IAEA Training Material on Radiation Protection in Diagnostic and Interventional Radiology
Adapted for Regional Training Course on RP of Patients for Radiographers
Accra, Ghana, 11-15 July 2011
RADIATION PROTECTION IN
DIAGNOSTIC AND
INTERVENTIONAL RADIOLOGY
L14: Radiation exposure in pregnancy
IAEA
International Atomic Energy Agency
Topics
•
•
•
•
Introduction
Effects and risks of in utero exposure
Typical doses
Practical implementation
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IAEA Training Material on Radiation Protection in Diagnostic and Interventional Radiology
Part 14: Radiation exposure in
pregnancy
Topic 1: Introduction
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International Atomic Energy Agency
Introduction
• Thousands of pregnant women are exposed
to ionizing radiation each year
• Lack of knowledge is responsible for much
anxiety and possibly unnecessary
termination of pregnancies
• For most patients, the radiation exposure
was medically appropriate and the radiation
risk was minimal
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Situation analysis
• Exposure of females of reproductive capacity:
• Intended medical exposure:
• Patients needing radiological procedures while pregnant
• Unintended or accidental medical exposure:
• Pregnancy not known or not declared
• Occupational exposure
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Example of justified use of CT on a pregnant
female who was in a motor vehicle accident
Courtesy: Fred Mettler
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A CT exam performed and then taken to the
operating room. The woman and the child survived
Free blood
Kidney ripped
off aorta (no contrast in it)
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Splenic laceration
Courtesy: Fred Mettler
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IAEA Training Material on Radiation Protection in Diagnostic and Interventional Radiology
Part 14: Radiation exposure in
pregnancy
Topic 2: Effects and risks of in utero exposure
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International Atomic Energy Agency
Fetal Radiation Risk
• There are radiation-related risks throughout
pregnancy which are related to the stage of
pregnancy and absorbed dose
• Radiation risks are most significant during
organogenesis and in the early fetal period
somewhat less in the 2nd trimester and least
in the third trimester
Most
risk
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Less
Least
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8
13
Malformations – gestationage dependent
Threshold ~ 0.1 Gy
Severe mental retardation*#
40% risk at 1 Gy
Threshold ~ > 0.3 Gy
15
Severe mental retardation, but
less risk
26
* Some data show a loss of 25
IQ points per Gy
# Spontaneous rate of SMR is
about 3%
Growth anomalies; e.g. head size
Organogenesis
“All or nothing” - lethal effects
Threshold (0.1? – 1 Gy)
Hereditary effects: assumed to be ~ 0.5% per Gy
0 Conception
Implantation
2
Fatal cancer risk: Childhood: ~ 6 % per Gy
In utero exposures
40 weeks
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In utero effects
Spontaneous
incidence
Additional incidence after
fetal dose of 25 mGy
> 15 %
~0
Malformations
~2-4%
~0
Serious mental
retardation
~3%
~0
Childhood cancer
~ 0.2 %
~ 0.2 %
Lifetime cancer
~ 33 %
~ 0.1 %
~1-6%
~0
Effect
Lethal effects, preimplantation
Hereditary effects
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Probability of bearing healthy children as
a function of fetal dose
Probability of NO
malformations
%
Probability of NO
childhood cancer
%
0
97
99.7
1
97
99.7
5
97
99.7
10
97
99.6
50
97
99.4
100
97
99.1
Possible malformations
Increased probability of
childhood cancer
Fetal dose (mGy)
> 100
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IAEA Training Material on Radiation Protection in Diagnostic and Interventional Radiology
Part 14: Radiation exposure in
pregnancy
Topic 3: Typical doses
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In utero doses from diagnostic and interventional
procedures
• Magnitude of dose depends on whether fetus is:
• Not in the beam and beam is distant from uterus
• Fetal dose typically < 0.01 mGy
• Not in the beam, but beam is close to the uterus
• Fetal dose typically < 0.1 mGy
• In the beam
• Fetal dose typically in the range 0.1 to 50 mGy
• Plain film ~ 1 mGy
• Barium enema ~ 5 mGy
• CT ~ 10 – 50 mGy
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IAEA Training Material on Radiation Protection in Diagnostic and Interventional Radiology
Part 14: Radiation exposure in
pregnancy
Topic 4: Practical implementation
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International Atomic Energy Agency
Diagnostic and Interventional procedures for
females of reproductive potential
• For all procedures:
• Signs asking female patients to notify staff if they are or
might be pregnant
• Appropriate languages
• Appropriate placement
• For procedures that could lead to significant
embryo or fetal dose:
• Radiological medical practitioner
• Procedures in place to ascertain pregnancy status
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Diagnostic and Interventional procedures for
females of reproductive potential
• 4 outcomes to the pregnancy question
• No possibility of pregnancy
• Proceed as normally
• Patient definitely or probably pregnant
• Pregnancy cannot be excluded
• low dose procedure
• high dose procedure
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Patient definitely or probably pregnant
• Review the justification
• Radiological medical practitioner
• Referring medical practitioner
• Decide whether to defer the procedure until after the
delivery (or pregnancy is ruled out)
• Does delaying procedure involve greater risk?
• Patient needs to be informed of benefits and risks
• If still justified, then the procedure should be optimized
• So that the fetal dose is the minimum consistent with the clinical
purpose
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Pregnancy cannot be excluded: low dose
• Low dose means fetal dose < ~10 mGy
• If pregnancy cannot be excluded but menstrual
period not overdue
• Proceed as normal
• If pregnancy cannot be excluded and menstrual
period is overdue
• Treat patient as probably pregnant
• Follow advice as in previous slide
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Pregnancy cannot be excluded: high dose
• High dose means fetal dose > ~ 10 mGy
• For these high dose procedures
• Either: Apply a “ten day” rule
• I.e. females of childbearing potential are always
booked for these procedures during the first ten
days of their menstrual cycle, when conception is
unlikely to have occurred
• Or: Book as any patient, but the procedure is not
performed and is re-booked if the attending patient is:
• In 2nd-half of their menstrual cycle, and
• Is of childbearing potential, and
• Pregnancy cannot be excluded
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Inadvertent exposure in pregnancy
• Can occur in two ways:
• A pregnant patient is asked whether she is or might be
pregnant and denies it
• Either deliberately or in ignorance of her condition; and
• Procedure takes place
• A pregnant patient is NOT asked and the procedure
takes place regardless
• Revised BSS requires the licensee to investigate
any inadvertent exposure of the embryo or fetus
• Dose and risk estimation
• Patient and referring doctor informed
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Termination of pregnancy
• Termination of pregnancy for fetal doses of less
than 100 mGy is NOT justified based solely upon
radiation risk
• For fetal doses in excess of 100 mGy, there can be
fetal damage, the magnitude and type of which is a
function of dose and stage of pregnancy
• In these cases decisions on termination should be based
upon individual circumstances
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Occupational Exposure of Pregnant Workers
• Pregnant medical radiation workers may work in a
radiation environment as long as there is
reasonable assurance that the fetal dose can be
kept below 1 mGy during the pregnancy
• Typically 3 options for pregnant workers
• No change in assigned work duties
• Change to an area where the radiation exposure may be lower
• Change to a role that has no radiation exposure
• Discussions are needed
• Pregnant worker must be informed of potential risks,
local policies and the dose limits
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Occupational Exposure of Pregnant Workers
• From an occupational dose perspective there are
few situations in diagnostic and interventional
radiology where a pregnant worker would actually
need to change their duties
• “Front line” operators in image guided interventional
procedures are a possible exception
• Need to use previous monitoring history to establish
likely levels of exposure
• Need to be confident that accidents with the potential for
occupational exposure are unlikely
• There will be other concerns of the pregnant
worker that will need to be taken into account
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Summary
• The radiation dose to the embryo or fetus from any
diagnostic or interventional procedure in current use should
present no risk of causing fetal death, malformation, growth
retardation or impairment of mental development
• For the majority of diagnostic procedures, giving fetal doses
up to about a milligray, the associated risks of childhood
cancer are very low
• For high fetal dose procedures, systems must be in place to
ascertain pregnancy status, with ensuing review of the
justification for each patient, and appropriate optimization if
the procedure is performed
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Where to Get More Information
• ICRP Publication 84. Pregnancy and Medical
Radiation (1999).
• ICRP Publication 90. Biological Effects after
Prenatal Irradiation (Embryo and Fetus)(2003)
• ICRP Publication 103. The 2007
Recommendations of the International
Commission on Radiological Protection (2007)
• Protection of Pregnant Patients during Diagnostic
Medical Exposures to Ionizing Radiation. Advice
from the HPA, RCR and CoR (2009)
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RADIATION PROTECTION IN DIAGNOSTIC RADIOLOGY