“ Radiation in Medicine" J. Battista, Ph.D., Medical Physicist London Regional Cancer Program http://www.macmillan.org.uk/Images/Cancerinfo What is a Physicist doing in a Hospital? • Diagnostic Imaging – x-rays, CT, nuclear medicine – Ultrasound, MRI • Therapeutic Medicine – X rays, lasers, ultrasound – Dose calibration – Treatment planning • Biophysics – Radiation biology • Radiation Protection – Room designs, emergency Radiophobia The Ugly Warfare & Terrorism Radiation Poisoning The Bad Nuclear Accidents The Good Diagnostic imaging Radiation therapy Radiophilia The Ugly Warfare & Terrorism Radiation Poisoning The Bad Nuclear Accidents The Good Diagnostic imaging Radiation therapy x rays rays • Radiography • Computed Tomography (CT Scan) • Nuclear Medicine • Planar, SPECT, PET • Radionuclide Therapy (Thyroid) BIG Local Doses • External Beam • Brachytherapy Therapy • Ultrasound (sound waves) No Dose • Magnetic Resonance Imaging (MRI) Diagnosis Radiation in Medicine Outline • What is Radiation? • How does it injure cells, tissue, organs ? • What do we know about its biological effects? • What do we know about its risks? • How is radiation used in medicine? • Question and Answer Period X-rays Ionizing Radiation • “Ionizes” atoms by liberating orbital electrons Incoming x-ray Knocked out electron atom • High energy x-rays can do this to atoms Radiation Dose a measure of concentration of energy locally absorbed in any absorber from any type of ionizing radiation m E X ray Electron Concentration of energy absorbed by a tissue sample D = E (absorbed)/m Unit is Joules/kg= Gray We can measure Dose in air and in plastic absorbers Dental Cone-Beam CT L. Kaci and D. Chambers, http://www.flukebiomedical.com/biomedical/usen/Diagnostic-Imaging-QA/CT-QA/76-424-4156.htm?PID=55264 We can measure Dose in “Phantoms” Optically Stimulated Luminescence L. Kaci and D. Chambers Schulich School of Dentistry Effective Dose (milli-Sv) • For partial body exposures • Useful to compare medical procedures • Uniform whole body dose with same ‘detrimental effect’ (e.g. cancer risk) • E = Σ ( Dose to Organ x Tissue Weighting per Organ) = D1W1 + D2W2 +D3W3 …etc… Effective Dose Spectrum CT Scan 7 mSv Chest x-rays 0.05 mSv 3/4/2014 Japan 19 Effective Doses (milli-Sv) Typical Natural Radiation near Earth 2.4 • Airport Security Scan • Passenger Flight (transatlantic) • Flight Crew mSv/yr +0.00005 mSv + 0.05 mSv + 5 mSv/year Medical Diagnosis • • • • • • Dental x-rays Chest x-rays Mammography CT scan abdomen GI-Barium Cardiac Fluoroscopy 0.005 mSv 0.05 mSv 0.4 mSv 7 mSv 8 mSv 10 mSv… A-Bomb survivors < 2,000 mSv Lethal Dose (whole body acute) 4,000 mSv Radiotherapy Effective Dose 3,500 mSv (assuming W=0.1; DRF = 0.5) 1 mSv 10 mSv 1000 mSv 100 mSv 3/4/2014 21 Cancer Risks from Diagnostic Radiology Procedure Typical Effective Dose (mSv) Chest x ray Equivalent # of Chest x rays Equivalent Background Radiation (@2.4mSv/yr) Added Lifetime Cancer Risk 0.00025 % (@0.005%/mSv) 0.05 0.4 1 8 1 week 2 months Barium x ray (enema) 8.0 160 3.3 years 0.002 % 0.04 % CT Scan Abdomen 7.0 140 3.0 years 0.035 % Cardiac Fluoro 10.0… 200… 4.2 years… 0.05… % Mammography NOTE : Natural mortality 0.25 % per year (Ontario) Outline • What is Radiation? • How does it injure DNA, cells, tissue, organs ? • What do we know about its biological effects? • What do we know about its risks? • How is radiation used in medicine? • Question and Answer Period Biological Damage Radiation “hits” DNA Radiation splits water OH Chemical Radicals DNA Damage Chromosome aberrations Scaling up to Chromosomes Chromosome Aberrations in Irradiated Cells V. Moiseenko UCSD http://microbiology.ucdavis.edu/kowalczykowski/geneti c%20recomb.htm DNA can Repair itself ! DNA is Naturally Damaged Natural DNA damage occurs at a rate of 1,000 to 1,000,000 molecular DNA lesions per cell per day ! This still constitutes a very small fraction of the human genome (Billions of DNA bases) Un-repaired or mis-repaired DNA sites: In critical genes (e.g. oncogenes), can potentially increase the chance of tumour formation Cancer is caused by a “perfect storm” of accumulated lesions Outline • What is Radiation? • How does it injure DNA, cells, tissue, organs ? • What do we know about its biological effects? • What do we know about its risks? • How is radiation used in medicine? • Question and Answer Period Exposure to radiation Ionizations, etc. Chemical changes Low doses Alterations in cell metabolism Stochastic High Doses Deterministic Microscopically observable damage Permanent modifications in functioning of some cells Death of individual cells 3/4/2014 Long delayed effects of radiation such as genetic changes or the induction of cancer 33 Radiation sickness (which can lead to death) in multicellular organisms 200,000 immediate deaths 40,0000 from radiation 200,000 still under study Atomic Bomb Survivors Study 3/4/2014 35 Cancer Mortality Risk Factors • From A-Bomb survivors • Lifetime risk of cancer mortality is: 5 % per Sv of effective dose 0.005% per mSv NOTE : Natural lifetime mortality probability 0.25 % per year (Ontario) Outline • What is Radiation? • How does it injure DNA, cells, tissue, organs ? • What do we know about its biological effects? • What do we know about its risks? • How is radiation used in medicine? • Question and Answer Period Medical Imaging with Radiation Ultrasound “Echos” Radiography and CT scans “Shadows” MRI “Music” CT is 3D x ray Vision ! http://www.fleshandbones.com/readingroom/pdf/940.pdf Computed Tomography (CT) X Ray Source • Tomos means “slice” (Greek) • A method of imaging internal crosssectional slices through a 3D object • Transmission CT Problem – Given: multiple transmission views through the object (i.e. projections) – Required: to reconstruct the internal distribution of local x ray attenuation X-Ray Detector Array Rules: The clues for ACROSS and DOWN numbers is the sum of digits. Only the digits 1-9 can be used (no repeats). CT – measures tissue density Raise a Drink to CT Ice Shaken or Stirred ? Ian Cunningham & J. Battista 1990 Cardiac CT Imaging Coronary study in 5 heart beats USA Compromise More Dose increases cancer risk Less Dose jeapardizes diagnosis – also very risky ! Radiation Therapy of Cancer • Ultra-High Dose to the tumour – Cell killing to < 1 cell – Increases odds of tumour control • Very Low Dose elsewhere – Keep healthy cells as much as possible to avoid ‘organ’ dysfunction – Reduce Side-Effects World’s First Cobalt-60 Treatment London, Ontario October 27, 1951 Tomotherapy London Regional Cancer Program Tomotherapy Intensity-Modulated Radiotherapy Dose Rate Dose 90 to 100% 30 to 90% 00 to 30% When Imaging meets Therapy Image-Guided Radiotherapy “Point Focus and Shoot” CT -Guided Adaptive Radiotherapy Image-Guided Radiotherapy Laser-Guided CT-Guided Summary Uncontrolled radiation can be harmful Highly-controlled radiation is used in medicine For diagnosis, radiation doses are kept “as low as possible” For therapy, high doses especially to tumour regions. Combining imaging with treatment leads to better tumour “hit” with fewer side effects. London has strong scientific and medical expertise Question and Answer Period That’s All Folks ! Radiation in Space J2. Battista, Ph.D. Chris on Space Station https://www.facebook.com/AstronautChrisHadfield Summary of Space Dose Levels Program Gemini Altitude Inclination Dose Dose Rate Duration Duration (km) (degrees) (mSv) (mSv/day) (days) (months) 454 30.0 0.5 0.9 0.6 0.0 1370 30.0 4.7 4.7 1.0 0.0 12.2 1.3 9.4 0.3 33.0 3.9 8.5 0.3 Apollo Skylab STS 381 50.0 72.0 1.2 60.0 2.0 435 50.0 170.0 2.1 81.0 2.7 570 28.5 26.5 3.2 8.3 0.3 78.0 7.7 10.1 0.3 2.1 0.2 9.1 0.3 7.1 0.4 17.8 0.6 337 STS/Mir ISS 28.5 341 51.6 99.0 0.7 137.5 4.6 355 51.6 140.0 1.0 140.0 4.7 350-450 51.6 100-200 0.6-1.2 4-6 http://srhp.jsc.nasa.gov/docs/hqbriefing99/HQBriefing99_files/slide0194.htm CONCLUSIONS • Life, as we know it, is possible with water, atmosphere, and magnetic shielding of Earth • Space radiation levels are estimates (Mixed Radiation, Low Dose Rate Exposure) • Space Station astronauts experience the most exposure (150 mSv) due to mission duration • Mars visitors may faces 10-fold higher doses (up to 1500 mSv = 150 rems) – 5% Enhanced risk of cancer upon return to earth ? – Within range of acute radiation sickness – Pray for no technical failures or solar/galactic flares So …who’d want to go there ? Roberta Bondar
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