ch.8,10,22 Radiographic Techniques and Error Corrections

Line Pairs and Millimeter

  • Measurements to evaluate a computer's ability to capture image resolution.

Pixel

  • Discrete unit of information.
  • Early concern that X-ray sensor pixels weren't accurate enough compared to film.

Digital X-rays

  • Offer advantages over film:
    • Speed
    • Less radiation
    • Ability to enlarge on a monitor
    • Easier to show patients details

Indirect Digital Radiography

  • Components: CCD camera and computer.
  • Existing X-ray film digitized using a CCD camera.
  • Image displayed on a computer monitor.
  • Process
    • X-ray taken onto a phosphor plate, then put into a scanner for conversion and enhancements.

Intraoral Sensor Protection

  • A finger cot under a disposable barrier sleeve may protect the wire or wireless sensor and prevent cross-contamination.
  • Plastic sleeves are generally sufficient.

Paralleling Technique

  • Sensor Placement
    • 90 degrees
    • Align sensor parallel to the long axis of the tooth

Long Axis of the tooth

  • Extends from root to crown.
  • Variations exist, but the tooth itself guides parallel sensor positioning.

Central Ray

  • Directed perpendicular to the film and the long axis of the tooth.
  • Increasing target-receptor distance ensures more parallel rays are directed at the tube.

XCPs or Beam Alignment Devices

  • Receptor holders that aid in capturing more of the tooth.

Bony Growths

  • Maxillary torus

Receptor Placement

  • Must be placed on the side of the bony growth.

Advantages of Paralleling Technique

  • Accurate, distortion-free images.
  • Simple; eliminates the need for horizontal and vertical angulation adjustments.
  • Applicable with digital sensors or film.
  • Provides clear images.

Common Errors and Correction

  • Failure to turn on the X-ray machine:
    • Possible causes: forgetting to push the button, electrical failure, machine malfunction.
    • Correction: Ensure the machine is on and listen for the audible exposure signal.
  • Overexposed Receptor:
    • Appearance: Dark or high density image.
    • Cause: Excessive X-rays/photons.
    • Correction: Check and reduce settings as needed.
  • Underexposed Receptor:
    • Appearance: Light or low density image.

Periapical Technique Errors

  • Incorrect Receptor Placement:
    • Problem: absence of periapical structures, dropped film corner.
    • Appearance: Root tip missing; no apex on the receptor.
    • Correction: Proper sensor placement, ensure PID is correctly angled.
    • Make sure no more than 1/81/8 of an inch of receptor edge extends beyond the occlusal or crown.
  • Tipped or Tilted Plane:
    • Cause: Receptor edge not parallel to the incisal/occlusal surface.
    • Usually happens when the patient isn't biting down.

Overlapping

  • Description
    • Central ray not directed through interproximal spaces.
    • It is an indirect horizontal angulation receptor.
    • Can happen with either digital sensor film.
    • May occur with paralleling or bisecting technique.

Foreshortening

  • Appearance: Teeth appear short with blunted roots.
  • Cause: Excessive vertical angulation.

Elongation

  • Appearance: Image stretched, teeth appear long.
  • Cause: Insufficient vertical angulation, often doesn't fit on image.

Cone Cut

  • Description: position indicating device (PID) alignment problems.
    • PID is misaligned, X-ray beam not centered over receptor.
    • Photons only hit part of the sensor.
    • Portion of the image remains unexposed (white).
  • Fix: Adjust the PID to fully cover the receptor.

Patient's Finger on Image

  • Avoid placing the patient's finger near the mouth.
  • This can leave a radiopaque shadow on the image.

Movement/Motion

  • Unsharpness:
    • Patient movement during exposure.
    • Solution: Stabilize the tube head, and instruct the patient to remain still.

Reverse/Backwards Film Placement

  • Problem:
    • Film placed backwards in the mouth.