Modern Dental Assisting Radiology Final

ALARA

As Low As Reasonably Achievable

Anode

The positive electrode in the x-ray tube. It is composed of a tungsten target that is embedded in the larger copper stem.

atom

basic unit of matter

Bremsstrahlung radiation

"Braking radiation." The sudden deceleration of electrons as they interact with highly positively charged nuclei.

Cathode

The negative electrode in the x-ray tube. Consists of a tungsten filament in a focusing cup made of molybdenum. The cathode supplies the electrons necessary to generate x-rays

Central ray

x-rays at the center of the beam

contrast

differences in degrees of blackness on an image

control panel

the portion of the x-ray unit that contains the master switch, the indicator light, the selector buttons, and the exposure button.

Density

The overall darkness or blackness of an image.

Dental Radiography

the process of recording images of the teeth and adjacent structures by exposure to x-radiation.

Digital imaging

A filmless method of capturing an image and displaying it by using an image receptor, an electronic signal, and a computer to process and store the image.

distortion

Change in the size of an image caused by incorrect vertical angulation

Dose (of radiation)

The amount of energy absorbed by tissues

Dosimeter

A device used to detect and measure an accumulated dosage of radiation

Electron

a negatively charged particle in the atom

Extension Arm

Flexible arm that is attached to the x-ray tubehead

Genetic effects

Effects of radiation that are passed on to future generations through genetic cells

image

film-based or 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 by which electrons are removed from atoms, causing the harmful effects of radiation in humans

Ionizing

Radiation that produces ionization, resulting in harmful effects

Kilovoltage

Highest voltage of x-ray tube used during an exposure

Latent

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

Master switch, indicator light, selector buttons, exposure button

components of the control panel

matter

anything that occupies space and has form or shape.

Milliampere (MA)

1/1000 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

Personal radiation monitoring badge

A device that measures exposure of personnel to ionizing radiation by measuring the intensity of visible light emitted from a crystal in the detector when heated. The intensity of light emitted is dependent upon the radiation exposure.

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

quality (of x-ray beam)

the mean energy or penetrating ability of the x-ray beam

Radiation

Forms of waves of energy emission through space or material

quantity (of x-ray beam)

The number of x-rays produced in the dental unit; the quantity of x-rays produced is controlled by milliamperage.

Radiology

The science or study of radiation as used in medicine

Radiograph

Image produced on photosensitive film by exposing the film to radiation and then processing it

Wilhelm Conrad Roentgen (1895)

Bavarian physicist, who discovered the x-ray in 1895.

What did Roentgen use to produce cathode rays?

Crookes tube (vacuum tube)

Otto Walkhoff

made the first dental radiograph

C. Edmund Kells

credited with the first practical use of radiographs in dentistry in 1896.

William D. Coolidge

electrical engineer who developed the first hot-cathode x-ray tube, a high vacuum tube that contained a tungsten filament.

nucleus

dense core of the atom composed of particles known as protons and neutrons

Braking Radiation

The primary kind of radiation produced int eh dental x-ray tubehead.

True

Electrons remain stable in their orbit around the nucleus until the radiograph photons collide with them.

True

The shorter the wavelength of the x-ray, the greater its energy.

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-radiation that is created when the primary beam interacts with matter

sensor

A solid-state image receptor that contains a silicon 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 (such as cancer, leukemia, and cataracts) but are not passed on 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

Frequency

The number of wavelengths that pass a given point in a certain amount of time. The shorter the wavelength the higher the frequency.

Collimator

restricts the size and shape of the beam

aluminum filter

The 0.5 mm thick sheet located inside the PID in the path of the x-ray beam that filters out the nonpenetrating, longer wavelength radiographs.

X-ray Tube

heart of the x-ray generating system. Has a vacuum environment that allows electrons to flow with minimum resistance between the cathode and anode.

PID

The open-ended lead-lined cylinder that extends from the opening of the metal housing. Available in 8, 12, or 16 in. Longer cone is more effective.

focusing cup

keeps electrons suspended in an electron cloud at the cathode.

True

When the circuit button is pressed, the circuit within the tubehead is completed, and electrons rapidly cross from the cathode to strike the anode.

True

MA controls the number of electrons produced and increases the quantity of electrons available for the production of x-rays.

True

Once the exposure button is pressed the electrons in the cloud are shot across the x-ray tube to the anode. The molybdenum cup in the cathode directs the electrons to the tungsten target in the anode.

Insulating oil

absorbs heat created by the production of x-rays. Less than 1% of the energy is converted to x-rays, with 99% lost as heat.

True

Scatter radiation is dangerous to both the patient and the operator. "6 ft rule"

Radiopaque

white or light; structures that radiation does not easily pass through

enamel, denses areas of bone, and metal restorations

Radiolucent

Dark or black; structures that radiation can easily pass through.

air spaces, soft tissues, abscesses, tooth decay, and dental pulp

85 to 100 KV

produces more penetrating dental x-rays with more energy and shorter wavelengths

65 to 75 KV

Produces less penetrating dental x-rays with less energy and longer wavelengths.

True

a change in kP (kilovoltage peak) results in a change in the density of a dental radiograph.

7 to 15 mA

recommended mA setting in dental radiography

Intensity

the combination of the number of x-ray photons (quantity), and the energy of each photon (quality). Affected by kP, mA, exposure time, and distance.

kV

Higher __ produces more penetrating radiographs.

acute radiation exposure

occurs when a large dose of radiation is absorbed in a short time, such as in a nuclear accident

chronic radiation exposure

Occurs when small amounts of radiation are absorbed repeatedly over a long period

critical organs of radiation exposure

Skin, thyroid gland, lens of the eye, and bone marrow.

MPD (maximum permissible dose)

the current MPD for persons occupationally exposed to radiation is 5.0 rems/year. Non occupationally exposed persons is 0.1 rem/year.

70 kV

A setting of around _______keeps patient exposure at a minimum.

automatic processor

Machine that automates all film processing steps

Beam alignment device

assists in the positioning of the position indicator device (PID)

bitewing

Image view that shows the crowns of both arches on one film

Calcium tungstate

common type of phosphor

cassette

Contains extraoral films during exposure

cephalometric film

Shows the bony and soft tissue areas of the facial profile

charge-coupled device (CCD)

A solid-state image sensor used in intraoral digital imaging

digital image

Electronic signals captured by sensors and displayed on computer monitors

digitize

Scanning of traditional film-based radiographs into a digital image

duplicating film

Film designed for use in film duplicating machines

emulsion

a coating on the x-ray film that contains energy-sensitive crystals.

extraoral film

film designed for use in cassettes

film speed

The sensitivity of the emulsion on the film to radiation

intensifying screen

The part inside an extraoral cassette that converts x-ray energy into visible light, which in turn exposes screen film.

intraoral film

Film designed for placement in the patients mouth

label side

Colored side of the film that faces the tongue

latent image

the invisible image o the x-ray film after exposure but before processing.

occlusal

Radiographic view that shows large areas of the maxilla or mandible

panoramic film

Used in cassettes to provide a wide view of both the upper and lower jaws