Fact vs Fiction Disclosures No financial disclosures for myself or family No off label uses will be discussed One exception I am a radiologist 25 years selling xrays for a living Mortgages and college tuition still to pay ID: 555867
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Slide1
Radiation Risk
Fact
vs
FictionSlide2
Disclosures
No financial disclosures for myself or family
No off label uses will be discussed
One exception: I am a radiologist
25+ years selling
xrays
for a living
Mortgages and college tuition still to paySlide3
Radiation Risk
Concept of Dose and Measurements
Relative Risk related to age and gender
Impact of Medical ImagingSlide4
Quiz 1
A.
Cujo
B. Godzilla
C. Barney
D. None of the above
Slide5
Quiz 2
Radiation induced carcinogenesis increases in likelihood with dose. It is considered a stochastic effect.
True or False
Current risk models for radiation carcinogenesis assume that a lower limit of radiation exists below which no risk of cancer is present?
A. True
B. False Slide6
Impact of Radiation Exposure
Stochastic and Deterministic Effects
Deterministic Effects
Severity increases with dose, effect is prompt
Lower limit threshold exists
Examples (
erythema
, infertility(3-6Sv), marrow suppression)
Stochastic Effects
Likelihood increases with dose, effect is delayed
Genetic Damage/Carcinogenesis
No threshold
Risk of lifetime death from 100mSv ~.8%
Examples (Leukemia…)Slide7
Dose Quantification
Sievert
vs
other units of measurement
Concept of Relative Dose
Absorbed dose
is used to assess the
potential for biochemical changes
in specific tissues. [Unit is the
milligray
(
mGy
)]
Equivalent dose
is used to assess how much
biological damage is expected
from the absorbed dose. (Different types of radiation have different damaging properties.)[For diagnostic radiation: The equivalent dose in
milliSievert
(
mSv
) = the absorbed dose in
mGy
.]
Effective dose
is used to assess the
potential for long-term effects
that might occur in the future.
Effective dose
is a calculated value, measured in
mSv
, that takes three factors into account:
the absorbed dose to all organs of the body,
the relative harm level of the radiation, and
the sensitivities of each organ to radiation.Slide8
Risk of Radiation Effects
Tissue dependent
Slowly dividing cells less sensitive
Marrow more sensitive than skeletal or neural tissue
Age dependent
Risk of carcinogenesis likely is reduced by half in older adults compared with 30 y/o
Risk in infants and young children is likely doubled compared with young adult
( National Research Council. Health risks from exposure to low levels of ionizing radiation. BEIR VII Phase 2. Washington, DC: National Academies Press; 2006.)Slide9
Graph shows estimated excess cancer mortality risk according to age at time of exposure in a stationary population, with U.S. mortality risk rates
,
that is exposed to a radiation dose of 10
mSv
(14). Data are averages between the sexes
.
Published
in: "Estimated Radiation Risks Potentially Associated with Full-Body CT
Screening1“
Brenner and
Elliston
Radiology Vol. 232, No. 3:
735-738
©RSNA,
2004
Relative Organ Risk and AgeSlide10
Risk of Exposure and AGE
The British Journal of Radiology, 81 (2008), 362–378Slide11
Relative Radiation Exposure of Ct
Background Radiation
Cosmic
Radon Gas (number one source for exposure)
Annual exposure
Man-made Radiation Exposure
Diagnostic Imaging
Contribution of CT
Change over timeSlide12
Quiz 3 “Mothra
”
Mothra’s
Weapons included
Poisonous Fangs
Hurricane Winds
Atomic Blast
None of the aboveSlide13
Quiz 4 Radiation Annual Dose
The Majority of the annual average dose of radiation received by the US population comes from:
A. Residua of atomic bomb tests and nuclear reactor accidents
B. Cosmic Radiation
C. Medical Imaging
D. Radon GasSlide14
U.S. Annual Dose Changing due to Medical Imaging Slide15
Relative Contributions of Radiation U.S. 2006Slide16
Strategies to Minimize Dose
Technical parameters in CT can be adjusted
GHS CT scanners are optimized to minimize dose
Scanned areas should be limited to that which is necessary
Alternative Diagnostic Strategies
Image Wisely
ACR Appropriateness CriteriaSlide17
Clinical Vignettes
Utilize the average reported doses for common radiological exams
Online Calculator: radiation induced carcinogenesis is utilized (xrayrisk.com)
Examples:not
intended to be a detailed evaluation of clinical decision making
Goal is to give a sense of the magnitude of impact in radiation induced carcinogenesis that different imaging algorithms may haveSlide18
Relative Risks of Alternative
Dx
Strategies
Liver Lesion Evaluation in 30 y/o female
Biliary
ultrasound identifies solid mass in liver of otherwise healthy female with nonspecific RUQ pain
Recommendation for definitive imaging suggested
Multiphasic
CT
Liver MRISlide19
Relative Risk of Radiation from Liver CTSlide20
Relative Risk of Multiple Liver CT’s for Lesion ObservationSlide21
Relative Risk of MRI for Cancer Induction from Radiation
No ionizing radiation is involved in MRI and therefore the added risk of cancer induction is zeroSlide22
SBS
vs
CTE
vs
MRE for
Crohn’s
Disease 25y/o Male
MR
Enterography
is ZERO……and likely more useful information than SBSSlide23
30 y/o Female with CP, Cough and
Hemoptysis
Modified Wells score = 1Slide24
Pleural Effusion Evaluation
CT
vs
Decub
Xrays
vs
US
50 y/o Male
Ultrasound is ZERO, no ionizing radiationSlide25
20 y/o Male RLQ pain
CT
vs
Physical ExamSlide26
25 y/o Female Chest Pain after Trauma and Normal CXR
1 more cancer case for every 900 patients managed this waySlide27
CT Utilization Optimization
Radiation Risk
Cancer induction risk is thought most likely proportional to dose
Younger pts and more rapidly dividing tissue is at greater risk
CT is leading source and current US Exp 2X prior
CT is 25%
Absolute risk is in range of ~1/150 to 1/2000
Radon is number 2 source that can be mitigated
Cost of CT to care is substantial ~1.3M/yrSlide28
Quiz 3 “Them”
Famous Actors as Cast Members
James
Arness
Fess Parker
James Whitmore
Leonard
Nimoy
All of the aboveSlide29
Quiz 4 Residential Radon
Residential radon gas can be excluded as a significant risk if:
A. I have city water and no risk from well water contamination
B. My neighbors house was tested and all my other neighbors are OK.
C. My house was tested.
D. My house is only 5 years old and has no basement.Slide30
Radon
Decay product of U-238 and Radium-226
Risk in Uranium miners well established
Residential Risk?
RR = 1.1 (1.0-1.3)
Smokers greaterSlide31
US Radon MapSlide32
SC Radon RiskSlide33
Residential Radon
Discovered by investigators of Stanley
Watras
Construction engineer at Nuclear Plant with no fuel (PA)
Set off alarm
Radiation was from home
2,700pCi/L (max safe home levels 4
pCi
/L)
Peak Areas
Appalachian Mountains
Iowa, fertile soil of upper
midwest
from
glaciationSlide34
The Discoverer of Residential RadonSlide35Slide36
Quiz 7 “Matango
”
A science research vessel studying the aftermath of radiation exposure is found
abandoned
by a pleasure yacht that becomes stranded. The
research vessel crew
is:
Blood thirsty savages
Members of Greenpeace
Mutated into “Mushroom People”
None of the aboveSlide37
Quiz 8 Fetal Radiation
Diagnostic medical imaging exposure of the fetus may likely:
A. Improve future academic performance
B. Double the risk of childhood malignancy
C. Result in injuries visible at birth
D. None of the aboveSlide38
News Article and Fetal Radiation
NCI sponsored
Included cases of
xrays
of abdomen/pelvis as well as CT
Small sample size therefore limited power
15% more cancers in patients with a history of exposure but difference was not statistically significant
Headline = “NO SIGNIFICANT RISK”Slide39
Carcinogenesis and Fetal Radiation
Carcinogenesis is believed to be a stochastic effect of radiation (i.e., no threshold dose). The risk of childhood malignancy after in
utero
irradiation was first reported in 1956 [1], though the association was not widely accepted until the early 1960s
Baseline risk of childhood cancer19/10,000
Baseline risk of fatal childhood (0-15 yrs) cancer [2]5/10,000
Excess risk of fatal childhood cancer per
rad
of fetal whole body dose [3]4.6/10,000
Excess risk of childhood cancer per
rad
of fetal whole body dose [4]6.4/10,000
Excess risk of childhood cancer per
rad
of fetal whole body dose [5]:6/10,000
Relative risk of childhood cancer after fetal radiation exposure of 5
rad
[6]:
2increased risk of childhood cancer of up to 2 times baseline for a standard pelvic CT.UCSF Department of Radiology GuidelinesSlide40
Carcinogenesis and Fetal Radiation
The relationship between carcinogenesis and gestational age is controversial [9]. The OSCC study suggests the risk is higher with exposure in the first trimester than with exposure in the second or third trimesters, with relative risks of 3.19, 1.29 and 1.30, respectively [10].
Assuming a relatively high fetal dose estimate of 5
rads
for a pelvic CT during pregnancy, the relative risk of fatal childhood cancer may be doubled. This relative risk may appear substantial, but it should be remembered that the baseline risk is very low, so that the odds of dying of childhood cancer go from 1 in 2000 (baseline) to 2 in 2000 (after 5
rads
).
risk comparisons driving 20,000 miles in a car
living in New York City for 3
years
Key point:
CT of the fetus should be avoided in all trimesters of pregnancy, because it may cause up to a
doubling of the risk of fatal childhood cancer
.
UCSF Department of Radiology GuidelinesSlide41
MRI in Pregnancy
Abdomino
-pelvic MRI
Highly accurate for appendicitis
Reported 100
Sens
and 94% Spec
Start with U/S and still can do CT if needed
Other findings:
ureteral
stone,
cholecystitis
,
infarcted
fibroid… visible
Discouraged in First Trimester
Heating concerns
Number one cause for MRI injury overall are thermal injuriesSlide42
Thermal Injury MRISlide43
Summary
Radiation Carcinogenesis is assumed to have no lower limit of exposure below which is 100% safe
Medical imaging has double the US annual population exposure to radiation and CT is primarily responsible
Residential radon gas is number one non-imaging cause for exposure
Fetal exposure to radiation is likely most sensitive period for carcinogenesisSlide44
Fetal Radiation References
1.Stewart
A, Webb J, Giles D, Hewitt D. Malignant disease in childhood and diagnostic irradiation in
utero
. Lancet 1956; 2: 447.
2.Roberts
PJ, Given-Wilson R, Gifford D, Bryan G. Pregnancy and work in diagnostic imaging. Report of a joint working party of the Royal College of Radiologists and British Institute of Radiology. British Institute of Radiology, London, 1992.
3.Mole
RH. Childhood cancer after prenatal exposure to diagnostic x-ray examinations in Britain. Br J Cancer 1990; 62: 152-168.
4.United
Nations Scientific Committee on the Effects of Atomic Radiation. Ionizing radiation: levels and effects. 1972 Report to the General Assembly, with annexes.
Vol
II. Effects. New York, United Nations, 1972.
5.Muirhead
CR, Cox R,
Stather
JW, et al. Estimates of late radiation risks to the UK population. Documents of the NRPB 4 [4]. Chilton: National Radiological Protection Board, 1993: 15-157.
6.Ginsberg
JS, Hirsh J, Rainbow AJ, Coates G. Risks to the fetus of radiologic procedures used in the diagnosis of maternal venous thromboembolic disease. Thrombosis and Haemostasis 1989; 61: 189-196.7.Damilakis J, Prassopoulos P, Perisinakis K, Faflia
C, Gourtsoyiannis N. CT of the sacroiliac joints: Dosimetry and optimal settings for a high-resolution technique. Acta Radiol 1997; 38: 870-875.8.Damilakis J, Perisinakis K, Voloudaki A, Gourtsoyiannis N. Estimation of fetal radiation dose from computed tomography scanning in late pregnancy: depth-dose data from routine examinations. Investigative Radiology 2000; 35: 527-533.9.Doll R, Wakeford
R. Risk of childhood cancer from fetal irradiation. Br J Radiol 1997; 70: 130-139.10.Gilman EA, Kneale GW, Knox EG, Stewart AM. Pregnancy X-rays and childhood cancers: effects of exposure age and radiation dose. J Radiol Prot 1988; 8: 3-8.11.Benjamin SA, Lee AC, Angleton GM, et al. Neoplasms in young dogs after perinatal irradiation. J Natl Cancer Inst 1986; 77: 563-571.12.http://www.physics.isu.edu/radinf/risk.htm. Accessed 3/14/06.13.ACOG Committee on Obstetric Practice. ACOG Committee Opinion. Number 299, September 2004. Guidelines for diagnostic imaging during pregnancy. Obstet Gynecol. 2004; 104: 647-651.Slide45
Reference Material
ACR Appropriateness
Criteria
https
://acsearch.acr.org/list
Acute Pancreatitis
RUQ pain
Flank Pain- recurrent
Sx
stone variant
Pyelonephritis
Crohn
dz
Palpable abdominal mass
Right Lower Quadrant Pain- pregnant
pt
variant (adults rec CT and peds we already do US)Rib fracturesHeadache Links for additional referencesBeir VII reporthttp://www.nap.edu/catalog.php?record_id=11340
Image Wiselyhttp://www.imagewisely.org/Xrayrisk.com