This paper describes a new robust method for 2D and 3D ultrasound (US) probe calibration using a closed-form solution. Prior to calibration, a position sensor is attached to the probe and is used to tag each image/volume with its position and orientation in space. At the same time, image information used to determine target location in probe coordinates. The calibration procedure uses these two pieces of information to determine the transformation (translation, rotation, and scaling) of the scan plane with respect to the position sensor. We introduce a novel methodology for real-time in-vivo quality control of tracked US systems, in order to capture registration failures during the clinical procedure. In effect, we dynamically recalibrate the tracked US system for rotation, scale factor, and in-plane position offset up to a scale factor. We detect any unexpected change in these parameters through capturing discrepancies in the resulting calibration matrix, thereby assuring quality (accuracy and consistency) of the tracked system. No phantom is used for the recalibration. We perform the task of quality control in the background, transparently to the clinical user while the subject is being scanned. We present the concept, mathematical formulation, and experimental evaluation in-vitro. This new method can play an important role in guaranteeing accurate, consistent, and reliable performance of tracked ultrasound.