DEN 111 Module 1 - Radiography Basics

Definition of Radiography

  • What Is a Radiograph?

    • "A picture produced on a sensitive surface by a form of radiation other than visible light".

  • What Is Radiography?

    • "The art or act of producing radiographs".

General Process of Radiography

  • Steps Involved:

    • Machine produces x-rays.

    • X-rays penetrate tissues.

    • The image is "pushed" onto a receptor by the x-rays.

Equipment Used in Radiography

  • Components include:

    • Tube head.

    • PID (Position Indicating Device).

    • Control panel.

    • Receptor holders (XCP/Rinn).

    • Types of Receptors:

    • Digital Sensors:

      • Example: Kodak

    • PSP (Photostimulable Phosphor):

      • Example: Kodak

    • Film:

      • Example: Kodak

Orientation of Teeth

  • Coronal vs Apical:

    • Coronal:

    • Towards/around the crown of the tooth.

    • Apical:

    • Towards/around the apex of the tooth.

  • Maxillary vs Mandibular:

    • Maxillary:

    • Refers to the upper jaw/top teeth.

    • Mandibular:

    • Refers to the lower jaw/bottom teeth.

    • Notation that apices of teeth point "out".

Radiation Safety Guidelines

  • Presented by: Ms. Lauren Incardona BS, RDH

    • Based on: Evelyn Thomson & Orlen Johnson’s "Essentials of Dental Radiography for Dental Assistants and Hygienists, 10th edition".

    • Credited to: Dr. Barb Ellis.

ALARA Principle

  • ALARA:

    • Acronym for "As Low As Reasonably Achievable."

    • Principle embraced by all radiograph technicians.

    • States that:

    • Every effort must be made to reduce radiation doses at all times.

    • Exposure should be kept to a minimum.

    • Benefits of exposing the patient should outweigh the risks.

    • Achieved through various methods.

Radiographer Protection Measures

  • Time Management:

    • Limit time spent near x-ray generating equipment.

    • Avoid errors to maintain good technique, reducing the need for retakes.

  • Shielding:

    • Structural Shielding:

    • A barrier between the operator and radiation source that includes:

      • 1mm of lead within the walls.

      • Alternative materials: plaster, cinderblock, and 3" of drywall or 3/16" of steel.

  • Distance:

    • Maintain a minimum of 6 feet away from the radiation source.

    • Stand at a 90-degree angle away from the source of radiation.

    • Stand at a 45-degree angle from where the primary beam exits the patient.

    • Important Note: NEVER hold an x-ray receptor in a patient’s mouth!

  • Monitoring Device:

    • Film Badge:

    • Radiosensitive film in a plastic or metal holder worn for 1 month at waist-level; records only exposure in the area worn.

    • Thermoluminescent Dosimeter (TLD):

    • Worn for 3 months; contains crystals that absorb energy from radiation. Upon heating, emitted light is measured, which correlates with the amount of radiation absorbed (very accurate!).

Patient/Client Protection Strategies

  • Radiograph Exposure:

    • Expose only necessary radiographs based on patient assessment.

    • Explain the radiographic procedure to gain client cooperation and avoid retakes.

    • Use digital sensor, PSP, or F-speed film, which require less radiation.

    • Utilize receptor holders (RINN), not the patient’s finger to stabilize the image receptor.

  • Protective Equipment:

    • Always use a lead apron (0.25mm to 3mm thickness of lead) and a thyroid collar.

    • Note: No thyroid collar is required for extraoral panx.

    • The thyroid gland, especially in children, is highly radiosensitive.

    • The lead apron protects reproductive and blood-forming tissues, absorbing 90% of scatter radiation.

  • Aluminum Filtration Techniques:

    • Types of Filtration:

    • Inherent:

      • Built into the x-ray machine (glass tube with insulating oil).

    • Added:

      • Discs of aluminum (0.5mm) placed in the path of the beam.

    • Total Filtration:

      • Sum of inherent and added filtration.

      • Requirements:

      • Total Filtration must be 1.5mm for machines operating below 70kVp.

      • Total Filtration must be 2.5mm for machines operating above 70kVp.

      • Purpose: Filters out long/lazy waves, allowing only short, productive waves.

  • Collimation:

    • Round disk of lead with a small opening that allows rays through.

    • Restricts the size and shape of the beam to have a diameter of 2.75" (7cm) at the patient’s face.

    • Rectangular Collimator:

    • Further reduces radiation by restricting x-rays to the size of a size 2 film, decreasing radiation by 60% over round collimation.

    • Note: Harder to align the film exactly with the collimator, potentially leading to more retakes and exposure.

  • Intensifying Screens:

    • Used in extraoral radiography (e.g., panoramic views).

    • Composed of plastic sheets covered with fluorescent material called phosphors, converting photon energy into visible light.

    • Located within the cassette, close to the film, reducing exposure time and the amount of radiation needed to expose a film.

Maximum Permissible Dose (MPD)

  • Definition:

    • Maximum dose equivalent of ionizing radiation an individual can receive in a specific period without producing significant effects.

  • Radiation Workers:

    • Whole body dose may NOT exceed 50mSv (5rem) per year.

    • This dose limit does not apply to individuals under the age of 18 or pregnant female workers, who are categorized as General Public.

  • General Public:

    • Maximum acceptable dose is 5mSv (0.5rem) per year.

    • Guidelines developed by the National Council on Radiation Protection & Measurements (NCRP).

Importance of Operator Competence

  • Operator Competence:

    • Stressed as the most crucial factor in reducing radiation exposure for both patients and providers!