Radiation Uses and Safety
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Transcript of Radiation Uses and Safety
Radiation Uses and Radiation Uses and SafetySafety
BI 245BI 245
Weise et al.2000. Plant Cell 12:1345
A plant cell
Sucrose
Sucrose
How can you measure sucrose molecules taken in by the cell?
Expose to Epidermal Growth Factor
Untreated Fibroblast Treated Fibroblast
How would you find out what new proteins are synthesized in the treated fibroblasts?
Labeling with RadioisotopesLabeling with Radioisotopes Radioisotopes are isotopes of atoms that Radioisotopes are isotopes of atoms that
decay and release energy in the form of decay and release energy in the form of particles or electromagnetic energy.particles or electromagnetic energy.
The energy released is a form of The energy released is a form of electromagnetic radiation (like light), but electromagnetic radiation (like light), but very energetic (short wavelengths)very energetic (short wavelengths)
This means if you put a radioisotope on a This means if you put a radioisotope on a molecule, you can find it with radiation molecule, you can find it with radiation detection instruments or film – just like detection instruments or film – just like light.light.
Radioactive Materials in Radioactive Materials in biomedical researchbiomedical research
Most commonly used Most commonly used radioisotopesradioisotopes– H3, C14, P32, P33, S35 -- all beta H3, C14, P32, P33, S35 -- all beta
emittersemitters In vivo and in vitro labelingIn vivo and in vitro labeling
– Na22, K40, Ca45, I125 -- all Na22, K40, Ca45, I125 -- all beta/gamma emittersbeta/gamma emitters Uptake studies for the ions, in vitro Uptake studies for the ions, in vitro
labeling for I125labeling for I125
Weise et al.2000. Plant Cell 12:1345
A plant cell
Sucrose
Sucrose
How can you measure sucrose molecules taken in by the cell?
What isotopes would be best to label sucrose?
How could you find out how much was in the cells?
Expose to Epidermal Growth Factor
Untreated Fibroblast Treated Fibroblast
How would you find out what new proteins are synthesized in the treated fibroblasts?
What isotopes could you use to label newly synthesized proteins?
How would you find those proteins?
Gel electrophoresis of Gel electrophoresis of proteinsproteins
In vivo labeled protein In vivo labeled protein experimentexperiment
Suppose you wanted to label a Suppose you wanted to label a DNA molecule?DNA molecule?
What isotopes What isotopes could you use?could you use?
How could you How could you find the labeled find the labeled DNA molecule.DNA molecule.
The radioactive molecules The radioactive molecules used in these experiments are used in these experiments are
sometimes called tracerssometimes called tracers Sugars, Lipids…C-14 or H-3Sugars, Lipids…C-14 or H-3 Proteins, C-14, S-35, or H-3 Proteins, C-14, S-35, or H-3
labeled amino acidslabeled amino acids Nucleic acids P-32, either as a Nucleic acids P-32, either as a
P32-labeled nucleotide or as P-32 P32-labeled nucleotide or as P-32 added to one end of the molecule.added to one end of the molecule.
Radioactivity vs RadiationRadioactivity vs Radiation
RadioactivityRadioactivity– Any spontaneous change in the state of
the nucleus accompanied by the release of energy. Alpha, beta, gamma, neutrons
Radiation– Refers to the actual particles or photons
emitted and the energy they carry.
Electromagnetic RadiationElectromagnetic Radiation
IonizingNon-ionizing
What defines the differences in What defines the differences in radionuclides and the radiation radionuclides and the radiation
they emitthey emit What type of radiation (alpha, beta, What type of radiation (alpha, beta,
gamma)?gamma)? How does that radiation interact with How does that radiation interact with
matter?matter? How much energy does the radiation How much energy does the radiation
have?have? How long with the radiation last (half-How long with the radiation last (half-
life of the radionuclide.life of the radionuclide.
Results of alpha decay Results of alpha decay processprocess
Alpha particlesAlpha particles
Move in straight Move in straight lineline
Lose little energy Lose little energy in each interactionin each interaction
But have many But have many interactions in the interactions in the pathpath
Consequently don’t Consequently don’t travel very far travel very far
Results of beta decay Results of beta decay processprocess
Electrons and Positrons Electrons and Positrons (betas)(betas)
Interaction Characteristics:•Ionize and excite atomic electrons•Few interactions per unit path length – few ions produced and low energy transfer.
Path Length > Range
•Large energy loss per collision•Path is not straight
Higher energy deposition at end of path
(more interactions at end of path)
Energy differencesEnergy differences
BetasBetas– H3 = 0.018 MeVH3 = 0.018 MeV– C14 = 0.156 MeVC14 = 0.156 MeV– P32 = 1.71 MeVP32 = 1.71 MeV
GammasGammas– Co60 = 1.33 MeVCo60 = 1.33 MeV– Cs137 = 0.66 MeVCs137 = 0.66 MeV
Half-Lives of Half-Lives of RadionuclidesRadionuclides
H-3H-3 12.26 years12.26 years C-14C-14 5730 years5730 years S-35S-35 87 days87 days P-32P-32 14.3 days14.3 days Am-241Am-241 432 years432 years
Radiation RiskRadiation Risk
All higher energy radiation poses some risk All higher energy radiation poses some risk to cells.to cells.– UV – induces thymine dimers in DNAUV – induces thymine dimers in DNA– Betas—induce changes in DNA, potentially Betas—induce changes in DNA, potentially
breakagebreakage– Gammas and alphas -- the same as beta, but Gammas and alphas -- the same as beta, but
generally more energetic, so more potential for generally more energetic, so more potential for damage.damage.
– X-rays -- sameX-rays -- same DNA repair systems are activated, but not DNA repair systems are activated, but not
perfect.perfect.
Radiation RiskRadiation Risk
High Dose (acute)High Dose (acute)– 100-400 rem –effects 100-400 rem –effects
blood cell counts, but blood cell counts, but people usually recoverpeople usually recover
– 400-1400 rem – GI track, 400-1400 rem – GI track, and epithelial cells and epithelial cells effected. Lower end effected. Lower end survive,. Upper end survive,. Upper end don’tdon’t
– Above 1400 rem..death Above 1400 rem..death likelylikely
Atomic Bomb VictimsAtomic Bomb Victims
Chernobyl nuclear Chernobyl nuclear meltdownmeltdown
Low DoseLow Dose– Risk related to chance Risk related to chance
of mutationof mutation– Above 50 rem, risk Above 50 rem, risk
proportional to doseproportional to dose– Below 50 rem, risk Below 50 rem, risk
assessment less clear.assessment less clear.– Effects below 10 rem Effects below 10 rem
unknown.unknown. Primary risk is Primary risk is
induction of cancerinduction of cancer
What factors influence What factors influence probability of radiation probability of radiation
damage?damage? Radiation DoseRadiation Dose
– TypeType– Activity (how much)Activity (how much)– Time of exposureTime of exposure
Types of exposureTypes of exposure
External ExposureHigh energy BetasGammas
Internal exposure – requires intake of radioisotope – Alpha, Beta and Gamma
External Exposure Reduction
• Time:reduce time spent in radiation area
• Distance:stay as far away from the radiation source as possible
• Shielding:interpose appropriate materials between the source and the body
Controlling Internal Exposure
PREVENT INTAKE!PREVENT INTAKE!– Safe Handling Practices!Safe Handling Practices!– Contamination ControlContamination Control
removable surface contamination airborne contamination
Standard Procedures help!– Personal
No eating, drinking, smoking, make-up application, etc when working with RAM
– Procedures Work in hood Wear PPE Clean up contamination Survey to make sure no contamination exists Monitor Air, to make sure procedure doesn’t release
dust or volatiles
Required PPERequired PPE
GlovesGloves LabcoatLabcoat DosimetersDosimeters Safety glassesSafety glasses
Inappropriate PPE!
Appropriate PPE, shielding, and monitoring
Exposures in perspectiveExposures in perspective
You are exposed to ionizing radiation You are exposed to ionizing radiation all the time. This is called all the time. This is called background radiation.background radiation.
Nuclear Medicine4%
Cosmic 8%
Medical X-rays10%
Internal Radionuclides
9%
Rocks and Soil7%
Nuclear Power0.1%
Consumer Products
3%
Radon59%
DOSE LIMITS
What’s my risk of getting cancer from a radiation exposure?
This is hard to determine. The most quoted estimate is that an exposure of 10000 workers to 1 rem of radiation would produce 4 cancers = 0.04%.
Consider that in the US as a whole the risk of cancer is about 25%
BUT!BUT! The public perception of radiation risk is The public perception of radiation risk is
that it is always “DEADLY RADIATION”!that it is always “DEADLY RADIATION”! This graphic shows how the media place This graphic shows how the media place
stories on radiation out of proportion to risk. stories on radiation out of proportion to risk. nb.nb. There were NO documented deaths due There were NO documented deaths due to radiation in the time shown here.to radiation in the time shown here.
Situation Cause of death2.0 mrem cancer from radiationtravelling 700 miles by air accidentcrossing the ocean by air cancer from cosmic raystraveling 60 miles by car accidentliving in Denver for 2 months cancer from cosmic raysliving in a stone building for 2 months cancer from radioactivityworking in a factory for 1.5 wk accidentworking in a coal mine for 3 hr accidentsmoking 1-3 cigarettes cancer; heart-lung diseaserock-climbing for 1.5 minutes accident20 min being a man aged 60 mortality from all causesliving in New York City for 3 days lung cancer from air pollution
Some Risk ComparisonsOne-in-a million chances of
dying
How do you find radiation or How do you find radiation or radioactive materialsradioactive materials
RadiationRadiation– With an exposure meter (reads the With an exposure meter (reads the
radiation field)..These are called ion radiation field)..These are called ion chamberschambers
Radioactive materialsRadioactive materials– With a counter (like a Geiger counter). With a counter (like a Geiger counter).
These measure individual radioactive These measure individual radioactive particles.particles.