X-Rays
Distance
Distance from the source of radiation to the image receptor. The distance of x-ray photons from the tube. Affects intensity.
X-Rays
Electromagnetic Radiation with very short wavelength. Produced when high velocity electrons are decelerated during interactions with a high atomic number material. Interaction of electrons with the specific atom.
Deceleration of Electrons
Electrons are decelerated when they hit an atom along its path. In the x-ray tube a target with very high atomic number is placed directly along its path. The x-ray tube is vacuumed, to make sure the electrons will hit the target.
Characteristic Interactions
Occurs when the incident electron interacts with an inner shell electron and ionizes the atom. We cannot control this since it depends on the binding energy of the atom.
Bremsstrahlung Interaction
Occurs when the incident electron interacts with the force field of the nucleus.
Infrared Radiation
Outer-shell electrons immediately drop back to their normal energy with the emission of __.
Kilovolt Peak, kVp
This potential difference is controlled by the ___. This gives the electrons the kinetic energy to travel.
Focusing Cup
This focuses the electrons into the target. It surrounds the filament on its back and sides, leaving the front open and facing the target.
Potential Difference
This is controlled by the kilovolt peak (kVp). This gives the electrons the kinetic energy to travel.
Amount of Voltage
(Potential difference) Thousands of kilovolts - create EM radiation that has a shorter wavelength. Very large amounts: 75,000 volts.
Tungsten Anode
Most important part, target stops electron flow produces x-ray beam.
Properties of X-rays
1. Highly penetrating 2. Invisible 3. Possess no mass 4. Electrically neutral and therefore not affected by either electric or magnetic fields. 5. Heterogenous, it can be produced in a wide range of energies and wavelength. 6. Travels in a straight line 7. Travels at the speed of light in a vacuum. 8. Can cause certain objects to fluoresce. 9. Cannot be focused by a lens. 10. Release very small amount of heat upon passing through. 11. Produce secondary and scatter radiation. 12. Produces chemical and biological changes in matter through ionization and excitation.
Lowest Energy
Approximately 15 to 20 keV, and is also a function of beam filtration. Low energy will not hit a person's body. The free space between 0 and 12. Filter high energy to allow it to pass.
Control Heat
By varying the milliamphere.
Single Incident Electron
Can cause numerous interactions in many different atoms before losing enough energy and join the current flow.
Higher Energy
Electrons can jump from outer to inner shells— this transition gives us __ in Xray.
Acceleration of Electrons
Electrons from the filament are accelerated towards the target by application of very high potential difference, in thousands of volts, between the cathode and anode.
Characteristic X-ray
Electrons released are very specific. Energy depends on binding energy in the shells/atom. Low atomic number, ___ have low energy.
Projectile Electrons
Electrons traveling from cathode to anode are known as _____. Almost travels in a speed of light.
Leakage Radiation
Emitted from the X-ray tube protective housing.
Radiographic Exposure Factors
Exposure factors influence and determine the intensity and energy of X-ray that will expose the patient.
Internal Component of X-ray Tube
Filament, Tungsten Anode, etc.
Molybdenum Target
For ______, with atomic number of 42, K-Shell characteristic photons could have energies from 17 to 20 keV. Used in mammography machine, lower kVp for soft tissues in the breasts.
Bremsstrahlung
German word for 'breaking' or 'slowing down.
sec, time of exposure in seconds
Higher time of exposure, longer hit the target, more electrons produced.
Tungsten Target
In ______, with atomic number 74 K-shell characteristic photons could have energies from 57 to 69.5 keV. Used in X-rays.
X-ray Production
In an x-ray tube, xrays are produced by energy conversion when fast-moving electrons from the filament of the x-ray tube interact with the target.
X-axis
In the X-ray emission spectrum, the energy of the X-ray beam is shown on this axis.
Y-axis
In the X-ray emission spectrum, the intensity of the X-ray beam is shown on this axis.
kVp, Kilovoltage Peak
Increase in control of potential difference, increase in quality of x-ray beam, faster electrons, increase in KE, increase in x-ray photons. Affect the number of x-ray photons reach image receptor.
mA, milliampere
Increase in mA, the hotter the filament, increase in electrons hitting target, increase in x-ray photons.
Filament
Most important part, source of electrons, located in the cathode.
Linear Accelerators
Project electrons to accelerate; create x-ray beam up to a maximum of 40 million volts. Electrons released by filament hits the atom or target area. Kinetic energy is converted into electromagnetic energy to form X-ray beam.
Radiation Intensity, Radiation Quantity
Refers to the amount of x-ray photons composing the x-ray beam and is measured by mR.
Radiation Energy, Radiation Quality
Refers to the energy of the x-ray beam and therefore its penetrability measured in HVL.
Continuous Emission Spectrum
Represents bremsstrahlung x-rays.
Discrete Emission Spectrum
Represents the characteristic x-rays.
Highest Energy
The _____ is equal to the to the kVp set on the control panel.
Accelerating Force
The ______ needs to raise the velocity of electrons from zero to 1/2 speed of light in a short distance (usually 1 cm distance).
Higher
The ______ the mA setting, the ______ the temperature of the filament, more electrons are boiled off.
Energy and Intensity
The _________ of the x-ray beam produced is shown in the x-ray emission spectrum.
Inverse Square Law
The decrease in the intensity of the X-ray photons follows the ___. This law states that the intensity of the X-ray beam decreases by a factor of four with the square of the distance.
Ionization
The ejection of an electron from an atom creating an ion pair a positively charged ion (cation) and a negatively charged ion (anion).
Bremsstrahlung Photons, Bremsstrahlung Radiation
The emission in bremsstrahlung interaction. Their energy is exactly the difference between the KE of entering and exiting electron. Thus, the higher the KE of the incident electron the higher the energy of the ______ produced.
Source of Free Electrons
The filament located in the cathode of the x-ray tube. How to produce: when the filament is heated, it will boil off electrons through a process called thermionic emission.
Thermionic Emission
The filament when heated will boil off electron, through a process called ________. Boiling off the outer shell of electrons from the atom of the filament by application of heat. *Filament is made of tungsten with a high melting(?) point
Milliamphere (mA)
The heat is controlled by the current supplied to the filament of an x-ray tube measured in _______.
K-Shell Characteristic Photon
The only kind of characteristic photons that has sufficient energy to be part of the useful beam.
Anode Heat
The projectile electrons interact with the outer-shell electrons but do not transfer sufficient energy to ionize them. Outer shell electrons raised to a higher energy level. Only excitation, a series of interaction
Milliroentgen, mR
The unit of radiographic exposure factors.
Characteristic Photons
These emissions are called _________ because their energy is characteristic of the energy difference between the binding energies of the shells involved in the interaction.
Radiation Dose
When X-rays are performed and absorbed.
Focusing of Electrons
When electrons are boiled off from the filament, the strong negative charge of the focusing cup, overcome the negative charge of individual electrons and forces the electrons together.
Kinetic Energy
When projectile electrons hit the target, they transfer their __ to the target. The __ of the electron is converted to heat energy (anode heat ~99%) or Electromagnetic energy in the form of x-rays (~1%)
Scattered Exposure
Where rad techs get the exposure.
X-ray Beams
X-ray photons consist of ____.
Remnant X-rays
X-ray that passes through the patient body without interacting.
Characteristic and Bremsstrahlung Interaction
X-rays are generated by 2 processes.
Primary X-rays
X-rays that emanate from the tube.
Scattered X-rays
X-rays that travel in a different direction after interacting with matter.
Technical Factors
mA, sec, kVp, Distance