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62 terms

Radiation biology and safety

X-ray (x-radiation)
A form of electromagnetic radiation used to produce dental images. Causes biological damage to living tissues.
Ionizing radiation
Process by which electrons are removed from an atom, resulting in an ion pair; a negatively charged free electron and the remaining part of the atom, now positively charged; waves contain energy sufficient to overcome the binding energy of electrons in atoms or molecules, creating ions; includes x-rays and gamma rays; can cause cell death in high doses over a short period of time and errors in the reproductive process (mutations) in lower doses over longer periods of time.
- cause damage to both somatic and genetic cells.
The movement of energy through space and matter.
Process of emission, transmission and absorption of radiant energy.
the conversion of an atom into and ion that forms an ion pair.
Electrostatic force or binding energy
Force that maintains electrons in their orbit
Non-ionizing radiation
Radiation that does not carry enough energy to ionize atoms but does have sufficient energy to cause excitation, which causes the movement of an electron to a higher energy state.
Part of the x-ray machine that houses the two main components of the x-ray machine: the cathode and anode. Tightly sealed, heavy metal
determines the amount of electrons that pass through the cathode. A high number of electron result in the production of a high number of x-rays. Also controls temperature determining the amount of thermeonic emission that occurs and the "boiling off" of electrons
Primary radiation (primary beam)
Unobstructed, short wave x-ray beams produced by the unit and emitted from the x-ray tube.
Secondary radiation
Long wave x-ray beams that strike an object (like the patients face) and are absorbed by the skin but are not strong enough to penetrate the image receptor.
- These beams are less penetrating than primary radiation
beams, but are still biologically damaging.
Scatter radiation
Is a long wave type of secondary radiation that is of concern to operators and office staff because when it hits matter, it's deflected in all directions and is biologically damaging.
- Filtration and lead foil in film packets help prevent this.
Roentgen and Coulomb
measures exposure to ionizing radiation in the air
Roentgen (R)
The traditional unit of measurement for determining the amount of ionizing radiation in the air
Coulomb per kilogram (C/kg)
The SI equivalent of the Roentgen (R)
** 1 C/kg = 3,880 R
RAD and Gray
- measures absorbed dose
- absorbed dose is the amount of radiation absorbed by tissues
Radiation absorbed dose (RAD)
The traditional unit of measurement for absorbed dose
Gray (Gy)
The SI equivalent of the RAD
** 1 Gy = 100 RAD
REM and Sievert
Measures dose equivalent
Roentgen equivalent (in) man (REM)
The traditional unit used to equate the effects of different kinds of ionizing radiation on human tissue
Sievert (Sv)
The SI equivalent of the REM
** 1 Sv = 100 REM
Dose rate
the amount of radiation given and absorbed by the body in a unit of time.
Acute radiation
A high, fast dose of radiation that will cause more damage than the same dose given over a long period of time.
Chronic radiation
The absorption of low doses of radiation over long periods of time and is used with dental x-rays.
Area involved
The biological effects of radiation increase as the area of the body exposed increases
Cells are not equally sensitive and various parts of the body have different degrees of _______.
Genetic cells
Reproductive cells; cells containing DNA, including eggs and sperm.
Somatic cells
Cells that are non-reproductive or rapidly dividing (e.g., skin, bones blood and connective tissues).
Radiosensitive cells
Cells that rapidly divide, are immature and are not highly specialized.
- reproductive cells, bone marrow, immature bone, small
lymphocytes, and the developing fetus are highly this and are
likely to suffer injury from exposure to ionizing radiation if
Radioresistant cells
Cells that are highly specialized or cells that have a higher metabolism. These cells are not as susceptible to radiation damage as radiosensitive cells.
Radiation causes more damage to rapidly changing, immature cells than to cells that are slow to reproduce, Children are at higher risk for radiation injury because their cells are rapidly dividing.
Radiosensitive organs
Some organs and areas of the body are more radiosensitive than others.
- The small lymphocyte, bone marrow, reproductive organs,
thyroid, skin, and eyes are examples.
Direct damage
cell damage results when ionizing radiation directly hits critical areas within the cekks suh as DNA
Indirect damage
Cell damage results when ionizing radiation causes chemical damage to the cell by ionizing the water in it.
Maximum permissible dose (MPD)
The dose equivalent of ionizing radiation that should not cause physical bodily damage in most people withing their lifetime.
MPD for radiation operators
5 REM per year
MPD for the public
.5 REM per year
Maximum Accumulated Dose (MAD)
A formula to determine an operators maximum accumulated lifetime radiation dose.
= (N - 18) x 0.05 Sv/yr
= (N - 18) x 5 REMs/yr
N = age the operator started exposing x-rays
Bitewing radiograph
An x-ray that records the coronal portion of the maxillary and mandibular teeth to diagnose interproximal decay, evaluate restorations, detect calculus, and assess the alveolar crest of bone and tooth eruption.
or lead diaphragm, is a metal disc that limits the size and shape of the x-ray beam as it exits the tubehead, reducing the total area of exposure and the amount of secondary radiation absorbed by the patient.
- the lead-lined tube further prevents secondary radiation from escaping from the tube and tubehead.
- improves diagnostic quality by reducing secondary radiation (which is one cause of film fogging)
2.75 inches (7 cm)
Federal regulations require that the diameter of the restricted beam (collimation) must not exceed _____(___) at the patients skin surface.
Film fogging
An error that is a result of improper safe lighting, light leaks, outdated films, improper film storage, contaminated solutions or developer solution that is too hot; a grayish appearance to dental x-ray film.
tube head
Part of the x-ray machine that houses the two main components of the x-ray machine: the cathode and anode.
- should have a recessed target to provide the recommended target-to-film distance.
used to absorb the long wavelength, low energy x-rays that are unable to reach the image receptor and are instead absorbed by the patient.
- inherent ______ is built into the x-ray tube and tubehead of the dental unit.
for added filtration an ______ filter is placed in the path of the x-ray beam.
2.5 mm; 1.5 mm
Federal requirements state that x-ray units operating at 70 kVp or more should have filtration equivalent to _____ of aluminum, units operating at less than 70 kVp should have the equivalent of _____ aluminum.
Position Indicating Device (PID)
An extension of the x-ray tubehead used to direct and limit the size of the x-ray beam.
- 8 inch, 12 inch, and 16 inch are available.
rectangular PID
Use of __________ is a popular method for limiting the size of the beam to just slightly larger to the size of a number two intraoral film.
16 inches.
What is the recommended target-to-film distance?
.25 mm
minimum required lead apron thickness
lead foil
What in film packets prevents backscatter radiation (or Radiation that has been deflected from its path; may include secondary radiation and can cause backscatter radiation.)?
reflector cup made of molybdenum; houses the tungsten filament and is the negative electrical terminal in the tubehead.
Measurement of force that causes electron to move from a negative to a positive source.
positive electrical terminal made of copper located in the tubehead that houses the tungsten target.
tungsten filament/wire contained within the cathode along which electrons are produced/passed to focal spot of tungsten target.
tungsten target
located at the end of the anode in the tubehead.
distributes heat generated when electrons hit target in the x-ray tube and eventually into the air
lead glass envelope (vacuum tube)
protective layer surrounding the parts of the xray tube, except for the port.
General (breaking) radiation
occurs after timer button is pressed when electron are pulled from the cathode to the tungsten target
Ionizing radiation
occurs when electron collide with an atom or when electron pass very close to an atom causing it to become excited and move
pocket dosimeter
Measuring device that measures cumulative exposure
- not as precise as other devices
film badge (or dosimetry badge)
radiosensitive film in a holder that is worn at waist level on protective clothing while exposing images.
- measures cumulative exposure for one month
- operator responsible for sending into monitoring company for evaluation
Thermoluminescence dosimer (TLD)
badge worn on clothing for 3 months which is then submitted to monitoring company for evaluation.
- most accurate
- companys create reports comparing occupational radiation exposure with the maximum permissible dose.