Abstract: In predicting failure of an x-ray tube in a computed tomography (CT) system, reference detector elements normally disposed on each end of the detector, receive x-rays directly from the x-ray tube. In accordance with the invention, the output values of the reference detector elements are utilized by a tube condition prediction algorithm to predict a failure in the x-ray tube of the CT system. The tube condition prediction algorithm utilizes at least one model of the CT system and at least one prediction routine, which typically is a Kalman filter, to generate the prediction. The prediction routine uses the model to analyze the output values of the reference detector elements in order to determine the condition of the x-ray tube and predict future performance of the x-ray tube.