R. Robertson

Publications (2)1.45 Total impact

• Article: Performance Measurements of CMOS Position Sensitive Solid-State Photomultipliers

  M. McClish, P. Dokhale, J. Christian, C. Stapels, E. Johnson, R. Robertson, K.S. Shah
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  ABSTRACT: We have designed position sensitive solid-state photomultipliers (PS-SSPM) using a complementary metal-oxide-semiconductor (CMOS) process. Four variations of the PS-SSPM design were fabricated, however, one of the variations did not function properly. The remaining three functional variations were characterized for their energy and coincidence timing resolution, spatial resolution, and scintillator array imaging. Each PS-SSPM is 1.5 × 1.5 mm², however, each device has different micro-pixel geometries and different micro-pixel electrical readout for event position sensing. When coupled to 1 × 1 × 20 mm³ LYSO, the energy resolution at 511 keV was measured as a function of bias. The same LYSO scintillator was used to measure the coincidence timing resolution. Results between the PS-SSPMs varied from 2.0 ns to 0.9 ns (FWHM) at 511 keV. Spatial resolution studies were conducted using a focused (15 μm beam spot diameter) pulsed 635 nm diode laser. For each PS-SSPM, the X and Y spatial resolution was measured between 70 and 75 μm (FWHM). Lastly, scintillator array images were generated using a CsI:Tl and LYSO array having 300 × 300 μm² and 500 × 500 μm² pixels respectively.
  IEEE Transactions on Nuclear Science 09/2010; · 1.45 Impact Factor
• Conference Proceeding: Performance measurements of CMOS SSPM as PET detector

  P. Dokhale, R. Nagarkar, R. Robertson, M. McClish, C. Stapels, J. Christian, G. Entine, M. Squillante, S. Cherry, K. Shah
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  ABSTRACT: We have designed and developed a complementary metal-oxide-semiconductor (CMOS) solid-state photomultiplier (SSPM). We have studied this novel SSPM as a readout of LYSO scintillator for use in positron emission tomography (PET). Here we present energy resolution, coincidence timing resolution, depth of interaction measurements and flood imaging studies with SSPMs coupled to LYSO seintilators. Two different sizes, 3 x 3 mm² and 1.5 x 1.5 mm² SSPMs were studied. The measured FWHM energy resolution with 511 keV gamma rays was 22% for the detector consisting 3 x 3 mm² SSPM coupled to a 3 x 3 x 15 mm³ LYSO and 11.2 % for the detector consisting 1.5 x 1.5 mm² SSPM coupled to 1.5 x 1.5 x 10 mm³ LYSO. The timing resolution measured was 1.8 ns for the 3 x 3 mm² detector in coincidence with a detector consisting LSO coupled to PMT. The coincidence timing resolution was 530 ps for 1.5 x 1.5 mm² detector. The measured depth-of-interaction resolution by coupling two 1.5 x 1.5 mm² SSPMs on opposite ends of a 1.5 x 1.5 x 20 mm³ LYSO scintillator was 2.5 mm. The flood histogram was recorded with a 4 x 4 LYSO array, each element measuring 1.5 x 1.5 x 15 mm³ coupled to a position sensitive SSPM (PS-SSPM) consist of a 4 x 4 array of SSPM elements. The flood image was distortion free, all 16 elements were clearly visible and well separated from each other.
  Nuclear Science Symposium Conference Record, 2007. NSS '07. IEEE;