BASIC SCIENCES High Density Avalanche Chamber (HIDAC) Positron Camera
نویسندگان
چکیده
A prototypepositroncamerahasbeenconstructedconsistingof two highdensityavalanche chamber (HIDAC) detectors operated in coincidence with a resolving time (2r) of 40 nsec. The detectors are multiwire chambers, with specially constructed lead converters added to improvethe photondetectionefficiencyat 511 keV.ThecurrentHIDACdetectorshavea singles efficiency of @—12%, a sensitive area of 31 x 31 cm and an intrinsic spatial resolution of <2 mmfull widthat halfmaximum(FWHM).Duringdataacquisition,the detectorsare rotatedaroundthe patientin orderto collecta completeangulardataset.A three-dimensional image of the positron distribution is reconstructed from a single scan by weighted backprojectionof the data into a matrixof either64 x 64 x 64 or 128 x 128 x 16 voxels. Thecamerapoint responsefunctionis deconvolvedby frequency-spacefiltering.Corrections aremadeduringbackprojectionboth for photonattenuationandfor spatialvariationsin point source sensitivity. The reconstructed image is fUrther corrected for contributions from acodentalandscatteredcoincidencesanddisplayedas a sequenceof two-dimensional transverse,sagittal,or coronalsections.Inaddition,three-dimensional displayis available using shaded graphics techniques. The prototype camera is currently undergoing clinical evaluation.
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