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.