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In the name of GOD Nuclear Medicine. Main topics. Structure of Atom Atomic notation Nuclear forces Stability factors Nuclear energy level Radioactivity Radioactive equations and units Half life Radioactive series Radioactive equilibriums Nuclear interactions Nuclear disintegrations
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Main topics • Structure of Atom • Atomic notation • Nuclear forces • Stability factors • Nuclear energy level • Radioactivity • Radioactive equations and units • Half life • Radioactive series • Radioactive equilibriums • Nuclear interactions • Nuclear disintegrations • Interaction of particles with matters • Radiation measurement unites • Measurement instrumentations (Free air chamber, Gaiger Muller , TLD chemical dosimeter and Film dosimeter) • Radiopharmacuticals • Imaging systems (rectilinear and gamma camera) • Clinical applications
Structure of the atom and The nucleus • isotope same Nproton, different Nneutron ( and ) isotone same Nneutron, different Nproton ( and ) isobar same (Nneutron+ Nproton), different Nproton( and ) isomer same Nproton, same Nproton, different nuclear energy state A the mass number (Nproton+ Nneutron) Z the atomic number (Nproton )
Nuclear forces • 1-Gravity force • 2-Columb force • 3-Nuclear force
Stability factors • 1-N/Z ratio • 2-Pair and odd • 3-Mass defect
Atomic mass and energy units • 1 amu = mass of =1.6610-27 kg • 1 eV =1 V1.602 10-19 C =1.602 10-19 J • Einstein’s principle of equivalence of mass and energy
Nuclear energy level • dssd
Radioactive equations and units • N0 is the initial number of atom • N is the remaining atom • λ is the decay constant
Activity • 1 Ci =3.71010 disintegrations/sec =3.71010 dps =3.71010 Bq
The half-life (T1/2) The mean life (T) The half-life (T1/2) & the mean life (T)
activity Transient equilibrium time Transient equilibrium • T1>T2 (1<2)
activity Secular equilibrium time Secular equilibrium • T1>>T2 (1<<2) A2= A1
Radioactivity and Radioactive series
Nuclear interaction • 1-Nuclear fission • 2-Nuclear fusion • 3-Others
particle decay • Q = the disintegration energy = the difference in mass between the parent nucleus and product nuclei • E 510 MeV (discrete energy)
Negatron(-) emission • An excessive number of neutrons or a high neutron-to-proton (n/p) ratio • anti-neutrino
0.511 MeV photon positron + 0.511 MeV photon free electron Positron(+) emission • A deficit of neutrons or a low n/p ratio • neutrino • Annihilation
The average energy of the particles is approximately Emax/3. The -ray spectrum
Electron capture • The unstable nuclei with neutron deficiency may increase their n/p ratio by EC.
An empty hole in a shell is filled by electron from outer shell with an emission of characteristic radiation. discrete energy h=EK - EL Characteristic radiation hole K L M
The absorption of characteristic x-rays by orbital electrons and reemission of the energy in the form of monoenergetic electrons discrete energy E=h-EM=EK – EL-EM hole K L M Auger Electrons
The excess nuclear energy is passed on to one of the orbital electrons which is then ejected from the atom. To create a vacancy in the involved shell, resulting in the production of characteristic photons or Auger electrons Conversion electron from K shell E = h-Eb Nuclear ray h Hole in K shell K Internal conversion
Activation of nuclides • The yield of a nuclear reaction • The number of bombarding particles • The number of target nuclei • The probability of the occurrence • Cross-section • 1 barn = 10-24 cm2 • The growth of activity • Saturation activity
Interaction of Neutron with matters • 1-Neutron capture • 2-Elastic interaction • 3-Inelastic interaction
Radiation exposure Traditional unit: Roentgen (R) = 2.58x10-4 coulomb/kg = 1esu/cm3 Module IV
Absorbed dose (D) Energy imparted to matter from any type of radiation D = E/m D:absorbed dose E: energy absorbed by material of mass ‘m’ Module IV
Units of absorbed dose The SI unit: gray (Gy) 1 Gy = 1 joule/kilogram Old unit : rad 1 Gy=100 rad Module IV
Relation between absorbed dose and exposure Dair (rad)=0.869X(R) or Dair(Gy)=34X(c/Kg) Dmed=fmed.X Dose rate=D’=dD/dt
Measurement Methods • Free air chamber • Chemical dosimeters • Calorimetric dosimeters • Scintillator • TLD • Film
Gaiger Muler dosimeter • ggfh
Film dosimeter Characteristic curve
Film badge • 1-and 6 for x ray between 15 to 85Kev • 2-for neutron • 3-for x ray between 75Kev to 2MeV • 4-for beta and low energy x ray
Radiation Detection and Safety Monitors used for detection of radioactivity reading multiplier scintillation probe (β- and γ-radiation) high sensitivity monitor pancake probe (α-, β- and γ-radiation)
Radiation Detection and Safety Personal dosimetry electronic dosimeter film badge thermo luminescent dose meter (TLD) finger ring (TLD) Dose limits recommended by the ICRP (1991): Occupational: 100mSv in 5 years, 50mSv maximum in any year Public: 5mSv in any 5 consecutive years
Radiation Detection and Safety Dose calibrator ionization chamber electrometer The exact amount of radioactivity can be assayed in a dose calibrator. A factor appropriate for the energy of the radionuclide is entered and the amount of radioactivity can be read directly.
Radiopharmacuticals Used for 1-Diagnostic 2-Therapy 3-Research