The numbers of medical imaging procedures using radiation have increased dramatically over the last two decades. Apart from the obvious benefits of those techniques - exceptional improvement in diagnosis, preventive medicine and screening - they also have some dark sides. Radiation-induced cancer risk and occurrence of health effects are two main reasons why these medical procedures can't be used unrestrainedly. With our medical radiation calculator, you can check the effective radiation dose from standard medical procedures. Find out what is the x-ray radiation of your prescribed DEXA scan or what's the chest CT dose.
The radiation doses in the calculator come from xrayrisk.com website.
X-ray radiation and the other radiation types
X-radiation is a form of electromagnetic radiation - just like light and radio waves - but has ionizing properties and a short wavelength ranging from 0.01 to 10 nanometers. As various human tissues absorb the X-rays differently, they found practical applications in medical procedures, such as:
- X-ray exam, also called projectional radiography - 2D low-dose imaging
- CT scan - virtual slices of the area of interest, made from combinations of many X-ray scans taken from different angles,
- fluoroscopy and angiography - real-time moving images of the patient's internal structures
- radiotherapy - treatment procedure, much higher doses than in medical imaging
Nuclear medicine imaging is also called radiology done inside out - the small amounts of radioactive materials are injected, inhaled or swallowed and they emitting radiation from within the body. Nuclear medicine is using different types of ionizing radiation, such as gamma rays, beta particles, and alpha radiation.
Effective doses for medical procedures and their natural background radiation equivalent
If you are wondering what it means that you get 5 or 10 millisieverts from your CT scan, check out the neat table below. The natural background radiation is estimated to 3-3.1 mSv/year.
|Target body organs||Procedure||Typical effective radiation dose||Natural background radiation equivalent|
|Abdominal region||CT – abdomen and pelvis||10 mSv||3 years|
|CT – abdomen and pelvis, repeated with and without contrast||20 mSv||7 years|
|CT – colonography||6 mSv||2 years|
|Intravenous pyelogram (IVP)||3 mSv||1 year|
|Barium enema (Lower GI X-ray)||8 mSv||3 years|
|Upper GI study with barium||6 mSv||2 years|
|Bone||Spine X-ray||1.5 mSv||6 months|
|Extremity (hand, foot, etc.) X-ray||0.001 mSv||3 hours|
|Bone densitometry (DEXA)||0.001 mSv||3 hours|
|Central nervous system||CT – Head||2 mSv||8 months|
|CT – head, repeated with and without contrast||4 mSv||16 months|
|CT – spine||6 mSv||2 years|
|Chest||CT – chest||7 mSv||2 years|
|CT – lung cancer screening||1.5 mSv||6 months|
|Chest X-ray||0.1 mSv||10 days|
|Mammography||0.4 mSv||7 weeks|
|Dental||Dental X-ray||0.005 mSv||1 day|
|Heart||Coronary CT Angiography (CTA)||12 mSv||4 years|
|Cardiac CT for calcium scoring||3 mSv||1 year|
Now you know that a single spine CT gives you 7 mSv, and that it's the dose you would get from natural background radiation in 2 years. But how is it related to radiation-induced cancer risk? It's not an easy question, as a direct causality between medical imaging and increased cancer risk is still not proved. Scientists don't agree on which model should be used: linear no-threshold theory, which always considers radiation harmful, summing all minor doses linearly to one larger, or other approaches assuming that very small doses are harmless or even beneficial to our health. That's why we decided to omit the risk part which sometimes appears in charts or other tools. Our medical radiation calculator shows only the average effective dose for the medical procedure, its equivalent in natural background radiation and standard annual radiation dose.
Medical radiation calculator - how can I find the radiation dose?
Let's have a look at this step-by-step example:
- Choose the procedure. You can select between five popular medical imaging techniques, let's pick the CT scan as an example.
- Select the type of the procedure. Assume you will have a standard brain CT.
- Enter the number of exams. For example, you recently needed to have two CT scans.
- Your total effective dose is displayed. In the field below you can see the interpretation of the results. The total effective dose is compared to the annual average radiation dose for a US citizen and to the natural background radiation per year. Two CT brain scans from our example correspond to 64.52 % annual US average or 129.03 % annual natural background radiation.
Remember that those are only reference, typical values for medical procedures. Estimates of the effective dose from can vary, depending on:
- scanned volume of the tissues
- patient size
- system and its operating technique
- desired resolution and image quality
and many other factors
If you have any doubts or concerns about the risks of a procedure, talk to your doctor or a radiology technician. Remember that imaging centers and hospitals are trying to use doses as low as reasonably achievable - it's called the ALARA rule - and the benefits of accurate diagnosis almost always outweigh the risks and costs.