X-RAY FLUORESCENCE COMPUTED TOMOGRAPHY

SYNCHROTRON RADIATION INDUCED X-RAY FLUORESCENCE COMPUTED TOMOGRAPHY WILL PROVIDE A MEANS OF NON-DESTRUCTIVELY MAPPING THE THREE-DIMENSIONAL DISTRIBUTION OF TRACE ELEMENTS WITHIN A SPECIMEN. MICRON SCALE SPATIAL RESOLUTION AND PPM LEVEL SENSITIVITY ARE POTENTIALLY ACHIEVABLE; HOWEVER, THERE ARE BOTH OBSERVATIONAL AND COMPUTATIONAL DIFFICULTIES. THE CHARACTERISTIC FLUORESCENT LINE RADIATION FROM A TRACE ELEMENT MUST BE DETECTED AGAINST THE BACKGROUND FLUX OF SCATTERED RADIATION AND FLUORESCENT RADIATION FROM MORE ABUNDANT ELEMENTS, AND ABSORPTION BY THE MATRIX OF BOTH THE INCIDENT EXCITING BEAM AND THE OUTGOING FLUORESCENCE RADIATION COMPLICATES THE TOMOGRAPHIC RECONSTRUCTION OF THE DISTRIBUTION OF THE FLUORESCING ELEMENT. RESEARCHERS ARE DESIGNING A WAVELENGTH DISPERSIVE SPECTROMETER THAT CAN BE ATTACHED TO FLUORESCENCE CT COLLIMATORS WITHIN THE CONFINES OF A BEAM HUTCH AT A SYNCHROTRON LIGHT SOURCE. RESEARCHERS ARE ALSO DEVELOPING A PRACTICAL IMPLEMENTATION OF AN ALGORITHM FOR ABSORPTION CORRECTED RECONSTRUCTION OF FLUORESCENCE CT DATA.