Radiology: Imaging Techniques and Error Solutions

• The correct position of the Frankfort plane for a diagnostically correct image is parallel to the floor.

Common Errors: Patient Preparation & Solutions

• Lead apron artifact can occur; use a lead apron without a thyroid collar for extraoral images to avoid this.

Patient Positioning Errors

• Having the chin too high results in a reverse smile line on panoramic images.
• Not standing or sitting with a straight spine can cause a tapered and blurred panoramic image.

Three-Dimensional Digital Imaging

• Allows for better resolution to show better detail with the panoramic unit.

Computed Tomography (2-D imaging)

• Used in dentistry for:
  • Implant planning.
  • Detecting diseases of the jaw.

Specialized Extraoral Imaging: Grid

• Used to reduce scatter radiation and increase image contrast.

Skull Radiology: Posteroanterior View

• Shows the frontal sinus, ethmoid sinus, orbits, and nasal cavity.

X-Ray Machine Components

• The cathode supplies the electrons necessary to produce x-rays.
• Changing the exposure time affects the quantity of x-rays produced.
• Insulating oil in the tube head absorbs heat created by x-ray production.
• A lead collimator restricts the size and shape of the x-ray beam.

Film Holders

• Examples include XCP, BAI instruments, and EEZEE-Grip.

Advantages of Automatic Film Processing

• Consistent and rapid results, less maintenance, and reduced equipment size.

Charge Coupled Device (CCD) Sensor

• Made of silicon and converts x-ray photons into an electrical charge.

Indirect Digital Imaging: Phosphor Storage Imaging

• A wireless method that uses reusable imaging plates coated with a storage phosphor.

Digitizing Images

• Converting traditional film-based images into digital format using a scanner.

Intraoral Film Placement

• Placed in the mouth with the white side facing the x-ray tube.

Extraoral Film Placement

• The film cassette should be placed perpendicular to the floor in a panoramic machine during exposure.

Patient Records

• Must contain the date of exposure, number and type of images, and the rationale for taking the images.

Ownership of Dental Radiographs

• The dentist owns the dental radiographs, even though the patient has rights to access their information.

Quality Assurance

• Includes quality control tests and quality administration procedures to ensure high-quality images.

Quality Control Tests

• Regular checks and maintenance of equipment and procedures to maintain standards.

Dental X-Ray Machines

• Calibration of dental x-ray equipment should be performed by a qualified technician.

Dental X-Ray Film Freshness

• The simplest method is to process a film from each new box.

Bitewing (BWX) Image

• Detects interproximal caries (cavities).
• Shows the crowns of the teeth, alveolar crest, and interproximal areas.

Periapical (PA) View

• Shows the entire tooth from crown to apex and surrounding bone.

Intraoral Full-Mouth Survey

• Includes bitewing and periapical images.

Anterior Region Film Size (Paralleling Technique)

• A size #1 film is typically used for anterior images with the paralleling technique.

Paralleling Technique: Five Basic Rules

• Image receptor is placed parallel to the long axis of the tooth.
• The central ray is directed perpendicular to the tooth and image receptor.
• A beam alignment device must be used.
• The patient’s head is positioned so the arch is parallel to the floor
• Use a large enough image receptor

Paralleling Technique: Anterior Placement

• Start with the anterior teeth when exposing a periapical film/sensor.
• Size #1 film/sensor: 6 images are used for maxillary and 4 images for mandibular.
• When using #2 film/sensor for anterior views: typically 6 anterior images are taken.

Minimizing Image Distortion

• Film should be placed in the mouth parallel to the tooth and as close as possible.

Vertical Angulation Errors

• Insufficient vertical angulation results in an elongated image.

Horizontal Angulation

• Refers to the direction of the x-ray beam in a horizontal plane, which dictates whether contacts are open.

Biological Effects of Radiation

• Acute Exposure: short-term high dose, immediate effects.
• Chronic Exposure: long-term low dose, effects may appear after years.
• Genetic Effects: seen in future generations, mutations in DNA.
• Somatic Effects: seen in the individual exposed, not passed on.

Five Steps in Film Processing

• Development, rinsing, fixation, washing, drying.

Film Processing: Time/Temp. Error

• A developer solution warmer than 83 degrees F results in a dark film.

Chemical Contamination

• Fixer solution on film before developing results in a clear film.

Clear Spots

• Can be caused by fixer solution coming in contact with the film before processing.

Legal Considerations

• Federal and State Regulations: Laws regarding x-ray equipment, operator qualifications, and safety procedures must be followed.

Developer Strength: Reference Radiograph

• A lighter daily radiograph indicates the developer solution is weak or exhausted.
• Administrative quality control plan includes:
  • Monitor x-ray equipment
  • Supply inventory.
  • Schedule maintenance
  • Record keeping logs

Record Keeping Log

• Includes date of exposure, number and type of images, rationale, and any retakes.

Handling Contaminated Films

• Films should be handled with gloved hands and follow infection control protocols.

Equipment and Supplies Decontamination

• Three steps to decrease contamination:
  • Use disposable barriers.
  • Heat-sterilize reusable items.
  • Disinfect surfaces.

Positioning Instruments

• Should be removed from sterilized packages immediately before use.

Transporting PSP Films

• Should be transported in a container to protect them from light.

Central Ray

• If not centered, results in a cone cut.

Discovery of X-Rays

• X-rays were discovered by Wilhelm Conrad Roentgen.

Properties of X-Rays

• Shorter wavelengths contain the greatest energy and usefulness.

Secondary Radiation

• Formed when the primary x-ray beam interacts with matter.

Contrast

• Refers to the difference in densities (shades of gray) on a radiograph.

Tissues with Highest Radiation Sensitivity

• Reproductive cells, lymphoid tissues, bone marrow, intestines, and mucous membranes.

Pregnant Patients

• The Guidelines recommend postponing routine dental imaging for pregnant patients.

Bisecting Technique

• Used when a patient has a small mouth, shallow palate, or tori.

Panoramic Machine Components

• Three main components are: tube head, image receptor, and head positioner.
• Tube head and image receptor rotate around the patient's head.

Panoramic Machine Exposure Controls

• kV (kilovoltage) and mA (milliamperage) parameters.

Exposure to Radiation

• Any exposure, no matter how small, has the potential to cause biological damage.

Informed Consent

• Must include the purpose of the images, benefits, risks, and the person who will be exposing and interpreting the images.

Negligence

• Occurs when the diagnosis made or the dental treatment delivered falls below the standard of care.

Processing Solutions

• The most critical component in film processing quality control is maintaining proper solution strength and levels.
• Change solutions every 3-4 weeks.

Fixer Strength

• Film should be left in full-strength fixer for at least twice the clearing time, typically around 10 minutes.

Uses of Dental Images

• Include detection of:
  • Caries (cavities).
  • Periodontal disease.
  • Abnormalities like cysts or tumors.

Dental Imaging

• Includes intraoral and extraoral radiographs.

Screens and Cassettes

• Areas of good film-screen contact should appear uniformly dense and clear.

Darkroom Lighting Quality Control Tests

• Light leaks, safelight testing, and equipment maintenance.