Understanding RadioactivityThe Basics

This Course This course is intended to provide a very

basic understanding of radiation, radioactivity, and interacting with radioactive patients.

This course is not intended to serve as health physics training.

Environmental Health & Safety/ Radiation Safety

Radiation is: The process in which energy is released

in the form of waves or particles from an unstable atom.

Naturally occurring and man-made

All around us.

Naturally Occurring Radiation Can come from many sources:

The ground that we walk on The mountains we climb The food we eat The water we drink The air we breathe Outer space And, even from ourselves

Man-Made Radiation Below are a few examples:

X-ray machines CT scanner, Linear Accelerator (Radiation Therapy),

Mammography, etc.

Radiopharmaceuticals & Implanted sources

Tc-99 and I-131 (Nuclear Medicine), I-125 and Cs-131 (Radiation Oncology)

Industrial sources Co-60 and Ir-192 (weld evaluation)

Radiation Exposure Rate & Radiation Exposure

As we progress through this course, you will see mR/hr and mrem being referenced.

Note: mR/hr refers to the rate of radioactivity

measured in air(in other words, how much radiation is being released from the source)

mrem refers to the amount of radiation an individual is exposed to.

Radioactivity Can be described as the process in which an

unstable atom releases energy and/or particles in an attempt to reach stabilization (non-radioactive form).

This process is referred to as radioactive decay. This can take minutes or years to complete;

depending on the substance (isotope) in question.

Example:

RadioactiveTechnetium 99

(Used in Nuclear Medicine)

Stabilization takes approximately 60 hours

StableRuthenium 99

Decays into..

Radioactivity-Half-Life

All radioactive substances have a “Half-Life”. Note that not all substances have the same “Half-Life”.

Radioactive “Half-Life” can be defined as the amount of time for a radioactive substance to decay to half of its original radioactivity.

Here is an example: Technetium-99 (Nuclear Medicine) has a “Half-Life” of 6 hours. If we measure 10 mR/hr initially (At the source) In 6 hours it would measure 5 mR/hr In 12 hours it would measure 2.5 mR/hr In 18 hours it would measure 1.25 mR/hr

As you can see, the amount of radioactivity diminishes over time.

A general rule of thumb is that radioactive substances require ten half-lives to decay almost entirely (1/1000th of original activity).

Radiation Exposure & Exposure Limits

We are all exposed to certain amounts of radiation every day.

The annual average natural radiation exposure in the United States is approximately 310 mrem for members of the general public.

Occupational radiation exposure limits are as follows (18 yrs of age or older): Whole body (deep dose) 5000 mrem Lens of eye 15,000 mrem Extremities (hands, etc.) 50,000 mrem

General public radiation exposure limit: 100 mrem

Radiation Exposure cont. Here are two examples (for perspective)

of common medical procedures that result in radiation exposure but, not a “Radioactive” patient.

A single-view chest x-ray = 10 -15 mrem

A dental x-ray = 1.5 mrem

Radiation Exposure-Taking it a Little Further

Radiation exposure rate: Lets assume that we have a radioactive source whose

measured activity is 10 mR/hr 3 inches from its surface

Radiation exposure: Now, we place our hand at the same distance (3 inches) from

the radioactive source and keep it there for one hour.

Radiation Exposure Rate & Radiation Exposure areequivalent. 10 mR/hr _ 10 mrem

However If we take the same source but, leave our hand over it (3 inches) for 1 minute, we only get .17mrem of radiation exposure.

It would take 500 hours at this exposure rate and distance to meet the annual maximum whole body exposure limit of 5000 mrem.

And, it would take 10 hours to reach the maximum allowable exposure (100 mrem) for the general public.

10 mR/hr

Radioactivity and Distance Relationship

The Inverse Square Law teaches us that intensity at a given point is reduced to ¼ of its value when the original measured distance is doubled. Example:

2 feet

4 feet

10 mR/hr 2.5 mR/hr

Radioactive & Non-Radioactive Patients

A Nuclear Medicine patient having just completed a cardiac stress study typically emits radiation at a rate of approximately 2mR per hour at one meter (approximately 3 feet).

A Radiation Oncology patient with an eye plaque usually emits radiation at a rate of approximately 2 mR per hour at one meter (from the eye plaque, not the entire patient)

A patient having just completed a Radiation Therapy session (Linear-accelerator) is not radioactive. They were exposed to radiation but, are not radioactive as a result.

A patient having just completed a CT scan is not radioactive. They too, were exposed to radiation but, are not radioactive.

The majority of imaging procedures do not result in a patient being radioactive.

Radioactive Patients-Radioactive Contamination

Radioactive contamination occurs when a radioactive material is somewhere that it was not intended to be. Here are some examples:

Radioactive material spill Radioactive material leakage Radioactive material release from a patient (blood and excreted waste)

Not all radioactive patients are considered to be a contamination risk. A select few procedures result in potential radioactive

contamination for a short period of time. For those few; patients are given very specific instructions prior to their

procedure. Those that pose the greatest risk are treated as in-patients and are

released once the risk has diminished.

Working Around Radiation-Should I be Worried?

Absolutely not! The MS State Department of Health sets all

radioactive standards. This includes both radiation exposures and specific

patient release requirements. These standards are very conservative (Low levels). They were put into place in order to ensure that no one

in the general public is in any danger of excessive radiation exposure or radioactive contamination as a result of being near radiation and/or radioactive patients.

Our staff are diligent in adhering to these standards.

What to Take Away From This? We are around many different sources of radiation

every day.

Not all procedures involving radiation result in a radioactive patient.

Most radioactive patients pose no exposure or contamination threat.

Radiation Safety Contacts Robert Nelson 984-1989 Mark Langston 815-1993 Dale Tallman 815-1989 Logan Cowart 815-5128