Understanding Radiation Doses From X-ray and CT Exams

It’s normal to be concerned about radiation exposure because, in large doses, it can damage healthy living tissues and increase the risk of cancer. However, the doses used in medical imaging procedures such as X-rays and CT scans are low, and the benefits of the lives we save using these methods in emergencies and early detection of cancer and disease far outweigh the risks involved.

Let’s put this into perspective by explaining how radiation is measured and the types used in medical procedures compared to naturally occurring background exposure.

How Is Radiation Dosage Measured?

In medical procedures, radiation is measured via effective dose, not the Geiger counters you see on TV that detect the intensity of radioactive emissions. The effective dose considers the biological effects, which vary with the sensitivity of the different body tissues. When it enters the body, some is absorbed, contributing to that patient’s dose, while what passes through does not contribute to their doses. 

The effective dose absorbed by a patient during medical procedures is measured in millisieverts or mSv. Doctors use this to evaluate the risk of exposure compared to everyday sources like natural background radioactive materials. Doctors always follow the ALARA principle (As Low As Reasonably Achievable) to minimize exposure as much as possible. 

Given the benefits of diagnostics that save countless lives daily, the minimal amount used in medical images is considered much more beneficial than the minimal risk it presents. 

Types of Radiation

We use electromagnetic radiation waves to perform detailed medical imaging tests crucial in diagnostics and treatments. The two main types of radiation used in medical imaging are ionizing and non-ionizing.

Ionizing Radiation

Ionizing radiation uses high-energy electromagnetic waves that remove electrons from atoms, causing the atom to become electrically charged, called an ion. These free electrons and ionized atoms can damage living tissues.

This form is widely used in X-rays, CT scans, and nuclear medicine. Electromagnetic waves are absorbed or passed through bones, tissues, and organs based on density. It produces a view with shades of gray depending on how much passed through. Bones are dense and absorb the most, so they appear almost white, while soft tissues allow more to pass through, appearing as shades of gray.

Non-Ionizing Radiation

Non-ionizing radiation uses lower-energy waves that do not remove electrons from atoms. It is used in tests like MRI scans and ultrasounds. Since it does not remove electrons and ionize atoms, it does not risk causing cellular damage in living tissues. 

For this reason, these tests are generally considered quite safe, like performing ultrasounds on pregnant women to check for the health of the fetus. 

How Much Radiation Is the Average Person Exposed to in Everyday Life?

Typically, we are exposed to about 3mSv annually naturally occurring background sources. Let’s explore more. 

Naturally Occurring Background Radiation

Naturally occurring background exposure comes from several sources, both natural and man-made, and is usually considered very safe. 

• Cosmic high-energy particles from our sun and stars constantly enter the Earth’s atmosphere from outer space. Those who live higher in the mountains are exposed to about 1.5mSv per year more than those living at sea level. Furthermore, taking a 10-hour flight in an airplane increases our exposure by about 0.03mSv.
• Terrestrial forms come from naturally occurring radioactive materials in the Earth’s crust, including uranium, thorium, potassium, and others.
• Radon is the largest source of background exposure, about 2mSv yearly, but it varies significantly depending on the location. It is a radioactive gas formed from the natural decay of uranium in the Earth’s crust. It typically seeps into buildings through cracks in foundations and can accumulate indoors. High-level areas can line and seal their foundations to reduce exposure. 
• Consumer products like smoke detectors, ceramic and granite tiles, and certain electronic devices contain radioactive materials, but the amount is generally very low.

How Much Radiation Is a Person Exposed to During an Imaging Test?

How much we are exposed depends entirely on the type of medical imaging and the body part being imaged since some body parts absorb more or require higher doses to produce detailed images. 

Here are some averages for different tests based on an average-sized adult and compared to the number of days of natural background exposure that would be equivalent. The exposure from standard digital X-rays is quite low, so these tests are considered safe. 

Frequently Asked Questions

Which Scan Has the Most Radiation?

Computed Tomography (CT) scans generally have higher doses than other medical imaging techniques. The exposure from a CT scan typically ranges from 2 to 10 millisieverts (mSv) per procedure, depending on the body part being imaged. For comparison, standard X-rays are usually in the 0.001 to 1.5 mSv range. 

Final Thoughts

Medical imaging techniques use different forms of radiation to produce highly detailed images of the body’s internal structures, which are crucial in patient diagnostics. While some forms of imaging, like X-rays and CT scans, expose us to ionizing forms, the effective doses measured in millisieverts are generally quite small and often comparable to the natural background levels. 

CT scans aside, the digitization of modern X-ray machines exposes us to even lower doses yet produces higher-quality images than ever before. Contact Maven Imaging today to learn more about our quality digital x-ray equipment and healthcare services.