A detector arm assembly is provided that includes a stator, a detector head, a radial motion motor, and a detector head belt. The stator is configured to be fixedly coupled to a gantry having a bore. The detector head includes a carrier section that is slidably coupled to the stator and configured to be movable in a radial direction in the bore relative to the stator. The radial motion motor is operably coupled to at least one of the detector head or the stator. The detector head belt is operably coupled to the radial motion motor and the carrier section. Rotation of the radial motion motor causes movement of the detector head in the radial direction.