X-rays are a form of electromagnetic radiation, similar to visible light. But X-rays have higher energy than light and can pass through most objects, including the body. Medical X-rays are used to generate images of tissues and structures inside the body. If X-rays traveling through the body also pass through an x-ray detector on the other side of the patient, an image will be formed that represents the “shadows” formed by the objects inside the body.

General practitioner, medical researcher, and founder of PrimeHealth Clinical Research, Iris Gorfinkel, M.D., told Bored Panda that probably the most common X-ray of all is the chest X-ray, simply because it's often done when people are coughing, especially longer than a couple of weeks. "Other common X-rays that are fairly routine are mammography (looking for breast cancer in women) and CAT scans (we'll do CAT scans of the chest, the abdomen, and that's often to look for various cancers as well)."

Even though X-rays have saved countless lives and helped in a range of important discoveries, scientists have shown concern over the health implications of getting one. "No radiation is considered particularly healthy because ionizing radiation can interfere with the way cells divide and cause normal cells to become cancerous cells," Gorfinkel explained. "But the reality of the amount of radiation with various studies is that it's actually very low, and does not tend to do that unless they are constantly repeated."

Experts estimate that 0.4 percent of cancers in the U.S. are caused by CT scans and that an average CT scan might raise the chance of fatal cancer by 1 in 2,000. However, this figure pales in comparison to the natural incidence of fatal cancer in the US of 1 in 5. 

"For the most part, for the vast majority of people getting X-rays, that's not a concern," Gorfinkel said. In other words, the risks are very little compared to the benefits of medical imaging.

To give you some context, the Earth is constantly bombarded by cosmic radiation, including X-rays. These rays are not harmless but they are unavoidable, and the radiation is at such low levels that its effects are virtually unnoticed. "There was always an ambient amount of radiation, in other words, just walking around on planet Earth, we have exposure," Gorfinkel said.

A chest X-ray is equivalent to a just few days of the amount of natural background radiation and a mammogram is three months worth. But a CAT scan of the abdomen, for example, is worth years of natural background radiation. Gorfinkel said it's important for people to realize that CAT scans, in general, are much higher in radiation than X-rays.

"I view them as invasive tests, even though people don't feel anything going on. Considering that a CAT scan of the chest or a CAT scan of the abdomen is equivalent to three years of natural background radiation, they should be done with careful thought—they shouldn't be just done willy nilly."