Radiation Protection

What year did Wilhelm Roentgent discover x-rays?

1895

What year did Clarence Dally become the 1st American Radiation fatality?

1904

When did Skin Erythema start being used for measurement?

1900 to 1930

What year did the ICRU (International Commission on Radiation Units and Measurements) use R for Roentgen?

1925

When was the Roentgen redefined to make it more accurate?

1962

What year did the international system of units (SI units) adopted?

1980

Radiographer responsibility?

Patient protection by avoiding repeats and utilizing ALARA concept

Radiologist/physician responsibility

Protect patient from ordering unnecessary exams

Safe use of radiation determines

if the extent of an injury outweighs the risk involved with radiation

Occupational exposure

Exposure from workplace

Medical exposure

Exposure from medical diagnosis/treatment

Public exposure

exposure from natural resources (not occupational or medical)

Radiation exposure

transfer of radiation energy through photon tissue interactions

Ionization

ability to remove electrons from atoms

Ionization in human cells results in (5)

Unstable atoms

Free electrons

Production of low energy x-rays

Formation of new molecules (harmful to cell)

Cell damage

Somatic

Radiation damage to “self”

Genetic

Radiation damage to germ cell’s genetic code (potential effect on future generations)

Sources of ionizing radiation (2)

Natural background radiation and Man made (artificial radiation)

Natural background radiation (82% of human exposure)

contained in the environment

(Cosmic, Terrestrial, Internal)

Natural background radiation (Internal)

Comes from human body

Natural background radiation (Terrestrial)

Comes from radioactive minerals like uranium and radium

Natural background radiation (Cosmic)

Comes from star

1 flight =

1 mrem per hour of flight

Artificial radiation (18% of huma exposure)

Made by humans

Photon- tissue interaction types (5)

Simple

Compton

Photoelectric

Pair production

Photodisintegration

Simple interaction AKA

Coherent

classical

simple scatter

Thompsons scatter

Simple interactions are produced by

low energy xray photon

Simple interactions excite electrons but

does not remove them

Simple interactions are of ______ image use

No image use

Compton interaction AKA

Compton scattering

Incoherent

Modified scattering

Compton interactions occur from

Photon striking outer shell electron that is loosely bound

Compton interactions are most dangerous to

Radiographer

Photoelectric interaction AKA

Photoelectric absorption

Photoelectric effect

In photoelectric interaction incoming photon interacts with

K shell (inner shell)

In photoelectric interaction the hole in K shell is filled by

electrons from outer shell causing characteristic photons

Photoelectric interaction is more dangerous for

patient

Pair production produced at photon energies above 1.2 Mev (does not occur in diagnostic radiography) involves

Interaction with incoming photon and atomic nucleus

Photodisintegration (Does not occur in diagnostic rad) are produced at photon energies

10 Mev and above

What are the 2 most common interactions in diagnostic imaging

Compton

Photoelectric

Compton results in:

scattering, partial absorption and is the source of exposure to rad

Photoelectric results in:

Complete absorption, produces image contrast and is source of major patient exposure

Grenz Rays are part of the:

electromagnetic spectrum comprising of low energy

Grenz rays range:

10 to 20 kVp

Grenz rays are low energy rays used to cure

Skin disease

Units of radiation measurement (6):

Traditional

International System of Units (SI)

Radiation exposure in Air

Unit of absorbed dose

Unit of Equivalent dose

Radioactivity

Roentgen (R) unit for measuring

amount of gamma x-rays in air

RAD (radiation absorbed dose) unit of measuring

absorbed energy from radiation

REM (Radiation equivalent man)

Unit for measuring biological damage from radiation

Curie unit of measuring

radiation activity

Coulomb/Kilogram (C/Kg) measuring

amount of gamma x-rays in air

Gray (Gy) measuring

absorbed energy from radiation

Sievert (Sv) measuring

biological damage from radiation

Becquerel measuring

radiation activity

Conversion from traditional to SI:

Divide by 100

Conversion from SI to traditional

Multiply by 100

1 R (Roentgen) =

1 R (Roentgen) = 2.58 × 10^-4 C/Kg

1 Gray=

1 Joule of energy deposited per kilogram of tissue

1 Gray also equals

100 RADs

Dose Equivalent=

absorbed dose x quality factor (type of radiation value)

1 Sv=

100 Rem

a radiation weighting factor (WR) is used to

modify absorbed dose to account for damage by different types of radiation

WR (weighting factor) takes into account LET (Linear energy transfer):

Amount of energy transferred per unit length of tissue traveled

What rays have low LET?

X-ray and Gamma rays

What rays have high LET?

Alpha/ Beta and Neurons (cause more biological damage)

Effective dose=

Absorbed dose x QF (quality factor) x WR (Weighting factor)