X-ray spectrum of CT system acquired by Compton spectroscopy using high resolution Schottky CdTe detector

摘要

Recently, x-ray computed tomography (CT) systems were developed dramatically; e.g. arnmulti-detector-row CT or a four-dimensional CT, but it has been expressed anxiety that arnpatient dose is increased. Analysis of x-ray spectrum is important for quality assurance andrnquality control of radiographic systems to estimate a quality of an imaging system and torndecrease a patient dose.rnThe aim of this study is to measure the x-ray spectra of CT system under clinical conditionsrnusing a high resolution Schottky CdTe detector. When measuring diagnostic x-ray spectra, thernlong distance from the x-ray source to the detector is requested for reducing a number ofrnphotons detected per unit time to prevent pile-up of the detector. However, that is veryrndifficult to set up the long source-to-detector distance in a gantry of a CT unit. For resolvingrnthis problem, the Compton spectroscopy is very suitable. Using this method, a number ofrnphotons detected per unit time can be reduced by detecting the scattered x-ray photons. If thern90˚ scattered photons can be detected, the energy correction and reconstruction of spectra canrnbe calculated easily by use of the Klein-Nishina formula.