radiographic imaging Flashcards
Electron
-A negatively charged particle in the atom
energy
the ability to do work, cannot be created or destroyed, but can change forms
extension arm
flexible arm that is attached to the x-ray tube head
genetic effects
effects of radiation that are passed on to future generations through genetic cells
image
film-based / digitally produced recordings of anatomic structures
image receptor
a recording medium for an image, normally film, phosphor storage plate (PSP), or a digital sensor
intensity
the total energy of the x-ray beam
ion
an electrically charged particle
ionization
process when elections are removed from atoms, causing harmful effects of radiation in humans
ionizing
radiation that produces ionization resulting in harmful effects
kilovoltage
highest voltage of x-ray tube used during exposure
latent period (laytent)
time between exposure to ionizing radiation and appearance of symptoms
lead apron
device used to protect the reproductive and blood-forming tissues from scatter radiation
magnification
the proportional enlargement of an image
components of control panel (4)
master switch, indicator light, selector buttons, exposure button
matter
anything that occupies space and has form or shape
millampere
one thousandths of an ampere; a unit of measurement used to describe the intensity of an electrical current
penumbra
the blurred or indistinct area that surrounds an image
photon
a minute (tiny) bundle of pure energy that has no weight or mass
primary beam
the most penetrating beam produced at the target of the anode
primary radiation
same as primary beam
quality (of an x-ray beam)
the mean energy or penetrating ability of the x-ray beam
quantity (of an x-ray beam)
the number of x-rays produced in the dental unit ; the quantity of x-rays produced is controlled by milliamperage
radiation
forms of waves of energy of energy emission through space or material
radiation monitoring badge
a devise that contains a film packet used to detect and measure radiation exposure of personnel
radiograph
image produced on photosensitive film by exposing the film to radiation then processing it
radiology
the science or study of radiation as used in medicine
scatter radiation
a form of secondary radiation that occurs when an x-ray beam has been deflected from its path by interaction with matter
secondary radiation
x-ray radiation that is created when the primary beam interacts with matter
sensor
a solid-slate image receptor that contains a silicone chip with an electric circuit
sharpness
a measure of how well an image reproduces the fine details or outline of an object
somatic effects
effects of radiation that cause illness and are responsible for poor health (cancer, leukemia, and cataracts) but are not passed off to offspring
thyroid collar
a flexible lead shield that is placed securely around the neck
tubehead
the part of the x-ray unit that contains the x-ray tube, the high-voltage and low-voltage transformers, and insulating oil
tungsten target
a focal spot in the anode
x-radiation
high-energy ionizing electromagnetic radiation
describe use of dental imagining
- needed for COE
- used to detect conditions not visible
what happens during ionizations
- x-ray photons (energy) collide with electrons in the electron shell and electrons are removed from shell
describe the properties of x-rays
- x-rays belong to electromagnetic radiation
- visible light, radar, radio, and tv waves
- electromagnetic radiation is composed of photons that travel through space at the speed of light in a straight line with wave like motion
- SHORTER WAVELENGTH - GREATER ENERGY
- bc they high energy they penetrate matter easily
identify the parts of the dental x-ray machine and the x-ray tube
-Tube head
•tightly sealed, heavy metal housing that contains radiograph tube
•contains insulating oils to absorb heat from x-rays
•tubehead seal keeps oil in and filters x-ray beams
•where x-rays are produced
•transformer alters the voltage of incoming electrical current
-extension arm
• attached for means of 360° extension
• horizontally and vertically
• never leave extended or it gets loose
-control panel
• on wall outside of x-ray area
• contains master switch(used to turn the machine on and off orange is on), an indicator light(comes on only one exposure button is being pushed and x-rays are being emitted), selector buttons, and an exposure button(Controls the flow of electricity to generate the x-rays)
• selector button is used to select exposure time (milliamperage and kilovoltage) therefore regulating the x-ray beam
explain how x-rays are produced
- x-ray machine is plugged in
- current travels from control panel to tube head through wires in extension arm
- current travels through the step down transformer to the filament of the cathode (110 or 220 volts to 3-5)
- filament uses votes to heat tungsten filament in cathode portion of x-ray tube (heat causes thermionic emission) -the release of electrons from tungsten filament
- electrons stay in cloud within focusing cup until expose button is pushed
- electrons in cloud are shot across x-ray tube to anode
- molybdenum cup in cathode directs electrons to tungsten target in anode
- when electrons strike target, energy of motion creates x-ray and heat (LESS THAN 1% OF ENERGY CONVERTED TO X-RAYS, 99% LOST AS HEAT)
- heat is carried away from copper stem and absorbed by insulating oil in tubehead
- x-ray travels through unleaded glass window of tube, tubehead seal and aluminum filter.
- aluminum filter removers the longer-wavelength x-rays from beam
- x-ray beam travels through the collimator, size is restricted, travels down PID and exits at opening (cheek)
identify the types of radiation
-primary radiation / useful beam / primary beam
•made up of x-rays that come from target of x-ray tube
-secondary radiation
•x-radiation that is created when primary beam interacts with matter
(secondary radiation is created when the x-rays of the primary beam contact the patient’s tissues)
-scatter radiation
•form of secondary radiation that occurs when an x-ray beam has been deflected from its path by matter
•deflected in all directions by patient tissues and travels to all parts of body and dental operatory
describe the three characteristics of the x-ray beam
-quality (wavelength and energy)
•energy or penetrating ability of x-ray beam
•controlled by kV, higher the kV more penetrating x-ray less energy longer wave lengths
- higher kV used when area is thick or dense (darkened or blackness of image)
- changing kV peak changes density
-quantity
•number of x-rays produced in the dental unit
•(A) ampere -unit used for # of electrons or current flowing throw cathode filament
-ampere is usually milliamperes
-7 to 15 mA
-intensity
•combination of quantity of x-ray photons and quality of each
•affected by kV peak, milliamoerage, exposure time and distance
describe how the kilovoltage affects the quality of the x-ray beam
-higher the kV more penetrating x-ray less energy longer wave lengths
describe how the milliamperage affects the quality of the x-ray beam
- Control the amount of time given to exposure of an image
- Time is too short or low MA image will not have correct overall density or will be light in appearance
describe the difference between contrast and density
-contrast is the range of shades (black to white) an image on a radiograph can appear to be, density is the overall darkness or blackness of an image
discuss the biological effects of radiation exposure on the human body
-Cumulative Effects
• when some tissue is damaged from exposure some do not return to original state
-Acute & Chronic Radiation Exposure
•acute-large dose of radiation is absorbed in short. Like a nuclear accident
•chronic -when small amounts of radiation is absorbed repetitively over a long period
-Genetic(sperm/ova) & Somatic (body) Effects
• damage to genetic cells is passed on generations called genetic mutations
•somatic effect is damage to all other cells but not passed on
- sometimes patients tissue absorbs x-ray
- ionization causes disruption of cellular metabolism and permanent damage to living cells and tissues
- The atoms that lose electrons become positive and then are unstable of interactings
identify the critical organs that are sensitive to radiation
-Skin
• reddening, erythema (more similar to sun burn)
-thyroid gland
• if collars were not used the radiation to thyroid gland could be significant
-Lens of the eye
• High dosage of radiation to the lens of the eye can cause Cataracs (a cloudiness of the lens)
-bone marrow
• significant radiation induced changes in bone marrow can result in leukemia
discuss how radiation is measured
-metric system/systeme internationale (SI)
- roentgen (R)
- radiation absorbed dose (RAD)
- roentgen equivalent in human (REM)
units:
- coulombs per kg (C/kg)
- the grey (Gy)
- sievert (Sv)
describe methods of protecting the patient from excess radiation
- aluminum filtration, removes the low energy long wave length least penetrating x-rays from the beam.
- collimator , used to restrict the size and shape of the x-ray beam to reduce patient exposure
- position indicator device (PID), used to detect the x-ray beam
- lead apron & thyroid collar
-fast speed film, faster the film speed the less radiation exposure to patient
(larger the crystals on the film the faster the film)
-Image receptor holding device, keeps patient’s hands and fingers from being exposed to x-radiation
(also hold the image receptor in a stable position and assist the operator and properly positioning the PID)
- exposure factor
- proper technique
describe measures used to protect the operator from excess radiation
- dosimeter/radiation monitoring badge
- stand behind wall
- equipment monitoring for leaks
explain the ALARA concept
AS LOW AS REASONABLE
-all exposure to radiation must be kept to a minimum or as low as reasonably achievable
radiolucent
means dark, body structures that radiation can easily pass through appear radiolucent on an image
Air spaces, soft tissues, abscesses, tooth decay, and dental pulp
radiopaque
means white or gray
body structures that radiation does not easily pass through appear radiopaque
tooth enamel, dense areas of bone and metal restorations
Maximum Permissible Dose (MPD)
-maximum dose equivalent that a body is permitted to receive in a specified period of time, the dose of radiation that the body can endure with little or no injury
