Unit 8

RADIOACTIVITY AND ITS USES

UNIT VIII

POST RN BSN

LIFE SAVING CON

Natural Radioactivity

• Radiation - the particles or rays emitted• Radioactivity - process by which atoms

emit energetic particles or rays– comes from the nucleus

• Nuclear symbols - what we use to designate the nucleus– Atomic symbol– Atomic number– Mass number

particleElectromagnetic wave

Unstable nucleus

Atoms which emit electromagnetic radiation or a particle by the spontaneous transformation of

their nucleus are called radioactive.

B115atomic symbol

atomic number of protons

mass number of protons and neutrons

Nuclear Symbols

Three Isotopes of Carbon

• Each nucleus contains the same number of protons

• Only the number of neutrons is different• With different numbers of neutrons the mass

of each isotope is different

Unstable Isotopes• Some isotopes are stable

• The unstable isotopes are the ones that produce radioactivity

• To write nuclear equations we need to be able to write the symbols for the isotopes and the following:

– alpha particles

– beta particles

– gamma rays

Types of radiation

• Beta Particle (β)

• Gamma Ray (γ)

-

• Alpha Particle (α)

Radioactive decay

Some atoms are radioactive this means their nucleus is unstable and decays to become more stable. When nuclei decay they emit or get rid of something from the nucleus

There are three types of radioactive decayAlpha decay : This is when 2 protons and 2 neutrons leave the nucleus to help it become stable Alpha particle. A positively charged particle that consists of two protons and two neutrons bound together. It is emitted by an atomic nucleus undergoing radioactive decay and is identical to the nucleus of a helium atom.

Beta Decay: This is when a neutron in the nucleus turns into a proton and electron. The electron then leaves the nucleus. Beta particles are high-energy, high-speed electrons or positrons emitted by certain types of radioactive nuclei such as potassium-40. The beta particles emitted are a form of ionizing radiation also known as beta rays.

Gamma decay, a high energy photon is emitted from the nucleus to attain a lower energy configuration. In the gamma decay of a nucleus, the emitted photon and recoiling nucleus each have a well-defined energy after the decay. Gamma rays are ionizing radiation, and are thus biologically hazardous. They are classically produced by the decay of atomic nuclei as they transition from a high energy state to a lower state known as gamma decay, but may also be produced by other processes.

Medical Applications of Radioactivity

• Modern medical care uses the following:– Radiation in the treatment of cancer– Nuclear medicine - the use of

radioisotopes in the diagnosis of medical conditions

• Based on the fact that high-energy gamma rays cause damage to biological molecules

• Tumor cells are more susceptible than normal cells

• Example: cobalt-60• Gamma radiation can cure cancer,

but can also cause cancer

Cancer Therapy Using Radiation

Nuclear Medicine

• The use of isotopes in diagnosis

• Tracers - small amounts of radioactive substances used as probes to study internal organs

• Nuclear imaging - medical techniques involving tracers

• Example:– Iodine concentrates in the thyroid gland

– Using radioactive 131I and 125I will allow the study of how the thyroid gland is taking in iodine

Tracers

• Radioactive tracers can be used to see how well organs in your body are working or to find areas of disease.

e.g. radioisotopes of iodine or technetium.

• Often these are mixed with a drug that collects in a particular organ in the body.

• If we then inject the drug into the body, then by detecting the radiation, we can examine that organ.

Preparing the Tracer

The tracer being injected into thhe Patient

Gamma Camera

A gamma camera detects the radiation coming from the patient and produces an image of where the radioactivity is in the body.

Obtaining the Image

• The gamma camera displays the position of each gamma ray that it detects.

• This is a bone scan made using technetium-99.

• Can you see where the patient was injected?

Tracers and their UsesBone : 99mTc used to detect cancer, stress fractures

and bone graft success.Thyroid: 123 I used to access over-active and under-

active thyroids, as well as thyroid tumours, cysts and goitres.

Lungs: 133Xe inhaled for ventilation studies (airways) and 99mTc administered for perfusion studies (blood flow).

Heart: 201Tl used to study muscle performance.Brain: 99mTc used to assess dementia and stroke

damage.Dilution analysis to access blood and water volumes (the tracer mixes with certain body fluids).

Body blood: 99mTc used to assess volume.Red cells: 51Cr is attached to these.Minerals: 24Na and 42K used to monitor body sodium and

potassium.

Radiotherapy• Rapidly dividing cells are particularly sensitive to damage by radiation.

For this reason, some cancerous growths can be controlled or eliminated by irradiating the area containing the growth. External irradiation can be carried out using a gamma beam from a radioactive cobalt-60 source,

• Internal radiotherapy is administered by planting a small radiation source, usually a gamma or beta emitter, in the target area. Iodine-131 is commonly used to treat thyroid cancer, probably the most successful kind of cancer treatment. It is also used to treat non-malignant thyroid disorders. Iridium-192 implants are used especially in the head and breast. They are produced in wire form and are introduced through a tube called a catheter to the target area. After administering the correct dose, the implant wire is removed to shielded storage.

• Treating leukemia may involve a bone marrow transplant, in which case the defective bone marrow will first be killed off with a massive (and otherwise lethal) dose of radiation before being replaced with healthy bone marrow from a donor.

Gamma KnifeThis technique is used for brain surgery . Instead of opening the patient's head the gamma rays from a Cobalt 60 source are focussed on the tumour. The location of the tumour would have been accurately mapped earlier using an MRI or CT scan