MonteCarloSimulation Study of SeveralCamera Designs forthePET Component ofa Dedicated Breast PET/CT Scanner

Inthis studyweusedMonteCarlosimulations to analyze thepatient imaging performance ofa rangeofcamera geometries forthePET portion ofa dedicated pendant breast PET/CTsystem. Performance wasassessed bycomparing NEC, rates, andscatter fractions forarangeofinjected FDG activities. ThesameLSO blockdetector (9x9arrays of3mm x3mm x20 mm crystals and3.3mm pitch) wasusedtocompose acylindrical, split-ring, five-sided box,anda planar dual-headed system. To simulate thepatient an anthropomorphic modelwas created consisting oftheNCAT phantom, volumes acting asthebrain and bladder, andoneofthreeCT-derived pendant breast shapes (representative ofsmall, medium,andlargevolumebreasts) appended totheleft chest wall, withFDG concentration ratios set tothosegiven byRamosetal.Systems weremodeled withLSO background, deadtimeeffects (256nsparalysable attheblock level, andnon-paralysable), a 7.5nscoincidence timewindow, andenergywindowof350to650keV.Thecylindrical scanner gavesignificantly higher NEC ratesacrossallviable injection activities (-5to-20mCi)regardless ofthebreast sizeimaged. Forthemediumsized breast, ataninjection activity of20mCi, thecylindrical scannershoweda 3-fold gaininNEC rate compared tothedual-headed system(32.4 vs.10.5kcps) atthe costofaslightly higher scatter fraction (0.28 vs.0.24). Additional simulations withan alternative cylindrical scannersystem composed ofDOIcapable detectors (APDfront endandPMT back)gavesomewhatlowerNEC ratescomparedwiththe conventional cylindrical design duetoalowereffective packing fraction. Basedonthese results thecylindrical scanner wasfound theoptimal geometryforpronededicated breastPET/CT imaging.