“ 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
Radiation in Medicine
No Dose • Ultrasound (sound waves) • Magnetic Resonance Imaging (MRI)
x rays • Radiography • Computed Tomography (CT Scan)
rays
• Nuclear Medicine • Planar, SPECT, PET • Radionuclide Therapy (Thyroid)
BIG Local Doses
• External Beam • Brachytherapy
Dia
gnos
is
Ther
apy
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
• High energy x-rays can do this to atoms
Incoming x-ray Knocked out electron
atom
Radiation Dose a measure of concentration of energy locally absorbed in any absorber from any type of ionizing radiation
Concentration of energy
absorbed by a tissue sample
D = E (absorbed)/m
Unit is Joules/kg= Gray
m
Electron
E X ray
We can measure Dose in air and in plastic absorbers
http://www.flukebiomedical.com/biomedical/usen/Diagnostic-Imaging-QA/CT-QA/76-424-4156.htm?PID=55264
Dental Cone-Beam CT
L. Kaci and D. Chambers,
Optically Stimulated Luminescence
L. Kaci and D. Chambers Schulich School of Dentistry
We can measure Dose in “Phantoms”
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…
3/4/2014 19 Japan
Effective Dose Spectrum
Chest x-rays 0.05 mSv
CT Scan 7 mSv
Effective Doses (milli-Sv) Typical Natural Radiation near Earth 2.4 mSv/yr
• Airport Security Scan +0.00005 mSv • Passenger Flight (transatlantic) + 0.05 mSv • Flight Crew + 5 mSv/year
Medical Diagnosis
• Dental x-rays 0.005 mSv • Chest x-rays 0.05 mSv • Mammography 0.4 mSv • CT scan abdomen 7 mSv • GI-Barium 8 mSv • Cardiac Fluoroscopy 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)
3/4/2014 21
1 mSv 10 mSv
100 mSv 1000 mSv
Cancer Risks from Diagnostic Radiology
Procedure Typical Effective Dose (mSv)
Equivalent # of Chest x rays
Equivalent Background Radiation (@2.4mSv/yr)
Added
Lifetime
Cancer Risk
(@0.005%/mSv)
Chest x ray 0.05 1 1 week 0.00025 %
Mammography 0.4 8 2 months 0.002 %
Barium x ray
(enema) 8.0 160 3.3 years 0.04 %
CT Scan Abdomen 7.0 140 3.0 years 0.035 %
Cardiac Fluoro 10.0… 200…
4.2 years… 0.05… %
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
Chemical Radicals
DNA Damage
Chromosome aberrations
OH
Scaling up to Chromosomes
Chromosome Aberrations in Irradiated Cells
V. Moiseenko UCSD
http://microbiology.ucdavis.edu/kowalczykowski/genetic%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
3/4/2014 33
Exposure to radiation
Ionizations, etc.
Chemical changes
Alterations in cellmetabolism
Permanent modifications infunctioning of some cells
Microscopically observabledamage
Long delayed effects ofradiation such as genetic
changes or the induction ofcancer
Death of individual cells
Radiation sickness (whichcan lead to death) in
multicellular organisms
Low doses
Stochastic High Doses
Deterministic
200,000 immediate deaths 40,0000 from radiation 200,000 still under study
3/4/2014 35
Atomic Bomb Survivors Study
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
Radiography
and CT scans “Shadows”
Ultrasound “Echos”
MRI “Music”
Medical Imaging with Radiation
CT is 3D x ray Vision !
http://www.fleshandbones.com/readingroom/pdf/940.pdf
Computed Tomography (CT)
• Tomos means “slice” (Greek)
• A method of imaging internal cross-sectional 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 Source
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
00 to 30% 30 to 90% 90 to 100%
Dose Rate Dose
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 !
J2. Battista, Ph.D.
Radiation in Space
Chris on Space Station
https://www.facebook.com/AstronautChrisHadfield
Summary of Space Dose Levels Program Altitude Inclination Dose Dose Rate Duration Duration
(km) (degrees) (mSv) (mSv/day) (days) (months) Gemini 454 30.0 0.5 0.9 0.6 0.0
1370 30.0 4.7 4.7 1.0 0.0
Apollo 12.2 1.3 9.4 0.3
33.0 3.9 8.5 0.3
Skylab 381 50.0 72.0 1.2 60.0 2.0
435 50.0 170.0 2.1 81.0 2.7
STS 570 28.5 26.5 3.2 8.3 0.3
78.0 7.7 10.1 0.3
337 28.5 2.1 0.2 9.1 0.3
7.1 0.4 17.8 0.6
STS/Mir 341 51.6 99.0 0.7 137.5 4.6
355 51.6 140.0 1.0 140.0 4.7
ISS 350-450 51.6 100-200 0.6-1.2 4-6
http://srhp.jsc.nasa.gov/docs/hqbriefing99/HQBriefing99_files/slide0194.htm
• 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
CONCLUSIONS
Roberta Bondar
So
…who’d
want to
go there ?