Impact of detector thickness on imaging   characteristics of the Siemens Biograph          DUO PET/CT with GATEN. N. Chatz...
AIMThe present paper is a Monte Carlo study of aSiemens Biograph DUO PET/CT with GATE,withemphasis given on PET imaging an...
Introduction 1/3Positron emission tomography - computedtomography PET-CT is a medical imaging techniqueusing a device whic...
Introduction 2/3Scintillation is a process of emittedcharacteristic light spectrum when ascintillator is absorbing ionisin...
Introduction 3/3GATE is an advanced opensource software , combinesthe advantages of theGEANT4 simulation toolkit,dedicated...
Materials and Methods   Simulation with Gate-Geant of the PET/CT Siemens Biograph DUO   GATE codes for (building the sim...
Materials and Methods   Software phantoms (inside the simulation):   (a) a cylindrical source phantom of radius 1 mm and...
Materials and Methods   Interaction phenomena :   i) Crystal energy blurring: resolution of 0.25 at    511keV.   (ii) D...
Results and Discussion   i) Diagram with    Characteristics of the    Biograph DUO PET/CT    (black line) and estimation ...
Results and Discussion   iii)Number of Counts –    Energy (MeV) ( pick at 0.25    MeV)   ii)Diagram Number of counts    ...
Results and Discussion   Root Mean Square (RMS) energy    is 99.06 keV   Mean energy is 407.5 keV   FWHM of energy and ...
Results and Discussion   Energy Resolution Of System    ◦ A) 2 cm LSO thickness    ◦ B) 3 cm LSO thickness       The pea...
Results and Discussion   As detector thickness    increases, the axial distribution    sensitivity of the number of    co...
Results and Discussion   The increase with thickness    of the photon detection    sensitivity of a block of 64    LSO cr...
Conclusions   Non-significant changes were observed for:    ◦   positron kinetic energy spectrum    ◦   interactions of p...
Thank You !http://env-hum-comp-res.teipir.gr/                  International Scientific Conference eRA-7
References:   Bailey,D.L., Meikle, S.R. 1994. A Convolution-Subtraction scatter correction method for 3D PET, Phys. Med. ...
   Michel, C., Eriksson, L., Rothfuss, H., Bendriem, B., 2006. Influence of crystal material on the performance of the HiR...
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Impact of detector thickness on imaging characteristics of the Siemens Biograph DUO PET/CT with GATE

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Impact of detector thickness on imaging characteristics of the Siemens Biograph DUO PET/CT with GATE

  1. 1. Impact of detector thickness on imaging characteristics of the Siemens Biograph DUO PET/CT with GATEN. N. Chatzisavvasd, T. J. Sevvosd, Em. M. Vlamakisd, A. A.Fotopoulos d, X. A. Argyriou d X. Tsantilasb, S. Kottoub ,P.H.Yannakopoulosd, A. Louizib , I. Kandarakisc, J. Malamitsib andD. Nikolopoulosa a Department of Physics, Chemistry and Material Science, Technological Educational Institute (TEI) of Piraeus, Petrou Ralli & Thivon 250, 122 44,Aigaleo,Athens,Greece b Medical Physics Department, Medical School, University of Athens, Mikras Asias 75, 11527, Athens, Greece c Department of Medical Instruments Technology, Technological Educational Institution of Athens, Ag. Spyridonos, Aigaleo, 122 10 Athens, Greece d Department of Engineering of Electronic and Computer Systems,Technological Educational Institute (TEI) of Piraeus, Petrou Ralli & Thivon 250, 122 44,Aigaleo,Athens,Greece International Scientific Conference eRA-7
  2. 2. AIMThe present paper is a Monte Carlo study of aSiemens Biograph DUO PET/CT with GATE,withemphasis given on PET imaging and, especially,to changes caused by changing the thickness ofthe LSO detector of a PET/CT. International Scientific Conference eRA-7
  3. 3. Introduction 1/3Positron emission tomography - computedtomography PET-CT is a medical imaging techniqueusing a device which combines system both aPositron Emission Tomography (PET) and an x-rayComputed Tomography. International Scientific Conference eRA-7
  4. 4. Introduction 2/3Scintillation is a process of emittedcharacteristic light spectrum when ascintillator is absorbing ionising radiation. LSO Scintillator : International Scientific Conference eRA-7
  5. 5. Introduction 3/3GATE is an advanced opensource software , combinesthe advantages of theGEANT4 simulation toolkit,dedicated to numericalsimulations in medicalimaging and radiotherapywritten in C/C++ International Scientific Conference eRA-7
  6. 6. Materials and Methods Simulation with Gate-Geant of the PET/CT Siemens Biograph DUO GATE codes for (building the simulation): (a) the entire PET detector arrangement (b) the light guides, photomultiplier tubes and related electronics (c) the digitizer (d) the shielding between PET and CT (e) the coincidence circuits and processors (f) the time-delay of PET (g) the data processing systems (h) the examination bed (i) the PET and CT gantry (j) the PET motions (gantry, bed) (k) the shielding of the room (l) the CT image reconstruction chain . International Scientific Conference eRA-7
  7. 7. Materials and Methods Software phantoms (inside the simulation): (a) a cylindrical source phantom of radius 1 mm and height 15 cm filled with F-18 FDG (b) human body phantom : ◦ (b-i) an ellipsoid of 8 cm minimum and 15 cm maximum radius mimicking the human main body. ◦ (b-ii) two cylinders of radius 5 cm and height 30 cm mimicking the human hands. ◦ (b-iii) a sphere of 14 cm radius mimicking the human head. ◦ (b-iii) A cylindrical F-18 FDG source of 0.5 cm radius and 5 cm height . International Scientific Conference eRA-7
  8. 8. Materials and Methods Interaction phenomena : i) Crystal energy blurring: resolution of 0.25 at 511keV. (ii) Detector characteristics: quantum detection efficiency of 0.98 , light output of 30000 photons/MeV, intrinsic resolution of 0.088 and transfer efficiency coefficient of 0.28. (iii) Energy window: between 250 and 650 keV (iv) Time Resolution: coincidence window of 120 ns, dead time window of 120 ns and dead time offset of 700 ns. (v) F-18 FDG source half life of 6586.2 s (vi) Slice time of 1 s and acquisition time of 10s. International Scientific Conference eRA-7
  9. 9. Results and Discussion i) Diagram with Characteristics of the Biograph DUO PET/CT (black line) and estimation from Gate Simulation (blue) ii) Diagram Number of counts – Energy Mev (2 picks at 0.2 MeV and 0.511 MeV) International Scientific Conference eRA-7
  10. 10. Results and Discussion iii)Number of Counts – Energy (MeV) ( pick at 0.25 MeV) ii)Diagram Number of counts – Energy Mev (2 picks at 0.2 MeV and 0.511 MeV) (± 1 deg) International Scientific Conference eRA-7
  11. 11. Results and Discussion Root Mean Square (RMS) energy is 99.06 keV Mean energy is 407.5 keV FWHM of energy and RER are 0.6 and 6% for the peak near 0.511 MeV As thickness increases, FWHM, RER and SNR increase International Scientific Conference eRA-7
  12. 12. Results and Discussion Energy Resolution Of System ◦ A) 2 cm LSO thickness ◦ B) 3 cm LSO thickness  The peak of the 3.0 cm thick crystals is sharper , more wide and has more counts than the one of the 2.0 cm thickness. This attributes to the higher detection efficiency of the thicker LSO detectors at 0.511 MeV International Scientific Conference eRA-7
  13. 13. Results and Discussion As detector thickness increases, the axial distribution sensitivity of the number of counted photons is enhanced at the centre, viz. the energy distribution is sharper. International Scientific Conference eRA-7
  14. 14. Results and Discussion The increase with thickness of the photon detection sensitivity of a block of 64 LSO crystals points in another way that blocks of thicker crystals detect and count more photons. International Scientific Conference eRA-7
  15. 15. Conclusions Non-significant changes were observed for: ◦ positron kinetic energy spectrum ◦ interactions of positrons with matter ◦ positron annihilation distance ◦ number of annihilation processes ◦ gamma ray production ◦ distribution and scattering of gamma-rays The detector absorption efficiency is strongly affected by the scintillator thickness. Possible use of 3.0 cm thick LSO crystals will increase detection efficiency of the system, RER and SNR But will delay signal process and increase the construction cost and may be accompanied by paralax effects . International Scientific Conference eRA-7
  16. 16. Thank You !http://env-hum-comp-res.teipir.gr/ International Scientific Conference eRA-7
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