Radiology Chapter five
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what is the affect of X-radiation on cells?
it causes biological changes in living cells, and adversely affects all living tissue
When can patient protection from radiation be used?
prior to, during, and after x-ray exposure
What is the first step in limiting the amount of radiation a dental pt recieves?
proper prescribing of dental radiographs
Who is responsible for prescribing dental radiographs? And what are the dental radiograph prescriptions made for?
- The dentist
How should the dentist determine how to prescribe radiographs?
- based on the pt's individual needs
- according to guidelines from the FDA for prescribing dental radiographs
What must the dental x-ray tubehead be equipt with for patient protection
- aluminum filters
- lead collimator
- position indicating device
2 types of filtration used in the dental x-ray tubehead
- inherent filtration
- added filtration
takes place whtn the primary beam passes through the glass window of the x-ray tube, the insulating oil, and the tubehead seal. The inherent filtration of the dental x-ray machine is equivalent to approximately 0.5 to 1.0mm of aluminum.
does inherent filtration alone meet the standards regulated by state and federal law?
no, so added filtration is required
refers to the placement of aluminum disks in the path of the x-ray beam between the collimator and the tubehead seal in the dental x-ray machine. They can be added to the tubehead in 0.5-mm increments. Their purpose is to filter out longer wavelength, and low energy x-rays from the x-ray beam.
the___________energy and ________________wavelength x-rays are harmful to the pt and not usedful in diagnostic radiography.
_______________of the x-ray beam results in higher energy, and more____________ useful beam.
the required thickness of this is regulated by state and federal law.
inherent and added filtration together.
state and federal law requirements for total filtration
- machine operating at or below 70 kVp require a minimum total of 1.5 mm aluminum filtration
- machines operating at above 70 kVp require a minimum total of 2.5 mm aluminum filtration
used to restrict the size and shape of the x-ray beam and to reduce the patient exposure
lead plate with a hole in the middle fitted directly over the opeing of the machine housing where the x-ray beam exits the tubehead
this collimator restricts the sized of the x-ray beam to an area slightly larger than a size 2 intraoral film and siginificantly reduces patient exposure
this collimator produces a cone shaped beam that is 2.75 inches in diameter, considerably larger than a size 2 film
appears as an extension of the x-ray tubehead and is used to direct the x-ray beam
position indicating device
appears as a closed, pointed plastic cone, when x-rays exit from it they penetrate the plastic and produce scatter radiation. Not recommended
Why aren't the conical PIDs used in dentistry anymore?
because they produced too much scatter radiation
What lengths are round and rectangular PIDs commonly available in?
Which lenght of PID is preferred and why?
- the long PID
- because less divergence of the x-ray beam occurs
Of the 3 types of PIDs, which is most effective in reducing pt exposure?
name devices used during x-ray exposure to protect the pt.
- thyroid collar
- lead apron
- fast film
- film holding devices
a flexible lead shield that is placed securely around the pts neck to protect the thyroid gland from scatter radiation. The lead prevents radioation from reaching the gland and protects the highly radiosensitive tissues of the thyroid.
When is the use of the thyroid collar recommended?
during all intraoral films
why is the use of the thyroid collar not recommended for extraoral films?
because it obscures information on the film and results in a nondiagnostic radiograph
a flexible shield that is placed over the patients chest and lap to protect the reproductive and blood-forming tissues from scatter radiation; it prevents the radiation from reaching these radiosensitive organs.
When is the use of a lead apron recommended?
for all intra and extraoral films
What is the single most effective method of reducing a pt's exposure to x-radiation?
the use of fast film
What is the fastest film speed available?
F-speed; reduces exposure 20% over E-speed
helps to stabilized the film position in the mouth and reduces the chance of movement. It also eliminates the need for the pt to hold the film in place.
How can the dental radiographer control the exposure factors?
- adjust the:
- kilovoltage peak
- time settings
a setting of ____________kVp keeps pt exposure to a minimum
Helps to ensure the diagnostic quality of films and reduce the amount of exposure a patient recieves
all retakes must be____________!
to produce diagnostic films one must what?
- have a thourgough knowledge of the techniques used and how to expose
- have an organized routine for taking films
techniques used most often in x-radiation
How is pt protection implemented after radiation exposure?
meticulous and proper film handling and film processing to prevent the existence of artifacts and other things on the film that will render them nondiagnostic, and therefor result in retaking films
Why must the dental radiographer also use proper protection measures for themselves?
- to avoid occupational exposure to radiation:
- primary radiation
- leakage radiation
- scatter radiation
What is the main rule for operator protection guidelines?
the dental radiographer must aviod the primary beam
What is the distance recommendation for the dental radiographer?
stand atleast 6 feet away from, and perpendicular to the beam; or used a protective barrier
What are the position recommendations for the dental radiographer?
- stand perpendicular to the beam
- never hold a film in place for a pt during x-ray exposure
- never hold the tubehead during x-ray exposure
What are the shielding recommendations for the dental radiographer?
stand behind a protective barrier such as a wall consisting of several thickness layers of common construction materials such as dry wall
the monitering of equipment and dental personnel; can identify excess occupational exposure
What must dental x-ray machines be monitered for?
any radiation, with the exception of the primary beam, that is emitted from the dental tubehead
measures the amount of x-radiation that reaches the body of the dental radiographer
What does the film badge consist of? When and where should it be worn and stored?
- a piece of radiographic film in a plastic holder
- worn at waist level
- whenever the radiographer is exposing films
- stored when radiographer is undergoing x-ray exposure
- stored in a radiation safe place
has been established at both the state and federal levels to protect the patient, operator, and general public from radiation hazards.
Radiation safety legislation
When and why was the radiation control for health and safety Act enhanced?
- to standardized the performance of the x-ray equipment
When and why was the consumer-patient radiation health and safety act at the federal level enhanced?
- to address the issues of the education and certification of persons using radiographic equipment
True or False. radiation legislation differs greatly from state to state so the dental radiographer must be familiar with the laws that apply to their workplace.
defined by the national council on radiation protection and measurements as the maximum dose equivalent that a body is permitted to recieve in a specific period of time. The dose of radiation that the body can endure with little or no injury
maximum permissable dose
What is the current MPD for occupationally exposed persons?
what is the current MPD for nonoccupationally exposed persons?
what is the MPD for an occupationally exposed pregnant women?
accumulated lifetime radiation dose that occupationally exposed workers must not exceed.
what is the formula that determines MAD?
MAD= (perosons age in years - 18) x 5 rem/year
How much radiation does one recieve from a tv set at 1 inch?
how much radiation does one recieve from airline travel at 39,000 ft?
0.5 mrem/ yr
how much radiation does one recieve from nuclear power plants at plant boundary?
how much radiation does one recieve from natural gas in a home?
How much radiation does one recieve from terrestrial backgrounds (rocky mountains)?
How much radiation does on recieve from dental x-rays?
How much radiation does one recieve from head/neck x-rays?
how much radiation does one recieve from chest x-rays (average)?
How much radiation does one recieve from radionuclides in the human body (i.e. potassium)
how much radiation does one recieve from building material (concrete)?
how much radiation does one recieve from drinking water?
states that all exposure to radiation must be kept to a minimum or "as low as reasonably achievable"
What are some ways that patient education about x-radiation are implemented?
- informal discussion
- printed material
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