Dental Radiology Chapter 3: Radiation Biology
Questions and Answers| Latest Update
Response of a cell to radiation exposure is determined by: -Mitotic activity (Cells that
divide frequently or undergo many divisions over time are more sensitive to radiation)
-Cell differentiation (Cells that are immature or are not highly specialized are more sensitive to
radiation)
-Cell Metabolism (Cells that have a higher metabolism are more sensitive to radiation)
Cells that are radiosensitive include -Blood cells
-Immature reproductive cells
-Young bone cells
Cell that is most sensitive to radiation -Small lymphocyte
Radioresistant cells include -Cells of bone, muscle, and nerve
Radiation Effects on Tissues and Cells -Cells are organized into larger functioning units of
tissues and organs
-Tissues and organs also vary in their sensitivity to radiation
Radiosensitive organs are composed of... -Radiosensitive cells
-Include lymphoid tissues, bone marrow, testes, and intestines
-Examples of radioresistant tissues include the: Salivary glands, kidney, and liver
In dentistry, some tissues and organs are designated as "critical" because... -They are
exposed to more radiation than are others during imaging procedures
,Tissue and Organ Sensitivity to Radiation: -Radiosensitive Tissues:
-Small lymphocyte: High
-Bone marrow: High
-Reproductive cells: High
-Intestinal mucosa: High
-Skin: Fairly high
-Lens of eye: High
-Oral Mucosa: Fairly high
-Radioresistant Tissues or Organs:
-Muscle tissue: Low
-Nerve tissue: Low
-Mature bone and cartilage: Fairly low
-Salivary gland: Fairly low
-Thyroid gland: Fairly low
-Kidney: Fairly low
-Liver: Fairly low
Critical Organ -If damaged, diminishes the quality of a person's life
Critical Organs exposed during dental imagine procedures in the head and neck region -
Thyroid gland
-Bone marrow
-Skin
-Lens of the eye
Radiation Measurements (Units of Measurement) -Used to define 3 quantities of
Radiation:
-Exposure
, -Dose
-Dose Equivalent
Two systems used to define radiation measurements -Traditional (Standard) System
-SI System (International System of Units)
Traditional Units of Radiation Measurement -Roentgen (R)
-Radiation absorbed dose (rad)
-Roentgen equivalent (in) man (rem)
SI Units of Radiation Measurement -Coulombs/kilogram (C/kg)
-Gray (Gy)
-Sievert (Sv)
Exposure Measurement -Exposure: The measurement of ionization in air produced by x-
rays
Traditional unit of exposure for x-rays -Roentgen (R)
-Way of measuring radiation exposure by determining the amount of ionization that occurs in
air
Roentgen -The quantity of x-radiation or gamma radiation that produces an electrical
charge of 2.58x10^-4 coulombs in a kilogram of air at standard temperature and pressure (STP)
conditions
-In measuring the roentgen, a known volume of air is irradiated
-Interaction of x-ray photons with air molecules results in ionization, or formation of ions
-Ions (Electrical charges) that are produced are collected and measured
Questions and Answers| Latest Update
Response of a cell to radiation exposure is determined by: -Mitotic activity (Cells that
divide frequently or undergo many divisions over time are more sensitive to radiation)
-Cell differentiation (Cells that are immature or are not highly specialized are more sensitive to
radiation)
-Cell Metabolism (Cells that have a higher metabolism are more sensitive to radiation)
Cells that are radiosensitive include -Blood cells
-Immature reproductive cells
-Young bone cells
Cell that is most sensitive to radiation -Small lymphocyte
Radioresistant cells include -Cells of bone, muscle, and nerve
Radiation Effects on Tissues and Cells -Cells are organized into larger functioning units of
tissues and organs
-Tissues and organs also vary in their sensitivity to radiation
Radiosensitive organs are composed of... -Radiosensitive cells
-Include lymphoid tissues, bone marrow, testes, and intestines
-Examples of radioresistant tissues include the: Salivary glands, kidney, and liver
In dentistry, some tissues and organs are designated as "critical" because... -They are
exposed to more radiation than are others during imaging procedures
,Tissue and Organ Sensitivity to Radiation: -Radiosensitive Tissues:
-Small lymphocyte: High
-Bone marrow: High
-Reproductive cells: High
-Intestinal mucosa: High
-Skin: Fairly high
-Lens of eye: High
-Oral Mucosa: Fairly high
-Radioresistant Tissues or Organs:
-Muscle tissue: Low
-Nerve tissue: Low
-Mature bone and cartilage: Fairly low
-Salivary gland: Fairly low
-Thyroid gland: Fairly low
-Kidney: Fairly low
-Liver: Fairly low
Critical Organ -If damaged, diminishes the quality of a person's life
Critical Organs exposed during dental imagine procedures in the head and neck region -
Thyroid gland
-Bone marrow
-Skin
-Lens of the eye
Radiation Measurements (Units of Measurement) -Used to define 3 quantities of
Radiation:
-Exposure
, -Dose
-Dose Equivalent
Two systems used to define radiation measurements -Traditional (Standard) System
-SI System (International System of Units)
Traditional Units of Radiation Measurement -Roentgen (R)
-Radiation absorbed dose (rad)
-Roentgen equivalent (in) man (rem)
SI Units of Radiation Measurement -Coulombs/kilogram (C/kg)
-Gray (Gy)
-Sievert (Sv)
Exposure Measurement -Exposure: The measurement of ionization in air produced by x-
rays
Traditional unit of exposure for x-rays -Roentgen (R)
-Way of measuring radiation exposure by determining the amount of ionization that occurs in
air
Roentgen -The quantity of x-radiation or gamma radiation that produces an electrical
charge of 2.58x10^-4 coulombs in a kilogram of air at standard temperature and pressure (STP)
conditions
-In measuring the roentgen, a known volume of air is irradiated
-Interaction of x-ray photons with air molecules results in ionization, or formation of ions
-Ions (Electrical charges) that are produced are collected and measured
