Term
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Definition
Electrons accelerated from the thermionically emitted cloud toward the anode.
** Represented by a straight arrow on diagrams |
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Term
| How are x-ray photons represented on diagrams? |
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Definition
| With a wave line and arrow |
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Term
| Describe Target Interactions |
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Definition
- The greater the quantity of electrons = greater quantity of x-ray photons produced(mAs)
- The greater the kinetic energy of electrons = greater quality of photons produced (kVp)
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Term
| Describe heat production as it relates to target interaction. |
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Definition
99% of kinetic energy produced by target interaction results in heat production.
** as kinetic energy of photons increases, so does efficiency; by the time therapeutic machines reach MeV's, most of energy is actually photons.
99% Heat, 1% X-Ray photons |
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Term
| Give another name for Bremsstrahlung |
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Definition
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Term
| What is the primary product produced from the electron cloud striking the anode? |
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Definition
Heat
99% heat, 1% x-ray photons |
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Term
Which way do incident electrons travel?
From what to what.... |
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Definition
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Term
| At what kVp range do characteristic photons begin to comprise the useful beam? |
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Definition
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Term
| Where is an x-ray photon produced? |
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Definition
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Term
| Define Inherent Filtration |
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Definition
| Found within the glass envelope. Most tubes have inherent filtration of 0.5-1.0mm al eq. |
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Term
| What does Al eq. stand for? |
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Definition
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Term
| What is added filtration and list several types? |
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Definition
Any filter added between the tube and the patient.
- Collimator
- Compound
- Compensating (wedge, trough)
* made of aluminum or sometimes clear lead, which allows you to see the collimator light |
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Term
| Describe a compensating filter |
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Definition
| Used for objects with unequal densities to try to provide a more uniform density on the film. |
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Term
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Definition
(double-wedge)
Used for differences in mediastinum and the lungs |
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Term
| Define Characteristic Interactions |
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Definition
Occur when incident electron interacts with an inner shell electron (k shell)
* Only the k shell characteristic photon has sufficient energy to be a part of the useful beam |
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Term
| List the 3 recommended minimum total filtration levels |
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Definition
1. Below 50kVp, 0.5mm al eq
2. From 50-70kVp, 1.5mm al eq
3. Over 70 kVp, at least 2.5mm al eq |
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Term
True or False
When the amount of filtration increases,
the % of attenuated photons increases |
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Definition
True
(direct relationship) |
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Term
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Definition
Half Value Layer
Amount of absorbing material required to reduce the intensity of the beam to half its original value |
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Term
| If kVp is increased, what needs to happen to the HVL? |
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Definition
Increased
* HVL will increase as kVp increases |
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Term
| Describe the filtration process and why filtration is used |
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Definition
The process of eliminating the undesirable low-energy x-ray photons by the insertion of absorbing materials into the primary beam.
* increasing the quality of the beam, hardening the beam |
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Term
| Define Bremsstrahlung Interactions |
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Definition
Electron passes close enough to the nucleus to allow its force field to alter its course, causing the electron to brake or slow down.
note: this lost energy is converted to an x-ray photon (brems photon). The energy of the brems photon is exactly the difference between entering and exiting kinetic energy of the electron.
ex: enters at 100 kev's and exits at 70 kev's = 30 kev's |
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Term
| At what level of kVp do brem rays get generated? |
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Definition
| Brem rays can happen at any kVp |
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Term
What kind of rays make up the majority of
useful x-ray beam? |
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Definition
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Term
Characteristic Interactions
Projectile electrons must have a potential of at least ____ or ____ kVp to contribute to the useful beam. |
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Definition
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Term
| How could you double the number of incident electrons produced? |
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Definition
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Term
List the energy levels for the following generators:
single phase
3-phase, 6-pulse
3-phase, 12-pulse |
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Definition
Single phase = ?
3-phase, 6-pulse = 35% more than single phase
3-phase, 12-pulse = 41 % more than single phase |
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Term
| How does the emission spectrum change when mA is the only thing that is increased? |
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Definition
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Term
| How does the emission spectrum change when kVp is the only thing that is increased? |
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Definition
| An increase in amplitude, as well as a shift to the right (indicating higher average energy) |
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Term
| Describe the x-ray emission spectrum |
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Definition
A way of graphically observing the different x-ray energies present in a particular beam
note: also allows us to see how certain factors affect the overall beam |
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Term
| What two types of interactions are x-rays created from? |
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Definition
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Term
| At what kV will characteristic x-rays begin to be produced for diagnostic purposes? |
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Definition
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Term
List the # of -e and EB (keV) for the shells
K
L
M
N
O
P |
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Definition
K 2 69.5 or 70
L 8 12.1
M 18 2.8
N 32 .6
O 12 .08
P 2 .00
** the further away from the nucleus, the better the energy! |
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