Radiation- the facts Maybritt Kuypers, SEH-arts KNMG
ACEP-RECAP 19 November 2008 Westfriesgasthuis
Linda A. Regan, MD,FACEP,
Assistant Professor, Emergency Medicine,
Johns Hopkins Medical Institutions
“How Much IsToo Much?
The REAL Risk of X –rays and CTs”
Total radiation dosages of imaging studies
ranging from plain radiography to CT
scanning and risks
Ways to avoid certain high RAD imaging
The rates of CT usage have dramatically
increased over the past 25 years[ 1,2]
In 1980, there were 3.6 millionCT’s per year
In 1998, there were 33 million CT’s per year
In 2006, there were 62 million CT’s per year
with 7 million in children < age of 15 years
In 2000, data was published on CT usage at the
University of New Mexico. 
33,713 consecutive CT exams
11% under 15 years
Peak group 36-50
99% Head CT without contrast
75% Chest with contrast
93% Abdomen with contrast (33% had prior)
30% had at least 3 scans; 7% had greater than 5
scans and 4% had more than 9 scans
Radiation Exposure (Roentgens)
Describes the amount of radiation in the air
Radiation Dose (Rads or MilliGrays or mGy)
Amount of energy adsorbed per unit mass of tissue
Equivalent Dose (REM or MilliSieverts or mSv)
Modifies Radiation Dose by biologic effects.
This is because all types of radiation are not equal
Effective Dose (MilliSieverts/mSv)
Accounts for where dose is adsorbed as all tissues are not equally
sensitive to radiation.
(The effective dose is averaged for age and sex )
Note:When comparing data, most authors
agree that for CT radiation:
1mSv = 1mGy
1mSv = 0.1 REM
Background Radiation ≈ 1-3 mSv per year
Where do we get our radiation exposure?
80-85% of radiation exposure
15-20% from medical imaging
TYPE OF STUDY (EFFECTIVE DOSE)
CXR (PA only) 0.02 mSv
CXR (PA and lat) 0.1 mSv
AbdXR 0.7 mSv
Cervical Spine 0.2 mSv
Thoracic Spine 1.0 mSv
Lumbar Spine 1.5 mSv
TYPE OF STUDY (EFFECTIVE DOSE)
Head CT 2 mSv
Neck CT 3 mSv
Chest CT 7 mSv
Chest CT for PE 15 mSv
Abd CT 7.5 mSv
Pelvis CT 7.5 mSv
Transatlantische vlucht Amsterdam - NewYork -
Amsterdam = ongeveer 0,05 mSv.
WHAT ISTHE BASELINE
It is based on baseline
Lifetime Attributable Risk (LAR)
The LAR or the Incidence of
cancer in the population is 42%
The Lifetime cancer mortality is
When we talk about the LAR of
radiation-induced cancers, we
are talking about
the percentage increase above
the baseline risk.
WHAT ISTHE RISK BASED ON
Radiation induced cancer
For a 10 mSv exposure,
there is postulated risk of 1
additional cancer per
1,000 patients with an average
of 50% mortality
Data from Atomic Bomb
Strong data increased risk over
Good data increased risk 50-100
Reasonable data increased risk
There is potentially NO threshold below
which there is NO risk.
However, most authors agree that
appreciable increase in relative risk
7 year period with 1.9% of patients having 3
or more visits (each with CT!)
130 patients underwent 1,744 CT's (55% ED)
Mean number of ED CT was 7.4 (max 41)
Mean cumulative dose: 64.7 mSv (max
Lifetime cancer mortality risk is higher for
children than for adults
LAR of cancer for a 10 year old at time of
Up to 50 mSv: 0‐2% increase over baseline
50‐500 mSv: 2‐17% increase over baseline
1 CT at age 1
Abdominal CT: LAR of dying from radiation
induced cancer is 1 in 550
Head: LAR of dying from radiation induced
cancer is 1 in 1500
if 600,000 abdominal and headCT’s are
performed per year, and we know that head
CT’s are ordered at a rate of 2:1 compared to
abdominal CT’s. . .
≈ 600 children will die from cancer
Given a background rate of 140,000 children
per year dying of cancer, this may seem like a
small rate.The increase is “only” 0.43%
Pediatric study 2000 2006 % increase
Head 443 544 23%
Chest 17 91 435%
Abd 148 220 49%
Cspine 38 177 366%
Adult study 2000 2005 %increase
Head 3504 5289 51%
Chest 490 1596 226%
Abd 1845 3179 72%
C-spine 260 1464 463%
Major increase in the 13‐17 year olds
where the numbers almost mirror adults
This is concerning!
physicians treat adolescents as adults by using
the same imaging ordering patterns
Neonate ≈ 0.075%
5 yo ≈ 0.04%
15 yo ≈ 0.013%
25 yo ≈ 0.008%
50 yo ≈ 0.006%
Neonate ≈ 0.14%
5 yo ≈ 0.09%
15 yo ≈ 0.07%
25 yo ≈ 0.05%
35 yo ≈ 0.02%
Even though doses for head CT are higher due to
the larger doses needed to penetrate the bone,
the risks are higher for abdominal CT
This is due to the radiosensitivity of the
abdominal organs.This increased risk continues
to be noted until around the age of 40
This is one of the main reasons to be concerned
about the increased use of CT scans in the
Spontneous abortion, birth defects, cancer?
Who is more at risk, mom or unborn child?
Before 2 weeks:
Fetal doses of > 100 mSv place the pregnancy at risk for
However, if implantation is maintained, there is no risk of
loss related to this exposure and teratogenic effects are
typically not seen
Between 2‐20 weeks teratogenic effects can be seen at
doses greater than 50‐150 mSv.
These can include growth retardation, mental delay and
retardation, as well as physical deformities.
At < 2 and > 20 weeks, the risk of teratogenic effects is
very unlikely, except in very high exposure doses
Always a risk…
Baseline risk of fatal childhood cancer is 1 in
At a fetal dose of 50 mSv, a Relative Risk of 2
this increases the risk of developing a fatal
childhood cancer to 2 in 2,000.
This risk may be higher in the first trimester
(RR of 3) and lower in subsequent trimesters
Type of study Fetal radiation dose in mSv or mGy
Abd X-ray 2-3
Lumbar spineAP/LAT 2
Abd CT 1-2
Pelvis CT 10-50
Chest CT for PE 0.06
Perfusion 0.22 !!
Radiology Staff/Department Dependent
Tube current modulations
Rotation time (detector row dependent)
Tube rotation time is decreased with faster
rotations, which occur with higher detector row
numbers.This decreases the dose delivered
Higher detector row scanners are capable of
thinner slices, the tube current is often increased
to maintain similar noise level and preserve the
Shielding (breast, thyroid, eye, gonads)
Overlap of images
Weight based tube current changes (under
Studies show that there is good quality under
80 kg at 50% reduced tube current.
Do we really need that many CTs?
USA vs. NL
Child vs Unborn vs Adult
Morbidty&mortality prevented by use
of CT/X ray vs.
Morbidity&mortality caused by CT/X ray
Remember you are not the only one making X-
rays and CTs…
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CT: reality, public perception, and policy.AJR.American Journal of
Roentgenology 177, 285-287.
2. Sodickson,A., P.F. Baeyens, K.P. Andriole, L.M. Prevedello, R.D. Nawfel, R.
Hanson & R. Khorasani. (2009). Recurrent CT, cumulative radiation exposure,
and associated radiation-induced cancer risks from CT of adults. Radiology 251,
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patterns of use and dose. Journal of Radiological Protection : Official Journal of
the Society for Radiological Protection 20, 353-359.
4. Hui, C.M., J.H. MacGregor, H.C.Tien & J.B. Kortbeek. (2009). Radiation dose
From initial trauma assessment and resuscitation: review of the literature.
Canadian Journal of Surgery.Journal Canadien De Chirurgie 52, 147-152.
5. Mettler, F.A.,Jr,W. Huda,T.T.Yoshizumi & M. Mahesh. (2008). Effective doses
in radiology and diagnostic nuclear medicine: a catalog. Radiology 248, 254-263.
6. Brenner, D., C. Elliston, E. Hall &W. Berdon. (2001). Estimated risks of
radiation-induced fatal cancer from pediatric CT. AJR.American Journal of
Roentgenology 176, 289-296.
7. Griffey, R.T. & A. Sodickson. (2009). Cumulative radiation exposure and cancer
risk estimates in emergency department patients undergoing repeat or multiple
CT. AJR.American Journal of Roentgenology 192, 887-892.
8. Online resource: http://www.bt.cdc.gov/radiation/prenatalphysician.asp
9. Broder, J., L.A. Fordham & D.M. Warshauer. (2007). Increasing utilization of
computed tomography in the pediatric emergency department, 2000-2006.
Emergency Radiology 14, 227-232.
10. Broder, J. & D.M.Warshauer. (2006). Increasing utilization of computed
Tomography in the adult emergency department, 2000-2005. Emergency
Radiology 13, 25-30. 2007). Computed tomography--an increasing source of
radiation exposure.The New England Journal of Medicine 357, 2277-2284.
12. Chen, M.M., F.V. Coakley, A. Kaimal & R.K. Laros Jr. (2008). Guidelines for
computed tomography and magnetic resonance imaging use during pregnancy
and lactation. Obstetrics and Gynecology 112, 333-340.
13. Online resource:
28. Kalra, M.K., M.M. Maher,T.L.Toth, L.M. Hamberg, M.A. Blake, J.A. Shepard
& S. Saini. (2004). Strategies for CT radiation dose optimization. Radiology 230,
Cosmic radiation in commercial aviation
Travel Medicine and Infectious Disease, Volume 6, Issue 3, May 2008, Pages 125-127
“International Commission on Radiological Protection recommends maximum mean
body effective dose limits of 20 mSv/yr (averaged over 5 years, with a maximum
in any 1 year of 50 mSv). Radiation doses can be measured during flight or may
be calculated using a computer-modelling program such as CARI, EPCARD,
SIEVERT or PCAIRE. Mean ambient equivalent dose rates are consistently
reported in the region of 4–5 μSv/h for long-haul pilots and 1–3 μSv/h for short-
haul, giving an annual mean effective exposure of the order 2–3 mSv for long-
haul and 1–2 mSv for short-haul pilots. Epidemiological studies of flight crew
have not shown conclusive evidence for any increase in cancer mortality or
cancer incidence directly attributable to ionising radiation exposure.Whilst there
is no level of radiation exposure below which effects do not occur, current
evidence indicates that the probability of airline crew or passengers suffering
adverse health effects as a result of exposure to cosmic radiation is very low.”
Some cosmic radiation dose measurements aboard flights
connecting Zagreb Airport
Applied Radiation and Isotopes, Volume 66, Issue 2, February 2008,
B.Vuković,V. Radolić, I. Lisjak, B.Vekić, M. Poje, J. Planinić
The estimated occupational effective dose for the aircraft crew
(A320) working 500 h per year was 1.64 mSv.
Another experiment was performed by the flights Zagreb–Paris–
Buenos Aires and reversely, when one measured cosmic radiation
dose; for 26.7 h of flight, theTLD dosimeter registered the total
dose of 75 μSv and the average dose rate was 2.7 μSv/h. In the
same month, February 2005, a traveling to Japan (24 h flight:
Zagreb–Frankfurt–Tokyo and reversely) and theTLD-100
measurement showed the average dose rate of 2.4 μSv/h
Straling die direct of indirect van bronnen buiten de
aarde afkomstig is. De kosmische straling maakt deel
uit van de natuurlijke achtergrondstraling. Het
stralingsniveau van de kosmische straling afhankelijk
van de hoogte boven het zeeniveau. Op zeeniveau
bedraagt het dosisequivalenttempo 0,3 mSv/a, op
3000 m hoogte ongeveer 1,2 mSv/a. Bij vliegreizen
veroorzaakt de kosmische straling een extra
op een transatlantische vlucht Amsterdam - New
York - Amsterdam ongeveer 0,05 mSv.