Evaluation of EDXRF configurations to improve the limit of detection and exposure for in vivo quantification of gadolinium in tumor tissue

MAURICIO SANTIBAÑEZ; MATIAS VÁSQUEZ; RODOLFO FIGUEROA; MAURO VALENTE

RADIATION PHYSICS AND CHEMISTRY (OXFORD)

PERGAMON-ELSEVIER SCIENCE LTD

Lugar: Amsterdam; Año: 2016 vol. 122 p. 28 - 34

0969-806X

In thispapertheconfiguration ofanEnergyDispersiveX-RayFluorescence(EDXRF)systemoptimizedforin vivo quantification ofgadoliniumintumortissuewasstudied.Thesystemwasconfigured usingXMI-MSIM softwaredesignedtopredicttheXRFspectralresponseusingMonteCarlosimulations.Thestudiedsetup iscomprisedofanX-raytube,tunedtodifferentvoltages,andacopper filter systemconfiguredwith variablethickness,whichemitsaspectrallynarrowbeamcenteredonthespecific excitationenergy.The valuesforthecentralenergyexcitationandthespectralwidthwereadjustedtooptimizethesystem,using like figures ofmerit:minimizationofthelimitofdetection,measurementuncertaintyandra-diation exposure.Thesevalueswereobtainedintwostages.The first wassuccessivesimulationsofincident spectrawithcentralenergyintherangeof50?70 keV.Thesecondwascomprisedofsimulationswith incidentspectraofdifferentwidths(8?29 keV),allwiththesamedeterminedcentralenergy,evaluatingthelimitofdetectiondependingontheexposure.Thismadeitpossibleto find thebestbalance betweensystemsensitivityandthedelivereddose.Theobtainedresultswerecomparedwiththose producedbyradioactivesourcesof 241Am whoseactivitywassettoproducethesameexposureasthe proposedsetup.Toevaluatethefeasibilityof in vivo quantification, asetoftumorphantomsof1?6 cm3 at differentdepthsandlabeledwithagadoliniumconcentrationof250ppmwasevaluated.Fromtheresultingspectrum,calibrationcurveswereobtainedinfunctionofthesizeanddepthofthetumor,allowingfortheevaluationofthepotentialofthemethodology.