Diagnostic Imaging Diagnostic Imaging and Malignancy Risk and Malignancy Risk Emergency Medicine Grand Emergency Medicine Grand Rounds Rounds June 12, 2008 June 12, 2008 Dr. Jay Green Dr. Jay Green Emergency Medicine Resident, Emergency Medicine Resident, PGY-2 PGY-2
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Diagnostic Imaging and Malignancy Risk Emergency Medicine Grand Rounds June 12, 2008 June 12, 2008 Dr. Jay Green Emergency Medicine Resident, PGY-2.
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Diagnostic Imaging and Diagnostic Imaging and Malignancy RiskMalignancy Risk
Emergency Medicine Grand RoundsEmergency Medicine Grand Rounds June 12, 2008June 12, 2008Dr. Jay GreenDr. Jay Green
Emergency Medicine Resident, PGY-2Emergency Medicine Resident, PGY-2
Learn what the diagnostic imaging Learn what the diagnostic imaging literature says about imaging and cancerliterature says about imaging and cancer
Discuss evidence from other sources Discuss evidence from other sources about the cancer risks of radiationabout the cancer risks of radiation How these sources quantify this riskHow these sources quantify this risk
Discuss how this information should Discuss how this information should translate to patient caretranslate to patient care
CaseCase
18M presents @ 210018M presents @ 2100 Typical story for appendicitisTypical story for appendicitis Mild Mild ↑WBC↑WBC Call general surgeryCall general surgery
Ask you to get a CT scan and call backAsk you to get a CT scan and call back
Local dataLocal data
FMC EDFMC ED 15% of patients get a CT15% of patients get a CT 18 000 ED CT scans/year18 000 ED CT scans/year
FMC, PLC, RGHFMC, PLC, RGH Unable to use proper pediatric CT dosesUnable to use proper pediatric CT doses
What radiation/radiobiology principles are What radiation/radiobiology principles are important to consider in this discussion?important to consider in this discussion?
Basics of radiation/radiobiologyBasics of radiation/radiobiology
Most radiosensitive tissuesMost radiosensitive tissues Bone marrow, thyroid, breast, lungBone marrow, thyroid, breast, lung
Bushberg et al. The Essential Physics of Medical Imaging. Williams & Wilkins Maryland. 1994
Basics of radiation/radiobiologyBasics of radiation/radiobiology
Some unitsSome units Gray (Gy)Gray (Gy)
Absorbed doseAbsorbed dose Energy absorbed per unit mass at specific point Energy absorbed per unit mass at specific point
(J/kg)(J/kg)
Sieverts (Sv)Sieverts (Sv) Effective doseEffective dose Weighted average of organ dosesWeighted average of organ doses Whole-body equivalent Whole-body equivalent
McNitt-Gray. AAPM/RSNA Physics tutorial for residents: topics in CT. Radiographics 2002;22(6):1541-53
Some doses and effectsSome doses and effects 10,000mSv10,000mSv
Radiation sickness, death within weeksRadiation sickness, death within weeks 1,000mSv1,000mSv
Radiation sickness, unlikely to cause deathRadiation sickness, unlikely to cause death 100-1000mSv100-1000mSv
Dose related increasing risk of carcinogenesisDose related increasing risk of carcinogenesis 50mSv50mSv
Clearly associated with increased cancer risk and the highest dose allowed Clearly associated with increased cancer risk and the highest dose allowed yearly in occupational exposureyearly in occupational exposure
20mSv/year averaged over 5 years20mSv/year averaged over 5 years Highest allowable dose for radiation workersHighest allowable dose for radiation workers
5mSv acute dose5mSv acute dose Reasonable evidence for increase in some cancersReasonable evidence for increase in some cancers
3-5mSv/year3-5mSv/year Typical dose rates of uranium miners in Australia and CanadaTypical dose rates of uranium miners in Australia and Canada
0.3mSv0.3mSv Round trip flight NY to LondonRound trip flight NY to London
Brenner DJ et al. Cancer risks attributable to low doses of ionizing radiation: assessing what we really know. Proc Nat Assoc Sci 2003;100(24):13761-6
Two basic forms of radiationTwo basic forms of radiation X-raysX-rays Gamma raysGamma rays
Both forms of EM radiationBoth forms of EM radiation Only difference is frequency (Hz) or Only difference is frequency (Hz) or
energy (eV)energy (eV)
Bushberg et al. The Essential Physics of Medical Imaging. Williams & Wilkins Maryland. 1994
EM radiation spectrumEM radiation spectrum
Bushberg et al. The Essential Physics of Medical Imaging. Williams & Wilkins Maryland. 1994
Gamma rays
X-rays
Ultraviolet
Visible light
eV or Hz
What does the literature say about What does the literature say about diagnostic imaging causing cancer?diagnostic imaging causing cancer?
American College of RadiologyAmerican College of Radiology
Difficulties with researchDifficulties with research Radiation-induced cancers delayed 1-2 Radiation-induced cancers delayed 1-2
decadesdecades Lifetime incidence of CA is 40%Lifetime incidence of CA is 40%
Amis ES et al. American College of Radiology White Paper on Radiation Dose in Medicine. Journal Am Coll Rad 2007
Brenner DJ et al. Cancer risks attributable to low doses of ionizing radiation: assessing what we really know. Proc Nat Assoc Sci 2003;100(24):13761-6
Ongoing researchOngoing research
No epidemiological data on CT scansNo epidemiological data on CT scans UK epidemiological study ongoingUK epidemiological study ongoing
Pearce & Parker, University of Newcastle Pearce & Parker, University of Newcastle upon Tyneupon Tyne
N=100,000N=100,000 Too early for any resultsToo early for any results
Ron E. Ionizing radiation and cancer risk: evidence from epidemiology. Pediatr Radiol 2002;32:232-7
In uteroIn utero
Risk to fetus initially described in 1956Risk to fetus initially described in 1956 Case-control studiesCase-control studies
Consistent association since 1956Consistent association since 1956
US hospital chart reviews confirm thisUS hospital chart reviews confirm this AXR has RR 1.39 (1.3-1.5) for childhood CAAXR has RR 1.39 (1.3-1.5) for childhood CA
N=15,000N=15,000
Confirmed in other studiesConfirmed in other studies
Doll R. Risk of childhood cancer from fetal irradiation. Br J Radiol 1997;70:130-9
Potential dose responsePotential dose response
Doll R. Risk of childhood cancer from fetal irradiation. Br J Radiol 1997;70:130-9
BUT…BUT…
Atomic bomb dataAtomic bomb data No increase risk to fetus of exposed mothersNo increase risk to fetus of exposed mothers
N=1263N=1263 Loss of follow-up in early years after bombLoss of follow-up in early years after bomb
Small cohort studies show no relationshipSmall cohort studies show no relationship
Doll R. Risk of childhood cancer from fetal irradiation. Br J Radiol 1997;70:130-9
TB surveillanceTB surveillance
Massachusetts 1925-1954Massachusetts 1925-1954 4940 women treated for TB4940 women treated for TB
2573 received avg 88 fluoro exams2573 received avg 88 fluoro exams
Followed for 30 yearsFollowed for 30 years
Boice JD et al. Frequent Chest X-Ray Fluoroscopy and Breast Cancer Incidence among Tuberculosis Patients in Massachusetts. Radiat Res 1991;125(2):214-22
ResultsResults
Younger = higher riskYounger = higher risk Risk of fractionated doses similar to single doseRisk of fractionated doses similar to single dose Similar results to other studiesSimilar results to other studies
Boice JD et al. Frequent Chest X-Ray Fluoroscopy and Breast Cancer Incidence among Tuberculosis Patients in Massachusetts. Radiat Res 1991;125(2):214-22
Davis FG. Cancer Res 1989;49:6130
Hildreth NG. NEJM 1989;321:1281
Pediatric CTPediatric CT
Pediatric CT different than adultPediatric CT different than adult Organ doses higherOrgan doses higher Increasing frequency faster than adultsIncreasing frequency faster than adults Children more radiosensitiveChildren more radiosensitive
More time to express cancerMore time to express cancer More dividing cellsMore dividing cells Females>malesFemales>males
Need different scanner settingsNeed different scanner settings
Brenner DJ. Estimating cancer risks from pediatric CT: going from the qualitative to the quantitative. Pediatr Radiol 2002;32:228-31
Brenner DJ. Estimating cancer risks from pediatric CT: going from the qualitative to the quantitative. Pediatr Radiol 2002;32:228-31
<20yo risk 1/800-1/2000
Pediatric CT riskPediatric CT risk
Complex modeling used to estimate riskComplex modeling used to estimate risk Peds risk much higher than adultPeds risk much higher than adult
~10-15x higher~10-15x higher
Brenner et al. Estimated risks of radiation-induced fatal cancer from pediatric CT. AJR 2001;176:289-96
Brenner et al. Estimated risks of radiation-induced fatal cancer from pediatric CT. AJR 2001;176:289-96
Pediatric CT riskPediatric CT risk
600,000 kids CT scanned/year600,000 kids CT scanned/year 140,000 will eventually die from CA140,000 will eventually die from CA
500 CA deaths attributable to CT500 CA deaths attributable to CT
1/12001/1200 risk that peds CT will cause fatal CA risk that peds CT will cause fatal CA
Brenner et al. Estimated risks of radiation-induced fatal cancer from pediatric CT. AJR 2001;176:289-96
Study in 1yoStudy in 1yo Cancer MortalityCancer Mortality
CT AbdomenCT Abdomen 1/5501/550
CT HeadCT Head 1/15001/1500
Risk in adultsRisk in adults
Used population data and modelsUsed population data and models Many assumptions Many assumptions considerable considerable
uncertaintyuncertainty Some calculations use atomic bomb dataSome calculations use atomic bomb data
ResultsResults In CanadaIn Canada
Risk of CA from imaging ~Risk of CA from imaging ~1/4501/450 (UK ~ (UK ~ 1/8001/800)) 784 cases of cancer per year 784 cases of cancer per year
Berrington & Darby. Risk of cancer from diagnostic x-rays: estimates for the UK and 14 other countries. Lancet 2004;363:345-51
Risk from full-body CT screeningRisk from full-body CT screening
Risk estimationRisk estimation Use atomic bomb data in estimatesUse atomic bomb data in estimates Dose = 12mSvDose = 12mSv ResultsResults
Single CT body in 45yo = Single CT body in 45yo = 1/12501/1250 mortality risk mortality risk
Brenner DJ & Elliston CD. Estimated radiation risks potentially associted with full-body CT scanning. Radiology 2004;232:735-8
Brenner DJ & Elliston CD. Estimated radiation risks potentially associted with full-body CT scanning. Radiology 2004;232:735-8
25yo = 1/740
45yo = 1/1250
65yo = 1/1700
Brenner DJ & Elliston CD. Estimated radiation risks potentially associted with full-body CT scanning. Radiology 2004;232:735-8
Is there applicable evidence from other Is there applicable evidence from other sources about the cancer risks of low dose sources about the cancer risks of low dose radiation?radiation?
How do these sources quantify this risk?How do these sources quantify this risk?
ButBut Include data on subjects exposed to similar Include data on subjects exposed to similar
doses to diagnostic imagingdoses to diagnostic imaging
Atomic bomb dataAtomic bomb data
N~30,000 dose range 5-100mSvN~30,000 dose range 5-100mSv 4119 solid cancers4119 solid cancers
77 cancers more than predicted77 cancers more than predicted
1/7141/714 risk of death from radiation in this risk of death from radiation in this rangerange
Pierce DA & Preston DL. Radiation-related cancer risks at low doses among atomic bomb survivors. Radiat Res 2000;154:178-86
Preston DL et al. Studies of mortality of atomic bomb survivors. Report 13: solid cancer and noncancer disease mortality: 1950-1997. Radiat Res 2003;160:381-407
Brenner DJ. Estimates of the cancer risks from pediatric CT radiation are not merely theoretical: comment on 0094-2405. Medical Physics 2001;28(11):2387-8
1-2% of CA deaths attributable to radiation1-2% of CA deaths attributable to radiation
Similar estimates to atomic bomb Similar estimates to atomic bomb cohortcohort
Cardis E et al. The 15-country collaborative study of cancer risk among radiation workers in the nuclear industry. Radiat Res 2007;167:396-416
Cardis E et al. Risk of cancer after low doses of ionising radiation: retrospective cohort study in 15 countries. BMJ 2005;331:77-82
When is ED CT optional?When is ED CT optional? Renal colic?Renal colic? Classic appendicitis?Classic appendicitis? Trauma pan-scan?Trauma pan-scan?
How does/should this translate to patient How does/should this translate to patient care?care?
Awareness of riskAwareness of risk
Survey of 76 abdo/pelvic CT patientsSurvey of 76 abdo/pelvic CT patients AskedAsked
Informed about risks, benefits, radiation doseInformed about risks, benefits, radiation dose Did they believe scan increased CA riskDid they believe scan increased CA risk
ResultsResults 7% told about risks of CT7% told about risks of CT
22% of EP’s22% of EP’s 3% believed scan increased CA risk3% believed scan increased CA risk
9% of EP’s, 47% of radiologists9% of EP’s, 47% of radiologists
Lee et al. Diagnostic CT scans: assessment and patient, physician, and radiologist awareness of radiation dose and possible risks. Radiology 2004;231:393-8
Informed consentInformed consent
US academic medical centersUS academic medical centers Survey of chairmen of radiology deptsSurvey of chairmen of radiology depts ResultsResults
Lee et al. Diagnostic CT scans: institutional informed consent guidelines and practices at academic medical centres. AJR 2006;187:282-7.
““Can sue your doctor if you believe you’ve Can sue your doctor if you believe you’ve been exposed to an excess amount of been exposed to an excess amount of radiation”radiation”
Injuryboard.comInjuryboard.com
Take-home pointsTake-home points
Risk of fatal CA from imaging 1/500-1/1500Risk of fatal CA from imaging 1/500-1/1500
Risk more significant in young (<30yo)Risk more significant in young (<30yo)
More awareness neededMore awareness needed
Risk discussion with patientsRisk discussion with patients
Informed consent?Informed consent?
ReferencesReferencesAmis ES et al. American College of Radiology White Paper on Radiation Dose in Medicine. Journal Am Coll Rad 2007Berrington & Darby. Risk of cancer from diagnostic x-rays: estimates for the UK and 14 other countries. Lancet 2004;363:345-51
Boice JD et al. Frequent Chest X-Ray Fluoroscopy and Breast Cancer Incidence among Tuberculosis Patients in Massachusetts. Radiat Res 1991;125(2):214-22Brenner & Hall. Computer tomography – an increasing source of radiation exposure. NEJM 2007;357(22):2277-84Brenner DJ. Estimates of the cancer risks from pediatric CT radiation are not merely theoretical: comment on 0094-2405. Medical Physics 2001;28(11):2387-8Brenner DJ et al. Cancer risks attributable to low doses of ionizing radiation: assessing what we really know. Proc Nat Assoc Sci 2003;100(24):13761-6Brenner DJ. Estimating cancer risks from pediatric CT: going from the qualitative to the quantitative. Pediatr Radiol 2002;32:228-31 Brenner et al. Estimated risks of radiation-induced fatal cancer from pediatric CT. AJR 2001;176:289-96 Brenner DJ. Radiation risks potentially associated with low-dose CT screening of adult smokers for lung cancer. Radiology 2004;231:440-5Brenner DJ & Elliston CD. Estimated radiation risks potentially associted with full-body CT scanning. Radiology 2004;232:735-8Bushberg et al. The Essential Physics of Medical Imaging. Williams & Wilkins Maryland. 1994
ReferencesReferencesCardis E et al. The 15-country collaborative study of cancer risk among radiation workersin the nuclear industry. Radiat Res 2007;167:396-416Cardis E et al. Risk of cancer after low doses of ionising radiation: retrospective cohortstudy in 15 countries. BMJ 2005;331:77-82Clemons M et al. Breast cancer risk following irradiation for Hodgkin’s disease. CancerTreatment Reviews 2000;26:291-302Doll R. Risk of childhood cancer from fetal irradiation. Br J Radiol 1997;70:130-9Giles J. Study warns of ‘avoidable’ risks of CT scans. Nature 204;431:391Lee et al. Diagnostic CT scans: assessment and patient, physicia, and radiologistawareness of radiation dose and possible risks. Radiology 2004;231:393-8Lee et al. Diagnostic CT scans: institutional informed consent guidelines and practices atacademic medical centres. AJR 2006;187:282-7.McNitt-Gray. AAPM/RSNA Physics tutorial for residents: topics in CT. Radiographics2002;22(6):1541-53 Panel discussion: section 1: helical CT and cancer risk. Pediatr Radiol 2002;32:242-4Pierce DA & Preston DL. Radiation-related cancer risks at low doses among atomicbomb survivors. Radiat Res 2000;154:178-86 Preston DL et al. Studies of mortality of atomic bomb survivors. Report 13: solid cancerand noncancer disease mortality: 1950-1997. Radiat Res 2003;160:381-407Preston DL et al. Solid cancer incidence in atomic bomb survivors: 1958-1998. RadiatRes 2007;168:1-64Ron E. Ionizing radiation and cancer risk: evidence from epidemiology. Pediatr Radiol2002;32:232-7