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w. w. d. w. > L <. Coded Aperture Thin Cone s. better res. small FOV lower eff. Collimator Thin Cone. Pinhole Thin Cone. Compton Cone Surface. PET Thin Line. - results similar to pinhole higher efficiency . changing L,d efficiency vs sp.res. 0 – 20 mm 1 – 0.009 %.
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w w d w > L < CodedAperture Thin Cones better res. small FOV lower eff. Collimator Thin Cone Pinhole Thin Cone Compton Cone Surface PET Thin Line • - results similar to pinhole • higher efficiency changing L,d efficiency vs sp.res. 0 – 20 mm 1 – 0.009 %
New Detector (Pin hole 0.7 mm tungsten, H8500 64 ch) (1.8 x 1.8 mm2)(1.0 x 1.0 mm2) Good pixel identification For 1.8 x 1.8 not so good for 1.0 x 1.0 -> better anode sampling is needed --> H8500 256 channels Flood Field irradiation Eg = 122 keV
Read-out electronics now the chip VA-HDR11 is used
Reconstruction of a 122 keV point-like source using the coded apertures Submillimeter spatial resolution High sensitivity (factor ~ 30) FWHM=0.93 mm 5 cps/MBq with pinhole Sensitivity=145 cps /MBq
simulation for our desktop detector 10Ci in 10 s 4444 pixels 1.25 x 1.25 mm2 FoV 22 cm2. Mask NTHT MURA 2222, =2, 1% transparent, thickness 1.5 mm W. Pitch 0.68 mm. Line source 10Ci in 10 s 2D source 10Ci in 10 s sensitivity improved by a factor 30! coded aperture collimators
High resolution preserving high SNR ? Ideal pinhole +perfect resolution -zero transmitted power Real pinhole +some signal through -degraded resolution Coded Aperture +signal of finite pinhole +resolution of ideal pinhole coded apertures
Coded apertures Figure adapted from:Fenimore and Cannon, Optical Engineering, 19, 3, 283-289, 1980. Example of apertures with known decoding pattern I (Image) = O (object) x A (aperture) There are decoding patterns G allowing: A G = d then A G = Ô, in fact Ô = R G = ( O× A ) G = O * (A G) = O * PSF