“ 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 ?