This presentation was recently given by Dr. Brett Heilbron on the CanadianEMR - Technology in Clinical Practice Cruise Conference - April 2013. Learning objectives for the session were to understand the risks associated with ionizing radiation, identify ways to optimize patient benefit and minimize risk and to discuss some of the controversies around medical imaging radiation. The presentation focuses on the use of a common technology in clinical settings - medical diagnostic imaging - and provides some guidance regarding this controversial topic.

1. Radiation in Medical DiagnosticRadiation in Medical Diagnostic
ImagingImaging
Brett Heilbron
Co-Director Advanced Cardiac
Imaging
Division of Cardiology
St. Paul’s Hospital / UBC

2. Disclosure & Acknowledgements
Honoraria, Advisory Boards, Research
funding
Investments: none

3. Learning ObjectivesLearning Objectives
 Understand the risks associated withUnderstand the risks associated with
ionizing radiationionizing radiation
 Identify ways to optimize patient benefitIdentify ways to optimize patient benefit
and minimize riskand minimize risk
 Discuss some of the controversies aroundDiscuss some of the controversies around
medical imaging radiationmedical imaging radiation

4. IntroductionIntroduction
 Radiation sources and terminologyRadiation sources and terminology
 Radiation health risk dataRadiation health risk data
 Radiation dose reduction techniquesRadiation dose reduction techniques
 The futureThe future

7. Radiation Sources & Dose
NCRP Report # 160

8. Radiation Terminology
Physical
Equivalent
Parameter Unit
Radiation
Exposure
No. of ions in air
produced by
photons
CTDI100 Coulomb (C) /kg
Radiation Dose Radiation energy
adsorbed at point
in pt.’s body
CTDIvol Gray (Gy)
Cumulative
Radiation
Exposure
Total radiation
energy adsorbed
by patient’s body
DLP Gy x cm
Effective Radiation
Dose
Biological effect of
radiation dose
received
E Sievert (Sv)

9. Effective Dose
E = DLP x 0.014 mSv x mGy-1
x cm-1
• Derived from phantom scanning by vendor
• Assumes entire chest was imaged
• Assumes “standard” organ sizes
• Assumes same anatomy for men & women
• Uses organ sensitivity assumptions subject to change
• Assumes risk independent of age

16. Epidemiologic Studies Of Pilots And Aircrew
Abstract
During flight, pilots and cabin crew are exposed to increased levels of cosmic radiation which
consists primarily of neutrons and gamma rays. Neutron dosimetry is not straightforward, but typical
annual effective doses are estimated to range between two and five mSv. Higher dose rates are
experienced at the highest altitudes and in the polar regions. Mean doses have been increasing over
time as longer flights at higher altitudes have become more frequent. Because there are so few
populations exposed to neutrons, studies of airline personnel are of particular interest. However,
because the cumulative radiation exposure is so low, statistical power is a major concern. Further,
finding an appropriate comparison group is problematic due to selection into these occupations and a
number of biases are possible. For example, increased rates of breast cancer among flight
attendants have been attributed to reproductive factors such as nulliparity and increased rates of
melanoma among pilots have been attributed to excessive sun exposure during leisure time
activities.
Epidemiologic studies conducted over the last 20 y provide little consistent evidence linking cancer
with radiation exposures from air travel.
Boice, John D. Jr.; Blettner, Maria; Auvinen, Anssi
Health Physics: November 2000 - Volume 79 - Issue 5 - pp 576-584

20. Perception of Risk

21. Risks are Relative

22. Relative versus Absolute Risk

25.  Prospective “step and shoot” gatingProspective “step and shoot” gating
 Prospective high-pitch spiralProspective high-pitch spiral
 Reduce kVp and mAReduce kVp and mA
 Limit Z-axis coverageLimit Z-axis coverage
 Iterative ReconstructionIterative Reconstruction
 Limit paddingLimit padding

26. LaBounty T, Earls J, Leipsic J, et al. Am J Cardiol 2010; 106:1663-1667

27. LaBounty T, Earls J, Leipsic J, et al. Am J Cardiol 2010; 106:1663-1667

28. Leipsic J, LaBounty T, Heilbron B, et al AJR 195: Sept 2010

29. Reducing Image Noise:Reducing Image Noise:
Adaptive Statistical Iterative ReconstructionAdaptive Statistical Iterative Reconstruction
Filtered backprojection ASIR

30. Leipsic, J et al AJR 197: Nov 2011

31. Leipsic, J et al AJR 197: Nov 2011

32. Chest radiographs – 2 views 0.06 mSv (5)
Natural Background (Annual) 3-7 mSv (1,4)
Nuclear
Tc-99m (rest+stress) (MIBI) 9 – 18 mSv (1,2)
Tl-201 (rest+stress) ~34 mSv (1,2)
Cardiac Catheterization 2-14 mSv
CCTA
Calcium Scoring 1-2 mSv
Prospective pulse / high-pitch spiral 0.5-4 mSv
Radiation Dose Comparison
(1) Society of Nuclear MediPulse Procedure Guideline for Myocardial Perfusion Imaging:
http://interactive.snm.org/index.cfm?PageID=1110&RPID=780&FileID=1302
(2) US Nuclear Regulatory Commission, Radiation Dose Estimates for Radiopharmaceuticals:
http://www.nrc.gov/reading-rm/doc-collections/nuregs/contract/cr6345/cr6345.pdf
(4) Journal of the American College of Cardiology, Vol. 47, No. 9, 2006. Radiation Exposure of Computed and Direct Intracoronary
Angiography.
(5) Committee to Assess Health risks from Low Levels of Ionizing Radiation, National Research Council, 2005.

33. Have you ever noticed that anyone
driving slower than you is an idiot and
anyone driving faster is a maniac?
George Carlin

34. Radiation Dose IssuesRadiation Dose Issues
Fully diagnostic image quality is the primary goal - ALARAFully diagnostic image quality is the primary goal - ALARA
Balance radiation risks against benefits ofBalance radiation risks against benefits of
diagnosis & risk of misdiagnosisdiagnosis & risk of misdiagnosis
Radiation dose estimates are impreciseRadiation dose estimates are imprecise
Uncertainty of risks of low-level radiationUncertainty of risks of low-level radiation
Radiation dose discussion is here to stayRadiation dose discussion is here to stay

35. Learning ObjectivesLearning Objectives
 Understand the risks associated withUnderstand the risks associated with
ionizing radiationionizing radiation
 Identify ways to optimize patient benefitIdentify ways to optimize patient benefit
and minimize riskand minimize risk
 Discuss some of the controversies aroundDiscuss some of the controversies around
medical imaging radiationmedical imaging radiation

36. Thank you