Radiological Exposures Flashcards Preview

FDM and CBRNE > Radiological Exposures > Flashcards

Flashcards in Radiological Exposures Deck (57):

What is Radiation?

  • Radiation is energy travelling through space
  • Sunshine is one of the most familiar forms of radiation. It delivers light, heat and suntans.
  • Beyond ultraviolet radiation fom the sun are higher-energy kinds of radiation which are used in medicine and which we all get low doses from space, air, earth and rocks.


What is Ionizing Radiation?

  • Energy emitted from a source is generally referred to as radiation.
  • Examples include heat or light from the sun, microwaves from an oven
  • Ionizing radiation is radiation with enough energy so that during an interaction with an atom, it can remove tightly bound electrons from the orbit of an atom, causing the atom to become charged or ionized.


Ionizing radiation

Any electromagnetic or particulate radiation capable of produciing ions, either directly or indirectly, by interaction with matter.


When ionizing radiation comes in contact with biological tissue, it is absorbed or slowed down and causes harm by transferring its energy to the tissues.


Where does Ionizing Radiation come from?


  • Atoms that spontaneously undergo radioactive decay
  • Emit radiation upon decay
  • Characterized by mode of decay and half-life
  • Always "on"


  • Electron and x-ray sources
  • Can be switched on and off


What is Electromagnetic Ionizing radiation?

  • Radiation that has no mass
  • X-rays and Gamma Rays
  • Less than 14 electron volts


Nonionizing radiation

Lasers, microwaves, and radio-frequency radiation does not create ions or charge particles



Radioactive forms of elements are called radionuclides. Some occur naturally in the environment, while others are man-made, either deliberately or as byproducts of nuclear reactions.


Americium - 241

  • Americium is a man-made radioactive metal that is solid under normal conditions. It is produced when plutonium absorbs neutrons in nuclear reactors.

A image thumb

Americium in the Environment



  • Am-241 is found in the environment in the form of microscopic dust
    • Americium deposits particles in the soil and water. Small particles in air can travel far from the release site.


Americium-241 Sources

  • Some smoke detectors contain very small amounts of Am-241.
  • Small amounts are found in the soil, plants and water from nuclear weapons testing.




Health Effects

  • Primarily an alpha emitter, but also emits some gamma rays.
  • It poses a more significant risk if ingested, swallowed or inhaled.


Cesium 137

Q image thumb

Cesium is a soft, flexible, silvery-white metal that becomes liquid near room temperature, but easily bonds with chlorides to create a crystalline powder.


The most common radioactive form of cesium is Cs-137 is produced by nuclear fission for use in medical devices and gauges. It is also one of the byproducts of nuclear fission processes in nuclear reactors and nuclear weapons testing.

A image thumb

Cesium 137 in the Environment

  • Cesium 137 bonds to chlorides to make a crystalline poweder, it reacts in the environment like table salt (sodium chloride):
    • Moves easily through the air
    • Dissolves easily in water
    • Binds strongly to soil and concrete


Cesium Sources


Where is it found?

  • Medical radiation therapy devices for treating cancer
  • Industrial gauges that detect the flow of liquid through pipes
  • Other industrial devices that measure thickness of materials


Cesium Health Effects

  • External exposure to large amounts of Cs-137 can cause burns, acute radiation sickness.
  • Increases the risk of cancer because of high-energy gamma radiation.
  • Internal exposure through ingestion or inhalation allows the radioactive material to be distributed in the soft tissues.



Wireless Information Systems for Emergency Responders (WISER)

  • WISER gathers chemical, biological and radiological information from a lot of sources including the National Library of Medicines Hazardous Substances Data Bank, known as the HSDB, CHEMM and REMM resources



Chemical Hazards Emergency Medical Management (CHEMM)

  • Content produced by the US Department of Health and Human Services for prepardeness and response, CBRNE Branch.



Radiation Emergency Medical Management


Sources of Exposure to Ionizing Radiation


  • 200 mrem

Medical exposures

  • 50 mrem

Internal radioactivity

  • 40 mrem

Cosmic rays

  • 30 mrem

Terrestrial radiation

  • 30 mrem

Other Soures

Total = 360 mrem


Alpha Particle

  • Does not travel far
  • Can be stopped by a piece of paper
  • Will transfer energy to the piece of paper
  • Outside the human body generally poses no risk to EMAT team members

Risk of Alpha

  • If you inhale, ingest or absorb radioactive atoms that give off alpha particles as they decay then internal contamination occurs.
  • Causes cellular damage
  • Transfers energy to atoms and molecules in the persons body causing ionization


Beta Particle

  • More penetrating than alpha particle. Will go through a sheet of paper or clothing
  • Travels further than an alpha particle
  • Can penetrate several millimeters into body


Gamma Rays


  • Electromagnetic ionizing radiation
  • Have no mass which means they are more penetrating
  • Easily gets into the body
  • Will penetrate through metals even lead


Why is PPE for Radiolgoical response

  • Protect workers from internal contamination
    • Prevents inhalation, absorption and ingestion of radiation particulate


External Irradiaton

  • Radiation source is outside the body
  • Most risk from x-rays or gamma-rays
  • Are able to penetrate into the body


Internal Irradiation

  • Radiation source is inside the body
  • Most risk from alpha and beta particles
    • Deposit a lot of enery over short distances (less than a mm)
    • Cellular damage



  • Atoms decaying per unit of time
  • Curie (Ci) = 3.7 x 1010 disintegrations per second (dps)
  • Bequerrel (Bq) = 1 dps

Half-live = time for half the radioactivity to decay


Units of Radiation "Dose"

  • Roentgen (R) - measure of exposure to x-rays or gamma rays
  • Radiation absorbed dose (rad) - measure of dose in tissues - 1 Gray = 100 rad
  • Rad equivalent man (rem) - measure of dose, corrected for effectiveness of the radiation - 1 Sievert = 100 rem


What is Radiation Exposure?

Exposure = Intensity x Time

  • Intensity is proporational to activity
  • Exposure is proportional to time

Exposure is proportionao to 1/distance2 from the source

  • If you double your distance away from the radiation source you only get 1/4 the exposure
  • If you triple your distance away from the radiation source you only get 1/9 the exposure


What are the adverse health effects of ionizing radiation?


  • Random process
  • Risk is function of dose
  • No threshold

All other health effects

  • Deterministic processes
  • Severity is a function of dose
  • Threshold usually exists


Acute Ionizing Radiation Effects

Deterministic effects

  • Prodromal syndrome: 75 rad
  • Bone Marrow (or Hematopoietic) syndrome 70 - 1000 rad
  • Gastrointestinal syndrome: > 1000 rad
  • Central nervous system syndrome: > 5000 rad
  • Approx 50% fatality: 400 rad
  • Near 100% fatality: 600 - 1000 rad



Delayed Ionizing Radiation Effects

Both random and deterministic effects

  • Random: cancer, genetic changes
  • Burns, cataract formation: 200 rem threshold
  • Growth and mental retardation (in utero irradiation): 5 rem threshold


Radiation Effects

Skin Changes

  • 300 rem : epilation in 2 - 3 weeks
  • 1000 rem: erthema in hours to weeks
  • 2000 rem: moist desquamation, ulceration
  • 2500 rem: ulceration
  • 3000 rem: blistering necrosis at 3 weeks


What are Lymphocytes?

  • One of several different types of white blood cells
  • 25 percent of new lymphocytes remain in bone marrow and become B cells
  • 75 percent of new lymphocytes go to thymus gland and become T cells


What is the role of B cell Lmphocytes?

  • B lymphocytes recognize antigens and become plasma cells that produce antibodies to fight them.


Radiation and Risk Perception

Radiation has all of the characteristics that increase perceived risk:

  • Involuntary exposure
  • Exposure not known to us (radiation cant't be sensed)
  • No benefit from the exposure
  • Usually delayed consequences
  • Potentially fatal consequences


What is the goal of radiation protection?


How do you measure what is an acceptable cold zone

Evacuate to Cold Zone

  • 10 mR/h
  • 60 000 dpm/cm2 beta amd gamma surface
  • 6 000 dpm/cm2 alpha surface contamination


Decision Dose

  • 50 rad to emergency responders
  • Triggers decision on whether to withdraw an emergency responder from within or near (but outside) the inner perimeter during the early phase of response.
  • Triggers decision on whether to withdraw an emergency responder from within the outer perimeter after prolonged activities


Acute Radiation Syndrome


Prodromal Signs

  • Earliest clinical sign = nausea and vomiting (at 75 rad)
  • Remove victims (including first responders who become victims) from the inner perimeter


What are the four important Dirty Bomb Radionuclides


  • Therapy, research, industrial radiography, food irradiation


  • research, industrial radiography, irradiators


  • therapy, industrial radiography


  • Industrial radiography


What is the purpose of medical countermeasures for radiation?

  • Block the uptake of radioactive material
  • Speed up the removal of internal contamination
  • Help the body recover from radiation exposure


What is the difference between a "dirty bomb" and an "improvised nuclear device" (IND)

Dirty Bomb

  • Uses conventional explosives to spead radioactive material
  • Fraction of the explosive power of an IND

Improvised Nuclear Device (IND)

  • Physical damage from heat and blast
  • Intense radiation at the moment of explosion
  • Radioactive fallout


Name 3 examples of isotopes that emit alpha radiation.

  • Americium-241 used in smoke detectors
  • All isotopes of uranium, whether natural, depleted or enriched
  • Polonium-210 used for anti-static devices


Name 3 examples of isotopes that emit beta radiation.

  • Tritium used in unpowered light sources in exit signs, compasses, gun sights
  • Strontium-90 used in eye therapy devices and thermo-generators
  • Iodine-131 used in nuclear medicine for diagnostic procedures


Name 3 examples of isotopes that emit gamma radiation.

  • Colbalt-60 used in cancer therapy, industrial raiography, food irradiators
  • Iridium-192 used in industrial radiography
  • Cescium-137 used in blood irradiators



The strength of a radioactive source is characterized by its activity, defined as the number of atoms per second undergoing radioactive decay.




"Radiological Half-life"

The rate at which a radioactive material decays is characterized by its half-life, defined as the time required for one half of its atoms to undergo radioactive decay (ie colbalt-60 has a half-life of 5.3 years).


After two half-lives, only one quarter of the radioactive atoms will remain; after 3 half-lives, one-eigth.


"Absorbed Dose"

The degree of radiation damage to an organ or tissue is directly related to the amount of radiation energy deposited in that tissue.


The basic quantity in radiation dosimetry is the absorbed dose, measured in units of gray.


A dose of one gray corresponds to one joule of energy deposited per kilogram of material (tissue).


"Equivalent Dose"

Some types of radiation are more effective at producing biological effects than others, even for the same absorbed dose in gray.

Weighting fractor

  •  1 for beta and gamma radiation
  • 20 for alpha radiation
  • 2.5 - 20 for neutrons depending on the energy

The SI unit for equivalent dose is the sievert (Sv)


"Acute Radiation Syndrome"



Is an acute illness caused by irradiation of the entire body (or most of the body) by a high dose of penetrating radiation (exceeding aboiut 1 Gy).


The syndrome usually begins within the first few hours or days following exposure, depending on the dose received.


Symptoms within minutes if greater than 10 Gy



Acute Radiation Syndrome



  • Decrease in blodd cell counts
  • Gastro-intestinal symptoms
  • Fever
  • Infections
  • Bleeding
  • Hair loss
  • Central Nervous system disorder


What is considered a lethal radiation dose in 50% of the population?

3.5 to 4.5 Gy


One half of the population will not survive beyond 30 days without treatment


Cutaneous Radiation Syndrome

Significant contamination with beta-emitting radioactive materials as well as exposure of the skin to X-ray or gamma radiation can lead to severe burns.


What are the three cardinal prinicples of radiation protection?

Justification: Any decision that alters radiation exposure situation should do more good than harm.

Optimization of Protection: The likelihood of incurring exposure, the number of people exposed, and the magnitude of their individual doses should all be kept as low as achievable.

Application of Dose Limits: The total dose to any individual from regulated sources in planned exposure situations other than medical exposure of patients should not exceed the appropriate limits specified by the ICRP. 



What are the dose limits for radiation protection


International Commission on Radiological Protection

​Radiation Workers

  • 50 mSv in any one year
  • Not more than 100 mSv in a 5 year period.

​General Public

  • 1 mSv per year from all licensed applications of radiation


What is the effective dose limit in emergencies?


500 mSv




Personal Dosimeters

Used to measure radiation dose of externally exposed individuals. They are used for detecting changes in readiation levels in the workplace and to provide information in case of accidental exposures.



Thermo-Luminescent Dosimeters (TLDs) consists of a detector which, when heated after an exposure to radiation, gives off light in proportion to the dose received