Chapter 2
What happens after x-ray exits tube head?
-X-rays can pass through patient with out any interaction -Can be completely absorbed by patient -Can be scattered
Involves an x-ray photon that has its path altered by matter
Coherent/Unmodified scatter
At the atomic level _________ effect accounts for most of the scatter radiation
Compton
It is the ejected electron in compton scatter and it also has a negative charge
Compton electron or recoil electron
An x-ray photon collides with a loosely bound outer shell electron and gives up part of its energy to eject electron from its orbit
Compton scatter
The __________ contains an on-off switch and an indicator light, and control devices (time, kilo-voltage, and milliamperage selectors) to regulate the x-ray beam
Control panel
What are the 3 visible component parts of the x-ray machine
Control panel,extension arm, and tubehead
What is the purpose of the anode?
Convert electrons into x-ray photons
Functions to dissipate the heat away from the tungsten target
Copper stem
_____ _______ consists of a flow of electrons through a conductor which is known as the _____ ______
Electrical energy, electrical current
The energy that is used to make x-rays
Electricity
X-ray photon passes through atom unchanged and leaves atom unchanged and are also responsible for producing densities and makes dental radiography possible
No interaction
What are the 4 possibilities that can occur when x-ray photons interact with matter?
No interaction, absorption/photoelectric effect, compton scatter, coherent scatter
In photoelectric effect the x-ray photon imparts all of its kinetic energy to the...
Orbital electron, is absorbed, and ceases to exit
At the atomic level absorption occurs as an result of the
Photoelectric effect
In ___________ ___________ an x-ray photon collides with a tightly bound inner shell electron and gives up all of its energy to eject the electron from its orbit
Photoelectric effect
In photoelectric effect what is the ejected electron termed?
Photoelectron
Generators on ________machines produced an x-ray beam with a _______ pattern, whereas ______ constant-potential x-ray machines produce a _________ beam of _________ wavelengths during radiation exposure
older, wavelike pattern, newer, homogeneous,consistent
Two electrical circuits are used in the production of x-rays:
(1) A low voltage, or filament, circuit and (2) A high voltage circuit
The three transformers that are used to adjust the electrical circuits are
1- step-down transformer 2- step-up transformer 3- autotransformer
Kinetic energy of electrons is converted into x-ray photons by 2 ways:
1. General (braking) radiation 2. Characteristic radiation
A step up transformer is used to increase the voltage from the incoming _____ or ______line voltage to the _______ to _______ volts used by the high voltage circuit
110-, 220-, 65,000, 100,000
Constant-potential machines also reduce patient exposure to radiation by __%
20%
The photoelectric effect accounts for ______% of the interactions of mater with a dental x-ray beam
30
Compton scatter accounts for __% of scatter in diagnostic radiography
62
Characteristic radiation requires _____ KvP and higher because the binding of the K shell electron is about ____ KeV
70, 70
Coherent scatter accounts for ____% of the interactions of matter with dental x-ray beams
8
Refers to the total transfer of energy from x-ray photon to the atoms of matter through which x-ray beam passes
Absorption
In production of x-rays both the amperage and the voltage can be
Adjusted
______ ______ describes an electrical current in which the electrons flow in two, opposite directions
Alternating Current (AC)
Sheets of 0.5-mm- thick aluminum placed in the path of the x-ray beam- filter out the nonpenetrating, longer wavelength x-rays
Aluminum discs
The measurement of the # of electrons moving through a conductor
Amperage
Current is measured in
Amperes (A) or milliamperes (mA)
Consists of a wafer-thin tungsten plate embedded in a solid copper rod
Anode/ positive electrode
Serves as a voltage compensator that corrects for minor fluctuations in the current
Autotransformer
Consists of a tungsten wire filament in a cup-shaped holder made of molybdenum
Cathode/ negative electrode
A path of electrical current is a
Circuit
Occurs when a low energy x-ray photon interacts with an outer shell electron
Coherent scatter
As thermionic emission occurs the outer shell electrons of the tungsten atom acquire enough...
Energy to move away from the filament surface and electron cloud forms around the filament
The ________ suspends the x-ray tubehead and houses electrical wires, and also allows for movement and positioning of tubehead
Extension arm
Uses 3 to 5 volts, regulates the flow of electrical current to the filament of the x-ray tube, and is controlled by the milliamperage settings
Filament circuit
Uses 65,000 to 100,000 volts, provides the high voltage required to accelerate electrons and to generate x-rays in the x-ray tube, and is controlled by the kilovoltage settings
High- voltage circuit
The energy and wavelengths vary based on
How electrons interact with tungsten atoms in the anode
What takes place in compton scatter?
Ionization
What takes place in the photoelectric effect?
Ionization
The voltage of the x-ray tube current or the current passing from the cathode to the anode is controlled by the
Kilovoltage peak (kVp)
A lead place with a central hole that fits directly over the opening of the metal housing, where the x-rays exit- restricts size of beam
Lead collimator
Component parts of the x-ray tube are
Leaded glass housing, negative cathode, and positive anode
Leaded glass vacuum tube that prevents x-rays from escaping in all directions
Leaded-glass housing
What are the component parts of the tubehead
Metal housing, insulating oil, tubehead seal, x-ray tube, transformer, aluminum disks, lead collimator, PID
Surrounds the x-ray tube and transformers and is filled with oil-- protects the x-ray tube and grounds the high voltage components
Metal housing/Metal body
In the x-ray tube, the amperage, or number of electrons passing through the cathode filament, can be increased or decreased by the
Milliamperage (mA)
Focuses the electrons into a narrow beam and directs the beam across the tube toward the tungsten target of the anode
Molybdenum cup
Open-ended, lead lined cylinder that extends from the opening of the metal housing of the tubehead- aims and shapes the x-ray beam, sometimes referred to as the cone
Position indicating device (PID)
Coil that receives the alternating electrical current is the
Primary or input coil
Refers to the penetrating beam that is produced at the target of the anode and exits tube head
Primary radiation
The electrical current that energizes the ______ coil induces a current in the _____ coil
Primary, secondary
The conversion from of AC to DC
Rectification
Transformers alter the voltage of the incoming electrical current and then
Route the electrical energy to the x-ray tube
A form of secondary radiation and is the result of an x-ray that has been deflected from its path by the interaction with matter
Scatter radiation
Output coil
Secondary coil
Refers to x-radiation thats created when primary beam interacts with matter
Secondary radiation
The dental x-ray tube acts as a ____-_____ in that it changes AC into DC while producing x-rays
Self rectifier
Characteristic radiation accounts for a very _____ part of x-rays produced in the dental x-ray machine
Small
Used to decrease the voltage from the incoming 110- or 220- line voltage to the 3 to 5 volts used by the filament circuit
Step-down transformer
Has more wire coils than in the primary coil
Step-up transformer
The high-voltage circuit uses both a
Step-up transformer and an autotransformer
What is the purpose of the cathode?
Supply the electrons necessary to generate x-rays
The electrical current is termed direct current (DC) when
The electrons flow in one direction through the conductor
A device that alters the voltage of incoming electricity
Transformer
A device that is used to either increase or decrease the voltage in an electrical circuit
Transformer
The ________ is a tightly sealed, heavy metal housing
Tubehead
Aluminum/leaded-glass covering of the tubehead that permits the exit of x-rays from the tubehead- seals the oil in the tubehead and acts as a filter to the x-ray beam
Tubehead seal
Coiled wire made of tungsten which produces electrons when heated
Tungsten filament
What are the 2 parts of the cathode?
Tungsten filament & the molybdenum
Plate of tungsten, which serves as a focal spot and converts bombarding electrons into x-ray photons
Tungsten target
What are the 2 parts of the anode?
Tungsten target & the copper stem
The measurement of electrical force that causes electrons to move from a negative pole to a positive one
Voltage
Voltage is measured in
Volts (V) or kilovolts (kV)
Heart of the x-ray generating system
X-ray tube
The tubehead contains the ______ that produces x-rays
X-ray tube
Most x-rays are produced in the _______ manner approximately ___% of the x-ray energy produced at anode can be classified as ________ ________
braking, 70, general radiation
In the x-ray tube the _____ produced in the _____ cathode are _______ toward the ______ anode
electrons, negative, accelerated, positive
Absorption depends on the _______ of the beam and the __________ of the absorbing ___________ or _________
energy, composition, matter, tissue
X-ray tube is a _____ vacuum tube from which all the __ has been ____
glass, air, removed
When electron strikes tungsten target their ________ _______ is converted to x-ray _________ and ________
kinetic energy, energy, heat
The rearrangement in characteristic radiation produces a ______ of energy that results in the production of an _________ __________
loss, x-ray photons
The photoelectron has a ________ charge it is readily __________ by other atoms because it has very little ____________ _________ atom that remains has a __________ charge
negative, absorbed, penetrating power, positive
One central area of the leaded-glass tube has a _____ that permits the x-ray beam to exit the tube and directs the x-ray beam toward the aluminum disks, lead collimator, and PID
window