Nuclear medicine imaging systems and methods having a secondary mechanism for controlling a detector head

Nuclear medicine (NM) imaging system includes a detector assembly coupled to a gantry. The NM imaging system also includes a positioning sub-system having a motion controller and a detector motor. The positioning sub-system also includes a proximity sensor device (PSD) coupled to a detector head of the detector assembly. The PSD is configured to be activated. In response to being activated, the PSD is configured to transmit an output signal to stop the detector motor from moving the detector head toward the object. The NM imaging system also includes a secondary circuit that, in response to the PSD being activated, is configured to determine whether the detector head has stopped moving toward the object and, if the detector head has not stopped moving toward the object, is configured to disable the detector motor.