What Is Radiation Dose in a CT Scan?

Radiation doses differ from medicine doses. Different types and units of measurement are used to measure radiation dosage.

In What Ways Can Radiation Doses Be Measured Differently?

You probably visualize an exact number when you think of the amount of medication you should take. However, the dose doesn’t determine the effects of radiation. Medical x-rays emit rays that are roughly analogous to those of the sun. The sun’s damage to the skin is proportional to how long a person spends in direct sunlight and how intense the light is.

Sunlight Effect Factors:

  • Intensity
  • Length of exposure
  • Skin Sensitivity

A radiation dose will tell us about the radiation’s effect on tissue and can be measured in several ways. 

Radiation Doses 

What these different doses can tell us:

  1. Absorbed dose- Assesses the potential for biochemical changes in specific tissues.
  2. Equivalent dose- Assesses how much the absorbed dose will cause biological damage. There are different types of radiation that have other damaging properties.
  3. Effective dose- Assesses the potential for long-term effects that might occur in the future.

The term “absorbed dose” describes the quantity of energy stored in tissue due to exposure to ionizing radiation. Milligrays are the standard for measuring the amount of dosage an organism absorbs (mGy). During a CT scan of the upper abdomen, the chest receives only a minimal quantity of radiation. Hence the absorbed dosage is modest. Due to direct exposure, the dose absorbed by the stomach, pancreas, liver, and other organs is highest.

Please note that this refers to the amount of energy a human body can take in. In contrast to sunshine, X-rays can travel through solid objects and deposit energy where needed, such as in the interior organs. The human body is not an obstacle to X-rays. The term “equivalent dose” refers to a measurement that accounts for the relative danger posed by various forms of radiation. (There are differences between types of radiation.)

Absorbed vs. Equivalent Dose

  1. The absorption dose describes how much energy is deposited in a small tissue area.
  2. An equivalent dose addresses the impact that the type of radiation has on that tissue. 

The Difference between the absorbed dose in tissue and the equivalent dose is as follows:

If you need to use radiation for a medical diagnosis: The milliSievert (mSv) dosage equivalent equals the milliGray (mGy) absorbed dose. The absorbed dose and the equivalent dosage are identical since all diagnostic radiation is equally benign. There is no substantive difference besides the units.

The effective dose, measured in mSv, considers three factors:

  • A dose absorbed by all body organs,
  • In addition, the radiation’s relative level of harm,
  • Radiation sensitivities of different organs.

Understanding how much of an effective dose to provide can help us adjust for sensitivity. The effects of radiation on various organs and tissues vary. A person’s head, for instance, has fewer nerve endings than the chest. The phrase “effective dose” compares the relative dangers of various medical interventions by focusing on the cumulative effects of those dangers over time. No specific patient is meant to be accounted for when calculating the effective dose. Depending on the patient’s size and the nature of the surgery, the actual risk could be higher or lower.

Here is an example of an absorbed, equivalent, and effective dose. If you have a CT of the abdomen, what is the dose for the abdomen?

  • Typical absorbed dose: 20 mGy
  • Typical equivalent dose: 20 mSv
  • Typical effective dose: 15 mSv 

What is the Radiation Exposure in a CT Scan? 

Ionizing radiation, such as that used in a CT scan, is harmful to living things. Its intensity is sufficient to penetrate the human body and produce sharp digital representations of the world outside. Exposure to this kind of radiation may increase your long-term risk of cancer. But keep in mind that you are constantly exposed to ionizing radiation. It usually occurs in nature. Radiation can come from a number of different sources, including cosmic rays from space and radon gas from rocks and soil, a phenomenon called “background” radiation.

Is There A Recommended Dose For Assessing Potential Long-Term Risks From Various Procedures? 

Effective dosage is the most crucial dose quantity for patients as it permits easy comparison of long-term dangers. Tissues’ short-term risk (weeks to months) can be evaluated with the help of absorbed dose and equivalent dose measures. Absorbed and equivalent doses are not particularly helpful for correct diagnostic procedures because there will be no immediate impacts from radiation exposure.

How Much Radiation Does The Typical Human Absorb Each Day?

We are continually bombarded by radiation from numerous sources, including naturally occurring radioactive elements, man-made radon gas, and extraterrestrial cosmic rays. The levels of this naturally occurring radiation, known as background radiation, change from region to region in the United States. Over the course of a year, the typical American is subjected to around 3 mSv (millisieverts) of radiation exposure.

Radon, a naturally occurring gas, is the primary contributor to annual background radiation levels in the United States (about 2 mSv). The radon concentration varies widely around the United States. Because our planet’s atmosphere shields us from some cosmic radiation, geography also plays a role. As a result, being at a higher altitude puts one at greater risk. Thus, residents of New Mexico and Colorado’s mountainous regions are subjected to roughly 1.5 mSv more radiation per year than those living in lower-lying areas. In addition, an airplane passenger’s exposure to cosmic rays is increased by around 0.03 mSv during a 10-hour flight.

What’s the Cancer Risk? 

Most people who get a CT scan don’t appear to increase their cancer risk significantly. The scan’s potential medical benefits outweigh the potential for future issues. Your doctor may find the information they need to help you through a CT scan. It usually signifies that they won’t need to operate to figure out what’s wrong with you. However, further caution is warranted in certain circumstances. Radiation is more harmful to children’s developing bodies, and they have more years to go before any noticeable impacts appear. Scans are sometimes performed repeatedly to help people manage health issues like kidney stones or Crohn’s disease. Doctors have no hard and fast rule about how many CT scans you can undergo without harm. However, the greater your quantity of CT exams, the greater your risk of developing cancer.

How Much Does The Extra Radiation Increase A Person’s Cancer Risk?

The amount of radiation a patient is exposed to is contingent upon numerous variables, including the nature of the test, the location of the examination, the patient’s size, age, and gender. Radiation experts feel that imaging procedures’ potential increase in cancer risk would be extremely low. However, the exact amount by which a person’s cancer risk might rise due to radiation exposure during imaging examinations is difficult to predict. The vast majority of research into the link between radiation exposure and cancer has focused on those who have been exposed to extremely high levels of radiation, like uranium miners and atomic bomb survivors. It is difficult to extrapolate from this research the risk associated with exposure to low radiation levels. Because of their increased vulnerability to radiation, children require special precautions.

Imaging tests that employ radiation should be reserved for when they are necessary due to the cumulative nature of radiation exposure over a lifetime and the proven link between radiation and an increased risk of cancer. Ultrasound and magnetic resonance imaging (MRI) are two examples of alternative imaging methods employed in numerous situations. However, if an x-ray, CT scan, or nuclear medicine scan (such as a PET scan) is the best approach to screen for cancer or other diseases, the person will likely benefit more than the small dosage of radiation might harm.