Dental Radiology and Radiation Physics – Vocabulary Flashcards

A comprehensive set of vocabulary flashcards covering key terms from the lecture notes on radiation history, physics, biology, protection, and equipment.

Radiation

Energy that can be emitted as waves or particles; in dentistry used for imaging and therapy.

X-Radiation

High-energy radiation produced when a beam of electrons collides with a metal target in an x-ray tube.

X-ray

A penetrating beam of energy that can produce image shadows on receptors.

Radiology

Science of radiation in medicine; includes diagnostic imaging and therapeutic uses of x-rays and radiant energy.

Radiograph

Image produced on a receptor by exposure to ionizing radiation; a 2D representation of a 3D object.

Dental radiograph

Photographic image produced on a receptor by the passage of x-rays through teeth and related structures.

Radiography

The art and science of making radiographs by exposing a receptor to x-rays.

Dental radiography

Production of radiographs of the teeth and adjacent structures by exposure of an image receptor to x-rays.

Dental radiographer

Person who positions, exposes, and processes dental x-ray receptors.

Image

A picture or likeness of an object.

Image receptor

Recording medium such as x-ray film, phosphor plate, or digital sensor.

Imaging, dental

Creation of digital, print, or film representations of anatomic structures for diagnosis.

Paralleling technique

Dental radiographic technique using a long target-to-receptor distance; introduced in 1896 and refined to long-cone paralleling by 1947.

Panoramic radiography

Extraoral radiographic technique that produces a broad view of the jaws and teeth.

Digital imaging

Imaging with digital sensors/processes; reduces waste and exposure; electronic storage; popular from late 1980s.

Cone beam tomography

Three-dimensional dental imaging introduced in 1999 that provides 3D views of oral structures.

Tube head

Tightly sealed metal housing containing the x-ray tube and components; directs x-rays toward the patient.

Cathode

Negative electrode of the x-ray tube; contains tungsten filament and molybdenum cup; source of electrons.

Anode

Positive electrode; tungsten target on a copper rod; converts electrons into x-ray photons.

Filament

Tungsten wire heated to release electrons (thermionic emission).

Molybdenum cup

Part of the cathode that focuses electrons toward the anode target.

Tungsten target

The anode surface where electrons are converted into x-ray photons.

Thermionic emission

Emission of electrons from a heated filament.

Primary radiation

The useful x-ray beam produced at the anode target.

Secondary radiation

X-radiation created when the primary beam interacts with matter.

Scatter radiation

Secondary radiation deflected from its path after interaction with matter.

Photoelectric effect

X-ray photon ejects an inner-shell electron, transferring all energy to the electron.

Compton scatter

X-ray photon deflects from matter, ejecting an outer-shell electron and losing energy.

Coherent scatter

Low-energy photon changes direction with no ionization.

General (bremsstrahlung) radiation

Continuous radiation produced when electrons decelerate in the target; ~70% of dental x-ray energy.

Characteristic radiation

Discrete x-ray energy produced when a high-speed electron ejects an inner-shell electron; occurs at 70 kVp and above.

Inherent filtration

Filtration inherent to tube components (about 0.5–1.0 mm aluminum).

Added filtration

Aluminum disk placed to filter out low-energy x-rays.

Total filtration

Sum of inherent and added filtration; regulated minimums depend on kVp.

Collimation

Restriction of beam size/shape to reduce patient exposure; round vs rectangular beams.

Position-indicating device (PID)

Extension of the tube head that directs the x-ray beam; longer = reduce divergence.

Milliampere (mA)

Current that controls the number of electrons in the filament; affects exposure.

Kilovolt peak (kVp)

Peak voltage determining x-ray energy and penetration.

Autotransformer

Voltage compensator that adjusts incoming voltage to the tube.

ALARA

As Low As Reasonably Achievable; principle to minimize radiation exposure.

Lead apron

Protective garment worn to shield the body; typically 0.25 mm lead equivalent.

Thyroid collar

Protective neck collar worn during radiography.

Exposure units: Roentgen (R)

Old unit measuring exposure in air.

Dose units: rad

Old unit measuring absorbed dose in tissue.

Dose equivalent: rem

Old unit combining absorbed dose with biological effect.

Gray (Gy)

SI unit of absorbed dose; 1 Gy = 1 joule/kg.

Sievert (Sv)

SI unit of dose equivalent reflecting biological effect.

C/kg (coulombs per kilogram)

SI unit of exposure.

Radiosensitive

Tissues or cells highly susceptible to radiation damage (e.g., lymphoid tissue, bone marrow).

Radioresistant

Tissues less susceptible to radiation damage (e.g., salivary glands, kidney, liver).

Critical organ

Organ whose damage significantly impairs quality of life (e.g., skin, thyroid, lens of the eye, bone marrow).

Transformers

Device used to either increase or decrease voltage in electrical circuit

Step down transformers

decrease voltage incoming 110- or 220 line voltage to the 3 to 5 volts used by filament circuit

• More wire coils in the primary coil than the secondary

• Happens when you turn on the machine

Step Up transformers

increase incoming voltage from 110- to 220- line to 65,000 to 100,000 volts used by circuit

• more coils in the secondary coil than the primary

• to get enough energy to shoot cathodes across to anode at high rate of speed

• Hit the EXPOSURE BUTTON

Autotransformer

voltage compensator. corrects for minor fluctuations in current

What are the kinds of interactions of x-radiation?

• No interaction

• PT absorbs

• Photoelectric effect

• Compton Scatter

Purpose of Cathode

Supply electrons necessary to generate x-ray

Tungsten filament

coiled wire made of tungsten which produces electrons when heated

Purpose of Anode

• convert electrons into x-ray photons

Tungsten target

• made of copper

  • serves as focal spot and converts bombarding electron into x-ray photons

Copper stem

Dissipate heat away from tungsten target

3 phases of radiation injury

1. Latent Period

2. Period of Injury

3. Recovery Period

Latent Period

time that elapses between exposure to ionizing radiation and appearance of observable clinical signs

Period of injury

Variety of cellular injuries may result

• cell death

• changes in cell function

• Breaking/clumping of chromosomes

• formation of giant cells

• cessation of mitotic activity

• abnormal mitosis

Recovery Period

• cellular damage followed by repair

• cells can repair some damage by radiation

• most damage caused by low level rad is repaired within cells of body

X-Ray Tube

heart of the x-ray generating system

• critical for production of x-rays and warrants a sep discussion from rest of machine

Physical attribute of x-ray tube

glass vacuum tube from which all air has been removed

Leaded glass-housing

leaded glass vacuum tube that prevents x-rays from escaping in all direction

• has a “window” that allows x-ray beam to exit the tube and directs the x-ray beam toward aluminum disks, lead collimator and PID

Components of Anode

• tungsten target

  • copper stem

Components of Cathode

• tungsten filament

• molybdenum cup

Electiricty

energy used to make x-rays

Direct Current

When electrons flow in one direction through the conductor

Alternating Current

an electrical current in which electrons flow in two, opposite directions

Rectification

conversion of AC to DC while producing x-rays

• ensures current is always flowing in the same direction (cathode to anode)