Ch.3 Flashcards
How is an image formed with x-ray photons ?
Formed by photons that pass through the patient and hit the IR
Differential absorption is dependent upon
- Part thickness
- Atomic #
- Tissue density
- Beam quality/energy
Processes required to create a radiographic image through differential absorption
- Beam attenuation
- Absorption
- Transmission
What forms the latent image ?
Transmitted photons
X-ray photon energy is deposited and absorbed by the part
Absorption
X-ray photon loses energy during interaction and changes direction
Scatter
X-ray beam absorption occurs through which interaction ?
Photoelectric ?
1 photon in = 1 photon, 1 characteristic x-ray photon out
Photoelectric
Probability of photoelectric is depended on the _______ of the incoming x-ray photon and the atomic number of the tissue
Energy
Scatter occurs during which reactions ?
Compton and Coherent
1 photon in= 1 photon and electron out
Compton
Can occur within all diagnostic energies and it more dependent on the energy of the incoming photon, NOT the atomic number of the tissue which is only an “opportunity” for the x-ray interactions to happen
Compton scatter
Provides no useful information if stricks the IR
Compton scatter
If this type of scatter does not strike the IR, it can lead to
Technologist and patient exposure
1 photon in= 1 photon out
Coherent scatter
This form of scatter causes excitement of the atom but no ionization
Coherent
Occurs in low energy x-rays (below 10kev)
Coherent scatter
Reduction of intensity of the primary x-ray beam through matter
Attenuation
Electromagnetic energy is transferred from the x-ray to the atoms of the patients biological tissue
Absorption
Photons pass through the patient, hit the IR, and have no interaction with structures of the body
Transmission
What is the other name for Exit Radiation
Remnant radiation
Remnant radiation consists of
Transmitted photons and absorbed photons
Transmitted and absorbed radiation create an image that represents
The area that is imaged
Scatter radiation causes unwanted exposure called
Fog
Absorbed radiation creates
Increased brightness or white areas on the displayed image
Transmitted radiation creates
Low brightness or black areas on the displayed image
High transmission =
More darkness/black
Low transmission =
More light /white
Probability of photoelectric effect is dependent on
Energy of the incoming x-ray photon and tissue atomic number
Higher kvp reduces the number of interactions overall, but the number of _____ interactions increases in comparison to the number of photoelectric interactions
Compton
X ray are attenuated exponentially and generally reduced by ______ for each ________ of tissue thickness
50%, 4-5cm (1.6-2in.)
Tissues composed of a higher effective atomic number will
Increase beam attenuation
Increasing the compactness/density of the atomic particles will
Increase beam attenuation
Higher kvp increases the energy of the x-ray beam and will
Decrease attenuation
Bone atomic #
13.8
Fat atomic #
6-7
Air atomic number
1-2
