An important characteristic of any scintillator is its temporal response to an impulse of radiation. Ideally, the response time for the induced luminescence is much shorter than the time interval between data acquisitions. As the response time approaches this time interval blurring results in the acquired images. The presence of a long secondary decay component is typically referred to as afterglow. In order to avoid conditions under which such blurring may occur, a study of the scintillator’s temporal characteristics is required. This is especially important for x-ray computerized tomography where an object is constantly in motion.