Detection performance of SIGaAs detectors for nuclear medicine

Thiscollaborationhasalreadyobtainedencouragingresultsabouttheperformanceof200and600mmthicksemi-insulatingGaAsdetectors,intermsofchargecollectionefficiency(c.c.e.),detectionefficiencyandimagingcapabilities,tobeusedassinglephotoncountingdetectorswithphotonsintheradiographicenergyrange.Thepossibleuseofsuchdetectorsinnuclearmedicineimpliesdetectionofmoreenergeticphotons,uptothe140keVofthe 99m Tcsource;thusefficientdetectorsmustbethickerthanthosepreviouslystudied.Inthispaper,wepresenttheresultsoftheinvestigationofelectricalanddetectionproperties(spectra,c.c.e.,energyresolution)ofaseriesofdetectors,whosethicknessrangesfrom 200to1000mm, when irradiated with radioactive sources over the energy range used in nuclear medicine.# 2001 ElsevierScienceB.V.Allrightsreserved. 1. IntroductionIn nuclear medicine, in applications as scinti-graphy and single photon emission computedtomography(SPECT)thephotonstobedetectedare emitted by a radioisotope present into thepatient thanks to a radiopharmaceutical (radio-isotope-taggedcompound),whichcanbeinjected,ingested or breathed [1], in order to ‘‘trace’’variousfunctionsofthebody.Oneoftheprimaryadvantages associated with the use of radionu-clides is the large signal (the emitted radiation)obtainedfromtherelativelysmallmassofradio-nuclide employed for a given study. The minutemass of the radiolabeled material allows for theobservation without disturbance of the systemunder study through pharmacological or toxico-logicaleffect.Thephysicalcharacteristicsofradio-nuclides that are desirable for nuclear medicineimaginginclude:asuitablephysicalhalf-life;decayvia photon emission; associated photon energyhigh enough to penetrate the body tissue withminimal tissue attenuation and low enough toallowingforminimalthicknessofcollimatorsepta;absenceofparticulateemission.