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Radiation in Medical Diagnostic Imaging

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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.

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Radiation in Medical Diagnostic Imaging

  1. 1. Radiation in Medical DiagnosticRadiation in Medical DiagnosticImagingImagingBrett HeilbronCo-Director Advanced CardiacImagingDivision of CardiologySt. Paul’s Hospital / UBC
  2. 2. Disclosure & AcknowledgementsHonoraria, Advisory Boards, ResearchfundingInvestments: none
  3. 3. Learning ObjectivesLearning Objectives Understand the risks associated withUnderstand the risks associated withionizing radiationionizing radiation Identify ways to optimize patient benefitIdentify ways to optimize patient benefitand minimize riskand minimize risk Discuss some of the controversies aroundDiscuss some of the controversies aroundmedical imaging radiationmedical imaging radiation
  4. 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
  5. 5. Radiation Sources & DoseNCRP Report # 160
  6. 6. Radiation TerminologyPhysicalEquivalentParameter UnitRadiationExposureNo. of ions in airproduced byphotonsCTDI100 Coulomb (C) /kgRadiation Dose Radiation energyadsorbed at pointin pt.’s bodyCTDIvol Gray (Gy)CumulativeRadiationExposureTotal radiationenergy adsorbedby patient’s bodyDLP Gy x cmEffective RadiationDoseBiological effect ofradiation dosereceivedE Sievert (Sv)
  7. 7. Effective DoseE = DLP x 0.014 mSv x mGy-1x 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
  8. 8. Epidemiologic Studies Of Pilots And Aircrew    AbstractDuring 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
  9. 9. Perception of Risk
  10. 10. Risks are Relative
  11. 11. Relative versus Absolute Risk
  12. 12.  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
  13. 13. LaBounty T, Earls J, Leipsic J, et al. Am J Cardiol 2010; 106:1663-1667
  14. 14. LaBounty T, Earls J, Leipsic J, et al. Am J Cardiol 2010; 106:1663-1667
  15. 15. Leipsic J, LaBounty T, Heilbron B, et al AJR 195: Sept 2010
  16. 16. Reducing Image Noise:Reducing Image Noise:Adaptive Statistical Iterative ReconstructionAdaptive Statistical Iterative ReconstructionFiltered backprojection ASIR
  17. 17. Leipsic, J et al AJR 197: Nov 2011
  18. 18. Leipsic, J et al AJR 197: Nov 2011
  19. 19. Chest radiographs – 2 views 0.06 mSv (5)Natural Background (Annual) 3-7 mSv (1,4)NuclearTc-99m (rest+stress) (MIBI) 9 – 18 mSv (1,2)Tl-201 (rest+stress) ~34 mSv (1,2)Cardiac Catheterization 2-14 mSvCCTACalcium Scoring 1-2 mSvProspective pulse / high-pitch spiral 0.5-4 mSvRadiation 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 IntracoronaryAngiography.(5) Committee to Assess Health risks from Low Levels of Ionizing Radiation, National Research Council, 2005.
  20. 20. Have you ever noticed that anyonedriving slower than you is an idiot andanyone driving faster is a maniac?George Carlin
  21. 21. Radiation Dose IssuesRadiation Dose IssuesFully diagnostic image quality is the primary goal - ALARAFully diagnostic image quality is the primary goal - ALARABalance radiation risks against benefits ofBalance radiation risks against benefits ofdiagnosis & risk of misdiagnosisdiagnosis & risk of misdiagnosisRadiation dose estimates are impreciseRadiation dose estimates are impreciseUncertainty of risks of low-level radiationUncertainty of risks of low-level radiationRadiation dose discussion is here to stayRadiation dose discussion is here to stay
  22. 22. Learning ObjectivesLearning Objectives Understand the risks associated withUnderstand the risks associated withionizing radiationionizing radiation Identify ways to optimize patient benefitIdentify ways to optimize patient benefitand minimize riskand minimize risk Discuss some of the controversies aroundDiscuss some of the controversies aroundmedical imaging radiationmedical imaging radiation
  23. 23. Thank you

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