Xray - Outcome 3 Flashcards
3 primary components of the x-ray unit
- Tube Head - from which the Xrays are generated
- Extension Arm - allows positioning of the tube head
- Control Panel - contains the regulating devices
Tube Head
The tube head is the housing that contains the x-ray tube. This is where x-radiation is generated. It consists of various components
The tube head is made of metal and lined with lead to protect the actual X-ray tube and to prevent the escape of radiation in any direction except toward the position indicating device (P.I.D.)
Extension Arm
The extension arm is wall-mounted. It is hollow to allow the passage of electrical wires from the control panel to the x-ray tube head. It folds up and can be swiveled from side to side, allowing positioning of the tube head
Control Panel
The control panel is mounted on the wall where it is electrically connected. The control panel consists of the indicator lights and activation buttons such as the ready lamp, tooth selection, and exposure times
Volt
The volt is the unit used to measure electrical potential or work capacity. Because dental x-ray equipment operates at very high voltages, it is customary to express voltage in terms of kilovolts
(1 kV = 1000 volts). The abbreviation is kV.
What is Kilovolt Peak?
The highest voltage to which the current in the tube rises during exposure is called the kilovolt peak, abbreviated kVp. Thus, if the x-ray machine controls are set at 65,000 volts, the maximum x-ray energy that can be produced during exposure is 65 kVp
basic principles of electricity specific to the production of x-radiation..
Electrical current is the flow of electricity through a conductor which is required for the production of x-rays. The electrical current (circuit) is controlled by a transformer. The x-ray tube and transformers are housed in the tube head and one in the control panel (Iannucci & Howerton, 2022). The three transformers are step-down, step-up, and auto transformer.
Why are transformers necessary?
The transformers are necessary because the line voltage coming to most dental offices is 110 or 220 volts and the x-ray tube operates at varying voltages. The low-voltage transformer is used to reduce the current to 3-5 volts which is enough to heat the cathode filament and form the electron cloud
The high voltage transformer
The high-voltage transformer produces a voltage of 65,000 – 100,000 volts which is necessary to propel the electrons across the tube. The high-voltage current begins to flow when the activator button is depressed. When the voltage is increased, the electrons travel faster and produce the strongest type of radiation
What is the purpose of a transformer?
The transformer is used to increase or decrease the electrical current.
Step-down transformer is for..
- is used to decrease the voltage to allow for heating of the filament.
A step-up transformer is for..
- is used to increase the voltage upon activation accelerating the electrons.
A autotransformer is for…
- is used to maintain consistency of the current, to correct fluctuations.
What is Constant Potential? (kVcp)
Constant Potential (kVcp) is the maintaining of consistent energy (acceleration) of electrons
What will a higher kilovolt peak setting do?
A higher kilovolt peak setting will produce x-rays with greater penetrating power (quality) and therefore, a greater capacity to pass through matter.
What is the ampere?
The ampere is the unit of quantity of electric current, or, the number of electrons flowing in an electrical circuit. Only a small current is required to operate the X-ray machine, therefore, the term milliampere (1/1000 of an ampere) is used. The abbreviation is mA
What milliampere (mA) do dental xray machines usually operate at?
The majority of dental x-ray machines operate at 10 or 15 mA
The milliamperage regulare determines…
The milliamperage regulator determines the number of X-rays produced by controlling the temperature of the tungsten coil. The higher the mA, the hotter the tungsten coil will become, and the greater will be the number of electrons produced in the electron cloud
What does the kilovoltage control?
The speed of each electronc
What does the milliamperage control?
The number of electrons
The timer regulates..
The timer regulates the length of time the current will pass through the X-ray tube, enabling the operator to predetermine the length of the exposure. The amount of time needed to adequately expose the film varies greatly depending on the anatomical feature (density, film speed, and distance to object and source to object distance)
The exposure switch
All dental X-ray machines are required to be equipped with an exposure switch of the “deadman” type, which automatically terminates the exposure when the finger ceases to press the timer button. This makes it necessary to maintain firm pressure on the button during the entire exposure
Mechanical Reduction of X-radiation - Aluminum Filter
an aluminum filter placed in the path of the primary beam before it leaves the unit. The filter is added in 0.5 mm increments usually to a required thickness of 1.5 – 2.5 mm. Only those x-rays with the shorter wavelengths pass through the filter; through the tissues to expose the film. The filter absorbs most of the longer wavelength rays so that the patient receives only those rays capable of exposing the film
Mechanical Reduction of X-radiations - Lead Collimator
The lead collimator collimates or restricts the size of the beam. The collimator is used to restrict the size/shape of the x-ray beam. Collimation of the primary beam reduces patient exposure and increases film quality by reducing the amount of scattered radiation formed. The collimator is a lead disc that threads onto a fitting over the Porte of the tube head housing and shapes the x-ray beam. In the center of the disc is a circular opening through which the X-rays pass. These X-rays comprise the useful beam or the central ray. The size of the useful beam is 2.75 inches in diameter
Three Types of Digital Imaging
- Direct Digital Imaging
- Indirect Digital Imaging
- Storage Phosphor Imaging (commonly referred to as indirect digital imaging)
Direct Digital Imaging
When using direct digital imaging, a sensor is used in place of a film. This sensor works like an exposed film. Once it is radiated, it must be processed. When the sensor has been struck, the source of radiation is activated producing an electronic charge on the sensor. The electronic charge is digitized and in turn, transmitted to the computer. This image is displayed within seconds. Once the image is captured and transmitted to the computer monitor, the software then enhances and stores the image.
Indirect Digital Imaging
A film-based radiograph is required. The radiographs are then scanned or photographed. The recreated image is compromised in quality as it is a copy
Storage Phosphor Imaging
Storage phosphor imaging uses a reusable imaging plate instead of a sensor. The phosphor-coated plate is similar to an intensifying screen. After exposure, the plate is electronically processed (scanned with a laser). This system is not as efficient
Dental Management Software
Computer software allows the dental radiographer to digitally enhance images. An image may have any of the following features enhanced:
Contrast
Brightness
Image size (zoom)
Sharpness
Inversion (white to black and black to white)
Pseudocolor alteration
automatic processor
machine that automates all film processing steps
beam alignment device
XPC kit - assists in the positioning of the position indicated device
emulsion
coating on the xray film that contains energy sensitive crystals
intensifying screen
part inside an extra oral cassette that converts xray energy into visible light, which in turn exposes screen film
cassette
contains extraoral films during exposure
latent image
invisible image on the xray film after exposure but before processing
anode
positive electrode in the xray tube
cathode
negative electrode in the xray tube
central ray
xrays at the center of the beam
contrast
differences in degrees of blackness on an image
density
overall darkness or blackness of an image
electron
negatively charged particle in the atom
image receptor
recording medium for an image, normally film, psp, or digital sensor
penumbra
burred or indistinct area that surrounds an image
photon
minute (tiny) bundle of pure energy that has no weight or mass
quality of xray beam
mean energy or penetrating ability of the xray beam
quantity of xray beam
number of xrays produced in the dental unit; the quantity of xrays produced is controlled by the milliamperage
secondary radiation
xradiation that is created when the primary beam interacts with matter
tungsten target
focal spot in the anode
