6.5 medical physics

• the range for simple scattering is 1-20keV
• simple scattering is when a x-ray photon interacts with an electron in the atoms, but has less energy required to remove it, bounces off and is scattered with no energy change
• photoelectric effect is when a x-ray photon is absorbed by one of the electron in the atom and the electrons uses this energy to escape the atom
• the range for the photoelectric effect is 30-100 kV
• Compton scattering is when an incoming x-ray photon interacts with a electron and that electron is ejected from the atom and the x-ray photon is scattered with reduced energy
• the range for Compton scattering is 0.5-5 MeV
• the range for pair production is 1.02 MeV
• pair production is when a x-ray photo interacts with the nucleus of the atom and caused an electron and positron to be produced
• soft tissues have low absorption coefficients so a contrast medium is used to improve the visibility of their internal structures
• the most common contrast materials are iodine and barium
• attenuation coefficient is proportional to the cube of the atomic number
• iodine is used as a contrast medium for liquids like blood flow
• barium is used to image the digestive system