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G. Mettivier , M.C. Montesi, P. Russo

Design of a compact gamma camera with semiconductor hybrid pixel detectors: imaging tests with a pinhole collimator. G. Mettivier , M.C. Montesi, P. Russo. Università di Napoli “Federico II” and INFN Napoli, Italy. Scope of the project. Design and build a compact gamma camera .

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G. Mettivier , M.C. Montesi, P. Russo

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  1. Design of a compact gamma camera with semiconductor hybrid pixel detectors: imaging tests with a pinhole collimator G. Mettivier, M.C. Montesi, P. Russo Università di Napoli “Federico II” and INFN Napoli, Italy 4th International Workshop on Radiation Imaging Detectors, Amsterdam, The Netherlands 8-12 September 2002

  2. Scope of the project • Design and build a compact gamma camera • for Tc-99m g -ray tracer (140 keV) • for sentinel lymph node (SLN) radio-guided surgery • using the medipix series of hybrid pixel detectors + collimator Design specifications of final system • CdTe pixel detector (1 mm thick) • Medipix2 readout chip (256x256 pixels, 55 mm pitch) • Spatial resolution 1-2 mm 4th International Workshop on Radiation Imaging Detectors, Amsterdam, The Netherlands 8-12 September 2002

  3. 4th International Workshop on Radiation Imaging Detectors, Amsterdam, The Netherlands 8-12 September 2002

  4. Scope of the present work To perform preliminary evaluations of the spatial resolution attainable with a pinhole tungsten collimator with the present imaging system • Medipix1 chip (64x64 pixels, 170 mm pitch) • 300 mm thick Silicon detector (low detection efficiency) 4th International Workshop on Radiation Imaging Detectors, Amsterdam, The Netherlands 8-12 September 2002

  5. 4th International Workshop on Radiation Imaging Detectors, Amsterdam, The Netherlands 8-12 September 2002

  6. Spatial resolution Point-like g source 0.6 mm FWHM at 46 mm Geometric efficiency 2x10-5 Collimator Field Of View 11 mm Si Pixel detector Medipix1 chip Chipboard or PGA Previous work Multi-hole collimator Setup d D 4th International Workshop on Radiation Imaging Detectors, Amsterdam, The Netherlands 8-12 September 2002

  7. h b Si pixel detector Medipix1 chip This work Experimental Setup Point-like g source Pinhole Collimator PGA chip carrier 4th International Workshop on Radiation Imaging Detectors, Amsterdam, The Netherlands 8-12 September 2002

  8. 0.35 mm h 7 mm b Experimental Setup Pinhole aperture a = 90 deg Pinhole minimum diameter d = 0.35 mm (de = 0.57 mm) Total (geometric+penetrative) on-axis efficiency S = de2 /16h2 de = effective diameter Total FWHM spatial resolution Rs2[ (h+b)de/b ]2 + (h/b)2 Ri2 4th International Workshop on Radiation Imaging Detectors, Amsterdam, The Netherlands 8-12 September 2002

  9. Results h = 16.5 mm h = 26.5 mm Point-like Co 57 gamma source (122 keV) h = 36.5 mm h = 46.5 mm Ethr = 15 keV Dt = 15 h b = 7.5 mm 4th International Workshop on Radiation Imaging Detectors, Amsterdam, The Netherlands 8-12 September 2002

  10. Results 0.2 cps/kBq 4th International Workshop on Radiation Imaging Detectors, Amsterdam, The Netherlands 8-12 September 2002

  11. Results D = 0.35 mm 4th International Workshop on Radiation Imaging Detectors, Amsterdam, The Netherlands 8-12 September 2002

  12. Conclusions Tested a prototype compact gamma camera Imaging performance at 10 mm source-collimator distance system sensitivity = 0.2 cps/kBq FOV = 20 mm Spatial resolution = 1 mm 4th International Workshop on Radiation Imaging Detectors, Amsterdam, The Netherlands 8-12 September 2002

  13. Future Developments Use of the Medipix2 readout ASIC (256x256 pixel, 55 micron pitch) Bump-bonded to a 1 mm thick CdTe pixel With respect to the present Medipix1 + Silicon detector: - Higher detection efficiency at 140 keV (30%) - Higher sensitivity (in the order of 1 cps/kBq) - Equal or better spatial resolution (1-2 mm) - Detection threshold settable up to about 100 keV Comparable with other prototype using arrays of scintillators Spatial resolution = 3.5 mm, FOV = 9 mm, Sensitivity = 10 cps/kBq (L. R. Mac Donald et al.) 4th International Workshop on Radiation Imaging Detectors, Amsterdam, The Netherlands 8-12 September 2002

  14. Acknowlegement This work has been done in the framework of the activities of the Medipix2 collaboration (www.cern.ch/MEDIPIX) which comprises 16 European research institutions. The Medipix2 chip has been designed by CERN (Geneva, Switzerland). The MUROS2 interface has been designed by NIKHEF (Amsterdam, The Netherlands). The Medisoft 4 software system has been written by Universita' di Napoli Federico II and INFN (Napoli, Italy). 4th International Workshop on Radiation Imaging Detectors, Amsterdam, The Netherlands 8-12 September 2002

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