Abstract: A system for medical diagnosis is provided. The system includes a gantry mounted on the base. The gantry has an annular support, which defines a cylindrical inner space. A detector head is fixed to the inner surface of the annular support. The annular support rotates along an axis of the inner space and is prevented from moving in horizontal and vertical direction and moving angularly. The system has a patient bed system, which is detachably attached to the base, and has a contact surface for supporting the patient. Pivot mechanism(s) and adjustable arm(s) enable the contact surface to have a plurality of configurations.