Topics for Today

• What are ions?

• How is radiation detected?

• How do you stop alpha radiation? Beta? Gamma?

• Nuclear Medicine

Readings for Today

• What are ions? Sections 5.7 and 5.8

Are ions bad for you?

Readings for Today

• Hazards Associated with Radioactivity Section 7.8

Are ions bad for you?

Topics for Friday

• Nuclear Fission– The BIG difference between U-235 and U-238– Nuclear Fission– Fission Products (Nuclear Waste and Fallout)– Quiz #2

Readings for Friday

• How does Nuclear Fission Work? Section 7.2.

Announcements

PRELAB QUIZ for Week #3

Due BEFORE your lab

this week

You will have three attempts

this week (and for all the rest).

QUIZ #2 Friday.Non-memory

calculators are allowed

Remember to sit in the DARK

colored seats!

Topics for Today

• What are ions?

• How is radiation detected?

• How do you stop alpha particles? Beta? Gamma rays?

• Nuclear Medicine

Ionizing Radiation

α and β particles

γ rays 0

0

0

-14

2

Ionizing Radiation

α and β particles

γ rays 0

0

0

-14

2

Ionizing radiation forms

ions.

Handout

• Ion worksheet

WHAT ARE IONS?

H2O

Ionizing radiation(alpha, beta, or gamma)

H2

O

H2O

++

Ionizing radiation +e-

Is this a chemical

process or a nuclear

process?

Is this a chemical

process or a nuclear

process?

Is it taking place in the

nucleus?

What is an ion?

A charged atom or molecule.

The charge can be positive or negative.

I- H2O+

What is an ion?

A charged atom or molecule.

The charge can be positive or negative.

I- H2O+How are ions

formed?

What is an ion?

A charged atom or molecule.

The charge can be positive or negative.

I- H2O+How are ions

formed?

Ions are formed when there are unequal numbers of protons and electrons.

Are ions bad for you?

YES? MAYBE?NO?

Are ions bad for you?

YES? MAYBENO?

Sodium in a Lake

• http://www.spikedhumor.com/player/FullScreen.aspx?file=http://www.spikedhumor.com/prerolls/78660/2/0/1/data.xml&item=1&timestamp=19&id=78660

Ions commonly found in nature.

Table Salt (sodium chloride)

Limestone

(calcium carbonate and magnesium carbonate)

Baking Soda

(sodium bicarbonate)

How is iodine utilized in your body?

Chapter 11: Nutrition

• Minerals: Macro and Micro

(page 511)How long until a

sample of I-131 is “gone” from a

patient’s body?

How is iodine used in your body?

Two iodine atoms

A gas

Elemental iodine?

I2 molecule?

How is iodine used in your body?

I2 molecule?

Two iodine atoms

A gas

Elemental iodine? Iodide Ion?

ORI-

WHAT ARE IONS?

END

How do we measure radiation?

How do we measure radiation?

Geiger Counter

Geiger Counter

• Filled with an inert gas (usually argon).

H2

O

H2O

++

Ionizing radiation +e-

Remember…

Geiger Counter

• Filled with an inert gas (usually argon).

Ar Ar+ + e-

Alpha, Beta, Gamma Radiation

Geiger Counter

• Filled with an inert gas (often argon).

Ar Ar+ + e- Detected by electronics

Geiger Counter

• Filled with an inert gas (often argon).

Ar Ar+ + e- Detected by electronics

How is this different from a beta particle?

Penetration Depths

What are the differences

between alpha, beta, and gamma

radiation?

Alpha Particles

21084Po 4

2He + 20682Pb

t½ = 138 days

Alpha Particles

np n

p

21084Po 4

2He + 20682Pb

t½ = 138 days

Alpha radiation

np n

p

Alpha radiation can generally be blocked by a piece of paper.

Alpha radiation

np n

p

Alpha radiation can generally be blocked by a piece of paper.

When is alpha

radiation dangerous

?

Where might you find alpha sources in your home?

“This device contains 0.9 microcurie of americium, a radioactive material…”

Beta Source

Cl β + Ar36

17

36

18

0

-1

t1/2 = 31,000 years

Beta radiation

What could stop a beta

particle?

Beta radiation

What could stop a beta

particle?

Gamma Source

Co β + Ni + 60

28

0

-1

60

27

t1/2 = 5.27 years

γ0

0

Gamma radiation

Ionizing Radiation

Symbol Mass Energy

Alpha Particle α 4 Low

Beta Particle β ~0 Medium

Gamma Ray γ

0 High

0

-1

0

0

4

2

Nuclear Medicine

How can we use beta and gamma

particles?

Review - Isotopes

Some isotopes are stable, some isotopes are radioactive

Iodine

131I- vs. 127I-

Iodine

131I- vs. 127I-

Where is iodine used in your

body?

Thyroid

The iodide ion (I-) concentrates in your thyroid

Thyroid

Produces hormones to help regulate heart rate, blood

pressure, metabolism, etc…

Beta (and gamma) decay of iodine

13153I 131

54Xe + 0-1β + 0

0γ

I-131 t ½ = 8.06 days

Review - Isotopes

Which isotope of iodine will

concentrate in the thyroid?

131I- vs. 127I-

Review - Isotopes

Which isotope of iodine will

concentrate in the thyroid?

131I- vs. 127I-

I-131? I-127? Both?

Review - Isotopes

Which isotope of iodine will

concentrate in the thyroid?

131I- vs. 127I-

I-131? I-127? Both!

Chemically speaking,

isotopes behave almost identically

• In thyroid scans, patients ingest potassium iodide (KI).

• In thyroid scans, patients ingest potassium iodide (KI).

Potassium ion (K+) Iodide ion (I-)

Thyroid

The iodide ion (I-) concentrates in your thyroid

Which isotope of iodine will the patient be given

to ingest?I-127 or I-131?

Beta (and gamma) decay of iodine-131

13153I 131

54Xe + 0-1β + 0

0γ

I-131 t ½ = 8.06 days

A gamma scintillation camera measures the gamma rays emitted from the thyroid at three directions, producing a picture of the thyroid.

• This nuclear medicine technique measure the degree of function of the thyroid. – That is, how well does

the thyroid take up iodine?

Figure 7.21 page 337

• “The yellow and red regions show areas of I-131 concentration.”

Thyroid scans

• Normal Indicates thyroid problem

Any other nuclear imaging

techniques?

• Positron Emission Tomography (PET)

Any other nuclear imaging

techniques?

• Positron Emission Tomography (PET)

Any other nuclear imaging

techniques?

Also requires the use of a radioisotope.

Positron Emission Tomography (PET)

What is a positron?

Positron Emission Tomography (PET)

A positron is an “anti-electron,” a type of anti-matter.

SAME mass as an electron

OPPOSITE charge

Known as β0

1

• Some positron emitters…

• 13N 10 min

• 15O 2 min

• 18F 110 min

t1/2ALL of these isotopes are man-made

• Some positron emitters…

• 13N 10 min

• 15O 2 min

• 18F 110 min

t1/2

How does 18F decay?

Positron Emission of 18F

F β + O 18

9

0

1

18

8

Positron

Positron Emission of 18F

F β + O 18

9

0

1

18

8

Positron

Compare with a beta particle…

Positron Emission of 18F

F β + O 18

9

0

1

18

8

Positron

How does this help us

image?

Annihilation Reaction

• An electron is never far away…

eβ +0

1

0

-12 γ0

0

Anti-Matter

Matter ENERGY!!

Positron Electron

Annihilation Reaction

• An electron is never far away…

eβ +0

1

0

-12 γ0

0

Anti-Matter

Matter ENERGY!!

What about the gamma rays?

Annihilation Reaction

• An electron is never far away…

eβ +0

1

0

-12 γ0

0

Anti-Matter

Matter

Equal energy gamma rays

are emitted in opposite

directions.

The gamma rays are detected here!

The gamma rays are detected here!

What can we learn from

PET?

• A common type of scan uses 18F “labeled” glucose.

• A common type of scan uses 18F “labeled” glucose.

• This glucose is metabolized in your body exactly as “normal” glucose.

• A common type of scan uses 18F “labeled” glucose.

• This glucose is metabolized in your body exactly as “normal” glucose.

• With PET, we can “see” exactly where the glucose is going!

So what?

• A common type of scan uses 18F “labeled” glucose.

• This glucose is metabolized in your body exactly as “normal” glucose.

• With PET, we can “see” exactly where the glucose is going!

• Like with I-131 imaging of the thyroid, PET measures REAL-TIME function of an organ (brain, for example), and NOT the anatomy.

Uses of PET

Used to diagnose disease Used to diagram brain function

• Like with I-131 imaging of the thyroid, PET measures REAL-TIME function of an organ (brain, for example), and NOT the anatomy.

Functional changes are noticed earlier than

structural changes in your body.

For example

• Cancer cells metabolize glucose different than normal cells.