Regional (AFRA) Training Course on Maintenance and Repair of Med iso Spirit Gamma Cameras - 11 -15 August 2008 Seibersdorf – Austria 1. Short overview about ionizing radiation and its interaction with matter 2. Revision about the main radiation detectors 3. Scintillation based detectors 4. Diagnostic images 5. Gamma Cameras 6. Quality Control 7. Radiation protection Regional (AFRA) Training Course on Maintenance and Repair of Med iso Spirit Gamma Cameras - 11 -15 August 2008 Seibersdorf – Austria Ionizing radiation Ionizing radiations are those which interact with matter through processes which generates ionization Ionizing radiation types Indirectly ionizing: Particles: Neutrons Electromagnetic: Gamma, X rays Directly ionizing: Charged particles: Alpha, Beta (+ or -), Protons Regional (AFRA) Training Course on Maintenance and Repair of Med iso Spirit Gamma Cameras - 11 -15 August 2008 Seibersdorf – Austria How these radiations interact with matter? Charged particles: Ionization Excitation Electromagnetic: Rayleigh Effect Photoelectric Effect Compton Effect Pair production Photonuclear Effect Regional (AFRA) Training Course on Maintenance and Repair of Med iso Spirit Gamma Cameras - 11 -15 August 2008 Seibersdorf – Austria Photo electric effect 1.swf X-ray Scattered ElectronPhotoelectron E = E 1 -EBinding Incoming Photon λ_1 Incoming Photon N Auger Electron Regional (AFRA) Training Course on Maintenance and Repair of Med iso Spirit Gamma Cameras - 11 -15 August 2008 Seibersdorf – Austria Compton Effect Scattered Photon E < E , λ > λ Incoming Photon,E 1, λ1 2 1 2 1 Scattered Electron Ee= E 1-E2-EBinding N Regional (AFRA) Training Course on Maintenance and Repair of Med iso Spirit Gamma Cameras - 11 -15 August 2008 Seibersdorf – Austria ) e T ( N Tmax Te Regional (AFRA) Training Course on Maintenance and Repair of Med iso Spirit Gamma Cameras - 11 -15 August 2008 Seibersdorf – Austria Pair production - Electron T Incoming Photon Eγ + Positron T Regional (AFRA) Training Course on Maintenance and Repair of Med iso Spirit Gamma Cameras - 11 -15 August 2008 Seibersdorf – Austria What happens after the interaction? • Characteristic X rays • Bremsstrahlungen • Heat Regional (AFRA) Training Course on Maintenance and Repair of Med iso Spirit Gamma Cameras - 11 -15 August 2008 Seibersdorf – Austria Which are the effects or ionizing radiation in matter? Which parameters are important to be considered? - Density - Conductivity Which would be the best material to detect ionizing radiation? - A solid? - A liquid? - A gas? Regional (AFRA) Training Course on Maintenance and Repair of Med iso Spirit Gamma Cameras - 11 -15 August 2008 Seibersdorf – Austria Gas based detectors Ionization chambers - Pulse mode - Charge mode Regional (AFRA) Training Course on Maintenance and Repair of Med iso Spirit Gamma Cameras - 11 -15 August 2008 Seibersdorf – Austria + + V + - + - + - + - + - + - - + - + - + - + - + - + E - -V Regional (AFRA) Training Course on Maintenance and Repair of Med iso Spirit Gamma Cameras - 11 -15 August 2008 Seibersdorf – Austria Regional (AFRA) Training Course on Maintenance and Repair of Med iso Spirit Gamma Cameras - 11 -15 August 2008 Seibersdorf – Austria 2 MeV 1 MeV Log Pulse Height Log Pulse Applied Voltage Regional (AFRA) Training Course on Maintenance and Repair of Med iso Spirit Gamma Cameras - 11 -15 August 2008 Seibersdorf – Austria Proportional counters ε = V rln( b / a ) Regional (AFRA) Training Course on Maintenance and Repair of Med iso Spirit Gamma Cameras - 11 -15 August 2008 Seibersdorf – Austria Regional (AFRA) Training Course on Maintenance and Repair of Med iso Spirit Gamma Cameras - 11 -15 August 2008 Seibersdorf – Austria Geiger-Müller Counters Regional (AFRA) Training Course on Maintenance and Repair of Med iso Spirit Gamma Cameras - 11 -15 August 2008 Seibersdorf – Austria Regional (AFRA) Training Course on Maintenance and Repair of Med iso Spirit Gamma Cameras - 11 -15 August 2008 Seibersdorf – Austria Semiconductors, metals, insulators Regional (AFRA) Training Course on Maintenance and Repair of Med iso Spirit Gamma Cameras - 11 -15 August 2008 Seibersdorf – Austria What happens when the electronic shells become closer? Distance between atoms Regional (AFRA) Training Course on Maintenance and Repair of Med iso Spirit Gamma Cameras - 11 -15 August 2008 Seibersdorf – Austria Atom Excited by Radiation Energy Atom is excited by Conduction Band interaction with radiation, moving an Forbidden Gap electron from the valence band to the Valence Band conduction band. Atom De-excites Emitting Light Photon Energy Energy of emitted Conduction Band photon equals the Photon energy of the gap Forbidden Gap and wavelength is too short. Valence Band Regional (AFRA) Training Course on Maintenance and Repair of Med iso Spirit Gamma Cameras - 11 -15 August 2008 Seibersdorf – Austria Inorganic Scintillators 2.swf 3.swf Regional (AFRA) Training Course on Maintenance and Repair of Med iso Spirit Gamma Cameras - 11 -15 August 2008 Seibersdorf – Austria Adding Impurity/Activator Energy Adding impurity Conduction Band to crystal adds Forbidden Gap extra energy levels in the Valence Band forbidden gap. Atom De-excites Emitting Light Photon Energy Atom de-excites in Conduction Band two-step process, Photon Forbidden Gap emitting lower energy, longer wavelength Valence Band photons. Regional (AFRA) Training Course on Maintenance and Repair of Med iso Spirit Gamma Cameras - 11 -15 August 2008 Seibersdorf – Austria Organic Scintillators Regional (AFRA) Training Course on Maintenance and Repair of Med iso Spirit Gamma Cameras - 11 -15 August 2008 Seibersdorf – Austria Photomultiplier tubes CRYSTAL Regional (AFRA) Training Course on Maintenance and Repair of Med iso Spirit Gamma Cameras - 11 -15 August 2008 Seibersdorf – Austria Photomultiplier tube ELECTRONS L I G H T Regional (AFRA) Training Course on Maintenance and Repair of Med iso Spirit Gamma Cameras - 11 -15 August 2008 Seibersdorf – Austria Photomultiplier tube Regional (AFRA) Training Course on Maintenance and Repair of Med iso Spirit Gamma Cameras - 11 -15 August 2008 Seibersdorf – Austria BLOCK DIAGRAM OF A RADIATION DETECTOR BASED ON A SCINTILLATOR (Pulse Mode) PRE F AMPLIFIER O AMPLIFIER T O M U DISCRIMINATOR L VOLTAGE or MCA T DIVIDER P L I E HIGH VOLTAGE R T U B E SCINTILLATOR Regional (AFRA) Training Course on Maintenance and Repair of Med iso Spirit Gamma Cameras - 11 -15 August 2008 Seibersdorf – Austria Diagnostic Imaging Radiology – x-ray machines, CT Nuclear Medicine Gamma cameras, PET Magnetic ressonance Regional (AFRA) Training Course on Maintenance and Repair of Med iso Spirit Gamma Cameras - 11 -15 August 2008 Seibersdorf – Austria X-ray tube Focusing cap Tungsten target Cupper Filament supports X rays Regional (AFRA) Training Course on Maintenance and Repair of Med iso Spirit Gamma Cameras - 11 -15 August 2008 Seibersdorf – Austria Radiology DETECTOR R Regional (AFRA) Training Course on Maintenance and Repair of Med iso Spirit Gamma Cameras - 11 -15 August 2008 Seibersdorf – Austria Effect of the scattered radiation Regional (AFRA) Training Course on Maintenance and Repair of Med iso Spirit Gamma Cameras - 11 -15 August 2008 Seibersdorf – Austria Grids OBJECT Grid Absorber strips Radiographic film Regional (AFRA) Training Course on Maintenance and Repair of Med iso Spirit Gamma Cameras - 11 -15 August 2008 Seibersdorf – Austria Regional (AFRA) Training Course on Maintenance and Repair of Med iso Spirit Gamma Cameras - 11 -15 August 2008 Seibersdorf – Austria CT Computerized Tomography X ray tube Detector Collimators Regional (AFRA) Training Course on Maintenance and Repair of Med iso Spirit Gamma Cameras - 11 -15 August 2008 Seibersdorf – Austria CT is based on the calculation of the absorption of radiation in a determined value of a material. This calculation is performed with information obtained in different position through the movement of the set x ray tube – detectors. Considering the following figure, each square represent a cube which is named ”voxel”. The attenuation of each beam will be derived from the sum of the individual contribution of each voxel. A11 A12 A11 A11 A21 A22 A23 A24 A31 A32 A33 A34 A41 A42 A43 A44 F1 F2 Regional (AFRA) Training Course on Maintenance and Repair of Med iso Spirit Gamma Cameras - 11 -15 August 2008 Seibersdorf – Austria The attenuation of a radiation beam after crossing a determine layer of a material is given by: -µx I = I 0e Where µ is the linear attenuation coefficient for the energy of the incident radiation an x the material thickness. For the beam F1 the total attenuation will be given by the sum of the attenuation in A 12 , A 21 , A 31 , A 41 . Therefore, I(F 1) will be equal to I 0(F 1) multiplied by the individual attenuations; -µ(A11)x -µ(A21)x -µ(A31)x -µ(A41)x I = I 0e .e .e .e Applying the Neperian logarithm to both sides of this equation we have: Ln(I) = Ln(I 0e-µ(A 11 )x.e-µ(A 21 )x.e-µ(A 31 )x.e-µ(A 41 )x)= LnI 0 - µ(A 11 )x - µ(A 21 )x - µ(A 31 ) - µ(A 41 )x. The same is valid for the beam F 2. Using a set of beams, we get a set of equations which variables are the attenuation coefficients for the ¨voxels¨. This set of equations can be solved applying numeric methods. Having the linear attenuation coefficients for each voxel available it is possible to generate an image of this set of ¨voxels¨ providing a gray scale greater or smaller depending on the calculated attenuation coefficient. Regional (AFRA) Training Course on Maintenance and Repair of Med iso Spirit Gamma Cameras - 11 -15 August 2008