Xray - Outcome 1 Flashcards
Roentgen ray
An X-Ray named after Wilhem Roentgen.
Roentgenograph
An image produced on photosensitive film.
Dental radiography
The method of recording images of dental structures by the use of x-radiation.
Dental radiographer
The person who takes the radiograph by positioning, exposing, and processing dental photographic film.
Radiology
The science or study of radiation as used in medicine.
Wavelength
The distance between two peaks of a wave in the same phase.
Frequency
The number of repetitions in a given period of time.
X-Radiation (a.k.a. X-Rays)
A beam of energy that has the power to penetrate substances and record shadow images on receptors (photographic film or digital sensors).
Dental radiograph
A photographic image produced on film by the passage of x-rays through teeth and related structures.
Do X-rays have short or long wavelengths?
The shorter the wavelength and the higher the frequency, the more energy. Because X-rays have a short wavelength with a high frequency they have the energy required to penetrate many materials
Appearance of x-rays
X-rays are invisible energy that cannot be sensed (tasted, heard, felt, or smelled)
Charge
X-rays have no particles therefore they cannot have a charge
Speed of x-rays
X-rays travel at the speed of light (3.0 x 10^8 m/s)
Wavelength
X-rays travel in waves and have short wavelengths with a high frequency
Path of travel
X-rays travel in straight lines and can be deflected, or scattered
Focusing capability
X-rays cannot be focused to a point and always diverge from a point
Penetrating Power of Xrays
X-rays can penetrate liquids, solids, and gases. The composition of the substance determines whether X-rays penetrate or pass through, or are absorbed
Absorption
X-rays are absorbed by matter; the absorption depends on the atomic structure of matter and the wavelength of the X-ray
Ionization capability
X-rays interact with materials they penetrate and cause ionization
Fluorescence capability
X-rays can cause certain substances to fluoresce or emit radiation in longer wavelengths (e.g., visible light and ultraviolet light)
Xrays Effect on receptor
X-rays can produce an image on a receptor
Xray Effect on living tissues
X-rays cause biological changes in living cells
Mass of X-rays
X-rays have no, mass, or weight.
Xray Production
Dental and medical X-rays are produced in an X-ray tube. Electrons are produced at the cathode end of an X-ray tube. When activated these electrons accelerate towards the positively charged anode. Here the high-speed electrons will collide with the anode to produce energy. Most of the energy is transformed into heat, but a small portion (1%) is converted into x-rays
Ionizing Radiation
X-rays are referred to as ionizing radiation as it has the capability of dislodging an electron from its orbit or creating an ion pair. Because X-radiation has the ability (energy) to do this; it is known as ionizing radiation. It is this ionizing effect of x-radiation that accounts for its potential for harmful biological effects (Iannucci & Howerton, 2022). Cells can be damaged or killed by ionizing radiation.
In order to produce dental x-rays, it is necessary to have:
A source of electrons
A high voltage to accelerate the electrons
A target to stop the electrons
Exposure
An exposure is defined as a measure of ionization in the air produced by x-radiation.
The roentgen (R) is the unit of …
The roentgen (R) is the unit of exposure ionization in the air. It does not describe what happens when the radiation enters body tissues and is absorbed.
radiation absorbed dose (rad) is…
The unit of absorbed dose is the radiation absorbed dose (rad), for the radiation from an X-ray machine does not become a dose until it is absorbed
Roentgen equivalent in humans (rem)
Roentgen equivalent in humans (rem) is not only the amount of a particular form of radiation absorbed but also includes the relative biological effect it has upon body tissues
1 R = 1 rad = 1 rem
1 R = 1 rad = 1 rem
MPD for operators
The maximum permissible dose (MPD) for operators in daily contact with roentgen rays should not be more than 5.0 rem per year
Factors Affecting the Penetrating Power of X-Radiation
The wavelength of the rays: the shorter the wavelength, the more energy, and the greater the penetrating power. The longer the wavelength, the less energy, and the lesser the penetrating power.
The distance from the source of the x-rays to the object; the shorter the distance, the greater the penetrating power. The further the object to the source is the lesser the penetrating power.
The density of the object to be penetrated: the less dense an object, the greater the penetrating power. It is because of this factor that radiographs can show the internal structure of objects. Enamel is less easily penetrated than pulp tissue and therefore when transposed the image appears different.
Types of X-radiation produced
There are various types of radiation in which all of them are a concern to the operator.
Primary (Primary beam)
Secondary
Scatter
Stray
Primary (Primary beam) xrays
Consists of the useful rays projected from the tube target (rays of shorter wavelength). It is collimated and filtered to remove less penetrating wavelengths.
Secondary Xrays
Consists of rays reflected by objects that are in the path of x-rays (patient, dental unit). The primary beam interacts with matter creating secondary radiation. Secondary radiation will cause film fog decreasing the diagnostic value of the film.
Scatter Xrays
A form of secondary radiation that results from penetrating matter causing deflection in various directions. This is the radiation that is a concern to the operator and patient.
Stray Xrays
Consists of rays that flow out from parts of the tube other than the window (faulty tube)
The denser an object (the higher the absorption) the object appears….
lighter on the radiograph. The x-radiation does not contact the film emulsion meaning the crystals are not energized leaving no latent image.
The less dense an object (the lower the absorption) the object appears…
darker/grayer
Differential Absorption
Different tissue types absorb different amounts of x-radiation (i.e. soft tissue, pulp).
Radiopaque
Tissues with high absorption of x-radiation, appear “white” on the finished radiograph (i.e. metal, bone, and enamel).
Radiolucent
Tissues with low absorption of x-radiation appear “dark” on the finished radiograph (i.e. caries, abscess).
used to describe the mean energy or
penetrating ability of the x-ray beam
Quality
is the overall darkness or blackness of an
image
density
regulates the temperature of the
cathode filament
milliamperage
refers to the variation of the true size
and shape of the object being imaged
distortion
is the interval of time during which
x-rays are produced
exposure time
refers to the number of x-rays produced
in the dental x-ray unit
quantity
results from the divergent paths of the
x-ray beam as they radiate from the focal
spot
magnification
refers to the capability of the receptor
to reproduce the distinct outline of an object
sharpness
refers to how sharply dark and light
areas are differentiated on an image
contrast
is the product of the quantity and quality
per unit of area per unit of time of exposure
intensity
controls the quality or wavelength of the
x-ray beam
Peak kilovoltage (kVp)
