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CT stands for Computed Tomography. CT scans (aka CAT scans) are medical imaging tests that are used to discover, treat, and monitor disease. They use ionizing radiation and computers to create images of internal organs.

Although a relatively new technology, CT has rapidly advanced along with computing power. There are tens of millions of CT scans done every year. As CT has advanced its importance in detecting disease such as appendicitis, strokes and tumors has increased and so has utilization. It is estimated that CT scan use is growing at about 10% per year.

In fact, at this time there is concern that CT scans are overused and delivering unnecessary high doses of radiation. There have been recent reports in the media regarding high dose CT scan injuries.

What are the side effects of radiation?

There are potentially many side effects, here are the most common:

• Burns
• Nausea, vomiting, diarrhea
• Weakness
• Hair loss
• Dizziness, headache
• Low blood counts
• Organ failure
• Gene mutations and cancer

How much radiation will I get from a CT scan compared to an xray?

Radiation is meaured a variety of ways. One of the units of measurement is Sieverts (Sv). This meaures the effect of radiation on the body. We are naturally exposed to radiation from many different sources such as the earth, atmosphere and space. Below is a short list comparing radiation sources (mSV is milliSieverts which is .001 Sv).

• Background radiation at sea level: 3 mSv per year
• Denver residents get: 6 mSv per year
• Cross country flight: 0.02 mSv
• X ray Chest: 0.06 mSv
• CT Head: 3 mSv
• CT Chest: 5 mSv (equivalent to 100 chest xrays)
• CT Abdomen: 5-10 mSv

Some experts believe that actual radiation doses may be higher for a CT scan of the abdomen and closer to 10-20 mSv. This occurs as multiple scans are made through the organs after IV dye is given. These passes are called "phases" and are done to see to detect subtle changes in tissue characteristics when exposed to the dye. For example, some malignant tumors will take up the dye right away and benign tumors take up dye much slowly. Multiple phases are needed to see this difference.

Experts believe that above 50 mSv there is a slight increase in risk of cancer. Given that some patients get multiple CT scans during a hospitalization or over their lifetime this number could easily be exceeded. In one highly publicized case a young child received 151 scans in the same area of the head (this test has usually 25-30 images spread over the whole head). The child ultimately developed facial burns. Other similar though less dramatic cases have been reported as well.

There are currently attempts to regulate and reduce CT scan radiation exposure. A law was recently passed in California which will require Radiology reports to include the total radiation dose delivered during a CT scan.

Although the medical community is working to reduce CT radiation exposure, patients should be aware and ask questions about the amount of radiation involved in a CT scan.  Ask if there are ways to reduce the dose or select another type of test if possible.

What are your thoughts on CT scan radiation? Please leave your comments below.