a patient positioned along the longitudinal axis and extending there through; b. at least two KV sources (102a and 102b) in the ring gantry, wherein the two KV sources (102a and 102b) are used for generating a beam of imaging radiation directed towards the patient's table used for stereotactic imaging; c. at least two movable detectors (103 and 104) arranged on the ring gantry and mounted iso-centrically on the ring gantry and separated by an angle of 90 degrees to detect the beam of imaging radiation after it has passed through the patient table; and d. the two movable detectors (103 and 104) are a first movable detector and a second movable detector, i. the first movable detector configured to be placed far from the patient plane to accommodate wider bore/ central opening and further configured to move closer to the patient's plane and to capture a full fan mode of X ray beam of imaging radiation with a FOV of at least 250 X 250 mm; ii. the second movable detector configured to be placed far from the patient plane to accommodate wider bore/ central opening and further configured to move further towards the iso-center of the ring gantry to capture a half fan mode of X-ray beam of imaging radiation with a greater FOV of 250 X 450 mm i. the first movable detector configured to be placed far from the patient plane to accommodate wider bore/ central opening and further configured to move closer to the patient's plane and to capture a full fan mode of X ray beam of imaging radiation with a FOV of at least 250 X 250 mm; ii. the second movable detector configured to be placed far from the patient plane to accommodate wider bore/ central opening and further configured to move further towards the iso-center of the ring gantry to capture a half fan mode of X-ray beam of imaging radiation with a greater FOV of 250 X 450 mm