Chapter 2 Interaction of X-radiation with matter
Of 1000 50 keV photons traveling through 5 cm of soft tissue, _____ interactions may be expected to occur.
666
The resulting radiographic image is formed from both ___________ and ________.
directly transmitted x-ray photons, indirectly transmitted (scattered) x-ray photons
The symbol Z indicates?
Atomic number of an atom.
X-rays may interact with ______ of the biologic material in the patient or _____ through without interaction.
Atoms, pass.
What energy does Photoelectric absorption occur?
1-50 kVp
What energy does Pair production occur at?
1.022 MeV
What energy does Photodisintegration occur at?
10 MeV
What energy does Coherent occur at?
10 keV, 1-50 kVp
100 kVp is equivalent to
100,000 eV or 100 keV
Atomic number of bone
13.8
What angle does the photon come out of the atom?
20 degrees
What energy does Compton scattering occur at?
35 keV, 60-90 kVp
Scatter
A change in direction of travel that may also involve a partial loss of radiation energy.
Process of Photodisintegration?
A high-energy photon collides with the nucleus of an atom, directly absorbs all of the photon's energy.
Photoelectric
A photon is completely absorbed by the atom of the tissue.
Auger effect
A vacancy exists in an inner electron shell of an atom (photoelectric effect), the energy liberated when this vacancy is filled, instead of emerging form the atom as fluorescent radiation, can be transferred to another electron of the atom, thereby ejecting the electron.
2 methods to limit the effects of indirectly transmitted x-ray photons?
Air gap and grid.
Auger electron
An emitted electron.
What interaction results in the conversion of matter into energy?
Annihilation reaction
In photoelectric absorption to dislodge an inner-shell electron from its atomic orbit, the incoming x-ray photon must be able to transfer a quantity of energy?
As large as or larger than the amount of energy that binds the electron in its orbit.
Small-angle scatter
Bending of its path.
What is not a type of interaction between x-radiation and biologic matter?
Bremsstrahlung
Fluorescent radiation is also known as?
Characteristic radiation
Which radiation that occurs when an electron drops down from an outer orbit to fill a vacancy in an inner orbit of the parent atom?
Characteristic radiation
Other names for Coherent scattering?
Classic, elastic, or unmodified scattering.
Which two interactions between x-radiation and matter may result in the production of small-angle scatter?
Coherent scattering and Compton scattering.
Reduce fog by _____.
Collimating the x-ray beam.
What interaction results in all-directional scatter?
Compton interaction
Attenuation
Decreasing the intensity of the primary photon beam that was directed toward a destination.
What are byproducts of photoelectric absorption?
Photoelectron and characteristic photon
Exit or image-forming photons
Emerge fromt he tissue and strike the radiographic image receptor below it.
Electrical voltage
Energy of the electrons inside the x-ray tube.
The amount of energy loss involved is simply _____ to the difference in the binding energies associated with each electron shell.
Equal
Unstable nuclei used in PET scanning are:
Fluorine-18, carbon-11, and nitrogen-13
Optimal x-ray image
Formed when only direct transmission x-ray photons reach the image receptors.
Compton scattered electron or secondary or recoil electron
Freed electron, possesses excess kinetic energy and is capable of ionizing other atoms.
The ______ the difference in the amount of photoelectric absorption, the _______ the contrast in the image.
Greater, greater
Why is the anode made up of the materials it is?
High melting points and high atomic numbers.
Auger effect is more prevalent in materials with ______ atomic number atoms.
Higher
Absorption
If the x-rays interact, electromagnetic energy is transferred from the x-rays to the atoms of the patient's biologic material.
The probability of occurence of photoelectric absorption depends on the energy of the ______ x-ray photons and the _____ _____.
Incident, atomic number
Compton scattering can also be called?
Incoherent, inelastic, or modified scattering.
Process of Compton scattering?
Incoming x-ray photon interacts with a loosely bound outer electron of an atom of the irradiated object. Dislodge the electron from its outer-shell orbit, ionizing it.
The probability of occurrence of photoelectric absorption _________ as the energy of the incident photon decreases and the atomic number of the irradiated atoms ______.
Increases markedly, increases
What shell does photoelectric absorption occur at?
K or L
Glass permits passage of all but the ______ energy components of the x-ray spectrum. Therefore acts as a filter.
Lowest
X-rays are carriers of?
Manmade, electromagnetic energy
X-rays are carriers of ____, _____.
Manmade, electromagnetic energy.
Rayleigh scattering
Net effect of coherent, or unmodified, scattering. Scientist who first explained it.
Average photon in the x-ray beam is about ____ _____ ____ ______ of the most energetic photon.
One third the energy. Ex. 100 kVp beam (energies of 100 keV or less = 33 keV
Annihilation radiation is used in what modality?
PET
What interaction between photons and matter involves a matter-antimatter annihilation reaction?
Pair production
Indirect transmission
Phons that transverse the patient and strike the image receptor.
What particle is considered to be a form of antimatter?
Positron
Direct transmission
Primary x-ray photons that transverse the patient without interacting.
Radiationless effect
Process does not include any x-ray emission
Differences in density level between radiographic images of adjacent structures as seen in a completed radiograph define?
Radiographic contrast
Neutrino
Surplus proton is replaced in the nucleus by a neutron while a positron and another particle.
Characteristic photon or Characteristic x-ray (photoelectric absorption)
The "released" energy is carried off in the form of a photon.
Absorbed dose (D)
The amount of energy absorbed per unit mass.
Primary radiation
The beam before it hits the patient or interacts with matter.
Photoelectron
The ejected orbital electron.
Peak kilovotage (kVp)
The highest energy level of photons in the x-ray beam
Compton scatter photon
The incident x-ray photon that surrendered some of its kinetic energy to free the loosely bound outer-shell electron from its orbit continues on its way but in a new direction.
Thompson scattering
The low-energy photon interacts with one or more free electrons
Fluorescent radiation (photoelectric absorption)
The number of x-rays emitted per inner-shell vacancy during the process of photoelectric absorption. Also known as characteristic x-rays.
Fluorescent yield
The number of x-rays emitted per inner-shell vacancy.
Milliampere-seconds (mAs)
The product of electron tube current and the amount of time in seconds that the x-ray tube is activated.
Material the anode is made up of?
Tungsten, rhenium, graphite, and alloy.
The thicker structure absorbs ______ as many photons.
Twice
Positron decay
When a neutrino is ejected from the nucleus.
Process of Photoelectric absorption?
X-ray photon interacts with inner-shell electron, ejects photoelectron, outer shell electrons fill empty spots emitting radiation (scatter).
Process of Pair production?
X-ray photon strongly interacts with the nucleus of an atom of the irradiated biologic tissue and disappears. Two new particles appear: positron and negatron.
Particles associated with electromagnetic radiation that have no mass or electric charge are?
X-ray photons
Permanent inherent filtration
X-ray tube glass wall and added aluminum w/in the collimator.
Mass density
measured in grams per cubic centimeters
kilovoltage peak (kVp)
measurement of the energy, voltage across the tube fluctuates.
