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73 Cards in this Set

  • Front
  • Back
what are cathode rays (electrons)
Streams of electrons passing from the hot filament of the cathode to the target of the anode in an x-ray tube.
who made the first dental radiograph
Otto Walkhoff, DDS, MD on January 14, 1896
what is the #1 error when taking x-rays?
film placement
in a standard dental x-ray unit, the quality of xradiation produced during exposure energization is controlled primarily by
kilovoltage (kV)
if the PID (or cone) is longer........
you will have higher quality film
who discovered x-rays
Wilhelm Konrad Roentgen on Nov 8, 1895
what is an autotransformer?
it has a single coil of insulated wire wound around a large iron core, which serves s both the primary and secondary coil, with the # of turns being adjustable. Serves as the kVp selector dial
Increasing the kVp of an x-ray machine increases the
number and energy of photons generated
name two processes of x-ray production
general radiation and characteristic raiation
the mean penetrability of an x-ray beam is not related to which of the following
separation of electrons from the tungsten filament results in what?
a small loud of electrons will form in the immediate vicinity of the filament. The temperature of the filament controls the quantity of electrons emitted from it
xrays are actually produced in the x-ray tube by
high-speed electrons interacting with the nucleus of target atoms giving off radiation
how is the focal spot of importance?
the size of the focal spot has a very important effect on the sharpness of the x-ray film image. The smaller the focal spot the sharper the x-ray image
which electron has the greatest binding energy to the nucleus
K shell electron
what are soft x-rays?
produced in lower kilovoltage range (60 to 65 kVP) has more x-rays with less energy, lower frequency, and longer wavelengths, less penetrating
what are x-rays?
weightless packages of pure energy (photons) that have no electrical charge and travel in waves with specific frequency at a speed of 3x10 m/s, the greater the frequency of the wavelength, the greater the energy of the photon, thus the more readily it will penetrate matter.
the target material (in the anode) for diagnostic tubes is:
what is an x-ray tube?
it is contained within the tubehead of the x-ray machine, a sealed leaded glass envelope from which air has been evacuated. Electrodes are designed so that electrons produced at the cathode (negative electrode or filament) can be accelerated to a high potential difference (voltage) toward the anode (positive or target electrode)
name two types of ionizing radiation
particulate radiation and electromagnetic radiation
what is a step down transformer?
it has fewer turns in the secondary coil than in the primary coil and it decreases voltage (low voltage)
at diagnostic levels, what percentage of the electron energy is converted to x-radiation at the anode?
less than 1%
describe the focusing of electrons
the cathode focusing cup (surrounding the filament)is designed so that its electrical forces cause the electron stream to converge onto the target or anode in the required size and shape.
true or false: X-rays cannot be focused to a point
x-rays used in dentistry can be heterogeneous or homogeneous depending on the varying wavelengths in the x-ray beam.
in the x-ray tube, x-rays originate in the
explain the kinetic energy of high speed electrons
the kinetic energy of a cathode electron released at the target will depend on the voltage being applied to the tube at that moment
the electron that revolve in shells around the nucleus
have a negative charge
filtration does what?
filters out long wavelengths (soft x-rays)
x-rays belong to which of the following radiation categories
electromagnetic radiations
what is a step-up transformer?
has more turns in the secondary coil than the primary (high voltage)
ionization occurs
when atoms lose electrons; they become deficient in negative charges and therefore behave as positively charged atoms
why are x-rays of prime importance for diagnosing as opposed to particulate?
X-rays do not deposit their energy in highly localized concentrations the way particulate radiation does. X-rays penetrate tissues for long distances.
which of the following statements most adequately decribes the radiation produced by high voltage
short wavelengths of high frequency
what is a cathode?
the negative terminal of the tube and consists of a tungsten wire (filament) wound in the form of a spiral set in a molybdenum cup-shaped
holder called a ocusing cup and positioned aprox. 1 inch away from the anode
in a standard x-ray unit, the quantity of xradiation produced during exposure enegization is controlled primarily by:
exposure time and milliamperage (mA)
the x-ray tube current, measured in mA's, refers to....
the # of electrons flowing per second from the filament to the target of the anode
the dental xray beam consists of photons of many different wavelengths, with the shortest wavelength photons determined by
kilovoltage peak (kVp)
what is a photon?
a quantum (bundle of energy) of electromagnetic radiation. Travels at the speed of light.
an xray photon is
a small bundle of pure energy with wave-like properties
describe tungsten
when the tungsten is heated, its atoms absorb thermal energy and some of the outer orbit electrons in the metal acquire enough energy to allow them to move a small distance from the surface of the metal
braking radiation can occur one of two ways, decribe the two
a. electron collides with the nucleus and all of its kinetic energy is converted into a single ray.
b. electron is slowed down and bent off its course by the positive pull of the nucleus. The kinetic energy lost is converted into an x-ray
name two electrical circuits necessary in the x-ray machine to provide x-rays in the x-ray tube
filament circut-provides a source of electrons by heating the filament to incandescence to "boil off" the electrons from the filament to the cathode
high voltage circuit- accelerates the cathode electrons from the cathode toward the anode high speeds
what is the electromagnetic spectrum?
when all forms of electromagnetic radiation are grouped according to their wavelength
what are hard x-rays?
x-rays produced in the high kilovoltage range (85 to 100 kVp), has more x-rays with greater energy, higher frequency, and shorter wavelengths, they are more penetrating
as the temperature is raised from increasing the mA what happens?
more electrons are emmitted and the flow of electrical current through the x-ray tube (mA) increases
true or false? protons have to match electrons, if they don't they are unstable
true statement
describe the production of high speed electrons
electric current is always in one direction (cathode to anode). The higher the potential (voltage) the greater the speed of these cathode electrons as they strike the target. They produce more energetic x-ray photons that have shorter wavelengths, higher frequencies and greater penetrating power
rollers in the developer machine have to coincide with the film size
compare x-rays to alpha and beta particles
X-rays have no electrical charge or mass and do not ionize matter rapidly. They have the ability to penetrate matter for long distances
alpha and beta particles do what?
Alpha has an enourmous electrical charge and mass that ionizes matter rapidly and penetrates tissue for very short distances.
Beta does not ionize matter as readily as an alpha particle and penetrates tissue farther than an alpha particle.
when you decrease the kVp you must also do what to the time?
increase the time for penetration
what is electromagnetic radiation?
The propagation of wave-like energy through space accompanied by electric and magnetic force fields
describe general radiation
most of x-rays produced by dental x-ray machines are called, Bremsstrhlung, brakes, brems or white. Called braking because radiation is produced by braking or decelerating of high speed electrons
decribe characteristic radiation
it is produced when high speed electrons hit and dislodge a (K) shell electron. Another electron in an outer shell quickly fills the void and an x-ray is emitted. This type of radiation only occurs when the kVp is 70 or above
what is the line focus principle?
the benson line focus principle was developed in 1918; is a method of reducing the effective focal spot size and is used in dental x-ray tubes. Target is placed at an angle to the cathode as angle of target is made larger, the projected focal spot becomes smaller "effective focal spot"
the PID moves up or down, explain
up (negative), down (positive). Going too much up or down will give you skinny long teeth or short fat teeth. Too much left or right causes overlapping.
describe the stopping of high-speed electrons at the target
when the fast cathode electrons enter the target of the x-ray tube, their kinetic energy (energy in motion) changes to other forms of energy. This interaction responsible for the generalization of heat is primarily of excitation rather than an ionizing effect.
what is homogeneous radiation?
the same energy photon is produced; x-ray photons will have less variation in wavelengths compared to brakes radiation
distinguish between kVp(kilovoltage peak) and keV (kiloelectron volts).
100 kVp= maximum voltage across the tube causing acceleration of electons is 100,000 volts. keV denotes the energy of any individual cathode electron in the beam 100 keV=100,000 electron volts
describe the production of x-rays
x-rays are generated when fast moving electrons collide with matter in any form. X-ray production is a process of energy conversion when electrons are suddenly decelerated (speed is reduced) in the target of the x-ray tube
what is the difference between wavelength and frequency?
wavelength is the distance between two successive crests or valleys.
frequency is the number of waves passing a particular point during a specified time interval (measured as cycles/sec=1hertz
describe thermionic emission
boiling off of electrons, which is the emission of electrons resulting from the absorption of energy
true or false? X-rays are a form of electromagnetic radiation.
when was the bisecting technique developed?
in 1904
Alpha and beta particles are what type of ionizing radiation?
what does excited state mean?
an electron vacancy in a shell
name the four conditions neccessary for the production of electrons
1. Generation of electrons
2. Production of high speed electrons
3. Focusing of electrons
4. Stopping of high speed electrons at the target
what is an anode?
it is a positively charged to attract electrons and is usually made of copper because of its good heat conductivity. A block of tungsten is set in the face of the copper anode at the center of the tube. This block of tungsten is reffered to as the target.
what is a transformer?
an electromagnetic device that changes AC to low voltage to high voltage or from high to low without loss of an appreciable amount of energy (less than 10%)
what is the focal spot?
it is an area on the target that electrons strike to generate x-rays. The electrons at the filament are set in motion toward the target by activating the high voltage circut (kVp) as the timer switch is pressed
what is the formula for intensity?
(quality, energy of particular photons)X(quanity, # of photons in the beam)
(area)X (exposure rate)
not until a target is hit is it called an x-ray
what is heterogeneous radiation?
Brem's radiation, it is not uniform and has a variety of energies and wavelengths. Cathode atoms have many reactions, speed of the cathode electrons varies according to kVp as it varies, filter at 70kVp, 1.5mm of aluminum filtration/federal regulation