Chapter 4: Radiation Quantities & Units

how much radiation is too much & how to protect

after realizing effects of radiation are bad they needed to figure out 2 things?

1900-1910

when did they realized effects of radiation are bad?

needed to develop standards for measuring and limiting radiation exposure, for awareness, desire, and reasons*

November 8, 1895

when was the discovery of x-rays?

Wilhelm Conrad Roentgen, University of Wurzburg, in Bavaria

who discovered x-rays and where?

Crookes, barium platinocyanide

x-rays were discovered using ___ tube & paper coated with ___

1896

when were x-rays discovered in America?

X

called x-rays because you solve for ___ in math and people didn’t know what they were

Wilhelm’s wifes hand with a ring

what was the 1st x-ray image of?

Clarence Madison Dally

who was the first American Radiation Fatality?

Clarence Madison Dally

American glass blower and tube maker and long time friend of Thomas Edison, 1st American person to die due to ionizing radiation at 39 years old, left arm amputated (skin lesions)

Thomas Edison

who discovered the fluoroscope?

first reports of injury due to radiation

examples are Somatic damage, Result of excessive occupational radiation exposure for early pioneers and excessive exposure of patients, Radiodermatitis, Cancer, Blood disorders

Somatic Damage

person who received the radiation is the person with the negative effects

1910

when was the 1st cancer death of a physician due to work and exposure to radiation

physicians and dentists

___ & ___ got skin lesions

radiologist

early ___ got blood disorders

Medical

___ community was alarmed by the increasing number of radiation injuries reported

British X-ray, Radium Protection Committee, 1921

Creation of the ___ and ___ in ___ to learn how to measure and control radiation

skin erythema dose

first unit used to measure radiation exposure, problems encountered, need to find a more reliable unit

skin erythema dose

quantity of radiation that causes diffuse redness over an area of skin SHORTLY after radiation exposure (unethical and unreliable)

all had the same goal

• First International Congress of Radiology, London, England, 1925

• International Commission of Radiation Units and Measurements (ICRU) formed in 1925

• Second International Congress of Radiology, Stockholm, Sweden, 1928

• National Council on Radiation Protection (NCRP)

what do these all have in common?

National Council on Radiation Protection (NCRP)

nonprofit, private, non-government organization that is responsible for radiation protection in U.S. (send out reports)

report 116

lists all of our occupational dose limits

tissue reactions & stochastic effects

what are the 2 categories of effects of radiation?

early, late

tissue reactions have ___ and ___ effects

early tissue reactions

reactions are nausea, fatigue, hair loss, skin reddening

late tissue reactions

reactions are cataracts, reduced fertility, organ atrophy

Stochastic Effects

reactions are cancer and genetic effects (hereditary or passed onto offspring)

always late (months/years)

Stochastic effects are always early or late?

threshold dose

up to this amount of radiation, not biological effects (don’t use anymore)

tolerance dose

how much radiation can they experience before any harmful effects (don’t use anymore)

1950s

Tolerance dose replaced by MPD in early ___s

1970s

Dose limits were calculated and established in the ___s to ensure that the risk from radiation exposure acquired on the job did not exceed risks encountered in “safe” occupations

1980

ICRU adopted SI units for use with ionizing radiation in ___

1985

NCRP adopted SI units for use in ___

1991

ICRP adopted the term, “effective dose”, in ___

no

___ dose is safe, lots of committees and works to get where we are today

• Roentgen (R)

• Coulombs per kilogram (C/kg)

exposure old and new unit of measure?

• Rad

• Gray (Gy) or (subunits)

Absorbed dose (D) old and new unit of measure?

• Rem

• Sievert (Sv)

Equivalent dose (EqD) old and new unit of measure?

• Rem

• Sievert (Sv)

Effective Dose (EfD) old and new unit of measure?

J/Kg

Air kerma unit of measure?

Exposure (X)

• The total amount of ionization (charge) an x-ray beam produces in a known mass of air, determines intensity of radiation

• SI unit:

– C/kg

– Coulomb/kilogram

Air Kerma

• SI quantity used to express how much energy is transferred from a beam of radiation to a material such as the patient’s skin.

  • Denotes a calculation of radiation intensity in air

  • Replacing quantity of exposure

  • Unit: Joules/Kilogram or J/Kg

Dose Area Product (DAP)

• Is the sum of air kerma over the exposed area of the patient’s surface

  • The entire amount of energy delivered to a patient by the x-ray beam

  • Is usually specified in units of mGy-cm2

Dose Area Product (DAP)

estimates total amount of energy delivered to patient while taking into account size of x-ray beam (area of tissue), dose over an area

Absorbed Dose (D)

• Deposit of radiation energy/unit mass by ionizing radiation

  • SI Unit: Gray (Gy)

  • Subunits

• – Gy x 100 = cGy (centi)

– Gy x 1000 = mGy (milli)

– Gy x 1,000,000 = μGy (micro)

Absorbed Dose (D)

how much energy being deposited into tissue, shows us how much and what biological damage is happening

1. Atomic number (Z)

2. Mass density of the tissue

3. Energy of the incident photon

The amount of energy absorbed by a structure depends on what 3 things?

higher

the ___ the atomic number and higher the mass density, the more absorption

lower

the ___ the energy of photon the more absorption

less

higher the energy, the ___ dose

absorb more

do these absorb more or less?

• bones & teeth

absorb less

do these absorb more or less?

• fat, air, muscles

absorbed dose (D)

amount of energy absorbed by a structure

dose equivalence

• Equal absorbed doses of different types of radiation produce different amounts of biologic damage in body tissue.

• This concept takes this biologic impact into consideration by using a specific modifying, or quality, factor to adjust the absorbed dose value (# assigned to tissues based on how sensitive to radiation)

#1, #20

dose equivalence has a # assigned to tissues based on how sensitive to radiation

ex:

x-ray = #___

particulate radiation = #___

the higher the number the more damaging the radiation

Equivalent Dose (EqD)

• Is the product of the average absorbed dose in a tissue or organ in the human body and its associated WR chosen for the type and energy of the radiation in question.

  • SI Unit: Sievert (Sv) or Millisievert (mSv)

Effective Dose (EfD)

Overall risk of exposure to humans from ionizing radiation.

1. Type of radiation

2. Tissue weight factors (WT)

3. Radiation weight factors (WR)

• SI Unit: Sieverts (Sv) or Millisieverts (mSv)

Collective EfD (ColEfD)

• Radiation exposure to a group or population

  • SI Unit: person-sievert

Total Effective Dose Equivalent (TEDE)

• Radiation dosimetry quantity that was defined by the Nuclear Regulatory Commission (NRC) to monitor and control human exposure to ionizing radiation (combing external & internal radiation, overall radiation exposure)

• Takes into account all possible sources of exposure

• Nuclear medicine technologists and interventional radiologists