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34 Cards in this Set
- Front
- Back
What are the ways X-rays interact with matter?
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1. Coherent scattering
2. Compton effect 3. Photoelectric effect 4. Pair production 5. Photo disintegration |
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How are the energy and wavelength of an X-ray related?
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They are inversely proportional.
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Whic X-rays interactions with matter are important to making the X-ray image?
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1. Compton effect
2. Photo electric effect |
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Coherent scattering: How are wavelengths and energies related?
What is the amoount of emergy? |
Equal wavelengths and energies of the incident and scattered rays.
Low |
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Compton effect: What interaction occurs?
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1. X-rays interact with the outer shell electrons.
2. The X-ray is scattered and reduced in energy. 3. An electron is ejected (Compton) and the atom is ionized. |
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What is the Comton Effect formula?
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Ei = Es + (Eb + Eke)
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Compton effect: How is energy and degree of deflection related?
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1. At 0 deg no energy is transferred.
2.More energy is transferred to the Compton electron up to 180 deg. 3. At 180 deg approx. 2/3 is transferred. |
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What is back scatter radiation?
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Radiation scattered back in the direction that the incident ray came from.
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What is the relationship between probabability of Compton Effect and X-ray energy.
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They are inversely proportional
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How do scattered X-rays affect the X-ray image?
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1. They have no diagnostic value
2. They reduce image contrast 3. They provide most of the radiation exposure that technologists receive. |
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What is the interaction with the Photo Electric effect?
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X-rays ionize inner shell electrons.
The x-ray is not scattered and its energy is totally absorbed. |
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What is the formula for Photo Electric effect?
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Ei = Eb + E ke
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What happens to the electron shells during the Photo Electric effect?
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1. A k shell electron is ejected
2. An electron from another shell, usually the L shell, fills the void. 3. In doing so radiation is emitted |
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What is Secondary radiation?
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When a k shell electron is ejected an electron from another shell, usually the L shell, fills the void.
In doing so radiation is emitted which is called Secondary Radiation. |
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Does Secondary radiation have diagnostic value?
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NO
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How is the probability of Photo Electric Effect and X-ray energy related?
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Probability is inversel proportional to the third power of X-ray energy.
P = 1/E cubed |
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How is the probability of Photo Electric Effect and Atomic Number related?
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Directly proportional to the third power of Atomic Number.
P= Zcubed |
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What is Pair production?
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The incident X-ray disappears and two electrons are created.
One Positron + and one Electron. |
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What is the Energy equivalance of an Electron?
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.51 MeV
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Is Pair Production useful for X-ray imaging?
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NO
But is very useful for PET imaging |
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What is Annihilation radiation?
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A Positron units with a free electron and themass of both is converted to X-radiation.
NB 1.02 MeV is produced |
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What is Photodisintegration?
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X-rays of sufficient energy avoid interaction with the electron cloud, but are absorbed by the nucleus.
A Nucleon is emitted. |
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What is Differential Absorption?
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The difference between X-rays that are absorbed photoelecrically and those transmitted to the image receptor.
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What percentage of X-rays incident on a patient reach the image receptor?
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1Percent
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What percentage of X-rays actually produce the image?
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0.5 percen
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What type of interaction is more likely to occur at low energies?
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Photo Electric
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What type of interaction is more likely to occur at high energies?
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Compton
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Name two other factors important in making an X-ray image.
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1. The X-ray emission spectrum
2. Mass density of patient tissue |
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What is low kVp used for?
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To image small differences in soft tissue by getting maximum differential absorbtion.
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What is the relationship between probabiltity of X-ray interaction and tissue.
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Probability is directly proportional to the mass density of the tissue.
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What are Contrast agents?
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Agents with high atomic number used to increase the visibility of organs.
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What is attenuation?
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The ntotal reduction nof the number of X-rays remaining in an X-ray beam after penetration through a given thickness of tissue.
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How are X-rays attenuated?
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Exponentially.
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What is the Half Value Layer?
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The depth ofmaterial that reduces the incident X-ray intensity to half its original value.
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