Roentgenology

• Projection

  A two-dimensional image of a part of the body made with a stationary x-ray source
• ROENTGENOLOGY

  The branch of radiology concerned with the use of x-rays for diagnostic and therapeutic purposes
• Sharpness

  Measures how well a boundary between two areas of differing radiodensity is revealed
• Spatial resolution

  Measures how well a radiograph is able to reveal small objects that are close together

  
• Penumbra

  Unsharpness, or blurring, of the edges
• Image sharpness influencing factors

  • Focal spot size
  • Film composition
  • Movement

  
• Focal spot size

  The size of the focal spot ranges from 0.6 to 1.0 mm2. The smaller the focal spot area, the sharper the image; the larger the focal spot area, the greater the loss of image sharpness.

  
• Film composition

  The emulsion of faster film contains larger crystals that produce less image sharpness, whereas slower film contains smaller crystals that produce more image sharpness.
• Image magnification

  A radiographic image that appears larger than the actual size of the object it represents

  
• Image magnification influencing factors

  • Target-receptor distance
  • Object-receptor distance

  
• Target-receptor distance

  The distance between the source of x-rays (focal spot on the tungsten target) and the image receptor. A longer PID and target-receptor distance result in less image magnification, while shorter PID and target-receptor distance result in more image magnification.

  
• Object-receptor distance

  The distance between the object being radiographed (the tooth) and the image receptor. The closer the tooth is to the receptor, the less the image is enlarged.

  
• Image distortion

  Results from the unequal magnification of different parts of the same object
• Image distortion influencing factors

  • Object-receptor alignment
  • X-ray beam angulation
• Object-receptor alignment

  The object and receptor must be parallel to each other
• 1. ray beam angulation

  The x-ray beam must be directed perpendicular to the tooth and the receptor

  
• Intraoral projections

  • Bisecting angle technique
  • Tube-shift technique
  • Occlusal projection
  • Bitewing projection
  • Paralleling technique
• Bisecting angle technique

  Also known as the bisecting-angle technique or bisection-of-the-angle technique. The image receptor is placed as close to the teeth as possible without deforming it.
• Rule of isometry

  Two triangles are equal if the triangles have two equal angles and share a common side
• Horizontal angulation

  The positioning of the PID and the direction of the central ray in a horizontal, or side-to-side, plane
• Vertical angulation

  The positioning of the PID in a vertical, or up-and-down, plane
• Foreshortened images

  Images that appear shortened, resulting from excessive vertical angulation
• Elongated images

  Images of the teeth that appear too long, resulting from insufficient vertical angulation
• Five rules for bisecting angle technique

  • The receptor must be positioned to cover the prescribed area of the tooth to be examined
  • The receptor must be placed against the lingual surface of the tooth
  • The central ray must be directed through the contact areas between teeth
  • The central ray of the x-ray beam must be directed perpendicular (at a right angle) to the imaginary bisector that divides the angle formed by the receptor and the long axis of the tooth
  • The x-ray beam must be centered over the receptor to ensure that all areas of the receptor are exposed
• Paralleling technique

  Also known as the extension cone paralleling [XCP] technique, right-angle technique, and long-cone technique. The receptor must be placed away from the tooth and toward the middle of the oral cavity.
• Five rules for paralleling technique

  • The receptor must cover the prescribed area of interest
  • The receptor must be positioned parallel to the long axis of the tooth
  • The central ray must be directed through the contact areas between teeth
  • The central ray must be directed perpendicular to the receptor and the long axis of the tooth
  • The x-ray beam must be centered over the receptor to ensure that all areas of the receptor are exposed
• Bite-wing technique

  Also known as the interproximal technique. Used to examine the interproximal surfaces of teeth.
• Principles of bite-wing technique

  • The receptor is placed in the mouth parallel to the crowns of both maxillary and mandibular teeth
  • The receptor is stabilized when the patient bites on the bite-wing tab or the bite-block of the beam alignment device
  • When using a bite-wing tab, the central ray of the x-ray beam is directed through the contacts of teeth, using a vertical angulation of +10 degrees
• Horizontal angulation (bite-wing)

  The central ray in a horizontal, or side-to-side, plane. Correct angulation results in "opened" contact areas, while incorrect angulation results in overlapped ("unopened") contact areas.
• Vertical angulation (bite-wing)

  The vertical, or up-and-down, plane. Correct angulation of +10 degrees is recommended when a bite-wing tab is used without a beam alignment device, while incorrect angulation results in a distorted image.
• Five rules for bite-wing technique

  • Receptor placement - The bite-wing receptor must be positioned to cover the prescribed area of teeth to be examined
  • Receptor position - The bite-wing receptor must be positioned parallel to the crowns of both maxillary and mandibular teeth
  • Horizontal angulation - When a bite-wing tab is used, the central ray of the x-ray beam must be directed through the contact areas between teeth
  • Vertical angulation - When a bite-wing tab is used, the central ray of the x-ray beam must be directed at +10 degrees
  • Receptor exposure - The x-ray beam must be centered on the receptor to ensure that all areas of the receptor are exposed
• Occlusal projection

  May include the palate or floor of the mouth and a reasonable extent of the contiguous lateral structures. Useful when patients are unable to open wide enough for periapical images.
• Purpose and uses of occlusal projection

  • To locate retained roots of extracted teeth
  • To locate supernumerary (extra), unerupted, or impacted teeth
  • To locate foreign bodies in the maxilla or the mandible
  • To locate salivary stones in the duct of the submandibular gland
  • To locate and evaluate the extent of lesions (e.g., cysts, tumors, malignancies) in the maxilla or the mandible
  • To evaluate the boundaries of the maxillary sinus
  • To evaluate fractures of the maxilla or the mandible
  • To aid in the examination of patients who cannot open their mouths more than a few millimeters
  • To examine the area of a cleft palate
  • To measure changes in the size and shape of the maxilla or the mandible
• Principles of occlusal projection

  • The receptor is placed with the tube side facing the arch that is being exposed
  • The receptor is placed in the mouth between the occlusal surfaces of maxillary and mandibular teeth
  • The receptor is stabilized when the patient gently bites on the surface of the receptor

  
• Types of occlusal projection

  • Maxillary topographic occlusal projection - examine the palate and the anterior teeth of the maxilla
  • Maxillary lateral occlusal projection - examine the palatal roots of molar teeth, may also be used to locate foreign bodies or lesions in the posterior maxilla
  • Maxillary pediatric occlusal projection - examine the anterior teeth of the maxilla and is recommended for use in children 5 years or younger
  • Mandibular topographic occlusal projection - examine the anterior teeth of the mandible
  • Mandibular cross-sectional occlusal projection - examine the buccal and lingual aspects of the mandible, used to locate foreign bodies or salivary stones in the region of the floor of the mouth
  • Mandibular pediatric occlusal projection - examine the anterior teeth of the mandible and is recommended for use in children 5 years or younger

  
• Localization techniques

  Methods used to locate the position of a tooth or an object in the jaws
• Purpose and uses of localization techniques

  • Foreign bodies
  • Impacted teeth
  • Unerupted teeth
  • Retained roots
  • Root positions
  • Salivary stones
  • Jaw fractures
  • Broken needles and instruments
  • Dental restorative materials
• Localization techniques

  • Buccal object rule - Same = Lingual; Opposite = Buccal
  • Right angle technique - Two views made at right angles to one another, best for the mandible
• Extraoral projections

  • Cephalometric
  • Posteroanterior (P-A) projection
  • Towne's view
  • Submentovertex
  • Panoramic
  • Water's view
• Panoramic view

  A large area of the maxilla and the mandible on a single projection