Cluster 1 Radphysics Flashcards
anything that occupies space. It is the material substance with mass of which physical objects are composed. The fundamental, complex building blocks of __ are atoms and molecules.
Matter
the scientific unit of mass, is unrelated to gravitational effects. The prefix kilo stands for 1000; a __ (kg) is equal to 1000 grams (g).
Kilogram
__ is measured in kilograms (kg), This occurs because of the mutual attraction, called gravity, between the Earth’s __ and Although __, the quantity of matter, remains unchanged regardless of its state, it can be transformed from one size, shape, and form to another.
Mass
is the ability to do work by virtue of position. A guillotine blade held aloft by a rope and pulley is an example of an object that possesses __. If the rope is cut, the blade will descend and do its ghastly task.
Potential energy
the energy of motion. It is possessed by all matter in motion: a moving automobile, a turning windmill wheel, a falling guillotine blade. These systems can all do work because of their motion.
Kinetic energy
is the energy released by a chemical reaction. An important example of this type of energy is that which is provided to our bodies through chemical reactions involving the foods we eat. At the molecular level, this area of science is called biochemistry.
Chemical energy
represents the work that can be done when an electron moves through an electric potential difference (voltage). The most familiar form of __ is normal household electricity, which involves the movement of electrons through a copper wire by an electric potential difference of 110 volts (V). All electric apparatus, such as motors, heaters, and blowers, function through the use of __.
Electrical energy
the energy of motion at the molecular level. It is the kinetic energy of molecules and is closely related to temperature. The faster the molecules of a substance are vibrating, the more __ the substance has and the higher is its temperature.
Thermal energy (heat)
the energy that is contained within the nucleus of an atom. We control the release and use of this type of energy in electric nuclear power plants.
Nuclear energy
is perhaps the least familiar form of energy. It is the most important for our purposes, however, because it is the type of energy that is used in x-ray imaging. In addition to x-rays, __ includes radio waves; microwaves; and ultraviolet, infrared, and visible light.
Electromagnetic energy
Energy emitted and transferred through space is called __.
radiation
is any type of radiation that is capable of removing an orbital electron from the atom with which it interacts. __ occurs when an x-ray passes close to an orbital electron of an atom and transfers sufficient energy to the electron to remove it from the atom.
Ionizing radiation
The orbital electron and the atom from which it was separated are called an __.
ion pair
These sources of ionizing radiation can be divided into two main categories
natural environmental radiation and man-made radiation.
results in an annual dose of approximately 3 millisieverts (mSv). onsists of four components: cosmic rays, terrestrial radiation, internally deposited radionuclides, and radon.
Natural enviromental radiation
__are particulate and electromagnetic radiation emitted by the sun and stars. On Earth, the intensity of __ radiation increases with altitude and latitude.
__ results from deposits of uranium, thorium, and other radionuclides in the Earth.
Cosmic rays
Terrestrial radiation
is a radioactive gas that is produced by the natural radioactive decay of uranium, which is present in trace quantities in the Earth. All Earth-based materials, such as concrete, bricks, and gypsum wall- board, contain __. __ emits alpha particles, which are not penetrating, and therefore contributes a radiation dose only to the lung.
Radon
__ results in 3.2 mSv annually. Diagnostic x-rays constitute the largest man-made source of ionizing radiation (3.2 mSv/yr). This estimate was made in 2006 by the National Council on Radiation Protection and Measurements (NCRP). Other sources of __ include nuclear power generation, research applications, industrial sources, and consumer items. Nuclear power stations and other industrial applications contribute very little to our radiation dose.
Man-made radiation
was an Englishman from a rather humble background who was a self-taught genius.
The crookes tube that bears his name was the forerunner of modern fluorescent lamps and x-ray tubes
William crookes
Discovered xrays using crookes tube with black photographic paper so he could better visualize the effects of the cathode rays in the tube. A plate coated with barium platinocyanide, a fluorescent material, happened to be lying on a bench top several meters from the Crookes tube in Nov 8, 1895
Wilhem roentgen
Demostrate the use of intensifying screen (IS) im 1896
Michael pupin
Found that by exposing 2 glass xray plates w/ emulsion surface together exposure time was halved
Charles l leonard
Discovered fluoroscopy using barium platinocyanide as the primary material and stopped his research in this area due __ suffered severe radiation burns that leads to his death
Thomas edison, clarence dally
Two devices designed to reduce the exposure of patients to x-rays and thereby minimize the possibility of x-ray burn were introduced before the turn of the 20th century by?
William rollins
__, and inserting a __ improved the diagnostic quality of radiographs. This first application of __ and __ was followed very slowly by general adoption of these techniques. It was later recognized that these devices reduce the hazard associated with x-rays.
Diaphragm, leather or aluminum filter, collimation and filtration
In 1907, __ introduced a substitute high-voltage power supply, an interrupterless transformer, for the static machines and induction coils then in use. Although the __ transformer was far superior to these other devices, its capability greatly exceeded the capability of the Crookes tube. It was not until the introduction of the Coolidge tube that the __ transformer was widely adopted
H.C. Snook
__ unveiled his hot-cathode x-ray tube to the medical community in 1913. It was recognized as far superior to the Crookes tube. It was a vacuum tube that allowed x-ray intensity and energy to be selected separately and with great accuracy. This had not been possible with gas-filled tubes, which made standards for techniques difficult to obtain. X-ray tubes in use today are refinements of the __ tube.
William D. Coolidge
1913, stationary grid (glitterblende in german) 2 months after applied for a patent for moving grid
Gustav bucky
probably unaware of Bucky’s patent because of World War I, also invented a moving grid. To his credit, Potter recognized Bucky’s work, and the Potter-Bucky grid was introduced in 1921
Hollis potter
Metal filters, usually aluminum or copper, are inserted into the x-ray tube housing so that low-energy x-rays are absorbed before they reach the patient. These x-rays have little diagnostic value
Filtration
__ restricts the useful x-ray beam to that part of the body to be imaged and thereby spares adjacent tissue from unnecessary radiation exposure.
Collimation
Today, most x-ray films are exposed in a cassette, with radiographic __ on both sides of the film. Examinations conducted with radiographic __ reduce exposure of the patient to x-rays by more than 95% compared with examinations conducted without radiographic __.
Intensifying Screens
Lead-impregnated material is used to make aprons and gloves worn by radiologists and radiologic technologists during fluoroscopy and some radiographic procedures.
Protective apparel
The same lead-impregnated material used in aprons and gloves is used to fabricate gonadal shields.
Gonadal shielding
Often, the barrier is lead lined and is equipped with a leaded-glass window. Under normal circumstances, personnel remain behind the barrier during x-ray examination.
Protective barrier
Distance between the 2 lines engraved on a platinum–iridium bar kept at the International Bureau of Weights and Measures in Paris, France.
Length
The kilogram was originally defined to be the mass of 1000 cm3 of water at 4° Celsius (°C). In the same vault in Paris where the standard meter was kept, a platinum– iridium cylinder represents the standard unit of mass— the kilogram (kg), which has the same mass as 1000 cm3 of water.
Mass
The standard unit of __ is the second (s). Originally, the second was defined in terms of the rotation of the Earth on its axis the mean solar day. In 1956, it was redefined as a certain fraction of the tropical year 1900. In 1964, the need for a better standard of __ led to another redefinition.
Time
__, sometimes called speed, is a measure of how fast something is moving or, more precisely, the rate of change of its position with time.
Velocity
The rate of change of velocity with time is __ . It is how “quickly or slowly” the velocity is changing. Because __ is velocity divided by time, the unit is meters per second squared (m/s2).
acceleration
states that if no force acts on an object, there will be no acceleration. The property of matter that acts to resist a change in its state of motion is called inertia. Also known as the law of interia
Newtons 1st law
law states that the force applied to move an object is equal to the mass of the object multiplied by the acceleration. __ is a definition of the concept of force. Force can be thought of as a push or pull on an object
Newton’s second law
states that for every action, there is an equal and opposite reaction. “Action” was Newton’s word for “force.” According to this law, if you push on a heavy block, the block will push back on you with the same force that you apply.
Newtons 3rd law
is a force on a body caused by the pull of gravity on it. Experiments have shown that objects that fall to Earth accelerate at a constant rate.
Weight
The product of the mass of an object and its velocity is called __, represented by p. The greater the velocity of an object, the more __ the object possesses.
Momentum
as used in physics, has specific meaning. The __ done on an object is the force applied times the distance over which it is applied.
Work
__ may be transformed from one form to another, but it cannot be created or destroyed; the total amount of __ is constant.
energy
is the rate of doing work. The same amount of work is required to lift a cassette to a given height, whether it takes 1 second or 1 minute to do so.
Power
Two forms of mechanical energy often used in radiologic science is?
Kinetic and potential energy
t is a form of energy that is very important to radiologic technologists. Excessive __, a deadly enemy of an x-ray tube, can cause permanent damage.
Heat
3 Ways to transfers heat
Conduction, convection, thermal radiation
is the transfer of heat through a material or by touching. Molecular motion from a high- temperature object that touches a lower-temperature object equalizes the temperature of both.
Conduction
is the mechanical transfer of “hot” molecules in a gas or liquid from one place to another. A steam radiator or forced-air furnace warms a room by
Convection
is the transfer of heat by the emission of infrared radiation. The reddish glow emitted by hot objects is evidence of heat transfer by radiation. An x-ray tube cools primarily by radiation.
Thermal radiation
normally is measured with a thermometer. A thermometer is usually calibrated at two reference point the freezing and boiling points of water. The three scales that have been developed to measure __ are Celsius (°C), Fahrenheit (°F), and Kelvin
Temperature
is the kinetic energy transferred from photons to electrons during ionization and excitation. Measured in j/kg
Air kerma
is the radiation energy absorbed per unit mass and has units of J/kg or Gyt. The units Gya and Gyt refer to radiation dose in air and tissue, respectively.
Absorbed dose (Gy)
which is used to express the quantity of radiation received by radiation workers and populations.
Sievert (Sv)
is the unit of quantity of radioactive material, not the radiation emitted by that material.
Becquerel (Bq).
John Dalton, an English school teacher, published a book summarizing his experiments, which showed that the elements could be classified according to integral values of atomic mass. According to Dalton, an element was composed of identical atoms that reacted the same way chemically. For example, all oxygen atoms were alike. They looked alike, they were constructed alike, and they reacted alike. They were, however, very different from atoms of any other element. The physical combination of one type of atom with another was visualized as being an eye- and-hook affair
Dalton atom
Some 50 years after Dalton’s work, a Russian scholar, __, showed that if the elements were arranged in order of increasing atomic mass, a periodic repetition of similar chemical properties occurred. At that time, about 65 elements had been identified. __ work resulted in the first periodic table of the elements.
Dmitri Mendeleev
After the publication of Mendeleev’s periodic table, additional elements were separated and identified, and the periodic table slowly became filled. Knowledge of the structure of atoms, however, remained scanty. Before the turn of the 20th century, atoms were considered indivisible. The only difference between the atoms of one element and the atoms of another was their mass. Through the efforts of many scientists, it slowly became apparent that there was an electrical nature to the structure of an atom.
Thomson atom
In the late 1890s, while investigating the physical properties of cathode rays (electrons), __ concluded that electrons were an integral part of all atoms. He described the atom as looking something like a plum pudding, in which the plums represented negative electric charges (electrons) and the pudding was a shapeless mass of uniform positive electrification. The number of electrons was thought to equal the quantity of positive electrification because the atom was known to be electrically neutral.
J.J. Thomson
Through a series of ingenious experiments, __ in 1911 disproved Thomson’s model of the atom. __ introduced the nuclear model, which described the atom as containing a small, dense, positively charged center surrounded by a negative cloud of electrons. He called the center of the atom the nucleus.
Ernest Rutherford
In 1913, __ improved Rutherford’s description of the atom. __ model was a miniature solar system in which the electrons revolved about the nucleus in prescribed orbits or energy levels. For our purposes, the __ atom represents the best way to picture the atom, although the details of atomic structure are more accurately described by a newer model, called quantum chromodynamics (QCD). Simply put, the __ atom contains a small, dense, positively charged nucleus surrounded by negatively charged electrons that revolve in fixed, well-defined orbits about the nucleus. In the normal atom, the number of electrons is equal to the number of positive charges in the nucleus
Niels Bohr
3 fundamental particles
Electron proton neutron
Because an atomic particle is extremely small, its mass is expressed in __ (amu) for convenience.
atomic mass units
When precision is not necessary, a system of whole numbers called __ is used. The __ of an electron is zero.
atomic mass numbers
The nucleus contains particles called __, of which there are two types: protons and neutrons. Both have nearly 2000 times the mass of an electron.
Nucleons
Atoms that have the same number of protons but differ in the number of neutrons are __; they behave in the same way during chemical reactions.
isotoPes
Electrons can exist only in certain __, which represent different electron binding energies or energy levels. For identification purposes, electron orbital shells are given the codes K, L, M, N, and so forth, to represent the relative binding energies of electrons from closest to the nucleus to farthest from the nucleus. The closer an electron is to the nucleus, the greater is its binding energy.
shells
Made of atoms
Matter
Central core contains nearly all the mass nucleons (proton + neutron)
Nucleus
Contains electron a negatively charged particle
Orbits or shell
electron-
neutron-
Lightest
Heaviest
Smallest chemical unit of an element or compound
Molecule
Any atomic specie
Nuclide
Outermost electron, unstable, unpair
Valence e-
A-
Z-
atomic mass
atomic mass number
Determine max number of electrons in each shell
Pauli exclusion formula
Energy possesed by an electron in the shell, energy required to cause ionization, energy required
Electron binding energy
Atomic nuclei that have the same atomic mass number but different atomic numbers are?
isobArs
Atoms that have the same number of neutrons but different numbers of protons are?
IsotoNes
__ have the same atomic number and the same atomic mass number.
IsomErs
is the emission of particles and energy in order to become stable.
Radioactivity
Many factors affect nuclear stability. Perhaps the most important is the number of neutrons. When a nucleus contains too few or too many neutrons, the atom can disintegrate radioactively, bringing the number of neutrons and protons into a stable and proper ratio. In addition to stable isotopes, many elements have radioactive isotopes or?
radioisotopes
Some atoms exist in an abnormally excited state characterized by an unstable nucleus. To reach stability, the nucleus spontaneously emits particles and energy and transforms itself into another atom.
Radioactive disintegration or radioactive decay
Radioactive matter is not here one day and gone the next. Rather, radioisotopes disintegrate into stable iso- topes of different elements at a decreasing rate so that the quantity of radioactive material never quite reaches zero.
Radioactive Half-life
What type of radiation is used in diagnostic ultrasonography and magnetic resonance imaging?
Non ionizing radiation
Many subatomic particles are capable of causing ionization. Consequently, electrons, protons, and even rare nuclear fragments all can be classified as __ if they are in motion and possess sufficient kinetic energy. At rest, they cannot cause ionization
Particulate radiation
Two main types of particulate radiation
Alpha particles and beta particles
An __ is a helium nucleus that contains two protons and two neutrons.
A __ is an electron emitted from the nucleus of a radioactive atom.
alpha particle
beta particle
X-rays and gamma rays are forms of __.
electromagnetic radiation
Ever present all around us is a field or state of energy called __. This energy exists over a wide range called an energy __. A __ is an uninterrupted (continuous) ordered sequence.
electromagnetic energy, continuum
is the smallest quantity of any type of electromagnetic energy, just as an atom is the smallest quantity of an element.
Photon
photons have no mass and therefore no identifiable form, they do have electric and magnetic fields that are continuously changing in a?
Sinusoidal fashion
The sine wave model of electromagnetic energy describes variations in the electric and magnetic fields as the photon travels with velocity c. The important properties of this model are __, represented by f, and __, represented by the Greek letter lambda (λ).
frequency, wavelength
Different from RF or visible light, ionizing electromagnetic energy usually is characterized by the energy contained in a photon. When an x-ray imaging system is operated at 80 kVp, the x-rays it produces contain energies ranging from 0 to 80 keV.
Ionizing radiation
This decrease in intensity is inversely proportional to the square of the distance of the object from the source. Mathematically, this is called the?
Inverse square law
are used routinely in x-ray diagnosis to describe the visual appearance of anatomical structures. Structures that absorb x-rays are called __. Structures that transmit x-rays are called __
radiopaque, radiolucent
X-rays are created with the speed of light (c), and they exist with velocity (c) or they do not exist at all. That is one of the substantive statements of?
Planck’s quantum theory.
was a German physicist whose mathematical and physical theories synthesized our understanding of electromagnetic radiation into a uniform model; for this work, he received the Nobel Prize in 1918.
Max planck
According to quantum physics and the physics of relativity, matter can be transformed into energy and vice versa. Nuclear fission, the basis for generating electricity, is an example of converting matter into energy. In radiology, a process known as?
Pair production
Electric charge comes in discrete units that are positive or negative. Electrons and protons are the smallest units of electric charge. The electron has one unit of negative charge; the proton has one unit of positive charge. Thus, the electric charges associated with an electron and a proton have the same magnitude but opposite signs.
Electrostatic
Four general laws of electrostatics describe how electric charges interact with each other and with neutral objects. Associated with each electric charge is an electric field. The electric field points outward from a positive charge and toward a negative charge. Uncharged particles do not have an electric field.
Electrostatic law
The electrostatic force is directly proportional to the product of the electrostatic charges and inversely proportional to the square of the distance between them.
Coulomb’s law
Electric charges have potential energy. When positioned close to each other, like electric charges have electric potential energy because they can do work when they fly apart. Electrons bunched up at one end of a wire create an electric potential because the electrostatic repulsive force causes some electrons to move along the wire so that work can be done.
Electric potential
The unit of electric potential is the?
volt (V).
is the study of electric charges in motion?
Electrodynamics
A __ is any substance through which electrons flow easily. one of the best. Water is also a good electric __ because of the salts and other impurities it contains. That is why everyone should avoid water when operating power tools.
conductor
An __ is any material that does not allow electron flow. Glass, clay, and other earthlike materials are usually good electric __.
insulator
__ is a material that under some conditions behaves as an insulator and in other conditions behaves as a conductor. materials are silicon (Si) and germanium (Ge).
semiconductor
__ is the property of some materials to exhibit no resistance below a critical temperature (Tc). __ was discovered in 1911 but was not developed commercially until the early 1960s. Scientific investigation into __ has grown in recent years and now focuses on high-temperature __. __ materials such as niobium and titanium allow electrons to flow without resistance.
Superconductivity
Modifying a conducting wire by reducing its diameter (wire gauge) or inserting different material (circuit elements) can increase its resistance. When this resistance is controlled and the conductor is made into a closed path, the result is an?
Electric circuit
__ measured in amperes (A). The ampere is proportional to the number of electrons flowing in the electric circuit.
__ is measured in volts (V), Electrons at high voltage have high potential energy and high capacity to do work. If electron flow is inhibited, the circuit resistance is high.
__- ratio of electric potential across the circuit element to the resistance measured in ohms (Ω)
Electric current
Electric potential
Electeic resistance
Electric current, or electricity, is the flow of electrons through a conductor. These electrons can be made to flow in one direction along the conductor, in which case the electric current is called?
Direct current
electrons oscillate back and forth is called?
Alternating current
is measured in watts (W). Common household electric appliances, such as toasters, blenders, mixers, and radios, generally require 500 to 1500 W of electric power. Light bulbs require 30 to 150 W of electric power. An x-ray imaging system requires 20 to 150 kW of __.
Electric power
Electrons behave as if they rotate on an axis clockwise or counterclockwise. This rotation creates a property called __. The __ creates a magnetic field, which is neutralized in electron pairs. Therefore, atoms that have an odd number of electrons in any shell exhibit a very small magnetic field.
electron spin
The proton in a hydrogen nucleus spins on its axis and creates a nuclear magnetic dipole called a?
magnetic moment.
The small magnet created by the electron orbit is called a?
Magnetic dipole
An accumulation of many atomic magnets with their dipoles aligned creates a?
Magnetic domain
is the ability of a material to attract the lines of magnetic field intensity.
Magnetic permeability
are available in many sizes and shapes but principally as bar or horseshoeshaped magnets, usually made of iron.
Permanent magnets
__ consist of wire wrapped around an iron core. When an electric current is conducted through the wire, a magnetic field is created.
Electromagnets
materials are weakly repelled by either magnetic pole. They cannot be artificially magnetized, and they are not attracted to a magnet. Examples of such __ materials are water and plastic.
Diamagnetic
materials include iron, cobalt, and nickel. These are strongly attracted by a magnet and usually can be permanently magnetized by exposure to a magnetic field. An alloy of aluminum, nickel, and
Ferromagnetic
materials lie somewhere between ferromagnetic and nonmagnetic. They are very slightly attracted to a magnet and are loosely influenced by an external magnetic field.
Paramagnetic
Non ionizing and ionizing , from orbits except gamma, no mass no charge travels at speed of light except cherenkov, potential energy
Electromagnetic radiation
Are “path length” Maximum distance transversed by ir b4 losing its energy, micrometer
Range
Numbers of ion pairs produced per unit per length
Si (specific ionization)
The rate of energy transfered per unit per length measured in kev/micrometer
Linear energy transfer
3 physical factors affecting the radiosenstivity of material/tissue/person/patient
Let ( linear energy transfer)
Rbe (relative biologic effectiveness)
Fractionation and protraction
An EMR that travels faster that the speed of light
Cherenkov radiation
Fraction or perecentage of the activity of a sample that decays per unit of time
Decay disintegration/ transformation constant
Time required for act of a sample to decay to 1/2 of its original value inside living tissue or living organsim shorter than usual half life
Biological half life
Longest half life the only type that has constant value
Physical half life
Combination of physical and biological half life
Effective half life
Occurs in elements w high atomic number and heavy in nuclides, long half life, atomic number 70 above
Alpha decay
Emits beta particle, no mass
Beta decay
Increase number of protons than neutrons
Increase number of neutrons than protons
Positron decay
Negatron decay
Because in isomers, emits gamma rays for ir to become stable
Isomeric transition
Gamma rays will interact/ionize a k-shell electron
Internal conversion/ k-conversion
Removal of electrom by a characteristic xray, characteristic xray ionizes an electron b4 going out of the atom ( __ electron- removed electron)
Auger process
Very unstable nucleus , e- from k-shell will be captived by the nucleus
Electron capture/ e- capture
__ From nucleus, only nuclear electromagnetic radiation
__ From orbits of atom
Gamma rays
Characteristic xrays
Production of heat, no removal, loss of energy, no ion pair, causes atom to vibrate
Excitation
There is a removal of electron e-, transfer of energy and production of ion pair
Ionization
Partial absorption, total reduction in the intensity of x ray beam product of scattering and absorption
Attenuation
__- high quality image (better image), high quality radiograph, high px dose
__- not high quality image but acceptable, low px dose
High mAs
High kVp
Factors that affect attenuation
Thickness of part
Density of part
Atomic number
“__” braking/sudden stop “__” radiation, high energy xray, hard xray, white xrays, needed for production of image in radiology energy released bc of the sudden stop of electron
Bremsstrahlung
Inner shell, low energy xray, soft xray, contribute nothing to image, results in scatter radiation, fogging, filling up, transfer and transition of e- from outer to inner
Characteristic x ray
Less than 10 kEv = 10 Kvp, 5-10% chance that this will happen in diagnostic imaging (wavelength of incident photon = wavelength of scatter photon), low energy xrays, coherent scattering rayleigh thomson, no ionization only excitation produces scatter radiation and heat
Classical scattering
Ionization in the outer shell, compton e- or recoil e- or secondary e-, scatter radiation can still cause another ionization, hazardous to radtechs, degrade image, contribute to fog, incoherent scattering
Compton scattering
Ionization at k- shell photo, electron-ejected electron, production of characteristic x-ray, production of ion pair, production of photoscreen, absorption (good effect provides white contrast, increase contrast), (bad effect increase px dose), no scatter
Photoelectic effect
No ionization, incident xray splits into 2 electroms w/ opposite charges , > 1.022 mEv of energy of incident photon, __ occurs in space, pet scan e- 0.511 mev/511kev, p+ 0.511 mev/511 kev.
Pair production
Bombards the nucleus, > 7 mev energy of incident photon, nucleus will decay and release alpha, beta, gamma, and other nuclear fragments, does not happen in medical, power plant accident or nuclear bombing
Photodisintegration
Process molecules w/ the 2 electrons w/ opposite charges unite or combine w/ thier energy, opposite of pair production
Annihilation
__ - to protect ourselves
__- important due to image production
Compton
Photoelectric effect
Thickness of the material required to reduce the intensity of ionizing radiation to half of its original value *compute the thickness of lead or shielding, so that occupant in the other room will only receive 50% of radiation
Half value layer
Is used b4 the use of hvl, 90% absorbed by shielding, 10% absorbed by occupant in the other room, thickness of material to reduce the intensity of ir to 1/10 of its orig value, requires more shielding w/c is more expensive
1TVL= 3.3 HVL
Tenth value layer/tenth value thickness (TVL)
__ Electric charges are uniformly destributed throughout the surfaces
__ Electric charges are more concentrated on the sharpest curvature/ greatest curvature
Electric charge destribution
Electric charge concentration
A circuit element are connected in a line along the same conductor
Series circuit
Contains elements that are connected at their ends rather than lie in a straight line along the conductor
Parallel circuit
One direction, from cathode to anode, sources such as batteries, fuel cells and solar cells
Direct current
__ Converts AC to DC parts of high voltage generator
__ Process of converting AC to DC
Rectifier
Rectification
Magnetic oxide of ion, most magnetic among all, non-like stone that when suspended by a string, it rotates back and forth
Magnetite/lodestone
Oscillate back and forth, sources such as powerplant
Alternating current
Unaligned=unmagnetized
Aligned=magnetized
Magnetic domain theory
Degree to which the material can be magnetized, ability of material to become magnetized by an external magnetic field
Magnetic susceptibility
Permeability-
Susceptibility-
It attracts
The one that is attracted
Divide a magnet into smaller pieces will only create smaller magnets w/ north and south poles
Dipole
Like charges repel unlike charges attracts
Attraction and repulsion
Some magnets can be magnetized through __
Ex: rotor inside, stator outside
Induction
Accidentaly discovered battery
Luigi galvani
Invented the voltaic pile
Allesandro volta
First wet cell battery that produces a reliable, steady, current of electricty; precursor of the modern battery
Voltaic pile (dagwood sandwich)
Discovered that electric current creates magnetic field, any charged particle in motion induces a magnetic field
Hans Oersted
Magnetic field cannot be used to produce electricity, Credited for discovery of induction in 1831, 1st dynamo in 1837
Michael Faraday
Determines the direction of current and the magnetic field
-motion
- field
-current
Right hand rule
Thumb
Index
Middle finger
States that the direction of the induced current opposes the action that induces it
Heinrich lenz/ lenz law
Application of the faraday’s lawM, converts mechanical energy to electrical energy (GME)
(GME)- converts electrical energy to mechanical energy
Electrical generator
Energy converter
Application of oersted experiments
Electroc motor
Acts as a switch that changing the polarity of the contact loop of wire, prolong the life of generator or motor periodically reverses the current direction
Commutator ring
Induction of opposing voltage in a single coil by its iwn changing MF
Self induction
Generation of an alternating current in a primary coil
__ where current is supplied (input) Np
__ where output is taken Ns
Mutual induction
Primary
Secondary
Changing the intensity, changes the magnitude of voltage, increase or decrease voltage, operates in AC
__ number of turns in primary coil
__ numbers of turns in secondary coil
Transformer
Np
Ns
Ns over np- turns ratio
Voltage and turns ratio
Current and turns ratio
Current and voltage
Greater than 1=?
Less than 1=?
Transformer law
VsNp = VpNs
IsNs = IpNp
IsVs = IpVp
Step up transformer
Stepdown transformer
3 major factors that affect electrical power losses in transformer
- Due to resistance
- Due to wear and tear
- Due to opposing current
12R losses
Husteresis loss
Eddy currents
2 coils of wire lying side by side, not efficient
2 electromagnets lying side by side, replaces air core transformer
Square doughnuts, powered continuous part for magnetic flux so that small fraction of the energy is loss by leakage, built about a square of core of ferromagnetic
Most advanced and use commercially/readily available, most expensive, most efficient among them all, most commonly used
Auto step down, lowers the current and increases the voltage
Air core
Open core
Closed core
Shell type
Autotransformer
__ Used to store charge temporarily and release through chemical reaction, acts like battery as both store electrical energy but it does not conduct electricity
__ Temporarily store charge can still be used
Capacitors
Battery
Adjust the voltage to precisely 220V
Line compensator
Actually read the voltage not the kVp
__ that allows the voltage to be monitored b4 examination
kVp meter
Pre-reading voltmeter
Numbers of e- from cathode to anode per second is measured in milliamperes (mA), quantity number and intensity of e- is determined by filament temperature
Control of mA
Make or break (there is exposure or no exposure)
Exposure timers
__ Is a Simple device that operates by clockwork, old machines and dental
__ special type of electric motor and a precision device designed to drive a shade at precisely 60 rps
__ most commonly used, efficient, sophisticated, expensive, complicated, accurate
__ apr or anatomically programmed radiography timers have comp store the technical factors in machine
__ 0.25 to 2.5 OD (acceptable values of OD in diagnostic, measures quantity of radiation reacting ir and terminate the exposure when sufficient radiation needed to produce the correct density on film
Mechanical timer
Synchronous timers
Electronic timers
mAs timers
Phototimer/automatic exposure control
Simple mechanical device use to check accuracy of the xray timer, flat metal disc with a small holes drilled near ome edge
Spinning top
Replaced the spinning top also called as semiconductor radiation detector
Solid state radiation detectors
Responsible for increasing the output voltage from the autotransformer to the kVp neccessary for x-ray production from v-kV
3 components
__ step up turns ratio, v-kV 500-100
__ step down A to mA
__ converts AC to DC (anode and cathode)
High voltage transformer
High voltage transformer
filament transformer
Rectifier (diode)
Ammount of fluctuation in the voltage, variation in x-ray supplied, the lower the __ the better
Voltage ripple
4 types of support assembly
Ceiling support system
Floor to ceiling system
Wall-mounted
C-arm support
A protective device that prevent x-ray from leakage, support for tube and protect from rough handling, last part that cools down, limit for leakage radiation -100mR/h at 1m
Protective housing/tube housing/tube shield
Does not pass throughthe window, secondary radiation, exits from housing
Leakage radiation
Thinnest part of glass envelope and housing so that x-rays can pass through window
Window/tube port/tube hole
Evacuated of air allow extremely high voltage , protects the tube, first part of the filtration system (filters low energy x-rays), provides an inherent filtration that is equivalent to 0.5mm Al. Thickness
Glass or metal envelope
Thungsten & thorium (1-2%)
Cathode and filament
To prolong the life
Emission of e- on a heated surface
Thoriated thungsten
Thermionic emission
Made of thungsten and rhenium (5-10%) 3,400 revolution/min
Area struck/bombarded by electrons that produces xray
Anode
Target
Actual area in the target bombarded by e- that produces of xrays
Focal spot
Melting point of thungsten
Atomic number of thungsten
3410*C
74
Angulation of anode so that actual focal spot is greater than effective focal spot 8-20* angulation of anode
Line focus principle/goetze principle
Actual area in the target, bigger, avoid larger/bigger area
Projected towards the px, smaller, to reduce px dose and increase spatial resolution
Actual focal spot
Effective focal spot
The intensity is greater on the cathode side than anode side, most noticeable w/small focal spot, short sid, large field
Anode heel effect
Phenomenon whereby most of the e- emitted by the cathode are driven back to it by the repulsion of the cloud of e-
Space charge effect
Two types of anode
Thungsten embedded in copper bar, no shaft, not rotating, reduce output
Rotates, molybdenum disk/shaft, rotating target, anode stem, rotor
Stationary anode
Rotating anode
Inside, rotates due to induction made of copper bars & soft iron around a molybdenum shaft
Outside, permanent magnet or an electromagnet
Rotor
Why is tungsten a material of choice?
Bc it can withstand tremendous amount of heat
0.3mm-__
0.5mm-__
1.0-2.0mm-__
Magnification
Bony parts
All radiographic exposure but require large exposure and short exposure time
3 Causes of xray tube failure
__ pinning/crackling anode
__ damage to beamings
__most common cause of tube failure
Single excessive exposure
Long exposure time
Tungsten vaporization
Tube rating charts
- Shows safe and unsafe radiographic technique factors, most important
- How long are we going to wait for anode to cooldown heat capacity: 350,000 hu 15 min to cooldown
- Heat capacity 1-2mhu 1-2 hrs cooldown
Radiographic tube rating chart
Anode cooling chart
Housing cooling chart
