WorksheetsChapter 7 Interactions with Matter: Test Review
Total questions: 56
Worksheet time: 28mins
Which goal best describes why understanding x-ray photon interaction is emphasized in this chapter?
To speed up imaging equipment maintenance
To minimize patient harm and produce better quality images
To reduce the cost of radiographic exams
To increase the number of images taken per session
Which three x-ray interactions occur within the range of energy used in diagnostic radiography?
Classical (coherent) scattering, Compton scattering, Photoelectric effect
Compton scattering, Pair production, Photodisintegration
Photoelectric effect, Pair production, Photodisintegration
Classical (coherent) scattering, Pair production, Photodisintegration
Which pair of interactions are specifically highlighted for their effects on both image quality and patient dose?
Classical scattering and pair production
Photoelectric absorption and Compton scattering
Compton scattering and photodisintegration
Pair production and photodisintegration
Which term is another name for classical scattering in x-ray interactions?
Photoelectric effect
Compton scattering
Coherent (Thomson) scattering
Pair production
In classical (coherent) scattering, what happens when a low-energy incident x-ray photon interacts with an orbital electron of a tissue atom?
The photon is completely absorbed, ejecting the electron from the atom
The photon transfers energy, the atom becomes excited, and the photon is released in a new direction
The photon increases in energy and continues in the same direction
The photon creates an electron-positron pair
What is a direct consequence of a photon undergoing classical scattering for patient safety considerations?
It reduces image scatter and lowers dose
It becomes a scatter photon that adds to patient dose
It is converted entirely into heat with no dose impact
It produces secondary radiation that exits the patient without interaction
A technologist needs to minimize contributions to patient dose from low-energy interactions. Which adjustment best reduces the likelihood of classical scattering events?
Use lower kVp to increase the number of low-energy photons
Increase beam filtration to remove low-energy photons
Increase mAs to produce more photons overall
Use a grid to absorb high-energy primary photons
Which statement best describes the initial event in a photoelectric interaction?
An x-ray photon scatters from an outer-shell electron without energy loss
An incident x-ray photon removes an inner-shell electron from a tissue atom
A nucleus absorbs the x-ray photon and emits gamma radiation
Two x-ray photons collide and annihilate
During a photoelectric interaction, what happens to the energy of the incident x-ray photon?
It is partially absorbed and partially scattered
It is converted entirely into heat in the detector
It is totally absorbed in removing the inner-shell electron
It remains unchanged as the photon passes through
What is the ejected electron produced by a photoelectric interaction called?
Auger electron
Compton electron
Photoelectron
Secondary proton
The kinetic energy of the photoelectron is equal to which of the following?
The binding energy of the orbital electron
The incident photon energy minus the binding energy
Twice the binding energy of the inner shell
The mass energy of the electron (511 keV)
Which outcome is directly associated with photoelectric absorption in diagnostic imaging?
Decreased patient dose with no effect on image
Significant contribution to patient dose
Only increased scatter reaching the detector
Production of positrons for therapy
A radiographer must balance technical factors to achieve which goal regarding photoelectric interactions?
Maximize absorption regardless of dose
Eliminate all absorption events
Strike a balance between image quality and patient dose
Ensure only outer-shell interactions occur
In the diagram of photoelectric interaction, which labeled particle is ejected from the atom after absorption of the photon?
Secondary x-ray
Incident photon
Ejected photoelectron
Nucleus
Which energy range is stated for incident x-ray photons that undergo photoelectric interactions in tissue?
5–15 kVp
20–120 kVp
150–300 kVp
>1 MeV
Why does the photoelectron have enough kinetic energy to cause further interactions before being captured elsewhere?
It retains the entire energy of the original photon including binding energy
Its energy equals the original photon energy minus binding energy, leaving usable kinetic energy
It gains energy from the nucleus after ejection
It is accelerated by the detector field
Which statement aligns with the responsibility emphasized for radiographers regarding photoelectric absorption?
Always use the highest possible kVp to reduce all interactions
Select technical factors that minimize image quality to reduce dose
Choose exposure settings that balance necessary absorption for image formation with patient dose
Depend solely on automatic exposure control without consideration of dose
In photoelectric interactions, what initially makes the atom unstable?
Creation of Compton scatter
Ionization that leaves an inner-shell vacancy
Emission of a bremsstrahlung photon
Addition of a neutron to the nucleus
What process helps the ionized atom regain stability after a photoelectric interaction?
Pair production
Auger electron emission only
Characteristic cascade
Coherent scattering
During the characteristic cascade that follows a photoelectric event, what is produced?
High-energy gamma rays
Secondary x-ray photons
Positron-electron pairs
Ultraviolet photons
Which factor does NOT influence the probability of a photoelectric interaction?
Energy of the incident photons
Atomic number of the tissue atoms
Incident x-ray photon energy relative to inner-shell binding energy
Number of protons in the x-ray tube target filament
For a photoelectric interaction to occur, the incident x-ray photon energy must be at least how large relative to the inner-shell binding energy of the tissue atom?
Less than the binding energy
Equal to or greater than the binding energy
Exactly half the binding energy
Twice the binding energy
How does increasing the atomic number of the tissue atoms affect the probability of a photoelectric interaction, assuming other factors are constant?
It decreases the probability
It increases the probability
It eliminates the interaction
It has no effect
Which statement best defines a Compton interaction in diagnostic imaging?
Annihilation of a positron with an electron, producing two photons
Absorption of a low-energy photon by a K-shell electron without scatter
Interaction where a moderate-energy x-ray photon ejects an orbital electron and is deflected with reduced energy
Emission of characteristic radiation after inner-shell vacancy is filled
During a Compton interaction, approximately how much energy can the incident photon lose before being scattered?
Up to one third of its energy
Exactly one half of its energy
All of its energy
Less than 5% of its energy
What immediate effect does the Compton interaction have on the target atom?
It becomes ionized and unstable
It undergoes nuclear fission
It returns to ground state without change
It becomes excited but not ionized
The ejected electron from a Compton interaction is also called the:
Auger electron
Photoelectron
Compton electron or secondary electron
Pair-production electron
Which outcome describes the scattered photon after a Compton interaction?
It is absorbed immediately and does not leave the atom
It becomes a Compton scatter photon that may undergo further interactions in tissue or reach the image receptor
It gains energy and travels in the original direction
It converts into an electron-positron pair
Which statement best explains why Compton interactions can contribute to patient dose and image fog?
The ejected electron has high energy and exits the patient without interacting
Secondary photons from characteristic interactions and deflected scatter add unwanted exposure before reaching the receptor
The incident photon is completely absorbed, reducing exposure
Compton scatter always travels perpendicular to the receptor, avoiding the image field
A moderate-energy x-ray photon enters a tissue atom and interacts with an orbital electron. Predict the most likely sequence of events.
Electron excitation, photon energy increases, photon continues straight
Orbital electron removal, atom ionization, photon loses energy and changes direction, ejected electron may cause further low-energy interactions
Photon passes between electrons, no energy loss, and exits unchanged
Inner-shell vacancy is filled immediately with no secondary effects
Which statement best describes how Compton scatter affects image quality?
It increases image sharpness by reducing noise.
It strikes the image receptor in the wrong place, causing image fog.
It removes all low-energy photons from the beam, improving contrast.
It only occurs at very low photon energies, eliminating blur.
In general diagnostic imaging, Compton scatter is characterized as:
Rare and clinically insignificant
One of the most prevalent interactions between x-ray photons and the human body
Dependent primarily on the atomic number of tissue
A process that completely absorbs x-ray photons
The probability of Compton scatter depends primarily on which factor?
Atomic number of the atoms involved
Mass density of the tissue only
Energy of the photon
Thickness of the image receptor
What proportion of their energy do Compton scatter photons typically retain, and why is this clinically important?
About one third; they contribute to patient dose only
About two thirds; they may exit the patient and expose the radiographer
Nearly all; they are reabsorbed in the patient
None; they are fully absorbed in the detector
During procedures where staff may be near the patient and x-ray tube during exposure, what is the recommended safety measure?
Increase kVp to reduce scatter production
Turn off automatic exposure control
Use appropriate shielding
Stand closer to improve communication
What is identified as the major source of occupational exposure for radiographers?
Photoelectric absorption
Bremsstrahlung radiation from the tube housing
Leakage radiation from the collimator
Compton scattering
Which action aligns with best practice regarding Compton scatter during image acquisition?
Maximize scatter to improve receptor exposure
Ignore scatter because it is atomic-number independent
Minimize scatter as much as possible to reduce image fog and exposure risk
Rely on higher atomic number tissues to reduce scatter probability
Which condition must be met for pair production to occur during an interaction between an x-ray photon and matter?
The photon energy is less than 0.5 MeV and interacts with orbital electrons
The photon energy exceeds 1.02 MeV and interacts with the nucleus
The photon scatters off an outer-shell electron with any energy
The photon is absorbed by the K-shell electron at 1.02 keV
In pair production, the high-energy photon interacting with the nucleus results in the creation of which two particles?
Two electrons
A neutron and a proton
A positron and an electron
Two positrons
What is the minimum energy each created particle must have immediately after pair production?
1.02 MeV
0.51 MeV
0.25 MeV
2.04 MeV
After formation, what typically happens to the positron produced in pair production?
It immediately binds to the nucleus
It travels until it strikes an electron, causing an annihilation event
It remains stationary at the point of creation
It converts directly back into a single photon without interaction
During the annihilation event resulting from a positron meeting an electron, their energy is converted into which of the following?
A single x-ray photon
Two x-ray photons
Heat and visible light
A neutron and gamma ray
Which statement best explains why pair production is not a concern in routine radiography?
Radiography uses photon energies too low to exceed 1.02 MeV required for pair production
Radiography lacks atomic nuclei for interaction
Radiography always uses neutrons instead of photons
Radiography prevents electrons from leaving atoms
Which statement best defines photodisintegration?
An interaction where moderate-energy photons ionize orbital electrons
An interaction where extremely high-energy photons strike the nucleus, making it unstable
The emission of characteristic x-rays from inner-shell vacancies
Scattering of low-energy photons without energy loss
During photodisintegration, how does the atom regain stability?
By capturing a free electron
By emitting a photon of lower energy
By ejecting a nuclear particle such as a proton or neutron
By transferring energy to an outer-shell electron
Which of the following is true regarding photodisintegration in radiographic practice?
It commonly contributes to image noise
It is responsible for most patient dose
It does not occur in radiography
It occurs only at diagnostic kVp with heavy shielding
A photon causes the ejection of a neutron directly from the atomic nucleus. Based on the description, which interaction most likely occurred?
Compton scattering
Photoelectric effect
Coherent scattering
Photodisintegration
Which statement best defines differential absorption in medical imaging?
The process by which all x-ray photons are absorbed equally by all tissues
The distinction between x-ray photons absorbed via the photoelectric effect and those that pass through the body depending on tissue composition
The scattering of x-ray photons after they exit the patient
The conversion of x-ray photons into visible light inside the image receptor
In the provided diagram of an x-ray beam interacting with a patient, which group of photons contributes directly to forming the image on the receptor?
X-ray photons that become scatter radiation
X-ray photons absorbed by the part
X-ray photons that penetrate the part and reach the image receptor
Primary x-ray photons before patient interaction
Which term describes x-ray photons that pass through the body and reach the image receptor?
Absorption
Transmission
Scatter
Attenuation only
Which statement about absorption is correct?
It refers to photons that reach the image receptor without interaction.
It refers to photons attenuated by the body that do not reach the image receptor, often via photoelectric interactions.
It is another term for scatter radiation after exiting the patient.
It happens only in low-density tissues.
Which pair correctly matches tissue property with x-ray interaction likelihood?
Radiopaque — low probability of absorption
Radiolucent — readily absorbs x-rays
Radiopaque — readily absorbs x-rays
Radiolucent — blocks transmission completely
A structure that appears dark on an x-ray due to lower density and lower probability of absorption is best described as:
Radiopaque
Radiolucent
Radiodense
Radioactive
Differential absorption across anatomical structures primarily depends on which factor?
Tube current
Body tissue density and composition
Exposure time
Image receptor type
Which scenario would most likely increase image receptor exposure due to transmission?
Imaging a less dense, radiolucent region allowing more photons to pass through
Imaging a highly radiopaque structure that readily absorbs x-rays
Using materials that increase photoelectric absorption in the patient
Maximizing scatter production within the body
A student claims that if all tissues absorbed x-ray photons equally, image contrast would increase due to pronounced differential absorption. What is the best evaluation of this claim?
Correct; equal absorption maximizes contrast.
Incorrect; without differences in absorption between tissues, differential absorption would be minimal and contrast would decrease.
Correct; equal absorption eliminates scatter.
Incorrect; equal absorption only affects patient dose, not image contrast.
