Effective dose & types of examinations

The mean dose for conventional X-rays varies from 0.001 - 10 mSv and in CT tests from 2 – 20 mSv. For intervention procedures (radioscopy), the effective dose varies from 5 – 70 mSv and in nuclear medical procedures from 0.3 – 20 mSv. 

Despite the fact that the number of diagnostic tests has dramatically increased in recent years, the mean per capita dose has remained virtually constant as a result of digitization and dose optimization (total radiation burden:  2.47 in 2000, 2.37 in 2008 and 2.51 in 2012). New techniques enable continued reductions in radiation dose. 
There is currently much research into the recent development of iterative reconstructions in CT examinations (= image reconstruction method). Depending on the examination type, a dose reduction of 30% is described and in isolated cases even a 70% reduction.  This all sounds very good, but the drawback is that dose reduction is often associated with loss of image quality. The images contain more noise and evaluation becomes more difficult.  In short, a precondition for dose reduction techniques is that the image quality remains sufficient to draw reliable conclusions.Many radiology departments have so-called low-dose protocols for children and screening.  Ask the radiology department in your hospital for more information on these specific protocols. 

Artificial radiation sources & natural background radiation

The total radiation burden can be subdivided into artificial radiation and natural background radiation.

In artificial radiation sources, you are deliberately exposed to radiation. Medical diagnostics are the major contributor. For other non-medical artificial sources, think of residual radioactivity in the atmosphere after nuclear bomb tests in the past and the nuclear reactor accident in Chernobyl (total contribution +- 1% of artificial sources). Worldwide, the mean burden of artificial radiation sources is 0.6 mSv/year.  Some countries are above this average value. For instance, in the United States, in view of the relatively high number of diagnostic tests, the mean artificial radiation burden is 3.0 mSv/year.

Everywhere in the world, you are exposed daily to natural background radiation; you can't escape it. The mean annual natural background radiation dose is about 2.0 mSv for Dutch citizens.  The worldwide mean value is 2.4 mSv/year.
Radon is the primary radiation source and is released from the soil and stony building materials.  Also cosmic radiation contributes to the natural background radiation (it is increasing in level). For instance, during a return flight from London - New York you are exposed to about 1.0 mSv.
Natural background radiation levels vary strongly. The worldwide mean dose is 2.4 mSv/year.
The highest natural background radiation values have been measured in:

• Ramsar (Iran): 260 mSv/year.
• Guarapari (Brazil): 70 mSv/year 
• Karunagappaly (India): 15 mSv/year

In summary:
Worldwide our annual exposure to artificial radiation sources is 0.6 mSv on average and 2.4 mSv from natural background radiation. Total: 3.0 mSv/year.

The Netherlands is below average (2.4 mSv/year in 2008 and 2.51 mSv/year in 2012).  Figure 1 lists the various sources contributing to the total radiation burden in the Netherlands and the United States.