X-Ray machine components Flashcards
Electricity
power source of x-ray machines
With direct current (DC), electrons flow?
In one direction
With alternating current (AC) power, electrons flow?
in two directions
Circuit
route the electrical current takes
How many volts does a high voltage circuit use to provide high energy to produce x-rays?
65,000 to 100,000 volts
Transformer
mechanism used in an electrical circuit to increase or decrease the voltage
Can be a step-up, step-down, or autotransformer type
Step-down transformer decreases the voltage from the incoming 110 or 220 volts to ?
3-5 volts, needed in the cathode
Control panel
Located outside the radiation room
Displays on-off switches and milliamperage/time/kilovoltage settings
Ampere
number of electrons per second
An increase in amperage increases?
the number of electrons that “work”
How many mAs do dental machines operate with?
5-15 mA
Voltage
force that moves electrons
KiloVoltage peak (kVp)
peak voltage of an alternating current
How much kVp do dental radiographs require?
70-90 kVp
kVp determines ?
the speed at which the electrons are propelled from the cathode
the penetrating power of the x-ray beam, called quality
Tubehead
protective tightly-sealed metal covering (housing)
The tube head contains?
X-ray tube, where x-rays are produced
High/low-voltage transformer alters the voltage of incoming electrical current
Insulating oil helps dissipate the heat
Tubehead seal made of leaded glass or aluminum keeps the oil in the tubehead and acts as a filter for x-ray beams
X-ray tube
heart of the system
Lead glass vacuum housing
Around 6 inches long and 1 inch in diameter. Air was removed to create a vacuum environment that allows the electrons to flow with minimal resistance
Contains two types of electrodes - the cathode and anode
Cathode (negative) electrode
supplies electrons that will generate x-rays
Controlled by milliAmperage (mA) settings
Tungsten filament
emits electrons when heated, an electron cloud forms around it
Molybdenum cup
focusing cup that keeps electrons suspended in an electron cloud
When the exposure button is pressed, the electrons are expelled towards the anode
Anode (positive) electrode
acts as the target for the electrons
controlled by kVp settings
Tungsten target
spot where the electrons hit to produce x-rays
Focal spot (target)
small area on the target on the anode
The electrons from the focusing cup of the cathode are directed towards this target
X-rays originate at the focal spot
Copper stem
dissipates excessive heat
X-ray production results in the generation of x-rays (1%) and heat (99%)
Position-indicating device (PID)
open-ended lead-lined cylinder that extends from the opening of the metal housing
it’s all inherent or attached to the x-ray tube head
What does the PID attach to and where does it direct the X-ray beams?
Attaches to the tube head and directs the x-ray beams to the object and receptor
What shape can the PID be in that allows the reduction of exposure?
Cylinder or a rectangle
Collimators can further restrict the — of the x-ray beam
Size
Where is the aluminum filter located?
inside the PID in the path of the x-ray beam
What is the role of the aluminum filter?
filters out non-penetrating, long wavelength radiation
Where is the open end of the PID placed?
against the patient’s face during receptor exposure
which PID further restricts scatter radiation? Long or Short
a long PID
Extension arm
Helps in positioning the tubehead - horizontal and vertical movement
Wires that run from the control panel to the tubehead are enclosed within this extension arm
When the machine is not in use the extension should be?
Folded in order to prevent the arms from becoming “loose,” which will cause drifting of the tubehead
where does the PID guide the primary beam of radiation?
Towards the patient
The inside is lined with a metallic layer to restrict the primary beams
What as the standard lengths of a PID?
8 inches and 16 inches
What type of rays do long PIDs (16 inches) produce more of?
Parallel rays and it reduces radiation exposure
Which type of PID reduces radiation exposure the most?
Rectangular lead-lined PID
Lead apron
0.25-3 mm lead shields protect patients from non-productive scatter radiation
What should the lead apron cover
The patient from the neck and extend over the lap to protect the reproductive areas
How should a thyroid collar be placed?
thyroid collar should snuggly wrap around the patient’s neck to protect the thyroid glands
*the thyroid gland, particularly in children, is one of the most sensitive organs
T/F: the use of lead aprons and thyroid collars for all patients is recommended in the book “Modern Dental Assistant”
True
Should lead aprons and thyroid collars be folded?
No, it could cause cracks; it should be hung up or laid over a rounded surface instead
Beam guiding device
Helps achieve paralleling technique better
Placed in the patient’s mouth with a portion positioned towards the x-ray tube
Also reduces exposure to the patient’s hand as the tool holds the receptor
Filtration
Absorbent materials, usually aluminum discs are placed in the path of the x-rays to filter out longer, non-productive wavelengths
Inherent filtrations
built into the machine and include glass tube, oil, and 0.5-2 mm thick aluminum layer
Added filtration
depends on the kVp used
- Below 70 kVp = 1.5 mm thickness of aluminum
- At and above 70 kVp = 2.5 mm thickness
Total filtration
sum of inherent and added filtration
Collimation
Metal barrier (lead diaphragm) with an opening in the middle that restricts the size and shape of the x-ray beam
What are the benefits of collimation?
Reduces fog, improves image quality, and restricts patient exposure
What does rectangular collimation do?
restricts the beam to an area slightly larger than a size 2 receptor and creates 60% less radiation exposure compared to a round PID
