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Physics U6 &HW

Which of the following is NOT one of the five basic x-ray interactions with matter? bremsstrahlung
which of the following x-rays would be most likely to undergo classical scattering? 5 keV
Which of the following interactions contributes to image noise? Compton scattering
Which of the following occurs in a Compton interaction? An atom is ionized
If Ei= incident x-ray energy, E(s)=scattered x-ray energy, E(b) =electron binding energy, and E(KE)= secondary electron kinetic energy, then which of the following is true? E(i) = E(s)+ E(b)+ E(KE)
If Ei= incident x-ray energy, E(s)=scattered x-ray energy, E(b) =electron binding energy, and E(KE)= secondary electron kinetic energy, then which of the following is true? E(s) = E(KE)+E(i)-E(b)
During Compton effect, most of the incident x-ray energy is given to which of the following? Scattered x-ray
After Compton scattering, the scattered x-ray has? longer wavelength
Compton interaction affects the image by increasing which of the following? Noise(fog)
The probability that an x-ray will interact with an outer shell electron is influence principally by The energy of the incident x-ray
The compton effect is independent of Z
The Compton effect is the principle source of image noise(fog)
If 45keV x-ray interacts with the K-shell electron in an atom of molybdenum(E(b)=20keV) and ejects it with 8keV energy what will be the enrgy of the scattered x-ray? 17keV
The probability that an x-ray will undergo Compton interaction decreases with increasing x-ray energy
The compton interaction involves so-called "unbound" electron because they have very low binding energy
Which of the following is the x-ray interaction that does NOT cause ionization? Classical Scattering
Compton-scattered x-rays have lower energy than an incident x-ray
If Ei= incident x-ray energy, E(s)=scattered x-ray energy, E(b) =electron binding energy, and E(KE)= photoelectric kinetic energy, then which of the following is true? E(i) =E(b)+ E(KE)
If Ei= incident x-ray energy, E(s)=scattered x-ray energy, E(b) =electron binding energy, and E(KE)= photoelectric kinetic energy, then which of the following is true? E(KE)=E(i)-E(b)
The photoelectric effect is principally associated with which of the following Absorption of an x-ray
A 50 keV x-ray has a 0.02 chance of photelectric interaction with muscle(Z=7.4). What is the chance of interacting with bone(Z=13.8)? .021024576
Which of the following has the lowest effective atomic number? fat
Photoelectric interaction with soft tissue is most likely with which of the following x-rays 0.3keV
during photoelectric interaction An electron is emitted from the atom
During operation at 80 kVp, which of the following photoelectric interactions is most probable? 30keV x-ray and bone
The radiographic image is formed principally by which of the following photoelectric interaction
the probability of photoelectric effect varies as the function of x-ray energy(E)? E(-3)
As a result of photoelectric interaction an electron leaves the atom
the photoelectric effect is The complete absorption of an x-ray with the subsequent emission of an electron
Lead has a K-shell electron binding energy of 88keV therefore an 84 keV x-ray can undergo photoelectric interaction with the L-shell electron
A 39keV x-ray interacts through photoelectric effect with a k-shell electron of barium(binding energy 37keV0 therefore the photoelectron will have 2 keV energy
the probability of photoelectric effect varies as what function of target atomic number (Z)? Z(3)
Anatomic structures that readily transmit rays are called radiolucent
differential absorption, although a complicated process, is basically the result of differences between photoelectric effect and transmission
when a radiograph is taken low kVp is necessary when soft tissue is imaged because it leads to high photoelectric effect
At what approximate x-ray energy is the probavility of a photoelectric interaction in soft tissue equal to the probability of compton interaction 20keV
which of the following has the greatest mass density bone
The colon is imaged during a barium enema examination principally because of differences in subject atomic number
Air-contrast studies such as a colon examination are successful principally for which of the following reasons there are differences in effective atomic number && in mass density
To optimize x-ray mammography the main x-ray interaction should be the photoelectric effect
Differential absorption between bone and soft tissue occurs principally for which of the following reasons There is a difference in effective atomic number
Angiography with iodinated compounds works principally because of the differences in effective atomic number
Differential absorption is The difference between those x-rays that are absorbed and those that are transmitted
As kVp increases the relative number of x-rays that interact with tissue decreases
In which of the following tissue does differential absorption most depend on differences in mass density lung and bone
How is photoelectric interaction with tissue related to the mass density(p) of the tissue it is proportional
Lungs are imaged on a chest radiograph principally because of the differences in which of the following tissue mass density
Differential absorption between lung and soft tissue occurs principally because of which of the following the difference in mass density
The reduction in intensity of an x-ray beam after it passes through tissue is called attenuation
x-ray transmission decreases exponentially, which also means that the number of x-rays is never reduced to zero
Which process contributes most to the radiographic image photoelectric effect
High kVp in chest radiograph will reduce patient dose
Increasing kVp in imaging will reduce skin dose
In high kVp chest radiography contrast depends most upon Mass density
Microcalcifications are imaged on mammograms principally because of Atomic number
More contrast is present froma barium examination than from an iodine examination because barium has a higher atomic number
Photoelectric effect is proprtional to Z(3)
what will increase the energy of bremsstrahlung radiation x-ray tube voltage
Compton interaction occur with outer shell electrons and result in recoil electron + photon of lower energy && reduced gray scale
At 60keV in soft tissue what predominates compton scattering
What does the interaction of the photons with matter depend on? the energy(kVp)& nature of the radiation photon; the atomic number(Z) of the subastance being irradiated
What is the difference between x-ray and gamma radiation; what are they identical in? their origin is different x-ray comes from the shells and gamma comes from the nucleus; Their therapeutic effects are identical
High energy photons liberate ____ ____ from the orbits of atoms by various types of interactions secondary electrons
What is ultimately responsible for the biologic effects of x-ray and gamma radiation the energy absorbed from the liberation of the secondary electrons and their spatial distribution
What is the name of the differnt types of electrons ejected from the energy shells of an atom by incident photons called secondary electrons
Name two different types of secondary electrons recoil electrons and photoelectrons
Only what contributes to biologic effects absorbed energy
What are the 4 types of diagnostically significant interactions transmission of photons unchanged; unmodified scattering; photoelectric effect with true absorption ; modified scatter
what are the 2 types of therapeutic radiology pair production and photodiscentigration
What interaction cause the blackness(density) on the film transmission of photons unchanged
what are the two key factors that the interactions depend on? kVp and atomic number
Atoms consist largely of what in the transmission of photons unchanged interaction empty space
The actual particles in the atom(protons, neutrons, and electrons) constitute about how much of the volume of the atom 10(-12) or one-million-millionth
A number of photons in any given x-ray beam passes directly through the atom without encountering an electron is called what type of interaction transmission of Photons unchanged
The bringing about of less orderly arrangement of photon's direction due to the deflection caused by charged particles(orbital electrons) interposed in the path of the beam is known as Scattering
Charged particles is also called Orbital electrons
What is another name for unmodified scattering? classical or Thompson scattering
What are the two types of scattering modified and unmodified
Unmodified scattering refers to the scattering of radiation by what relatively free charged particles(electrons) or outer shell electrons of an atom
Eplain classical scattering(unmodified)(where do electromagnetic waves pass;what does the electrical field of radiation do; what happens to the photon; what happens to the electron; what stays the same in the photon and what changes) near an electron;sets the electron oscillating w/the same freq. of the incident electromagnetic waves;disappears in the electron;the electron then forces the radiation out & stops ocillating; photon is traveling in a differ direct but has the same energy
What is the new photon or scattered photon called and why "in step" b/c this type of scattering of primary/incident photon is caherent or equal to the orginal energy
There is NO______ of energy from photo to electron in unmodified scattering. The ONLY thing that has changed is what? transfer; the direction of the Incident photon)(now called scattered)
When does classical scatter occur only if the incident photon does not have sufficient energy to dislodge the orbital electron; its predominant below energies of 10 keV
Does unmodified scattering have practical use in the Diagnostic Radiology NO
Photoelectric interaction with true absorption creates secondary radiation
Where does photoelectric absorption take place aand how much energy does it have takes place when an incident photon(the primary beam) interacts with an inner atomic electron and has enough energy to eject the electron from its shell
All the energy of the photon during photoelectric interaction with true absorption must be what equal or exceed the binding energy of the electron
During photoelectric interaction with true absorption the photons energy will be transferred where to the dislodged electron
The nam given to the ejected orbital electron photoelectron
what is the process called when the electron is given kinetic energy photoelectric process
What interaction gives the white or clear image on a film photoelectric interaction with true absorption
What is the formula for the Photoelectric Interaction with True Absorption? E(i)= E(b) + E(ke)
During the Photoelectric Interaction, the secondary radiation occurs when the atom _______ the now vacant hole left by the dislodged __________. Fill; Electron
When is the secondary radiation created and what is it characteristic of? Radiation is created when the hole is filled and is characteristic of the shell that is now filled
What is the energy of the secondary radiation? The inner-shell (K) binding energy - the binding energy of the shell the electron was pulled from (usually L)
During the Photoelectric Interaction with True Absorption, what type of energy is the secondary radiation? Weak and not of diagnostic importance
The probability of occurrence for Photoelectric Interaction with True Absorption is dependent upon what 2 things? 1)The kVp of the incident photon 2)The atomic number of the irradiated substance
The probability of occurrence for Photoelectric Interaction is ______________ proportional to the _______ of kVp. Inversely Proportional; Cube of kVp (1/kVpᶾ) (photon energy)
The probability of occurrence for the Photoelectric Interaction is __________ proportional to the ________ of the atomic number of the irradiated substance. Directly Proportional; Cube of Z (Zᶾ) (Atomic #)
As probability increases kVp__, wavelength___, Fequency____, Hardness of the beam___, and quality of the beam___ decreases;increases;decreases;decreases;decreases
As the Atomic # of the irradiated substance increases the probability of occurrence for the Photoelectric Interaction ___________. Increases
If you know the energy of the incident photon and the atomic number of the irradiated substance, what is the formula for the probability of occurrence? Probability = Zᶾ/kVpᶾ
What is the energy of the photon for the Photoelectric Interaction w/ True Absorption? Up to 50 kVp numbers
Photoelectric Interaction w/ True Absorption usually occurs with atoms of ________ atomic numbers. High
During Photoelectric Interaction w/ True Absorption, why is it possible to see contrast differences in substances that have close atomic numbers? The Density of the substances
The greater the density of a substance being irradiated means the ___________ the probability of Photoelectric Interaction. Greater
Modified scattering is also referred to as the ___________ __________. Compton Effect
During Modified scattering, what kind of electron does the incident photon interact with? Loosely bound outer-shell electron
The Compton Effect occurs at photon energies up to _______ kVp. 100 kVp
During the Compton Effect, the electron that interacts with the photon becomes a __________ or (AKA) ___________ electron. Recoil or (AKA) Compton Electron
The amount of energy gained by the recoil electron depends on the __________ it's hit by the incident photon Angle
During the Compton Effect, what becomes of the energy from the incident photon? Some is used dislodging the electron and the remainder is divided between the recoil
During the Compton Effect (Modified Scattering) the more direct the hit of the incident photon to dislodge the electron, the __________ energy will be transferred to the ___________ Electron. More; Recoil
During Modified Scattering, the less direct the hit of the photon on the electron, the _________ energy will remain with the _________ photon. Less; Scattered
During the Compton Effect, how is the scattered photon different from the incident photon? Traveling in a different direction; Energy (frequency) is decreased and wavelength
Give the formula for the transfer of energy from the incident photon during the Compton Effect: E(i)= E(s) + E(b) + E(ke)
Give the subscripts for the Compton Effect formula: 1)i, 2)s, 3)b, 4)ke 1)i=Incident photon 2)s=Scattered photon 3)b=Binding energy of electron 4)ke=Kinetic
This is radiation that is scattered 180° from the direction of travel of the incident photon: Backscatter Radiation
Backscatter radiation is also known as ________ and puts the _________ on the radiographic image. fog; gray
1)Photoelectric Interaction: Photon energy: 2)Compton Scattering: Photon energy: 3)Thompson Scattering: Photon energy: 1)Up to 50 kVp 2)Up to 100 kVp 3)Below 10 keV
What interactions occur with INNERSHELL electrons? Photoelectric Interactions w/ True Absorption
What interactions occur with OUTERSHELL electrons? Unmodified Classical (Thompson) Scattering & Modified Scattering/Compton Effect
Which interaction is responsible for Fog? Modified Scattering / Compton Effect
What interaction does not involve an electron? Transmission of Photons Unchanged
Which interactions eject orbital electrons? Photoelectric and Compton
Which interaction can cause images of the cassette locks on the back of the cassette to show up on the Radiograph? Backscatter from Modified Scattering
Which interaction increases the scale of contrast and actually "degrades" contrast? Compton Scattering
What devices are available to reduce the negative effects of Compton Scattering? Collimation and Grids
Increasing the hardness (quality) of the beam and Increasing kVp will have what effect on the probability of Compton Scattering? Decrease the probability( also increase of frequency and wavelength)
Increasing the photon energy ____________ the probability of Compton Scattering and ____________ the problem caused by Compton Scattering. Decreases; Increases
Why does the problem with Compton Scattering increase as the energy of the incident photon increases? The scattered photons produced from the interaction will be strong enough to (1) continue traveling in a straight line to the film & (2) are stronger when they reach the film
Why does the probability of occurrence decrease as the kVp increases? Because the number of interactions will decrease as the photon's energy increases (it will not interact with an electron and go straight through the patient to the film)
What are some cassettes designed with to prevent backscatter lead lined backs because it can cause images of back locks of the cassette to show up on the film if not
Pair Production occurs with photon energies of: At least 1.02 MeV
What subatomic particle does the photon interact with during Pair Production Interaction? The Nucleus
During Pair Production, a photon disappears into a ___________ of an atom and ejects 1 _____________ electron and 1 ____________ electron. Nucleus; Negative; Positive
What is the name of and what becomes of the ejected negative electron during Pair Production? Negatron; Behaves like any other electron
What becomes of the ejected Positron during Pair Production? Slows by interacting with other atoms and combines with an electron
Why would a Positron combine with an electron from another atom? Because it's charge is positive and will combine with subatomic negative particles (electrons)
After a Positron combines with an electron it forms a ___________. Positronium
A Positronium is an _________ atom which is very ___________. The subatomic particles that created to form a Positronium _____________ eachother. Exotic Atom; Very Unstable; Annihilate
When the Positronium explodes it creates _______ Photons of ___________ energies 2; equal
If the incident photon was 1.02 MeV, what would be the energy of the resulting gamma photons be and how will they travel? 0.51 MeV Each; Travel in opposite directions
During Pair Production the first conversion is from energy to ______. The Second conversion is from ____________ to __________. Matter (photon to positronium); Matter to energy (positronium to 2 photons)
The reaction that causes the Positronium to produce 2 photons is called the _____________ Reaction. Annihilation
Pair Production occurs with photon energies from _________ to __________. 1.02 MeV to 10 MeV
What is differential absorption? the difference b/t those x-rays absorbed photoelectrically and those not absorbed; this is how an x-ray image is formed
Differential Absorption increases as kVp is decreased
Absorbed radiation and appears clear radiopaque
Allows radiation to pass through and appears black radiolucent
The interaction b/t x-rays and tissue is proportional to the mass density of the tissue mass density
if mass density is doubled then what happens to the photoelectric interaction it is doubled
Radiation that is absorbed by a given percent per each incremental thickness of matter exponential attenuation
Created by: atesta0824



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