DEN 130 1 H - Dental Radiology- 38

FOUNDATIONS OF RADIOGRAPHY, RADIOGRAPHIC EQUIPMENT, AND RADIATION SAFETY

LEARNING OBJECTIVES (LESSON 38.1)

  • Radiation Physics, Parts of the Dental X-ray Machine, and Production of X-ray Images   - Key Terms: Pronounce, define, and spell key terms related to dental radiography.   - Uses of Dental Imaging: Describe the uses of dental imaging in clinical practice.   - Discovery of X-radiation: Discuss historical advancements and key pioneers in dental radiography.   - Radiation Physics Topics: Explore key concepts, which include:     - What occurs during ionization.     - The properties of x-rays.   - Dental X-ray Machine Components: Identify the components of the dental x-ray machine and the x-ray tube.

INTRODUCTION TO DENTAL IMAGING

  • Role of the Dental Assistant:
      - Importance of understanding dental imaging.   - Enables detection of conditions invisible in the oral cavity.   - Fundamentals of atomic and molecular structure.   - Working knowledge of ionizing radiation and properties of x-rays.

  • Radiation Effects:
      - Radiation produced for dental radiographs can damage living tissues.   - All radiation exposure, regardless of dose, carries potential biological risks.   - Essential to have knowledge of radiation characteristics to minimize exposure.

USES OF DENTAL IMAGES

  • Early Detection and Assessment:
      - Detect dental caries early.   - Identify bone loss in initial stages.   - Locate abnormalities in soft and hard tissues surrounding the teeth.   - Evaluate growth and development of dental structures.   - Provide vital information during procedures like root canal therapy.   - Serve to document a patient's dental condition over time.

DISCOVERY OF X-RADIATION

  • Wilhelm Conrad Roentgen:
      - Discovered x-rays on November 8, 1895.   - Initially referred to as roentgen rays; radiology was known as roentgenology.   - Received numerous honors, including the first Nobel Prize in Physics in 1901.

PIONEERS IN DENTAL RADIOGRAPHY

  • Contributions from Key Individuals:   - Otto Walkhoff: Created the first dental radiograph.   - Dr. C. Edmund Kells: Implemented the first practical radiographs in dentistry in 1896.   - Dr. W.H. Rollins: Pioneer in radiation safety; principles still in practice today.   - Emphasis on progressive improvements in technology for diagnostics.

RADIATION PHYSICS

  • Building Blocks of Matter:
      - Energy and matter are foundational to understanding radiography.   - Atoms: Basic matter form that contains energy.   - Energy Defined: Capacity to perform work.   - Matter Defined: Anything with form that occupies space.

ATOMIC STRUCTURE

  • Components of an Atom:
      - Contains two parts: Central nucleus and orbiting electrons.   - Nucleus composition: Number of protons and neutrons; electron arrangement.   - Stability of electrons disrupted only by x-rays.

NUCLEUS

  • Structure and Function:
      - The central core of an atom made of protons (positive charge) and neutrons (no charge).   - X-rays do not alter the nucleus but can change direction or get scattered;   - They do not render atoms radioactive.

ELECTRONS

  • Characteristics:
      - Negatively charged, tiny particles with negligible mass.   - Orbit in defined paths (electron shells) determined by electric binding energy, akin to gravitational forces.

IONIZATION

  • Process Explained:
      - Photons can dislodge electrons, creating ions that are electrically unbalanced.   - Ions disturb atomic stability leading to potential interactions with tissues.

PROPERTIES OF X-RAYS

  • Nature of X-rays:
      - Form of energy capable of penetrating matter.   - Belong to electromagnetic radiation alongside light waves, radar, etc.   - X-rays travel in photons at light speed with wavelike patterns.   - Key Factor: Shorter wavelengths correlate with higher energy.

COMPONENTS OF THE DENTAL X-RAY MACHINE

  • Essential Parts:
      - Primary Components: Tubehead, extension arm, control panel.

TUBEHEAD

  • Structure and Role:
      - Heavy metal housing that contains the x-ray tube.

COMPONENTS OF THE TUBEHEAD (SLIDE 1 OF 2)

  • Metal Housing:
      - Encases the x-ray tube and filled with insulating oil.

  • X-ray Tube Seal:
      - Made of leaded glass or aluminum; retains oil and filters x-ray beam.

  • Transformer:
      - Alters incoming electrical current voltage to necessary levels.

COMPONENTS OF THE TUBEHEAD (SLIDE 2 OF 2)

  • Aluminum Filter:
      - 0.5 mm thick, filters out weaker x-rays to enhance beam quality.

  • Lead Collimator:
      - Controls the shape and size of the exiting x-ray beam.

  • Position Indicator Device (PID):
      - Open-ended cylinder that aligns the x-ray beam for optimal exposure.

X-RAY TUBE

  • Functionality:
      - Heart of the x-ray generation system.   - Glass construction, approximately 6 inches long and 1 inch in diameter.   - Vacuum maintains controlled electron flow from cathode to anode.

CATHODE

  • Components and Purpose:
      - Contains a tungsten filament in a molybdenum cup.   - Supplies electrons; heating increases electron production.

ANODE

  • Structure and Operation:
      - Composed of a tungsten target in a copper stem for heat dissipation.   - Converts kinetic energy from electrons into x-ray photons.

POSITION INDICATOR DEVICE (PID)

  • Functionality:
      - Aim the x-ray beam accurately at the film in the patient's mouth.   - Available in cylindrical or rectangular shapes.

EXTENSION ARM

  • Construction:
      - Houses wiring between tubehead and control panel, allows tubehead positioning.   - Should never be held during exposure for safety.

CONTROL PANEL

  • Key Features:
      - Master switch, indicator lights, selector buttons, and exposure button.   - Regulatory devices for exposure time, milliamperage, and kilovoltage settings.

MASTER SWITCH AND INDICATOR LIGHTS

  • Operation:
      - Master switch powers the machine on/off.   - Indicator lights show machine status; orange indicates power, red indicates x-ray emission.

EXPOSURE BUTTON AND SELECTOR BUTTONS

  • Functions:
      - Controls electricity flow for x-ray production; exposure time measured in impulses.   - 60 impulses equals 1 second; 30 impulses equals 0.5 seconds.   - Milliamperage (mA) measures current through tungsten filament.   - Kilovoltage peak (kVp) selector influences x-ray beam penetration capability.

X-RAY PRODUCTION (SLIDE 1 OF 3)

  • Process Overview:
      - X-ray machine operation begins when plugged in, leading electric current flow through components.   - Current travels into the cathode filament circuit powered by 3-5 V to heat the filament, leading to thermionic emission.

X-RAY PRODUCTION (SLIDE 2 OF 3)

  • Electron Acceleration:
      - Activation of high-voltage circuit upon exposure button press accelerates electrons from cathode to anode.   - Electrons directed to tungsten target, converting kinetic energy into x-ray energy and heat upon impact.

X-RAY PRODUCTION (SLIDE 3 OF 3)

  • Energy Conversion:
      - Less than 1% of energy produces x-rays while approximately 99% generates heat, dissipated through copper stem and insulating oil.   - X-rays exit through the tubehead seal, aluminum filter, and travel through the collimator.

INTERACTIONS OF X-RAYS WITH MATTER

  • Possible Outcomes of X-ray Contact:
      - No Interaction: Photon passes without absorption.   - Photoelectric Effect: Photon ejects inner shell electron, transferring full energy.   - Compton Scatter: Photon knocks out outer shell electron, losing part of energy.   - Coherent Scatter: Photon scatters without loss of energy.

TYPES OF RADIATION

  • Categories:
      - Primary Radiation: X-rays from the x-ray tube's target (primary beam).   - Secondary Radiation: Result of primary beam interaction with matter.   - Scatter Radiation: A form of secondary radiation deflected during interactions.

RADIOGRAPHY CHARACTERISTICS

  • Radiolucent and Radiopaque:
      - Radiolucent: Structures allowing x-rays to pass, appearing dark (e.g., air spaces).   - Radiopaque: Do not allow x-ray passage, appearing white (e.g., metal).

CHARACTERISTICS OF THE X-RAY BEAM

  • Key Features Needed for Quality Radiography:
      - Quality: Energy or penetrating ability of the x-ray beam.   - Quantity: Number of x-rays produced by the unit.   - Intensity: Combination of quantity and quality factors.

CONTRAST

  • Image Clarity:
      - Ideal contrast highlights whites of metal restorations, blacks of air, and various grays.   - Higher kVp results in lower contrast; lower kVp increases contrast with fewer grayscale shades.

DENSITY

  • Image Darkness:
      - Density indicates radiograph darkness essential for diagnostic clarity.   - Determined primarily by milliampere seconds (mAs) settings.

OTHER FACTORS INFLUENCING DENSITY

  • Influential Elements:
      - Distance from tube to patient, developing time, temperature, and patient body size.

GEOMETRIC CHARACTERISTICS

  • Impact on Radiograph Quality:
      - Sharpness: Image detail and resolution quality.   - Distortion: Size changes due to angulation errors.   - Magnification: Enlargement affecting image portrayals.

LEARNING OBJECTIVES (LESSON 38.2)

  • Focus Areas:
      - Effects of radiation on the human body.   - Measuring radiation.   - Radiation safety practices and the ALARA concept.

RADIATION EFFECTS

  • Health Risks:
      - Ionizing radiation damages living tissues and cells, with effects varying depending on amount and exposure type.   - Despite low dose in dental radiography, risk of biological change exists.

TISSUE DAMAGE: IONIZATION

  • Ionization Risks:
      - Process of electron removal leads to cellular disruption and potential long-lasting effects on living tissues.

BIOLOGIC EFFECTS OF RADIATION

  • Delayed Effects:
      - Changes in chemistry, cells, tissues can take time to manifest, with a latent period before effects are noted.

CUMULATIVE EFFECTS

  • Lifetime Impact:
      - Repeated exposures lead to accumulating tissue damage, not fully reversible, similar to sun exposure.

ACUTE AND CHRONIC RADIATION EXPOSURE

  • Definitions:
      - Acute: Large dose over a short time (e.g., nuclear accident).   - Chronic: Small doses over extended periods, effects may take years to appear.   

GENETIC AND SOMATIC EFFECTS

  • Cellular Impact:
      - Genetic cells: Reproductive cells, damage passed to future generations.   - Somatic cells: Damage localized to the individual; not heritable.

CRITICAL ORGANS

  • Vulnerable Areas:
      - Include skin, thyroid gland, lens of the eye, and bone marrow that are sensitive to radiation damage.

RADIATION MEASUREMENT (SLIDE 1 OF 2)

  • Measurement Systems:
      - Traditional (standard) and modern (Système Internationale - SI) systems used for quantifying radiation exposure.

RADIATION MEASUREMENT (SLIDE 2 OF 2)

  • Measurement Units:
      - Traditional: Roentgen (R), rad, rem.   - SI: Coulombs per kilogram (C/kg), Gray (Gy), Sievert (Sv).

MAXIMUM PERMISSIBLE DOSE

  • Safety Standards:   - Occupational exposure limit set at 5.0 rem/year (0.05 Sv); non-occupational is 0.1 rem/year (0.001 Sv).   - Dental staff should aim for zero operational exposure through strict protocols.

RADIATION SAFETY

  • Considerations:
      - Background radiation from natural and artificial sources.   - Benefits of diagnostic imaging outweigh risks followed by careful protocols.

DENTIST’S RESPONSIBILITIES FOR DENTAL IMAGING

  • Practices and Protocols:
      - Prescribing necessary radiographs, maintaining equipment, ensuring proper training, complying with regulations, and obtaining informed consent.

PROTECTIVE DEVICES

  • Required Equipment:
      - Tubes must include aluminum filters, lead collimators, and PIDs to reduce patient radiation dosage; monitored regularly for safety standards.

ALUMINUM FILTRATION

  • Function:
      - Removes low-energy, non-diagnostic x-rays; regulated to 2.5 mm thickness for machines operating at 70 kVp or more.

COLLIMATOR

  • Purpose:
      - Restricts x-ray beam size to reduce exposure during imaging as per federal regulations.

POSITION INDICATOR DEVICE

  • Usage:
      - Direct x-ray beam; available in varied dimensions for different radiography methods.

PATIENT PROTECTION

  • Mandatory Safety Measures:
      - Lead apron and thyroid collar essential for all patients to minimize exposure to scatter radiation.

FAST-SPEED FILM

  • Efficiency in Imaging:
      - Larger silver bromide crystals allow for quicker imaging; reduces patient exposure significantly.

IMAGE RECEPTOR-HOLDING DEVICES

  • Application:
      - Keeps patient's fingers away from radiation; stabilizes film/sensor position.

EXPOSURE FACTOR

  • Control Parameters:
      - Key settings include kilovoltage peak (kVp), milliamperage, and exposure time to minimize radiation while ensuring diagnostic images.

PROPER TECHNIQUE

  • Importance of Technique:
      - Essential for producing quality images; retakes due to poor technique increase patient exposure.

X-RAYS DURING PREGNANCY

  • Guideline Stance:
      - American Dental Association allows for regular imaging with lead protection, ensuring minimal fetal exposure.

OPERATOR PROTECTION AND MONITORING

  • Chronic Risk Avoidance:
      - Following safety practices ensures occupational exposure is minimized effectively.

RADIATION MONITORING

  • Detection Methods:
      - Utilize film badges, pocket dosimeters, thermoluminescent dosimeters to track exposure.

RULES OF RADIATION PROTECTION

  • Best Practices:
      - Avoid direct line of x-ray beam, utilize barriers when available, stand at right angles if barriers are absent, maintain safe distance of 6 feet during exposure.

EQUIPMENT MONITORING

  • Safety Maintenance:
      - Regular checks for leaks and malfunctions to ensure equipment safety standards.

PEDIATRIC PATIENTS

  • Positioning Protocols:
      - Utilize lead aprons covering both parent and child during exposures when cooperation is limited.

ALARA CONCEPT

  • Principle Definition:
      - As Low As Reasonably Achievable; aims for minimal radiation exposure through comprehensive safety practices.

PATIENT QUESTIONS (SLIDE 1 OF 2)

  • Philosophy of Communication:
      - Prepare for patient inquiries regarding x-ray safety and importance; clear communication builds trust.

PATIENT QUESTIONS (SLIDE 2 OF 2)

  • Reassurance Statements:
      - Address radiograph need based on individual assessments, highlight protective measures and advanced technology to minimize exposure.