Radiation: The FactsMaybritt Kuypers, SEH-arts KNMG

ACEP-RECAP 19 November 2008 Westfriesgasthuis

Source

Linda A. Regan, MD,FACEP, Assistant Professor, Emergency

Medicine, Johns Hopkins Medical Institutions

“How Much Is Too Much? The REAL Risk of X –rays and CTs”

What will you know at the end of this talk?

Total radiation dosages of imaging studies ranging from plain radiography to CT scanning and risks

Ways to avoid certain high RAD imaging studies

Epidemiology

The rates of CT usage have dramatically increased over the past 25 years[ 1,2]

In 1980, there were 3.6 million CT’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

Who is getting these studies?

In 2000, data was published on CT usage at the University of New Mexico. [3]

33,713 consecutive CT exams 11% under 15 years Peak group 36-50 55% males 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

Quick Guide to Ionizing Radiation [4,5]

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 )

Quick guide

Note: When comparing data, most authors agree that for CT radiation:

1mSv = 1mGy1mSv = 0.1 REMBackground Radiation ≈ 1-3 mSv

per yearWhere do we get our radiation

exposure? 80-85% of radiation exposure 15-20% from medical imaging

BOSTON Fire Dept.

Radiation dose comparisonTYPE 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 - New York - Amsterdam = ongeveer 0,05 mSv.

Baseline vs Radiation induced cancer

WHAT IS THE BASELINE CANCER RISK?

It is based on baseline population data

Lifetime Attributable Risk (LAR) The LAR or the Incidence of

cancer in the population is 42% The Lifetime cancer mortality is

20%

When we talk about the LAR of radiation-induced cancers, we are talking aboutthe percentage increase above the baseline risk.

.

WHAT IS THE RISK BASED ON MSV?

Radiation induced cancerFor a 10 mSv exposure,

there is postulated risk of 1 additional cancer per1,000 patients with an average of 50% mortality

Data from Atomic Bomb survivors [6]:

Strong data increased risk over 100 mSv

Good data increased risk 50-100 mSv

Reasonable data increased risk 10-50 mSv

The take home message

There is potentially NO threshold below which there is NO risk.

However, most authors agree that >100mSv appreciable increase in relative risk

Repeat Visitors to the ED [7]

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 330mSv)

CT’s in Pediatric Patients [6]

Lifetime cancer mortality risk is higher for children than for adults

LAR of cancer for a 10 year old at time of exposure

Up to 50 mSv: 0‐2% increase over baseline50‐500 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

Stated in another way…

if 600,000 abdominal and head CT’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 cancerGiven 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%

6 year database review of 6,073 CT scans4,138 pediatric ED patients [8]Pediatric study

2000 2006 % increase

Head 443 544 23%

Chest 17 91 435%

Abd 148 220 49%

Cspine 38 177 366%

5 year database review of 46,553 CT scans 27,625 adult ED patients [9]

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 oldswhere the numbers almost mirror

adults

This is concerning! physicians treat adolescents as adults

by using the same imaging ordering patterns

Total Lifetime Attributable Risk (LAR) of Death from Cancer [10]

HEAD CT

Neonate ≈ 0.075% 5 yo ≈ 0.04% 15 yo ≈ 0.013% 25 yo ≈ 0.008% 50 yo ≈ 0.006%

ABD CT

Neonate ≈ 0.14% 5 yo ≈ 0.09% 15 yo ≈ 0.07% 25 yo ≈ 0.05% 35 yo ≈ 0.02%

ABD worse than Head

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 younger population

MIT Museum

Pregnant patient needs CT

Any conerns??

Spontneous abortion, birth defects, cancer?

Who is more at risk, mom or unborn child?

My Pregnant Patient Needs a CT![8,12]

Before 2 weeks: Fetal doses of > 100 mSv place the pregnancy at risk for

spontaneous miscarriageHowever, if implantation is maintained, there is no risk of

loss related to this exposure and teratogenic effects are typically not seen

Teratogenic effects 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

Carcinogenic effects

Always a risk…Baseline risk of fatal childhood

cancer is 1 in 2,000At 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 (RR 2)

Pregnant , PE?

CT or ventilation- perfusion scan?

Fetal Radiation

Type of study Fetal radiation dose in mSv or mGy

Abd X-ray 2-3

Lumbar spine AP/LAT 2

Abd CT 1-2

Pelvis CT 10-50

Chest CT for PE 0.06

Ventilation 0.02

Perfusion 0.22 !!

Latest fashion @ Harvard

What Can I Do to Limit Radiation? [28]

Radiology Staff/Department Dependent Tube current modulations Tube current 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 image quality.

What Can I Do to Limit Radiation?

Individual DependentShielding (breast, thyroid, eye,

gonads)Overlap of imagesWeight based tube current changes

(under 70kg)Studies show that there is good

quality under 80 kg at 50% reduced tube current.

Discussion &

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…

Cheers!

Original references

1. Nickoloff, E.L. & P.O. Alderson. (2001). Radiation exposures to patients fromCT: reality, public perception, and policy. AJR.American Journal ofRoentgenology 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 251,175-184.

3. Mettler, F.A.,Jr, P.W. Wiest, J.A. Locken & C.A. Kelsey. (2000). CT scanning:patterns of use and dose. Journal of Radiological Protection : Official Journal ofthe Society for Radiological Protection 20, 353-359.

4. Hui, C.M., J.H. MacGregor, H.C. Tien & J.B. Kortbeek. (2009). Radiation doseFrom 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 dosesin radiology and diagnostic nuclear medicine: a catalog. Radiology 248, 254-263.

6. Brenner, D., C. Elliston, E. Hall & W. Berdon. (2001). Estimated risks ofradiation-induced fatal cancer from pediatric CT. AJR.American Journal ofRoentgenology 176, 289-296.

Original references

7. Griffey, R.T. & A. Sodickson. (2009). Cumulative radiation exposure and cancerrisk estimates in emergency department patients undergoing repeat or multipleCT. AJR.American Journal of Roentgenology 192, 887-892.

8. Online resource: http://www.bt.cdc.gov/radiation/prenatalphysician.asp9. 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 computedTomography in the adult emergency department, 2000-2005. EmergencyRadiology 13, 25-30. 2007). Computed tomography--an increasing source ofradiation 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 forcomputed tomography and magnetic resonance imaging use during pregnancy and lactation. Obstetrics and Gynecology 112, 333-340.

13. Online resource:http://brighamrad.harvard.edu/education/fetaldose/fetaldose.pdf28. 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 230,619-628.

extra

Cosmic radiation in commercial aviationTravel Medicine and Infectious Disease, Volume 6, Issue 3, May 2008, Pages 125-127Michael Bagshaw

“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.”

extra

Some cosmic radiation dose measurements aboard flights connecting Zagreb AirportApplied Radiation and Isotopes, Volume 66, Issue 2, February 2008, Pages 247-251B. 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, the TLD 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 the TLD-100 measurement showed the average dose rate of 2.4 μSv/h

extra

www.nrg.eu 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 dosisequivalent:

op een transatlantische vlucht Amsterdam - New York - Amsterdam ongeveer 0,05 mSv.