Ch1&2

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RAF9059 Consultancy Meeting to
Improve the Radiation Protection
Curriculum for Radiographers
Kelli Welch Haynes, MSRS, RT(R)
United States
IAEA
International Atomic Energy Agency
INTRODUCTION TO RADIATION
PROTECTION
CHAPTER 1 and 2
IAEA
International Atomic Energy Agency
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W HAT A RE X-R AYS ?

A form of ionizing radiation
▬ Ionizing radiation is radiation that
produces positively and negatively charged
particles (ions) when passing through matter
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C ONSEQUENCES OF
I ONIZATION IN H UMAN
C ELLS
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H OW W E C AN S AFELY C ONTROL THE U SE OF
“R ADIANT E NERGY ”

Employ effective methods to eliminate those hazards

Control radiation produced from an x-ray tube and ensure
radiation safety during all medical radiation procedures
▬ Limiting the energy deposited in living tissue by radiation can
reduce the potential for adverse biologic effects
FIGURE 1-1 Radiant energy is emitted from the xray tube in the form of waves (or particles). This
manmade energy can be controlled
by the selection of equipment components and
devices made for this purpose and by the selection
of appropriate technical exposure factors
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EFFECTIVE RADIATION
PROTECTION

Ongoing responsibility of diagnostic imaging professionals to
ensure radiation safety during all medical radiation procedures

Effective measures employed by radiation workers to
safeguard patients, personnel, and the general public from
unnecessary exposure to ionizing radiation

Unnecessary radiation
▬ Any radiation that does not benefit a person in terms of diagnostic
information obtained for the clinical management of medical needs
▬ Any radiation exposure that does not enhance the quality of the study
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N EED TO S AFEGUARD A GAINST
S IGNIFICANT AND C ONTINUING
R ADIATION E XPOSURE

Based on evidence of harmful biologic effects
▬ Damage to living tissue of animals and humans
exposed to radiation
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J USTIFICATION AND R ESPONSIBILITY
FOR I MAGING P ROCEDURES

Benefit vs. risk
▬ Patient can elect to assume
the relatively small risk of
exposure to ionizing radiation
1. To obtain essential diagnostic
medical information when illness or
injury occurs
2. When a specific imaging
procedure for health screening purposes
is prudent
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R ADIATION E XPOSURE TO THE
G ENERAL P UBLIC

Should always be kept at the lowest possible
level
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D IAGNOSTIC E FFICACY
▬ The degree to which the diagnostic study accurately
reveals the presence or absence of disease in the patient
▬ Provides the basis for determining whether an imaging
procedure or practice is justified
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R ESPONSIBILITY FOR D ETERMINING
N ECESSITY OF A P ROCEDURE FOR THE P T

Referring physician
▬ Accepts basic responsibility for protecting the pt from
unnecessary radiation exposure
▬ Relies on qualified imaging personnel

Radiographer and participating radiologist
▬ Share in keeping pt medical radiation exposure at the
lowest possible level
▬ Ensure that both occupational and nonoccupational
doses remain well below allowable levels
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K EEPING O CCUPATIONAL AND
N ONOCCUPATIONAL D OSES W ELL B ELOW
M AXIMUM A LLOWABLE L EVELS

Use the smallest radiation exposure that will produce useful images

Produce optimal images with the first exposure

Avoid repeat examinations
FIGURE 1-4 A, Posteroanterior chest projection requiring a repeat examination because of multiple external
foreign bodies (several necklaces and an underwire bra) that should have been removed before the x-ray
examination.
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ALARA PRINCIPLE

ALARA
▬ Intention behind these concepts of radiologic practice:
▬ to keep radiation exposure and consequent dose to the
lowest possible level
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R ESPONSIBILITY FOR
M AINTAINING ALARA
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PATIENT PROTECTION AND
PATIENT EDUCATION

Educating patients about imaging procedures helps to ensure the highest quality of
service

Answer questions about the potential risk of radiation exposure honestly

Inform patients of what needs to be done, if anything, as a follow-up to their
examination
(From Radiology and radiation protection: Mosby’s
radiographic instructional series, St Louis, 1999, Mosby.)
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R ISK OF I MAGING P ROCEDURE VS
P OTENTIAL B ENEFIT

Risk (in general terms)
▬ The probability of injury, ailment, or death resulting from an activity

Risk (in the medical industry) with reference to the radiation
sciences
▬ The possibility of inducing a radiogenic cancer or genetic defect after
irradiation

Willingness to accept risk
▬ Perception that the potential benefit to be obtained is greater than the risk
involved
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B ACKGROUND E QUIVALENT R ADIATION
T IME (BERT)

BERT
▬ A method that can be used to reduce patient fears and
anxiety
▬ Compares the amount of radiation received with natural
background radiation received over a given period of time
▬ Based on annual U.S. population exposure of
approximately 3 millisieverts per year (300 millirems per year)
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RADIATION

Energy
▬ Ability to do work

How radiation relates to energy
▬ Radiation refers to energy that passes from one location to
another and can have many manifestations.
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T YPES OF R ADIATION
1.
Mechanical vibration of materials
a. Ultrasound
2.
The electromagnetic wave
a. Radio waves
b. Microwaves
c. Infrared
d. Visible light
e. Ultraviolet
f. X-rays
g. Gamma rays
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E LECTROMAGNETIC WAVES

In electromagnetic waves, electric and magnetic fields fluctuate
rapidly as they travel through space.

Electromagnetic waves are characterized by their
1. Frequency
2. Wavelength

Dual nature of electromagnetic radiation (wave-particle duality)
▬ This form of radiation can travel through space in the form of a wave but can
interact with matter as a particle of energy.
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T HE E LECTROMAGNETIC S PECTRUM

Electromagnetic spectrum
▬ The complete range of frequencies and energies of
electromagnetic radiation (see Table 1-2 in the textbook).
Insert Figure 1-7.
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I ONIZING AND N ONIONIZING
R ADIATION
1.
Ionizing radiation (x-rays, gamma rays, and high-energy)
ultraviolet radiation (energy above 10 eV)
2.
Nonionizing radiation (low energy ultraviolet radiation, visible
light, infrared rays, microwaves, and radio waves)
▬ Nonionizing radiations do not have sufficient kinetic energy to eject
electrons from atoms
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I ONIZING R ADIATION

Conversion of atoms to ions

Electromagnetic radiation with high enough frequency
transfers sufficient energy to orbital electrons to remove them
from the atoms to which they were attached

Has undesirable result of potentially producing some damage
in the biologic material

The amount of energy transferred to electrons in
biologic tissue by ionizing radiation is the basis of the
concept of radiation dose
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PARTICULATE R ADIATION

Form of radiation that includes alpha particles, beta
particles, neutrons, and protons (subatomic particles
that are ejected from atoms at very high speeds)

Possess sufficient kinetic energy to be capable of
causing ionization by direct atomic collision
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A LPHA PARTICLES

Emitted from nuclei of very heavy elements, such as uranium
and plutonium, during the process of radioactive decay

Each contain two protons and two neutrons

Are simply helium nuclei

Have a large mass and a positive charge twice that of an
electron
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A BILITY OF A LPHA PARTICLES TO
P ENETRATE M ATTER

Particulate radiations vary in their ability to penetrate
matter

Alpha particles
1. Are less penetrating than beta particles.
2. Lose energy quickly, travel a short distance in biologic matter, so they are
considered virtually harmless as an external source of radiation.
3. As an internal source of radiation, can be very damaging if emitted from a
radioisotope deposited in the body
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B ETA PARTICLES (B ETA R AYS )

Are identical to high-speed electrons except for their origin

Are 8,000 times lighter than alpha particles and have only one
unit of electrical charge (-1) as compared with the alpha’s two
units of electrical charge (+2)

Will not interact as strongly with their surroundings as alpha
particles do. Capable of penetrating biologic matter to a
greater depth than alpha particles, with far less ionization
along their paths.
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H IGH -S PEED E LECTRONS T HAT A RE
N OT B ETA R ADIATION

Are produced in a radiation oncology treatment
machine called a linear accelerator

Use
▬ To treat superficial skin lesions in small areas
▬ To deliver radiation boost treatments to breast tumors at
tissue depths typically not exceeding 5 to 6 cm
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B ETA R AYS WITH A L ESSER
P ROBABILITY OF I NTERACTION

Can penetrate matter more deeply and therefore
cannot be stopped by an ordinary piece of paper like
an external alpha particle

Either a thick block of wood or a 1-mm-thick lead
shield would be required to absorb them
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P ROTONS

Positively charged components of an atom

Have a very small mass, which, however, exceeds that of an
electron by a factor of 2800

Number of protons in the nucleus of an atom constitutes its
atomic number, or “Z” number
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N EUTRONS

Are the electrically neutral components of an atom

Have approximately the same mass as a proton

If two atoms have the same number of protons
but a different number of neutrons in their
nuclei, they are referred to as isotopes.
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R ADIATION D OSE S PECIFICATION :
E QUIVALENT D OSE

Equivalent dose (EqD)
▬ A radiation quantity used for radiation protection purposes when a
person receives exposure from various types of ionizing radiation
▬ Enables the calculation of the effective dose (EfD)
▬ The SI unit of EqD is the sievert (Sv)
▬ 1 sievert equals 100 rem
▬ Both occupational and nonoccupational dose limits are expressed
as EfD and may be stated in sieverts (rem)
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E FFECTIVE D OSE (E F D)

Effective dose (EfD)
▬ Takes into account the dose for all types of ionizing radiation
to irradiated organs or tissues in the human body
▬ By including weighting factors for specific body parts, EfD
takes into account the chance of individual irradiated organs or
tissues for developing a radiation-induced cancer
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B IOLOGIC D AMAGE P OTENTIAL

Biologic damage
▬ Produced by ionizing radiation while penetrating body tissues
primarily by ejecting electrons from atoms composing the tissues

Result of destructive radiation interaction at the atomic level
▬ Molecular change
▬ Cellular damage
▬ Organic damage
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S OURCES

OF I ONIZING
R ADIATION
Natural radiation (natural background radiation)
▬ Terrestrial radiation (uranium-238, radium-226 and thorium- 232 in crust of earth)
▬ Cosmic radiation (from the sun (solar) and beyond the solar system (galactic)
▬ Internal radiation from radionuclides

Manmade (artificial) radiation
▬ Consumer products
▬ Nuclear fuel
▬ Atmospheric fallout from nuclear weapons testing
▬ Nuclear power plant accidents
▬ Medical radiation
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M EDICAL R ADIATION

Medical radiation exposure results from the use of
diagnostic x-ray machines and
radiopharmaceuticals in medicine

The two largest sources of artificial radiation are
1. Diagnostic medical x-ray
2. Nuclear medicine procedures
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VARIABILITY OF P T D OSE FOR
I MAGING P ROCEDURES

Because of the large variety of radiologic equipment and differences
in imaging procedures and in individual radiologist and radiographer
technical skills, the patient dose for each examination varies
according to the facility providing imaging services

The amount of radiation received by a patient may be indicated in
terms of
1. Entrance Skin Exposure (ESE) and glandular dose
2. Bone marrow dose
3. Gonadal dose
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R EDUCING
O CCURRENCE
P OSSIBILITY OF THE
OF G ENETIC D AMAGE IN
F UTURE G ENERATIONS
THE

Through efficient application of radiation protection measures
on the part of the radiographer.

By limiting the widespread substitution by many emergency
department facilities of unnecessary CT scans for simple chest
x-ray studies.
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N EW D ATA ON M EDICAL R ADIATION
E XPOSURE

NCRP Report No. 160, released on March 3, 2009, reflects usage patterns through
2006.

The number of medical procedures involving ionizing radiation has increased
dramatically since the 1980s.

Because of this, exposure of the U.S. population from medical sources has
increased.

Increased use of imaging modalities such as CT and cardiac nuclear medicine
examinations

NCRP Report No. 160 “estimates the total amount of radiation delivered in 2006
and compares those amounts to the estimates published in 1987”
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D IFFERENCES IN R ADIATION
E XPOSURE FROM 1980 TO 1982
AND D ATA FROM 2006

In NCRP Report No. 93, medical radiation was estimated to
contribute 0.54 mSv to manmade background radiation. In 2006,
that number had increased to 3.0 mSv, an increase of more than a
factor of 5.

The main reason for the increase is increased usage of CT. With the
advent of multislice spiral CT, the utility of this imaging modality in
areas such as emergency medicine has increased dramatically. In
1980, use of CT resulted in a collective dose of 3700 personsieverts. In 2006, that number rose to 440,000 person-sieverts.
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M EDICAL B ENEFIT OF CT

The use of CT does have tremendous medical benefit
in the diagnosis of disease and trauma.

New total annual background radiation
▬ The new total annual background radiation, 6.25 mSv per
person, is almost twice as large as the old estimate of 3.6 mSv.
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T HE END!

Review the questions at the end of the
chapter.
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