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Feasibility Study of Improving the Quality of PEM Images by Considering TOF and the DOI Correction

Rashidi, Mehdi | 2020

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 52996 (46)
  4. University: Sharif University of Technology
  5. Department: Energy Engineering
  6. Advisor(s): Hosseini, Abolfazle
  7. Abstract:
  8. Breast cancer is the most common type of cancer in women and the second cause of death among them. The chance of successful treatment would be significantly increased if the disease is diagnosed at its early stages. There are numerous methods to diagnose breast cancer. One of the most important methods is positron emission mammography (PEM).The main aim of this study is to investigate the feasibility of improving PEM images by considering the time of flight corrections and the penetration depth of the rays in the crystals.In this study, a commercial PEM system, Naviscan PEM, is simulated using the GATE software. In the first phase of the study, two opposing planar detectors are used to study the effect of time of flight, with each detector being composed of 12 blocks with 2x6 array, and each block being composed of 169 LSO crystals with 13x13 array. First the system was studied with three coincidence windows (6, 5, and 10 ns), which 32% increase occurred in the maximum of the NECR diagram in the 6 ns coincidence window due to the constancy of the corretct coincidence counts and the 56.7% decrease in the random coincidence count. Accounting for the time flight in the four coincidence resolutions 100, 350, 650, and 900 ps would improve the maximum of the NECR diagram. According to the obtained results, the NECR diagram's maximum occurs in the 6 ns coincidence window and 100 ps resolution which can cause 42.3 increase in the NECR diagram's maximum without accounting for the time of flight.In the second phase of the study, the Phoswich detector with LSO and BGO crystals of different thickness was used to study the effect of penetration depth. Acording to the results, the optimal thickness would be 5 mm for the LSO crystal in the first layer and 9 mm for the BGO crystal in second layer, which would cause 54% increase in the NECR diagram maximum relative to the time of the NECR diagram's maximum obtained from the effect of the time of flight in the coincidence window of 6 ns and the resolution of 100 ps.In this study by considering the time of flight corrections and the effect of the penetration depth of the rays in the crystals, the resolution was increased from 2.4 mm FWHM to 1 mm FWHM
  9. Keywords:
  10. Breast Cancer ; Time of Flight ; Simulation ; Positron Emission Mammography ; Geant4 Application for Tomographic (GATE)Emission ; Image Enhancement

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