What Is Radiation?

Return to Calculator

Radiation is the process by which energy waves or particles pass through objects, the atmosphere, or people.  Radiation comes from both man-made sources and natural sources.

Man-made sources of radiation include:

Medical Radiation:  The greatest source of man-made radiation is from medical procedures, such as X-rays, CT scans, nuclear medicine and radiation therapy.

tvConsumer Products:  Low levels of radiation exist in many consumer products like televisions, cell phones, airport X-ray systems, road construction materials, fluorescent lamp starters, camping lantern mantles and more.

Nuclear Fuel:  Although minimal, people are exposed to radiation from nuclear fuel from the mining process through nuclear power plant energy production.  Individuals are sometimes exposed from other activities involving radioactive materials.

Natural radiation is present in the environment every day.  Sources include:


Earth: Sources from the earth like building materials and the gasses like radon from the earth's crust.

Space: Cosmic rays from space.

Our Body: Internal radiation from your own body's absorption of radiation.

Imaging Tests

Return to Calculator

An Angiography is a medical imaging technique, sometimes known as arteriography. It is used to see blood vessels and organs of the body. It is most commonly used to view the heart chambers, veins and arteries. The technique is done by injecting a dye, known as contrast, directly into an artery and taking an X-ray of the part of the body in question.

A CT (or CAT scan) takes multiple pictures of your body using radiation that are combined to make a cross-sectional 3D image. Dye (contrast) may be used to enhance the image.

An Echo stress test test is an exam of the heart without radiation that utilizes exercise and an ultrasound (sonograph) to evaluate the functioning of the heart.

A Fluoroscopy is a medical imaging technique that looks at real-time moving images of the body. The patient will either ingest a contrast agent or lay on a fluorescent screen while an X-Ray source records the real-time images of the body’s anatomy and function.

An MR (magnetic resonance) exam uses magnetic and radio waves to take pictures of thin slices of your body from different angles without radiation. MRs include MRIs and MRAs. Your test may include dye (contrast) to take the image.

A Nuclear exam uses radioactive materials to image certain body areas and functions. This includes nuclear stress tests and nuclear bone scans. Nuclear exams generally have the highest level of radiation exposure of all tests.

A PET (positron emission tomography) scan uses a radioactive material to take pictures to evaluate many types of cancers, heart disease and other abnormalities of the body.

An Ultrasound (sonography) uses high-frequency sound waves to produce pictures of the inside of the body without radiation.

An X-ray works like a camera, sending a small amount of radiation through the body to record a black and white image on a special film.


Return to Calculator

Ionizing radiation is a form of energy that is used in imaging centers, hospitals and clinics to perform certain medical diagnostic imaging procedures, like CT scans. However, not all imaging procedures require radiation.

In some instances, you may have alternative imaging tests that may provide the same results with no radiation.

Most doctors are open to a dialogue about radiation exposure prior to ordering a test and will discuss any appropriate clinical alternatives including alternative imaging procedures without radiation exposure:

Magnetic resonance (MRI and MRA) imaging tests use a magnetic field and radio waves to create detailed images of the organs and tissues within your body. MRI and MRA tests can be used to replace CT and PET testing in certain clinical situations.

Ultrasound testing (sonography) is an imaging method that uses high frequency sound waves to produce images of the structures within your body. Ultrasounds can be used to replace CTs in certain clinical situations.

An Echo stress test is a process to image the heart that uses exercise and an ultrasound (sonogram) to evaluate the functioning of the heart. Echo stress can be used to replace a nuclear stress test in certain clinical situations.

You are encouraged to discuss alternatives with your doctor before any imaging test used primarily as a non-clinically urgent diagnostic exam.

Questions To Ask

Return to Calculator

Questions to AskBalancing the risks and benefits of a medical imaging test involves careful consideration of many factors.  If a medical imaging test is your best option, educate yourself about the procedure and medical conditions related to it, and then discuss this with your doctor.

Five Key Questions to Ask Your Doctor

  1. What will be the outcome of the test results?  It is important to understand what the next clinical steps are as you consider a diagnostic test ... will the outcome be an elective surgery ... physical therapy ... medically necessary surgery?
  2. Are you a candidate for an imaging test that does not involve radiation, such as an MRI or ultrasound?  Some conditions can be diagnosed effectively (and in some cases more effectively) with an MRI or ultrasound.
  3. Should I do something else before the test?  There are accepted clinical practices that can support earlier diagnosis and treatment of certain conditions.  Often times these tests and treatments require no imaging testing and therefore no risk to the patient.  It is important to discuss all options with your doctor.
  4. How do I select a facility that has a comprehensive patient radiation safety plan?  You always have the option to select the facility that best meets your needs.  Facilities have different accreditations and safety protocols that you can request prior to an exam.
  5. How much does the procedure cost?  X-rays, ultrasounds and alternative treatments are usually less expensive than MRs or CT scans, and may be able to provide your doctor with the information they need.