Ch 9 Radiography

Radiography
Chapter Objectives

  • Define the principle of radiant energy and discuss how X-rays (Roentgen rays) are generated.

  • Identify the perils of radiation and describe its effects on the body.

  • Explain factors for measuring radiation and their relevance to biological effects of radiation exposure.

  • List acceptable methods for radiation protection in a dental facility.

  • Discuss the composition of conventional film packets. Describe types of dental radiographs available and qualities necessary for diagnosis.

  • Identify methods used to expose conventional and digital dental radiographs.

  • Describe methods used to produce a processed dental radiograph.

  • Explain the procedure to display a digital image and the types of enhancements available.

  • Discuss types of radiograph mounts and methods to store processed films, and explain the procedure for storage and transfer of digital radiographs.

  • List and describe common radiographic errors and their causes.

  • Understand terms related to 3D cone beam computerized tomography.

Definition and Production of X-Rays

  • Parts of X-ray tube:-

    • Cathode: a negatively charged electrode that emits electrons.

    • Filament: a thin wire that, when heated, releases electrons.

    • Anode: a positively charged electrode that attracts electrons from the cathode.

    • Focal spot: the small area on the anode that the electron stream is directed toward; X-rays originate here.

    • Aluminum filter: A filter used to absorb low-energy X-ray photons.

    • Collimator: A diaphragm, usually lead, used to restrict the size and shape of the X-ray beam.

    • Aperture: opening or hole through which radiation passes

    • Filter: Used to remove low energy x-rays from the x-ray beam.

    • PID (Position-Indicating Device): An open-ended, lead-lined cylinder or cone that is used to aim and shape the X-ray beam.

  • Control factors:-

    • Milliampere (mA): determines the quantity or number of X-rays produced

    • Kilovolt power (kVp): determines the quality or penetrating power of the X-rays.

    • Exposure time: the interval during which X-rays are produced.

    • Target-film distance

    • Target-object distance

    • Film speed

  • Types of radiation:-

    • Primary radiation: the original undeflected useful beam of radiation that emanates from the X-ray tubehead.

    • Secondary radiation: radiation formed when the primary X-rays strike the patient or come into contact with any matter or substance

    • Scattered radiation: a form of secondary radiation that occurs when an X-ray beam has been deflected from its path by interaction with matter.

    • Leakage radiation: radiation that escapes in all directions from the tube or tube head due to malfunction or leakage.

Properties of Roentgen Rays

  • Dangers of working with radiation

  • Hazards with radiation exposure

  • Effects on human cells:-

    • Sensitivity

    • Cumulative effect

    • Mutation effect

Types of Radiation Exposure

  • Acute exposure: When a large dose of radiation is absorbed in a short period of time.

  • Chronic exposure: When small amounts of radiation are absorbed repeatedly over a long period.

Measurement of Radiation Energy

  • Roentgen (R): measures radiation by determining the amount of ionization that occurs in air

  • Rad (Radiation Absorbed Dose): measures the amount of radiation absorbed by a tissue

  • Rem (Roentgen Equivalent Man): is the product of absorbed dose (rad) and a quality factor specific for the type of radiation

  • Relative biological effectiveness (RBE)

  • Coulomb

  • Maximum permissible dose

Radiation Protection

  • Erythema dose

  • As Low As Reasonably Achievable (ALARA) principle

  • Dosimeter

  • Lead aprons and shields

  • Phantom

Conventional Radiographs

  • Periapical film packet: Used to examine the entire tooth and supporting bone.

  • Bitewing film packet: Captures the crowns of the upper and lower teeth, useful for detecting interproximal caries (cavities between teeth).

  • Occlusal film packet: A large film used to capture a larger area of the maxilla or mandible; useful for detecting cysts, fractures, or impacted teeth.

  • Extraoral film: Films used outside the mouth, such as panoramic and cephalometric films.

  • Film speeds (A-F)

  • Cephalometric film/headplate

  • Cephalostat

  • Panoramic radiograph

  • Intensifying screen

Digital Radiographs

  • Charge-Coupled Device (CCD)

  • Phosphor Storage Plates (PSP)

Indirect Digital Imaging

  • PSP (Phosphor Storage Plates)

  • Digitizing conventional radiograph

  • Types and uses of enhancement:-

    • Magnification

    • Color substitution

    • Digital subtraction

Diagnostic Qualities for Dental Radiographs

  • Contrast: refers to the visual differences between shades ranging from black to white in adjacent areas of the radiographic image.

  • Density: Density refers to the overall blackness or darkness of a radiographic image.

  • Detail

  • Definition

  • Radiolucent: the portion of the image that is dark or black

  • Radiopaque: the portion of the image that appears light or white

Techniques for Exposure of Radiographs

  • Bisecting angle technique

  • Paralleling technique

Positioning Terms for X-Ray Exposure

  • Sagittal plane: divides the body into right and left sides

  • Ala-tragus line: imaginary plane from the ala of the nose to the tragus of the ear.

  • Frankfort plane: Imaginary plane from the orbital ridge to the external auditory meatus

  • Positive angulation

Positioning Devices

  • Position-Indicating Device (PID)

  • Film-holding instrument

  • Biteblock

  • Individual film holder

  • Biteloop/tab

  • Film safe container

X-Ray Surveys

  • Full Mouth Survey (FMS or FMX)

  • Bitewing Survey (BWS or BWX)

  • Edentulous survey

Radiographic Film Processing

  • Developing

  • Rinsing

  • Fixing- Hyposulfite

  • Drying

  • Safelight

  • Duplicating radiographs

Mounting Radiographs

  • Horizontal window

  • Vertical window

  • Bitewing window

  • Identification dot

  • Viewbox

Assorted Radiographic Errors

  • Elongation

  • Foreshortening

  • Overlapping

  • Cone cutting

  • Clear films

  • Under developing

  • Over developing

  • Reticulation

  • Fog

  • Penumbra

  • Herringbone effect

3D Radiology

  • Voxels add the third dimension

  • Axial view

  • Sagittal view

  • Coronal view

  • Volumetric view

  • Cone Beam Volumetric Tomographic (CBVT)

  • Tomography

  • Tomogram

  • Polytomography

  • Laminagraphy