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Rad physics review
2012 ARRT radiation physics content
| Question | Answer |
|---|---|
| Half life of Radium-226 | 1622 years |
| Half life of Cesium-137 | 30 years |
| Half life of Cobalt-60 | 5.27 years |
| Half life of Iridium-192 | 73.83 days |
| Half-life of Iodine-125 | 59.4 days |
| Half-life of Palladium-103 | 16.99 days |
| Half life of Gold-198 | 2.7 days |
| Half life of Radon-222 | 3.82 days |
| What are the five ways brachytherapy can be administered? | Interstitial Intracavitary Intraluminal Intravascular Topical |
| Define radioactivity | process by which an unstable element reaches stability through the release of excess energy in the form of electromagnetic radiation |
| The result of a nucleus releasing two protons and two neutrons in order to regain stability | alpha decay |
| The result of a high neutron/proton ratio where a neutron is converted into a proton, increasing the atomic number (anti-neutrino) | Negatron Beta decay |
| The result of a low neutron/proton ratio where a proton is converted to a neutron (neutrino) | Positron Beta decay Requires 1.02 MeV |
| The amount of energy required to remove an electron from an atom | Binding energy |
| The process when photons interact with a material, giving up their energy, and being removed from the beam | Attenuation |
| Define wave theory | Electromagnetic energy travels through space via waves |
| What are the properties of Electromagnetic waves? | They can travel in a vacuum. They have a wavelength and frequency. The wavelength and frequency are inversely proportional. It's velocity is the speed of light. |
| What is the speed of light? | c=3.0*10^8 |
| What is the inverse square law? | I1/I2 = (D2/D1)^2 |
| What controls X-ray beam quality? | kVp |
| What interaction is the main source of x-ray production in a therapy unit? What is the second source of x-rays in the therapy unit? | Bremsstralung Characteristic Interaction |
| What happens during a Bremsstralung interaction? | The incident electron is slowed down by the positive charge of the nucleus, and changes direction. The change in energy is released as an x-ray photon. |
| What happens during a characteristic radiation interaction? | The incident electron collides with an inner shell electron of the atom. This leaves an opening in the inner shell which is then filled by an electron in the next shell. A cascade effect occurs. The energy released by each cascade is given off as an x-ray |
| What are the five interactions that occur between photons and matter? | Coherent scatter Compton Scatter Photoelectric effect Pair production Photodisintegration |
| Which interaction with matter does not eject an electron from the atom? | Coherent scatter The low energy photon causes the electrons to vibrate and release excess energy in the form of a secondary photon. |
| What is the most common photon interaction with matter? | Compton scatter |
| Which photon interaction with matter creates secondary radiation through a characteristic interaction? | Photoelectric |
| Which photon interaction with matter occurs only when the incident photon is greater than 10 MeV? | Photodisintegration |
| Which photon interaction with matter occurs only when the incident photon is at least 1.02 MeV? | Pair Production |
| In pair production, what is the energy of the two resulting photons created? | 0.51 MeV |
| What are the two types of electron interactions with matter? | Collision (elastic, inelastic) Radiative |
| An _____ collision is one where the incoming electron gives all its energy to the particle encountered. | Elastic |
| An _____ collision is one where the electron only gives part of its energy to the encountered particle. | Inelastic |
| What is the importance of a Bragg peak? | Heavily charged particles, like protons, will deposit the maximum dose when they are close to being stopped in the material, creating a Bragg peak. We can use this to deposit max dose to the target while reducing dose beyond the target. |
| What is the SI unit for absorbed dose? | Gray (Gy) |
| What is the SI unit for exposure? | Gray in air/Air Kerma |
| What is the SI Unit for effective dose? | Sievert (Sv) |
| What is the SI Unit for radioactivity? | Becquerel (Bq) |
| 1 Gy = ? rad | 1 Gy = 100 rad |
| 1 Sv = ? rem | 1 Sv = 100 rem |
| What is another unit for exposure? | Roentgen |
| What are the four fundamental units of the metric system? | Time in seconds Distance in meters Mass in kilograms Electrical current in amperes |
| The number of atoms per gram is given by Avogadro's number. What is Avogadro's number? | 6.0228 x 10^23 |
| In a chemical symbol, what do the letters X, Z, and A stand for? | X is the element symbol Z is the atomic number (#protons) A is the atomic mass (protons+neutrons) |
| What is the octet rule? | The outer shell of an atom can have no more than 8 electrons. |
| What is the formula to find the maximum number of electrons in a shell? | 2n^2, where n is the shell number. Shells are numbered beginning from the nucleus going outward. |
| What causes ionization? | An electron being ejected from or captured by the atom causing the atom to become charged. |
| What energy ranges are commonly used in radiation therapy? | 200 keV - 50 MeV |
| What material is used for the target in an X-ray tube? | Tungston |
| What 4 materials make up Cerrobend? | Bismuth, Lead, Tin, Cadmium (BLT with Cheese) |
| The phenomenon where the effective energy of the beam increases as it passes through a filter. | Beam hardening |
Created by:
kcorbitt
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