MONTE-CARLO METHODS FOR THE IN-VIVO ANALYSIS OF CISPLATIN USING X-RAY-FLUORESCENCE

A Monte Carlo method has been used to model the measurement of cisplat in uptake with in vivo X-ray fluorescence. A user-code has been writte n for the EGS4 Monte Carlo system that incorporates linear polarisatio n and multiple element fluorescence extensioins. The yield of fluoresc ent photons to the mainly Compton scattered background is computed for our detector arrangement. The detector consists of a mutually orthogo nal arrangement of X-ray tube, aluminium polariser and high purity ger manium scintillation detector. The influence of tube voltage on the mi nimum detectable concentration is modelled for 100 through 150 kVp X-r adiation. The code is able to predict absorbed dose to the patient whi ch will influence the optimal choice of tube voltage. The influence of alterations to collimator design and scatterer construction can also be examined. A minimum detectable concentration of 50 ppm is determine d from measurements with a 115 kVp X-ray source and a 615 ppm cisplati n sample in a water phantom. (C) 1998 Elsevier Science Ltd. All rights reserved.