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Primary Articles

Citation:

Bednarz, B., & Xu, G. X. (2008). A feasibility study to calculate unshielded fetal doses to pregnant
patients in 6
-
MV photon treatments using monte carlo methods and anatomically realistic phantoms.

Medical
Physics, 35
(7),
3054
-
3061. doi:10.1118/1.2938519.

Type of Study:
Quantitative

Location/Setting:

Rensselaer Polytechnic Institute


Laboratory Setting

Key Concepts/Variables:

Concepts:

Effects of a 6
-
MV external photon beam radiation treatment on a



fetus. Monte Carlo dosimetry study.





Intervention/Independent Variable: Absorbed radiation
dose to the fetus,


different treat
ment plans using pregnant patient models
,







and 3 gestational stages.



(secondary radiation to the pregnant phantom patient)




Dependent variabl
es: lethality, CNS abnormalities, cataracts, growth







r
etardation, malformations, behavioral disorders,







e
levated risk of childhood cancer (Harmful Effects)


Controlled variabl
es:

Design Type:


Either Quasi
-
experimental or Pre
-
experimental (no randomization


all calculations used a


6
-
MV photon radiation beam to treat the phantom patients



patients are simulated
)


Prospectiv
e because the study begins with the independent variable and looks forward


for the effect.

Type of group comparison is Within
-
subjects because subjects being


compared are the same p
eople of different cond
itions (
3 mths, 6 mths, 9 mths).



Time frame is Longitudinal because data are collected at two or more points in time over


an extended period.

Qual. Tradition:

N/A

Sample:

Size: RPI
-
P series computational phantoms representing female anatomy of the pregnant mother and
fetuses at 3 different gestational periods

Data Sources:


Statistical Tests:

Monte Carlo calculations
, statistical errors were equal to or below 10%

Findings:

For all treatment plans, except treatment plan 7 the absorbed dose to the fetus increased with
increasing stage of gestation.
This increase in dose with gestational stage can be attributed to the decrease in
the distance between the fetal body and the fie
ld edge as the fetus increases in size.

In order to evaluate the
range of dose throughout the fetus, measurement locations should consider the initial size of the fetus and the
gestational change of fetal size throughout the course of treatment and shield
ing should be modified to account
for this variation. The computational approach to obtaining organ
-
averaged equivalent dose, as demonstrated
in this study, is obviously more convenient and versatile than measurements involving dosimeters such as TLDs
pla
ced in several cavity locations that correspond to individual organs.

Recommendations:

An accurate dosimetry method is needed to both reduce the uncertainty in the derived
dose
-
response relationship and better manage the risk in such treatment procedures.

Shielding should be
designed to lower the fetal dose below the recommended dose range of 5
-
10 cGy (determined by the TG
-
36
after a careful evaluation of the epidemiological data of risks to the fetus after radiation exposure)

The above
recommendations are

difficult to implement in clinical situations because there is currently no physical phantom
representing the pregnant female.

Strengths:

In the calculations, the absorbed dose to the fetus is the averaged value over the entire fetal volume,
thus is more

representative of the true anatomy.

Weaknesses:

No randomization, very small sample size, the use of simulated patients instead of real
-
life
subjects.

Overall:

The number of pregnant patients who undergo radiation therapy has been
increasingly

partially

due to
the improvements in cancer detection and the tendency for women to delay their pregnancy until later
reproductive ages. Pregnant patients have been treated for tumors in a variety of sites including the brain,
breast, nasopharynx and knee. Treatmen
t plans are developed with the additional consideration for the fetal
exposure. Simple techniques have been used to redue the dose outside the treatment field by adjusting the
gantry angle, field size, treatment beam energy, and patient position.
The study

demonstrates the feasibility to
accurately determine the absorbed organ doses in the mother and fetus as part of the treatment planning and
eventually in risk management.





Citation:
Sechopoulos, I., Vedantham, S., Suryanarayanan, S., D'Orsi, C. J., &
Karellas, A. (2008). Monte carlo
and phantom study of the radiation dose to the body from dedicated CT of the breast.

Radiology, 247
(1), 98
-
105. Retrieved from
http://radi
ology.rsna.org/content/247/1/98.full.pdf+html


Type of Study:

Quantitative

Location/Setting:

Laboratory

Key Concepts/Variables:


Design Type:

Prospective Quasi
-
experimental

Purpose:

To prospectively determine the radiation dose absorbed by the organs a
nd tissues of the body during
a dedicated computed tomography of the breast (DBCT) study using Monte Carlo methods and a phantom. The
effectiveness of a lead shield for reducing the dose to the organs was also investigated.

Statistical Tests:

Monte Carlo

Findings:

The inclusion of a 1mm lead sheet inside the table top between the patient and the x
-
ray source does
not substantially lower the dose to the higher
-
exposed organs, but it does decrease the dose to the uterus (by
up to a factor of twenty). The dos
e to the uterus, representative of the fetus in the first trimester, was found to
be low, in the range of 0.2 uGy to 1.2 uGy from a 4.5 mGy DBCT acquisition, depending on the x
-
ray spectrum
used. Although there is a wide variability in estimates of damage
or increase of risk to the fetus from different
levels of x
-
ray radiation, all studies seem to suggest that damage to the fetus or increase in risk of damage to the
fetus is possible at several orders of magnitude above the levels found in this study.
Even

though these radiation
levels to the fetus are minimal, it was found that the presence of the 1mm lead shield decreased these levels
substantially, introducing the possibility of lowering the dose to the fetus further.

Aside from the protection to
the ute
rus/fetus, which is of particular interest, the presence of the lead shield did not contribute substantially
to the protection of the body.

Weaknesses:

The main limitation in the study is the use of a mathematical phantom
(anthropomorphic
phantom)
with simplified organ distribution and shapes. This could result in both under and over estimates in
the order of 15
-
40%. This error, although substantial, still allows assessment of the importance of the dose to
the organs and other tissues outside the pr
imary x
-
ray field receive from DBCT imaging. The Monte Carlo
dosimetry method should be used only as a guideline
.





Citation:
Lazarus, E., Debenedectis, C., North, D., Spencer, P. K., & Mayo
-
Smith, W. W. (2009). Utilization of
imaging in pregnant patien
ts: 10
-
year review of 5270 examinations in 3285 patients
--
1997
-
2006.

Radiology,
251
(2), 517
-
524. doi:10.1148/radiol.2512080736

Type of Study:
Quantitative

Purpose:

To document the utilization of radiologic examinations in the pregnant population in a sing
le academic
medical center during the 10
-
year period from 1997
-
2006.

Location/Setting:

academic institution

Key Concepts/Variables:

number of patients, number of each type of imaging examination, date of the
examination, and the estimated radiation dose to the fetus from 1997 to 2006.

Design Type:

experimental or
nonexperimental? Retrospective

Qual. Tradition:

Sample:

5270 examinati
ons in 3285 patients

Data Sources:

database compiled by a medical physics department for every study using ionizing radiation in
pregnant patients. The database included examinations from conventional radiography, CT, nuclear medicine
imaging and fluorosco
py.

It e
xcluded MRI and US because
these do not use radiation.

Statistical Tests:

Holm test, p
-
value

Findings:


-

The overall utilization rate increased from 38.2 in 1997 to 79.0 in 2006, an increase of 107%.
Conventional radiography was the most frequentl
y performed radiologic examination
, followed by CT,
nuclear medicine and finally fluoroscopy.

-

In 2006, the use of CT pulmonary angiograms to evaluate pulmonary embolism was increased, however,
despite this increase, the number of nuclear medicine perfusio
n and ventilation
-
perfusion scans did not
decrease substantially.

-

The average estimated fetal radiation exposure was 0.43mGy for conventional radiography and
0.40mGy for nuclear medicine imaging.

-

For conventional radiographs in which the fetus was within

the beam of radiation, the average radiation
dose was 3.24mGy. For conventional radiographs in which the fetus was not within the beam of
radiation, the average radiation dose to the fetus was 0.01mGy.


-

The average yearly estimated radiation dose from im
aging to the fetus of pregnant patients who
underwent imaging examinations increased from 0.82mGy in 1997 to 2.1mGy in 2006.

-

During the 10 years of the study, the greatest percentage of radiation delivered by radiologic
examinations was due to CT of the ab
domen and pelvis.

Recommendations:

Knowledge of this increase in imaging of the

pregnant population
may raise awareness of
the potential of adverse effects of increased imaging in the pregnant population and help monitor the
inappropriate use of radiologic imaging in the future.

Strengths:

This study demonstrates the increase in number of pregnant woman

undergoing studies involving
radiation and thus the need to ensure they are aware of the radiation risks involved.

Weaknesses:

The study was limited by its retrospective design and by the possibility that some pregnant
patients were not known to be pregn
ant at imagine, and thus, not included in the database. As well, the method
of basing the total pregnant population on the number of deliveries does not account for elective or
spontaneous termination of pregnancies. Results were also limited because they
were accumulated from a
single academic institution, which may not reflect practice patterns throughout the country.



Citation:

Type of Study:

Location/Setting:

Key Concepts/Variables:

Design Type:

Qual. Tradition:

Sample:

Data Sources:

Statistical Tes
ts:

Findings:

Recommendations:

Strengths:

Weaknesses:




Reviews

Citation:
Whitt, C. K. (2010). Protecting pregnant women.

Radiologic Technology, 81
(4), 387
-
389.

Information Gathered:

-

Ionizing radiation is energy that produces positively and negatively charged particles (ions) when passing
through matter.

-

High
-
energy photons in ionizing radiation can damage DNA. The developing fetus’ sensitivity to radiation
varies with the stage of de
velopment, magnitude of dose, and length of exposure

-

Much of the information regarding the effects of radiation in human fetuses came from studying atomic
bomb survivors in Nagasaki and Hiroshima, Japan, who were irradiated with high doses while in utero.
These effects can be grouped into 3 types: teratogenetic (causing fetal malformations), carcinogenic
(cancer causing), or mutagenic (causing genetic changes).

-

In 1970, the International Commission on Radiation Protection proposed the “10
-
day rule” to prot
ect
potentially pregnant patients. (whenever possible, performing abdominal exams on women of child
-
bearing age should be restricted to within 10 days of the onset of their last menstrual cycle.

-

The most crucial time to avoid radiation exposure is from
the 8
th
-
15
th

week of gestation. It is during this
time that DNA proliferation in the brain is at its highest. At the 26
th

week of pregnancy,
the fetuses
exposed to radiation at this stage are no more sensitive to the effects of radiation than are newborns,

because the fetus is fully developed (although not fully grown).

-

Magnetic resonance imaging (MRI) and ultrasonography do not use ionizing radiation to examine the
body.

-

Radiological technologists can increase protection and reduce scatter through collima
tion. Use of
collimation limits the x
-
ray beam so that it strikes the body part under study and minimizes radiation
outside the collimated field.











Title: Radiation Exposure and Pregnancy

Date: June 2010

Health Physics Society
-

Specialists in
Radiation Safety
-

Fact Sheet


Information Gathered:

-

Our best knowledge indicates that there is a threshold below which negative effects are not observed

-

Most standard radiological test and treatments produce radiation doses below 50mSv, which is believed
t
o not pose an increase in health risks to the fetus.

-

The most radiosensitive period appears to be between the 8
th
-
15
th

weeks after conception.

-

A woman who is breast feeding may have to stop breast feeding for a period of time after receiving a
nuc med sca
n with radiopharmaceutical. In the case of x
-
rays and CT scans, the breast milk is not
affected.

Citation:
McCollough, C. H., Schueler, B. A., Atwell, T. D., Braun, N. N., Regner, D. M., Brown, D. L., & LeRoy, A. J.
(2007). Radiation exposure and pregnan
cy: When should we be concerned?

Radiographics : A Review
Publication of the Radiological Society of North America, Inc, 27
(4), 909
-
17; discussion 917
-
8.
doi:10.1148/rg.274065149

Information Gathered:

-

Conclude that fetal risks are minimal and, therefore, t
hat radiologic and nuclear medicine examinations
that may provide significant diagnostic information should not be withheld from pregnant women.

-

However, although the risks are small, it is important to ensure that radiation doses are kept ALARA.

-

Depending

on the position of the fetus in the mother, it may be possible to use a lead shield to protect
the uterus from external radiation (scatter emanating from the exposed tissue or imaging equipment) if
the area of interest is outside the uterus. However, beca
use the dose from external scatter radiation is
minimal, the use of lead shielding is left to the discretion of the technologist. It may off the patient a
sense of protection and reassurance, although unnecessary.

-

CT is associated with higher levels of ra
diation exposure than is radiography

-

Examples: Chest CT


0.2 mGy; Abdomen CT
-

4 mGy; Abdomen/Pelvis CT
-

25 mGy

-

Examples: Nuc Med Bone Scan
-

5 mGy; Nuc Med WB PET Scan
-

15 mGy; Nuc Med Thyroid scan
-

0.2 mGy

-

1977 the National Council on Radiation Protectio
n and Measurements, “The risk of abnormality is
considered to be negligible at 50 mGy or less when compared to other risks of pregnancy, and the risk of
malformations is significantly increased above control levels only at doses above 150 mGy. Therefore,
e
xposure of the fetus to radiation arising from diagnostic procedures would very rarely be cause, by
itself, for terminating a pregnancy.”





Citation:
Ratnapalan, S., Bentur, Y., & Koren, G. (2008). "Doctor, will that x
-
ray harm my unborn child?".

CMAJ :

Canadian Medical Association Journal = Journal De l'Association Medicale Canadienne, 179
(12), 1293
-
1296.
doi:10.1503/cmaj.080247

Information Gathered:

-

Ventilation Perfusion Scan
-

will expose the fetus to 0.06
-
0.1 rad

or computed tomography (CT)
angiography
-

will expose the fetus to 0.45 rad to rule out pulmonary emboli. The threshold dose is 5 rad.
As the physician, your decision should be based on the individual operator and the diagnosis sensitivity
and specificity
of the unit, because both procedures are below 5 rad (teratogenic dose).

-

Ionizing radiation in the form of x
-
rays and gamma
-
rays are short
-
wavelength electromagnetic rays.
Low
-
energy photons in x
-
rays and high
-
energy photons in gamma
-
rays can alter the nor
mal structure of
a living cell both directly and indirectly.

-

The fundamental effects of ionizing radiation on the developing fetus are intrauterine growth
retardation and defects in the CNS (microencephaly, mental retardation). The most vulnerable period
is
8
-
15 weeks’ gestation. This effect is associated with radiation doses above 10
-
20 rads.

-

See Table 1 for stages of gestation, exposure and effects

-

Direct exposure of a fetus to radiation occurs when the fetus is located within the field being imaged.
In
direct exposure is due to scattered radiation from maternal tissues. The fetal dose depends on the
radiation dose delivered and the distance
between the fetus and the area being imaged.

-

Radiation exposure dose is inversely related to the distance (to the
power of 2) from the radiation
source. A lead shield may reduce indirect exposure, but internal scatter in the mother will allow some
radiation to reach the fetus.

-

The International Commission of Radiological Protection reported that the risk of induction

of childhood
solid tumors is similar to that of leukemia and that the risk of cancer in later life is similar to that
following irradiation during childhood. In contrast, there are studies that suggest an increase in
childhood cancer after in utero exposu
re to 1 rad.

-

Although there is no evidence that MRI is associated with adverse fetal effects, it should be avoided
during the first trimester, unless it is critical for diagnosis of a serious maternal condition.

-

The high perception by physicians of terat
ogenic risk, associated with radiation could lead to
unnecessary anxiety for pregnant women who have been inadvertently exposed and who seek
counseling. It could also lead to delays in needed care for pregnant women.

-

There is no indication that radiodiagno
stic doses of ionizing radiation during pregnancy increase the
incidence of gross congenital malformations, intrauterine growth retardation or abortion. The risks of
such exposure are far below the spontaneous risks.

-

Ionizing radiation can case 2 types of

effects: deterministic and stochastic. Deterministic
-

there is a
threshold value; once this value is exceeded the effects of radiation are observed. Loss of tissue
function and organ damage. Stochastic
-

there is no threshold dose under which damage is ab
solutely
excluded, damage can occur from a single random modification in a cell component (ie.DNA)



Citation:

Brent, R. L. (2006). Counseling patients exposed to ionizing radiation during pregnancy.

Revista
Panamericana De Salud Publica = Pan American Jou
rnal of Public Health, 20
(2
-
3), 198
-
204. Retrieved from
http://www.ncbi.nlm.nih.gov/pubmed/17199913

Information Gathered:

-

This paper will help inform medical personnel about the real risks to the embryo from ionizing radiation,
provide suggestions on
counseling patients, recommend procedures to follow when evaluating a
patient, and offer guidance on when to schedule elective x
-
ray studies that are needed.

-

The recommendation of most official organizations, including the National Council on Radiation
Pro
tection and Management indicate the exposures of 0.05 Gy or less will not increase the risk of birth
defects or miscarriage.

-

The hazards of exposures in the range of diagnostic radiology (0.2mGy
-
0.05Gy) represent an extremely
low risk to the embryo, when
compared with the spontaneous mishaps that can befall human embryos

-

See Table 1

-

Many physicians approach the evaluation of diagnostic radiation exposure with either of two extremes:
a cavalier attitude, or panic.
Frequently, an opinion/physician’s personal

bias about radiation effects or
his/her ignorance of the field of radiation biology is provided to the patient.

-

4 situations: what procedure to perform (emergency)? What procedure to perform (elective) and when?
What to do if patient has procedure then la
ter finds out they were pregnant at the time? And what to
do when a woman gives birth to a baby with birth defects?

-

0.05 Gy = 0.05 Sv = 5 rads

-

The threshold for
major malformations is 0.20 Gy.

-

Low exposures to the embryo may occur when radiation therapy is

directed toward the head, neck,
upper chest, or the extremities.

-

Administered radionuclides are special problems bcuase each radionuclide has a different half
-
life,
metabolism, and excretion. Therefore each patient needs the expert evaluation of a compet
ent medical
or health physicist to determine what the fetal exposure of radiation will be or has been.

-

Systematic approach to evaluating
possible effects of radiation to the fetus; after obtaining 10 essential
pieces of information.

-

If the diagnostic study is performed in the first 14 days of the menstrual cycle, should the patient be
advised to defer conception for several months, based on the assumption that the deleterious effect of
radiation to the ovaries decreases with increasin
g time between radiation exposure and a subsequent
ovulation? Ie. Radioiodine therapy






Case Studies

Citation:
Bohuslavizki, K. H., Kroger, S., Klutmann, S., Geiss
-
Tonshoff, M., & Clausen, M. (1999). Pregnancy
testing before high
-
dose radioiodine treat
ment: A case report.

Journal of Nuclear Medicine Technology, 27
(3),
220. Retrieved from
https://login.proxy.hil.unb.ca/login?url=http://proquest.umi.com.proxy.hil.unb.ca/pqdweb?did=44559490&Fmt
=7&clientId=10774&RQT=309&VName=PQD

Information Gathered:

-

Routi
ne urine pregnancy testing is performed on all women of child
-
bearing age before the
administration of radioiodine. Patients are requested to affirm that they are not pregnant at the time of
signature in a standardized written informed consent.

-

Pregnancy
was terminated because there was a significant teratogenic risk due to the absorbed dose of
at least 0.2 Gy to the uterus/fetus from FDG PET and radioiodine treatment AND the patient was
required to have further radioiodine treatment.

-

Recommend sufficient

contraception for at least 1 month before radioiodine treatment in women of
childbearing age since serum pregnancy testing has an inherent diagnostic gap of about 1 week from
conception.

Title: In utero exposure to therapeutic radiation for Hodgkin lymph
oma

Year: October 2009, vol:55

Information Gathered:

-

Many of the data on the effects of exposure to ionizing radiation during pregnancy have arisen from
studies on survivors of the atomic bombs used in WWII.

-

As with all teratogens, the risk to the fetus de
pends on timing and dose of exposure. Fetal exposure to
radiation depends on several factors, including the target dose, the size of the radiation field, and the
distance between the edges of the field and the fetus as well as gestational age.

-

Gestational

Stages:

o

Preimplantation Period
-

First 14 days after conception
-

the number of cells in the embryo is
relatively small, radiation can either be lethal or have no apparent effect (“all or none”
response)

o

Organogenesis
-

between 2
-
8 weeks post conception
-

em
bryo is extremely sensitive to the
teratogenic effects of ionizing radiation, mainly resulting in congenital malformations and
growth retardation, affecting the CNS.

o

Between 8
-
15 weeks post conception
-

the CNS is especially radiosensitive, causing microce
phaly
(small head circumference) and mental retardation.

o

After 25 weeks, the CNS becomes less sensitive to radiation

-

Another concern is that radiation exposure during pregnancy might be associated with a carcinogenic
effect, which can include an increased risk of childhood solid tumors or leukemia.

-

Radiotherapy should not be an absolute contraindication in pregnant pati
ents diagnosed with cancer
located remote from the pelvic area. The predictive effects and dose should be estimated by qualified
medical personnel (radiation oncologist or physicist) and discussed with the woman.

Citation:
Han, B. H., Han, J. Y., Choi, J.

S., Ahn, H. K., & Nava
-
Ocampo, A. A. (2010). Conventional barium enema
in early pregnancy.

Journal of Obstetrics and Gynaecology : The Journal of the Institute of Obstetrics and
Gynaecology, 30
(6), 559
-
562. doi:10.3109/01443615.2010.497874

Information Gat
hered:

-

Concerns regarding the potential consequences of fetal exposure to x
-
ray radiation could result in
misperception of fetal risk and unnecessary pregnancy terminations. (Brent)

-

Studied 7 women in Seoul, Korea, who underwent a conventional barium enema. They found out they
were pregnant after the fact and were concerned for the health of their babies.

-

Estimated radiation dose varied widely, from approx. 7
-
40 mGy.

-

The gestational

ages at time of exposure ranged from 2 weeks to 8 weeks gestation.

-

Appropriate teratogen risk counseling may have a major impact towards the decision to continue with
pregnancy or abort the fetus, potentially saving the lives and changing family histories
. (Brent)

-

Follow
-
up test were done on 5 of the 6 babies (1 baby was aborted, 1 baby couldn’t be found to follow
-
up on) and there were no abnormalities found.

-

Radiation
-
induced cancer is considered a stochastic effect where the probability of radiation
-
ind
uced
cancer rises as exposure to radiation increases. However, there is great debate on whether cancer risk
is increased even at low levels of radiation, including exposure during fetal life.

-

Most diagnostic radiation procedures result in a fetal
-
absorbed

dose of 10mGy for direct or nuclear
medicine imaging

-

The dose threshold for inducing major malformations, growth retardation and neurodevelopmental
alterations appears to be above 100mSv.