Everything You Need to
Know About
Radiation Protection
Kelli Haynes, MSRS, RT(R)
Program Director &
Associate Professor
Radiation Protection
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45 questions of the 200 will be radiation
protection (22.5%)
10 -Biological Aspects of Radiation
15-Minimizing Patient Exposure
11-Personnel Protection
9-Radiation Exposure and Monitoring
Biological Aspects
of Radiation
10 Questions
Cell Radiosensitivity
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Cells and tissues vary in
their degree of radiosensitivity
Immature cells are nonspecializedrapid cell division
Mature cells are specialized-divide
slower if at all
DNA-most radiosensitive part of cell
High
Lymphocytes
 Spermatogonia
 Erythroblasts
 Intestinal crypt
cells
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Low
Muscle cells
 Nerve cells
 Chondrocytes
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Dose Response Relationships
Graphic representation of the
relationship between the amount of
radiation absorbed (dose) and the
amount of damage (response)
 Linear or nonlinear
 Threshold or nonthreshold
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Linear
Threshold
Dose
Dose
Linear
NonThreshold
Response
Response
NonLinear
Threshold
Dose
Dose
NonLinear
Nonthreshold
Response
Response
Relative Tissue
Radiosensitivities
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LET
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RBE
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OER
Linear Energy Transfer (LET)
Photons deposit or transfer energy
as they travel
 The average energy deposited per
unit of path length
 Assesses potential tissue and
organ damage
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LET
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High-LET Radiation
Alpha particles
Beta particles
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Low-LET Radiation
Gamma rays
X-rays
Relative
Biologic Effectiveness
Measures biologic effectiveness of
radiations having different LET’s
 Influenced by radiation type, cell or
tissue type, physiologic condition,
and biologic result
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Oxygen Enhancement Ratio
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Response to radiation is greater when
irradiated in the oxygenated state
Radiation dose required to cause response w/o O2
OER= Radiation dose required to cause response w/ O2
Cell Survival and Recovery
LD 50/30
 Adults-3-4 Gy (300-400 rad)
 Recovery may occur
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Somatic Effects
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Biologic damage sustained by
living organisms as a consequence
of exposure to ionizing radiation
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Classified as either early (acute) or
late
Short-term vs. Long-term
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Nausea
Fatigue
Redness of skin
Loss of hair
Intestinal disorders
Fever
Blood disorders
Shedding skin
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Cancer
Embryologic effects
(birth defects)
Formation of
cataracts
Carcinogenesis
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The production or origin of cancer
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Experiments have shown that
radiation induces cancer
Cataractogenesis
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Cataracts-opacity of the eye lens
2 Gy results in partial or
complete vision loss
Threshold, nonlinear
dose-response
relationship
Sterility
Female sterility based on age
of the subject-more radiosensitive
when younger
 Temporary sterility-2 Gray (200rad)
 Permanent sterility-5 Gray (50 rad)
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ACUTE RADIATION
SYNDROMES
Hematopoietic Syndrome
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Whole-body doses ranging from 1
to 10 Gy (100 to 1000 rad)
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Reduction of blood cells in
circulation results in a loss of the
body’s ability to clot blood and fight
infection
Gastrointestinal Syndrome
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Appears at a threshold dose of
approx. 6 Gy (600 rad) and peaks
after a dose of 10 Gy (1000 rad)
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Without treatment, a dose of 6-10
Gy may cause death in 3-10 days
Cerebrovascular Syndrome
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Doses of 50 Gray
(5000rad)
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Death within 2 hours
or up to 2 days
Embryonic and Fetal Risks
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Fetus is very sensitive
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Fetal radiosensitivity
decreases as gestation
progresses
Genetic Effects
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GSD-used to assess
the impact of gonadal dose
Dose equivalent to the
reproductive organs
that would bring genetic
injury to the total population
PHOTON
INTERACTIONS
WITH MATTER
Coherent Scattering
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Photon of low energy
interacts with atom.
No net energy has
been absorbed by
the atom.
Low-energy
photons,1-50 kVp
Contributes to fog
Compton Scattering
• Moderate energy xrays, 60-90 kVp
• Interaction with outer
shell electron
• Electron ejected,
Atom is ionized
• Photon loses energy
and recombines with
an atom
• Fog and Scatter
Compton Scattering
FIGURE 2-6 Compton scattering is responsible for most of the scattered radiation produced during a radiologic
procedure. (From Radiobiology and radiation protection: Mosby’s radiographic instructional series, St. Louis, 1999,
Mosby.)
Photoelectric Absorption
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Most important interaction
between x-ray photons and the
atoms of the pt’s body for
producing useful images
Higher energy x-rays (23-150
kVp), more likely to penetrate &
not interact
Interaction b/t photon and inner
shell electron
X-ray is absorbed
Electron ejected
Attenuation
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Process that decreases the intensity of
the beam
Refers to both absorption and scatter
processes
Thickness of body part (mass density)
Type of tissue (atomic number)
Minimizing Patient
Exposure
15 Questions
Exposure Factors
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kVp
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mAs
Shielding
Protects gonads when w/i 5 cm of
collimated beam
 Females receive
more exposure due
to location
of organs
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Types of Shields
Flat contact
shields
 Shadow shields
 Shaped contact
shields
 Clear lead
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Beam Restriction
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Purpose-confine useful
beam
Reduce scatter
Types
Cones
Collimators
Filtration
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Effect on skin and
organ exposure
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Effect on beam energy
NCRP Report #102
The useful beam shall be
limited to the smallest area
practicable and consistent
with the objectives of the
radiological or fluoroscopic
examination.
Exposure Reduction
Patient
positioning
 AEC
 Patient
Communication
 ALARA
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Image Receptors
Film-screen systems
 Intensifying screens
 Digital Image receptors
 CR and DR
 Film speed
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Image Receptors
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Digital
CT, CR, DR, DF,
NM, MR, & US
Photons on a
detector
Electronic image
Matrix
Patient dose
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Film
Intensifying screens
convert photons and
expose film
Analog image
Patient dose
Grids
As grid ratio increases patient dose
increases
 Increases contrast
 Absorbs Compton scatter
 Improves quality
 Increases patient dose
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Fluoroscopy
Pulsed or
Intermittent
 Exposure factors
 Positioning
 Fluoroscopy
time
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Personnel Protection
11 Questions
Sources of Radiation
Exposure (3)
Primary x-ray beam
 Secondary radiation
1. Scatter
2. Leakage
 Patient
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Basic Methods of
Protection
Protective Devices
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Protective structural shielding
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Primary Barriers
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Secondary Barriers
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Lead Shields
Protective Devices
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Aprons
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Gloves
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Thyroid shields
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Protective glasses
Portable (mobile) units
Lead apparel
 Exposure cord
 Stand at right
angles to the
patient
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Fluoroscopy
Protective curtain
 Bucky slot cover
 Cumulative timer
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NCRP Report #102
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Fluoroscopy Exposure Rates
General Purpose: 10 R per minute
Non-image Intensified: 5 R per minute
High Level Control: 20 R per minute
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Exposure Switch Guidelines
Switch must be of the dead-man type
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Radiation Exposure
and Monitoring
9 Questions
Units of Measurement
Quantity
SI
Traditional
Exposure
Coulomb/kg roentgen
Absorbed dose
gray
Dose equivalent sievert
rad
rem
Dosimeters
Film Badge
Economical
 Parts
 Monitors x and
gamma rays
 Temperature and
humidity can
cause fog
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Pocket Ionization
Chambers
Most sensitive
 Must be charged
to zero
 Accurate from
0-200 mR
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OSL Dosimeter
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Aluminum oxide
detector
Optically stimulated
luminosity occurs
when struck by
laser light
Accurate reading
as low as 1mrem
TLD’s
Look similar to
film badge
 Lithium fluoride
 Ionization causes
crystal to change
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NCRP #116
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Annual occupational
effective dose- 50 mSv
(5rem)
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Public Exposure- 1 mSv
Embryo/fetus exposure50 mSv/month
Dosimetry records
NCRP #160
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Typical effective dose
per exam; varies from
0.1 mSv for a chest
xray to 1.5 for a lumbar
spine
Interventional- ~3mSv
CT- range from 2mSv
for a head to 10 mSv
for a spine
That’s All Folks!
www.ARRT.org
haynesk@nsula.edu
Review Questions
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What is the most radiosensitive part of
the cell?
Which is more radiosensitive, immature
or mature cells?
This is a picture of what?
Review Questions
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What is LET?
What is LD 50/30?
What is an example of an early somatic
effect?
Late somatic effect?
What is carcinogenesis?
Review Questions
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What is the threshold dose for cataracts?
What is the threshold dose for temporary
sterility?
What is the threshold dose for
permanent sterility?
What is the threshold dose for
cerebrovascular syndrome?
Review Questions
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What is the threshold dose for
hematopoietic syndrome?
What is the threshold dose for
gastrointestinal syndrome?
What are some types of shields?
What is filtration?
What does NCRP Report # 102 state?
Review Questions
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Why do we use a grid?
What are the 3 sources of radiation
exposure?
What is the SI unit of measurement for
exposure?
What is the SI unit of measurement for
absorbed dose?
Review Questions
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What is the traditional unit of
measurement for dose equivalent?
What is the sensing material in an OSL
dosimeter?
What is the sensing material in a TLD
dosimeter?
What does NCRP # 116 state?