Interaction of X-Radiation with Matter Flashcards
The processes of interaction between radiation are under the control by the Radiographer
By selection of ___ and ___
- ___ controls ___, or ___, of the ___ in the x-ray ___, and to some degree also affects the ___ or number of ___ in the ___.
- ___ controls the ___ of radiation that is directed toward a patient during a selected x-ray ___.
The processes of interaction between radiation are under the control by the Radiographer
By selection of kVp and milliampere-seconds (mAs)
- kVp controls quality, or penetrating power, of the photons in the x-ray beam, and to some degree also affects the quantity or number of photons in the beam.
- mAs controls the quantity of radiation that is directed toward a patient during a selected x-ray exposure.
X-RAY ABSORPTION IN BIOLOGIC TISSUE
- interacts with the ___ of the ___ and be absorbed (at atomic level only)
- Interact with the ___ and be ___, causing some ___
- Pass through ___
- If ___ is transferred from ___ to the ___ of the patient, this process is called absorption.
- The amount of ___ absorbed per ___ is the absorbed dose (__).
X-RAY ABSORPTION IN BIOLOGIC TISSUE
- interacts with the atoms of the tissue and be absorbed (at atomic level only)
- Interact with the atoms and be scattered, causing some indirect transmission
- Pass through without interaction
- If energy is transferred from x-rays to the atoms of the patient this process is called absorption.
- The amount of energy absorbed per unit mass is the absorbed dose (D).
FILTRATION
What does filtration do and what are the different types?
FILTRATION
What does filtration do and what are the different types?
- Filtration removes the radiation with longer wavelengths
- Added filtration and permanent or inherent filtration
Filtration
Permanent or Inherent Filtration
- glass ___
- ___ oil
- ___ in collimator (b/c you never take exposure without collimator)
Added Filtration
- ___ sheet
- < 50 kVp = ___ of AlEq
- 50-70 kVp = ___ of AlEq
- > 70 kVp = ___ of AlEq
- (can be more than 2.5mm of AlEq due to wear and tear)
Filtration
Permanent or Inherent Filtration
- glass envelope
- dialetric oil
- mirror in collimator (b/c you never take exposure without collimator)
Added Filtration
- Aluminum sheet
- < 50 kVp = .5mm of AlEq
- 50-70 kVp = 1.5mm of AlEq
- > 70 kVp = 2.5mm of AlEq
- (can be more than 2.5mm of AlEq due to wear and tear)
Primary Radiation
Primary radiation is the x-ray ___ that emerges from the ___ and is directed toward the ___.
Primary Radiation
Primary radiation is the x-ray photon beam that emerges from the x-ray tube and is directed toward the image receptor.
Energy of Photons in Diagnostic X-ray Beam
- 1 volt of energy = ___
- 100 kVp of energy = ___ Volts —– 100,000 =___ or 100 ___
For a typical x-ray unit, the ___ of the beam is about ___ the ___ of most of the ___.
100 kVp contains ___ with the average of approximately of ___.
Energy of Photons in Diagnostic X-ray Beam
- 1 volt of energy = 1 electron volts (eV)
- 100 kVp of energy = 100,000 Volts —– 100,000 = eV or 100 keV
For a typical x-ray unit, the energy of the beam is about 1/3 the energy of most of the energetic photons.
100 kVp contains 100 keV with the average of approximately of 33 keV.
Primary, Exit, and Attenuated Photons
- Exit, or image- formation, photons (photons __ and __) are photons that pass through the ___ being radiographed and reach the ___.
- The ___ of the path of photon ___ represents what is called ___ that ___ the appearance of a completed radiographic image by ___ the sharp outlines of ___ structures.
- Attenuated photons (photons __ and __) are photons that have interacted with the ___ of the patient’s ___ and been ___ or ___ such that they do not reach the ___
Primary, Exit, and Attenuated Photons
- Exit, or image-formation, photons (photons 1 and 2) are photons that pass through the patient being radiographed and reach the radiographic IR.
- The bending of the path of photon 2 represents what is called small-angle scatter that degrades the appearance of a completed radiographic image by blurring the sharp outlines of dense structures.
- Attenuated photons (photons 3 and 4) are photons that have interacted with the atoms of the patient’s biologic tissue and been scattered or absorbed such that they do not reach the radiographic IR
PROCESSES OF INTERACTION
What are the 5 types of interaction between x-radiation and matter?
Which 2 of the 5 are important in diagnostic radiology?
PROCESSES OF INTERACTION
What are the 5 types of interaction between x-radiation and matter?
- Coherent Scatter
- Compton Scatter
- Photoelectric Absorption
- Pair Production
- Photodisintegration
Which 2 of the 5 are important in diagnostic radiology?
Compton scattering and photoelectric absorption
COHERENT SCATTERING
• ___ scattering • ___ scattering • ___ scattering
- ___ photon interacts with the atom. (___ wavelength)
- Causes the atom to momentarily ___ and the atom radiates ___ in the form of ___.
- A relatively ___ process that results in no loss of ___ as x-rays ___.
- It occurs with ___ photons, typically less than ___ keV.
- ___ and ___ scattering play essentially no role in radiography (it could if we didn’t use filtration)
COHERENT SCATTERING
• Classical scattering • Elastic scattering • Unmodified scattering
- Low energy photon interacts with the atom. (Long wavelength)
- Causes the atom to momentarily vibrate and the atom radiates energy in the form of electromagnetic waves.
- A relatively simple process that results in no loss of energy as x-rays scatter.
- It occurs with low-energy photons, typically less than 10 keV.
- Rayleigh and Thompson scattering play essentially no role in radiography (it could if we didn’t use filtration)
COMPTON SCATTERING
- ___ energy interacts with a ___ bound ___-shell electron, the incoming x- ray ___ surrenders a portion of its ___ energy to dislodge the ___ from its orbit.
- The energy-degraded x-ray __ then continues on its way but in a ___ direction. The ___-speed electron ejected from its orbit is called a Compton-scattered electron, or ___, or “___” electron.
- Causes radiographic ___ on the image (get rid of fog by using grid, proper filtration, collimation)
COMPTON SCATTERING
- Photon energy interacts with a loosely bound outer-shell electron, the incoming x- ray photon surrenders a portion of its kinetic energy to dislodge the electron from its orbit.
- The energy-degraded x-ray photon then continues on its way but in a new direction. The high-speed electron ejected from its orbit is called a Compton-scattered electron, or secondary, or “recoil” electron.
- Causes radiographic fog on the image (get rid of fog by using grid, proper filtration, collimation)
Photoelectric Absorption
- Diagnostic radiology energy range: ___ to ___ kVp (mammography =
- This is the most ___ mode of interaction between x -ray ___ and the ___ of the patient’s body for producing ___.
Photoelectric Absorption
- Diagnostic radiology energy range: 23 to 150 kVp (mammography = <40kVp)
- This is the most important mode of interaction between x -ray photons and the atoms of the patient’s body for producing useful images.
PHOTOELECTRIC ABSORPTION DEPENDS ON…
PHOTOELECTRIC ABSORPTION DEPENDS ON…
- Z # of the tissues (atomic #) - soft tissue looks dark on film & bone will absorb more than surrounding tissues - will look white on image
- Energy of the beam - lower energy beam or longer wavelength - will increase radiation dose to patients (b/c less filtration)
CONTRAST MEDIA
- Has a higher ___ number (___) than the surrounding tissue.
- More absorption of ___
CONTRAST MEDIA
- Has a higher atomic number (z number) than the surrounding tissue.
- More absorption of primary beam
Pair Production
- The incoming ___ (equivalent in energy to at least ___ ) strongly interacts with the ___ of the atom of the irradiated object and ___.
- In the process, the ___ of the photon is transformed into two new particles: a ___ (electron) and a ___
- The ___ eventually recombines with any atom that needs another ___. The ___ interacts ___ with a nearby electron.
- During the interaction, the ___ and the ___ annihilate each other, with their rest masses converted into ___, which appears in the form of two ___ photons, each moving in the ___ direction.
Pair Production
- The incoming photon (equivalent in energy to at least 1.022 MeV) strongly interacts with the nucleus of the atom of the irradiated object and disappears.
- In the process, the energy of the photon is transformed into two new particles: a negatron (electron) and a positron
- The negatron eventually recombines with any atom that needs another electron. The positron interacts destructively with a nearby electron.
- During the interaction, the positron and the electron annihilate each other, with their rest masses converted into energy, which appears in the form of two 0.511-MeV photons, each moving in the opposite direction.
USE OF ANNIHILATION RADIATION IN POSITRON EMISSION TOMOGRAPHY
- Known as ___ scans
- Used in ___ along with ___ units
-Uses a source of ___ are injected as ___ (Fluorine -18, Carbon -11, Nitrogen -13)
- -Source of ___
- -Formation of ___ photons
USE OF ANNIHILATION RADIATION IN POSITRON EMISSION TOMOGRAPHY
- • Known as PET scans
- • Used in nuclear medicine along with CT units
- • Uses a source of positrons are injected as radionuclides (Fluorine -18, Carbon -11, Nitrogen -13)
- Source of positrons
- Formation of annihilation photons
Photodisintegration
- An incoming ___-energy photon (___) collides with the nucleus of the atom of the irradiated object and absorbs ___ the photon’s energy.
- This energy ___ in the nucleus creates an ___ that is usually alleviated by the emission of a ___.
- if sufficient energy is absorbed by the ___, other types of emissions will be possible, such as a proton or proton-neutron combination (deuteron), or even an ___ particle.
Photodisintegration
- An incoming high-energy photon (> 10MeV) collides with the nucleus of the atom of the irradiated object and absorbs all the photon’s energy.
- This energy excess in the nucleus creates an instability that is usually alleviated by the emission of a neutron.
- if sufficient energy is absorbed by the nucleus, other types of emissions will be possible, such as a proton or proton-neutron combination (deuteron), or even an alpha particle.
