1. Applications of Nuclear Science I PAN 2015
Dr. Robert McTaggart
South Dakota State University
July 29, 2015

2. Outline Isotopes for Medicine Isotopes for Industry
Gamma Sterilization
Food Irradiation
Environmental Analyses
Isotopes from Fission
NORMs
Neutron Activation Analysis
Medical Physics
Radiation Therapy
Medical Imaging
Health Physics

3. Isotopes for Medicine
Radioisotopes can either be used for localized radiation therapy, sterilization of equipment or fluids, or as radiotracers that can be tracked by medical imaging
Probably the most ubiquitous of the medical isotopes is Technetium- 99m, which is used in imaging the skeleton and the heart, but also in many other studies
They are typically produced by a nuclear reactor, an accelerator, or a cyclotron.

4. Isotopes of Interest Iodine-131 (8 days) Arthritis
Emits both gammas and betas
Primarily used in treating thyroid cancer since the thyroid uptakes iodine.
Also produced by fission
Arthritis
Erbium-169 (9.4 days)
Dysprosium-165 (2 hours)
Yttrium-90 (64 hours)

5. Radiation Therapy Alpha Therapy Brachytherapy Neutron Capture Therapy
Bismuth-213 (46 minutes), very high gamma ray (8.4 MeV)
Lead-212 (10.6 hours), melanoma, breast cancer, ovarian cancer
Brachytherapy
Iodine-125 (60 days), prostate and brain
Palladium-103 (17 days), prostate
Yttrium-90 (64 hours), liver
Copper-67 (2.6 days)
Neutron Capture Therapy
Boron-10
Gadolinium-157

6. Medical studies Iron-59 (46 days), iron metabolism in the spleen
Sodium-24 (15 hours), electrolytes
Technetium-99m (6 hours), bone, heart, brain, lungs, etc.
Xenon-133 (5 days), lung ventilation
Ytterbium-169 (32 days), cerebrospinal fluid
Chromium-51 (28 days), blood flow

7. Gamma Sterilization Cobalt-60 (5.27 years) Cesium-137 (30 years)
Higher energy gamma rays (1.17, 1.33 MeV)
Requires more shielding, but sterilizes the entire volume in a shorter time
Cesium-137 (30 years)
Lower energy gamma rays (0.662 MeV)
Takes more time to deliver a dose
Less Shielding required
Alternative: Electron Beam Irradiation
Good for irradiating surfaces only

8. Medical Imaging Positron Emission Tomography
Carbon-11, Nitrogen-13, Oxygen-15, Fluorine-18 can be attached to sugars to study brain behavior.
Gallium-68 (68 minutes)
A positron is emitted, it annihilates with a nearby electron, and two gammas are released back-to-back.
Detectors based upon particle physics register the gamma rays and determine where the gammas came from.

9. Carbon-14 and Hydrogen-3
Carbon-14 is a major research tool for biology as a radiotracer.
Carbon-14 dating is important for archaeological studies.
Tritium (Hydrogen-3) is used as a tracer in drug development.
Used copiously in Exit signs!

10. By special request, Fe-55, 2.7 years
Emits X-rays
Used in space missions for power-free source of X-rays to use in X-ray Fluorescence for elemental composition.
Analyzes electroplating solutions, detects Sulphur content in the air.
Also used in metabolism research

11. Neutron Activation Analysis
Another method of isotopic analysis that complements X-ray Fluorescence and Mass Spectrometry.
Some isotopes can absorb a neutron (i.e. it gets “activated” by becoming radioactive) and emit a set of characteristic photons.
The photons are detected using a high purity germanium detector.
Typically it is the heavier metals that are useful in NAA.

12. Elements accessible to neutron activation

13. Let short-lived isotopes decay
Sample Preparation
Irradiation
Let short-lived isotopes decay
Counting of Nuclear Decays
Data Analysis

14. Counting
Irradiation
Delay
Counting
Activity
Time
Once the foil is removed, the isotope is no longer produced and only undergoes decay.
In general, there is an irradiation time, a delay time between irradiation and counting, and the actual counting time.
The number of counted events is related to the neutron flux.

15. Signal to noise
Background events are produced by partially captured gamma-rays from our source or from the environment.
Some of this cannot be helped, since the detector often contains only part of the incoming radiation’s energy, not all of it.
There is a lower limit of detection based upon the count of a null sample and the gaussian nature of the response from the detector.

16. Neutron Activation Analysis examines many elements at once

17. Sample NAA spectrum

18. Examples of NAA
Analysis of mercury, arsenic, or other metals in hair or fingernails.
Isotopic analyses for meteorites, volcanic rocks, Native American pottery.
Impurities in industrial and agricultural products.
Environmental analysis.
Sulfur content in coal prior to use in a power plant.
Nutritional studies for plants, animals, people.
Forensics of metals in guns/bullets.
Trace elements in semi-conductors and photovoltaics.
Assay of rare earth metals in raw materials.
Beneficial for areas that require knowledge of composition and contamination.

19. Naturally Occurring Radioactive Materials (NORMs): No activation necessary

20. Medical Physics
Radiation Therapy

21. How do photon radiation beams interact with matter?
Attenuation of a photon beam by an absorbing material is caused by 5 major processes in the energy ranges produced by medical linear accelerators
Coherent Scattering
Photoelectric Effect*
Compton Effect*
Pair Production*
Photodisintegration

22. Biological Basis of Radiation Therapy in a Nutshell
Ionizing radiation can induce detrimental biological effects in organs and tissues by depositing energy that may damage DNA
Rapidly proliferating tissues are relatively radiosensitive

23. Why use protons in therapy?

24. Imaging with X-rays
X-rays are scattered by elements with lots of electrons.
This produces a dark image for the negative.
Bone appears white because calcium has more electrons than tissue, which is oxygen, hydrogen, and carbon.

25. Imaging with neutrons (a reverse X-ray)
Neutrons are absorbed or scatter off of lighter Z materials, particular hydrogen.
Carbon and Boron also have high neutron cross sections.
Metals have low neutron cross sections, so one may use neutron radiography to image organic material wrapped in metals.
Metals prevent X-rays from getting through, but not neutrons.

26. Health Physics
The health physicist is dedicated to supporting a safe working environment for radiation workers and the public.
Such efforts include
Environmental Analyses of air/water/soil for radionuclides
Development of procedures for nuclear power operations
Construction of radiation shielding for medical physics facilities
Production and delivery of radioisotopes in nuclear medicine
Design and use of radiation detectors
Emergency management operations
Studies of radiation biology
Oversight of radiation doses received by workers.
Use of irradiation to sterilize medical products