Study Notes for Radiation Biology and Protection test 2

Review Test 2

  • Contains questions focusing on the topics of Radiation Biology and Radiation Protection.
    • Number of questions: 57
    • Relevant Chapters:
    • Chapter 3: Radiation Biology (PPT Week 3)
    • Chapter 4: Radiation Protection (PPT Week 4)

Radiographic Techniques

  • Key concepts include the understanding of different types of radiographs:

    • Maxillary Periapicals (PAs)
    • Anterior
    • Posterior
    • Mandibular PAs
    • Anterior
    • Posterior
    • Bitewings
    • Anterior
    • Posterior

  • Study the visibility of different anatomical landmarks in various types of radiographs (PPT week 4).

Theories of Tissue Damage from Radiation

Direct vs. Indirect Theory of Tissue Damage

  • Direct Theory: Photons directly damage critical cellular components.
  • Indirect Theory: Active free radicals or ions are created during the interaction of photons with water inside cells.
    • Results in the formation of hydrogen peroxide, a toxin that can damage cells.

Concepts Related to Radiation Effects

  • Ionization: The process through which atoms gain or lose electrons, becoming ionized.
  • Stochastic Effects: This refers to effects such as cancer, which are related to the probability of occurrence rather than severity. These effects do not have a threshold level of exposure.
  • Non-Stochastic Effects: Effects such as erythema or burns, which require a certain threshold level of exposure to occur.
  • Dose Response Curve: Used to illustrate the relationship between the dose of radiation and the observed health effects.
  • Cumulative Effects: Refers to the total biological damage as a result of multiple exposures over time.
  • Somatic Effects vs. Genetic Effects:
    • Somatic effects affect the individual, while genetic effects can affect descendants.

Radiosensitivity of Tissues

Highly Radiosensitive Tissues

  • Bone marrow (blood tissues, small lymphocytes)
  • Reproductive tissues
  • Lymphatic tissues
  • Intestinal mucosa
  • Skin
  • Mucous membranes
  • Lens of the eye

Less Radiosensitive Tissues

  • Nerve tissue
  • Mature skeletal tissue
  • Heart muscle
  • Thyroid, kidney, liver (medium sensitivity)

Factors Influencing Cell Sensitivity

  • Mitotic Activity: Rapidly dividing cells are more sensitive to radiation.
  • Metabolism: Cells with high metabolic activity exhibit higher sensitivity.
  • Cell Differentiation: Immature (undifferentiated) cells are more sensitive to radiation damage than mature cells.

Units of Measurement in Radiation

Measurement TypeTraditional UnitSI Unit
Exposure in AirRoentgenNone
Absorbed DoseRADGray (Gr)
Dose EquivalentREMSievert (Sv)

Maximum Permissible Dose (MPD)

  • Occupational exposure limit:

    • Traditional: 5 rem/year (5000 mrem)
    • SI: 0.05 Sv/year (50 mSv)

  • Non-occupational exposure limit:

    • Traditional: 0.1 rem/year (100 mrem)
    • SI: 0.001 Sv/year (1 mSv)

  • Note: 1 mSv is approximately equivalent to occupational exposure of 1 mSv per week.

  • Milli: Represents 1/1000 (hence, move the decimal point three places).

Radiation Effects

Types of Responses

  • Non-threshold Response:
    • Characterized as linear on a graph indicating increased risk with exposure.
    • Suggests all radiation exposure is harmful.
  • Threshold Response:
    • Exhibits a non-linear graph; indicates that effects manifest only after a certain exposure level has been reached.

Non-Stochastic Effects

  • Visible, occur at a certain exposure threshold.
  • Examples of effects:
    • Loss of hair
    • Cataracts
    • Radiation sickness
    • Fetal death
    • Decreased fertility
  • Earliest sign: Erythema, which is redness of the skin.
  • Important to note: below a certain level of radiation, these effects will not manifest.
  • Latent Period: The time between exposure to radiation and the first detectable effects.

Stochastic Effects

  • The likelihood of occurrence increases with dose.
  • No threshold for these effects (non-threshold).
  • Potential outcomes include:
    • Genetic mutations
    • Leukemia
    • Cancer
  • Graph representation is linear; risk increases with increased dose.

Law of Bergonie and Tribondeau

  • States: “The damage from radiation is inversely proportional to cell differentiation.”
  • This means that:
    • Tissues that are more easily harmed by radiation have:
    • More undifferentiated cells (immature).
    • More mitotic activity (multiplication occurring).
    • Longer active proliferation phases.

Landmarks and Radiographic Identification

  • Key dental landmarks to recognize, which are often included on tests:
    • Maxillary:
    • Anterior nasal spine
    • Mandibular foramen
    • External oblique ridge
    • Mandibular:
    • Internal oblique ridge
    • Mental foramen
    • Lingual foramen

Dental Anatomy Radiographic Identifiers

  • Common identifiers in tooth anatomy:

    • A = Amalgam
    • E = Enamel
    • D = Dentin
    • B = Bone crest
    • CH = Pulp chamber
    • PL = Periodontal ligament
    • L = Lamina dura (radio-opaque)
    • T = Trabeculation
    • R = Root apex
    • C = Canal

  • Bone types:

    • Cortical bone: Highly radiopaque
    • Cancellous bone: Predominantly radiolucent.

Final Study Tips

  • Ensure familiarity with the structures, knowing which are radiolucent and which are radiopaque.

  • Review the photos emphasizing the distinctions between both categories.

  • Take quizzes to reinforce knowledge for chapters 3 and 4.

  • Manage study time effectively to assure comprehensive preparation.

  • Remember: "YOU'VE GOT THIS!"