RADIATIONRADIATION

Radiation BasicsRadiation Basics

RadiationRadiation – – Energy in Energy in transittransit:: Radiation is energy that comes from a source and Radiation is energy that comes from a source and

travels through some material or through space. travels through some material or through space.

Two Types of RadiationTwo Types of Radiation

• IonizingIonizing radiation has radiation has highhigh energy and energy and displaces electrons from their orbits displaces electrons from their orbits creating charged atoms (ions)/moleculescreating charged atoms (ions)/molecules– Creates Creates DNA damageDNA damage– Cell Cell deathdeath– Bystander effectBystander effect– GenomicGenomic instability instability

• Non-ionizingNon-ionizing radiation creates heat due radiation creates heat due to to lowlow energy energy – Infrared, MRIInfrared, MRI

Electromagnetic Electromagnetic SpectrumSpectrum

10-14 10-12 10-10 10-8 10-6 10-4 10-2 1 102 104 106 108

Wavelength in Meters

1010 108 106 104 102 1 10-2 10-4 10-6 10-8 10-10 10-12 10-14

Broadcast

Short waveTV

FM

RadarInfrared

Near Far

Visible

UltravioletX Rays

Gamma Rays

Cosmic Rays Power Transmission

Ionizing Radiation Nonionizing Radiation

Energy - Electron VoltsHigh Low

Radiation Effects

•Most all cells in the body are SOMATIC CELLS – Cells that make Lungs, heart, brain, etc

• Reproductive cells are GERM CELLS– Cells that make Sperm and Egg

•DNA has checkpoints that correct mistakes during replication– Genomic Instability results when

checkpoint doesn't correctly repair the DNA

Four Types of MutationsPoint mutations are small changes

– usually a single nucleotide base. (A,C,T OR G)

1)Insertions - an extra nucleotide base is added into an existing gene.

2)Frame shift mutations - either addition or deletion of one or two nucleotide bases.

3)Substitutions- the replacement of one nucleotide base with a different nucleotide base.

4)Inversion- Nucleotide bases are switched

Ionizing Radiation SourcesIonizing Radiation Sources

Types of Radioactive Types of Radioactive DecayDecay

U-238 U-238 radioactive radioactive decaydecay

• Unstable atoms randomly decay in stable Isotopes

• Isotopes are different forms of an element

Same number of protons, but different number of neutrons Process is called transmutation

Some reactions take place very quickly; they have a short half-life, t1/2.

half-life: the time it takes for half of the atoms in a sample to decay.

Decay

Half-life

Half-life

Every radioactive isotope has a different half-life.

Isotopes with short half-lives do not occur in nature, but must be generated in the laboratory.

RadonRadon• Produced from Produced from

radiumradium in decay in decay chain of chain of uraniumuranium

• Escapes into air – Escapes into air – short lived decay short lived decay products emit alpha products emit alpha particles – stick to particles – stick to dust, inhaled, dust, inhaled, deposit in lung – deposit in lung – high but localized high but localized radiationradiation

• Second most Second most significant cause significant cause lunglung cancer cancer

What is carbon dating?

How can we tell how old fossils are?

Carbon dating

Carbon dating revolves around carbon-14, a radioactive isotope.

1 147 1

14 10 6n N C H

Carbon-14 is generated in the upper atmosphere through a bombardment reaction:

Neutrons generated by cosmic rays

becomes 14CO2 in the atmosphere

Carbon-14 goes through the same cycle as carbon-12

Carbon dating

14

Over time, carbon-14 decays by emission:

14 14 06 7 1C N e 1/2 5,730t years

Carbon dating

When the organism dies, it no longer consumes carbon from the environment.

The number of carbon-14 atoms in the dead organism will decrease over time.

Carbon dating

Ratio not to scale

An archeologist looks at the ratio of carbon-14 to carbon-12.

Carbon dating works reliably up to about 10 times the half-life, or 57,300 years (beyond that time, there is not enough carbon-14 left to detect accurately).

Carbon dating only works on material that has once been living: tissue, bone, or wood.

Radioactive dating

the composition of the atmosphere over time

the age of rocks that are billions of years old

the age of a once-living organism

Information can be extracted from the ratio of specific isotopes

Carbon-14 and carbon-12

Oxygen-18 and oxygen-16

Uranium-238 and plutonium-239

Health Effects of RadiationHealth Effects of Radiation

Ionizing Ionizing radiationradiation

• Capacity to damage Capacity to damage core genetic core genetic blueprint - DNAblueprint - DNA

→ → cancercancer

→ → other health effectsother health effects

→ → genetic damagegenetic damage

• Many different Many different isotopesisotopes

• Behave differently Behave differently biologicallybiologically

Fetal radiation riskFetal radiation risk

• There are radiation-related There are radiation-related risksrisks throughout pregnancy that are throughout pregnancy that are related to related to the stage of pregnancy and absorbed the stage of pregnancy and absorbed dosedose

• Radiation risks are most significant during Radiation risks are most significant during organogenesisorganogenesis and in the early fetal and in the early fetal period, somewhat less in 2period, somewhat less in 2ndnd trimester, trimester, and least in 3and least in 3rd rd trimestertrimester

• Less Least

Most risk

Medical Radiation ExposureMedical Radiation ExposureProcedureProcedure EffectivEffectiv

e dose e dose (mSv)(mSv)

EquivaleEquivalent CXRnt CXR

EBR EBR (days)(days)

Equivalent Equivalent aircraft aircraft flight hoursflight hours

Probability of Probability of fatal cancerfatal cancer

Chest x-ray Chest x-ray (PA)(PA)

0.020.02 11 33 22 1:625,0001:625,000

CT brainCT brain 33 150150 456456 300300 1:42001:4200CT chestCT chest 88 400400 12171217 800800 1:16001:1600CT CT abdo/pelvisabdo/pelvis

1111 550550 16731673 11001100 1:11001:1100

CT coronary CT coronary angioangio

1010 500500 15211521 10001000 1:12501:1250

Conventional Conventional coronary coronary angioangio

3-113-11 150150 456456 300300 1:42001:4200

Ba enemaBa enema 8.78.7 435435 13231323 870870 1:14001:1400mammographmammographyy

0.10.1 55 1515 1010 1:1250001:125000

Nuclear Nuclear myocardial myocardial perfusion perfusion studystudy

1212 600600 18251825 12001200 1:10001:1000

Nuclear bone Nuclear bone scanscan

4.44.4 220220 669669 440440 1:28001:2800

CT ScannersCT Scanners

CT ScannersCT Scanners

Radiotherapy: Radiation Treatment

• Used for 4 out of 10 people with Cancer

• Most hazardous when a brain tumor is being irradiated and the surrounding tissue is vital for normal brain function.

VIDEO: http://www.nhs.uk/conditions/Radiotherapy/Pages/Introduction.aspx

Radiotherapy may be used:

to cure an illness - for example, by destroying a tumor (abnormal tissue)

to control symptoms - for example, to relieve pain

before surgery - to shrink a tumor to make it easier to remove

after surgery - to destroy small amounts of tumor that may be left

Radiotherapy• Smoking kills – in a terrible

way sometimes • Smokers have 1 in 7

chance of getting cancer• Smoke Deposits Polonium

210 in the lungs • 210Po is a radioactive

element • Tobacco Smoke is a

mixture of over 7000 chemicals•70 are known

carcinogens – (cancer causing agents)

Radiotherapy•High doses of

ionizing radiation can kill cells;

•They are used to kill cancer cells and harmful microorganisms.

Radiotherapy

•Tumors can be treated using •gamma rays (nuclear radiation)

•high energy X-rays •Both have the same wavelength

Definition: tumor n. a swelling, especially from an abnormal growth of tissue, whether benign or malignant.It comes from the Latin tumor from tumere ‘ to swell’

Radiotherapy

•Several treatments are usually given over a time period of several weeks to minimize the side effects •Nausea•Vomiting •Fatigue

Exposure to UV Waves Sun Damage

Early Melanoma Detection

Smoke Detectors

• Some smoke detectors contain a small amount of Americium-241• half life of 460 years.

• They consist of an ionization chamber linked to a simple electronic alarm circuit.

Smoke Detectors

• The Americium ionizes the air between the plates, causing a current to flow.

• Smoke entering the detector absorbs some extra alpha particles than the air would , lowering the current, and triggering the alarm.

RADIOACTIVE TRACERS

The use of radioactive elements in everyday situations

Allow non-invasive medical tests

Dating – determining age

Have Very Short Half-Life

Radioactive Iodine is swallowed. A gamma probe is used to detect and measure the thyroid. Checks function and if diseased.

IODINE- 131

Half – Life = 13 hours

Technetium-99

Technetium is injected into the bloodstream and travels to the heart.

Doctors use special cameras to follow the tracer

Half-Life = 66 hours