Radiation Physics 2 Flashcards
What force maintains electrons and protons in the shells?
Electrostatic forces
What balances electrostatic forces?
Centrifugal forces of rotating electrons
What is the term for the energy used to remove an electron from its shell?
Electron binding energy
What shell is binding energy the greatest?
The K shell since it’s closest
What is ionization?
What happens when a neutral atom loses an electron
When does ionization happen and what electrons are usually lost?
When things are heated up or when high speed collisions with x-rays or particles are made. Usually outer shell electrons are lost
What is electromagnetic energy?
Movement of energy through space or matter as a combination of electric and magnetic fields
When is electromagnetic energy generated?
When the speed of an electrically charged particle is altered
What are the two processes by which x-rays are produced?
Bremsstrahlung and characteristic radiation
How is bremsstrahlung produced?
By the suddens stopping or slowing of an electron at the target
How does this slowing down occur?
The electron passes near the positive nucleus, giving up its energy as a photon
When is characteristic radiation produced?
When a high speed electron displaces an electron from the inner shell of the tungsten, causing ionization of the atom
Once the inner shell electron is removed, what happens?
An outer shell electron drops in to fill the void emitting a photon in the process
What determines the energy of the x-rays produced by a metal?
The atomic number, higher=more energy
What happens to the intensity of the beam when using a longer collimator?
It decreases
What are two ways we can compensate for a long collimator?
Increase the mA or the current, more electrons produced
Increase the exposure time, does not change intensity but more electrons overall
What is attenuation?
The reduction in intensity of an x-ray beam as it travels through matter
What 3 things affect attenuation?
Energy of initial beam
Thickness of absorber
Density of absorber
After attenuation, the average energy of the beam is higher or lower?
Higher, low energy photons are attenuated or removed
What is the name for the effect of low energy photons being removed?
Filtration that results in beam hardening
What are the 3 kinds of interactions that attenuate the x-ray beam?
Coherent scattering, photoelectric absorption, and compton scattering
Describe the process of coherent scatter
A photon passes near an outer shell electron, gives its energy to the electron and disappears
The electron moves up a shell, then falls back down releasing a photon at an angle
What is a downside to coherent scatter?
The photon going off at an angle distorts the image slightly
Describe compton scattering
A photon collides with an outer shell electron, loses some energy, and get deflected. The photon loses energy and the electron gains it
What types of tissues will cause photoelectric absorption?
Hard or calcified tissues, causes radiopacities
What is the SI unit for radiation?
KERMA, kinetic energy released in matter
The KERMA is expressed in units of?
Gray or gy, 1 gy is 1 joule/kg
What else is measured in grays
The absorbed dose
How is the equivalent dose measured? What is it used for?
Sieverts, used to compare biological effects of different types of radiation on given tissue or organ
What is the effective dose used to measure? Unit of measure?
The risk to humans, sieverts
When the beam exits a specimen it forms a ?
Data set
Aluminum filtration is used to remove what types of photons?
Soft, low energy, long wavelength leaving the hard high energy short wavelength
What is fluorescence?
Instantaneous transmission of visible light upon application of a stimulus, used in extra oral radiology
