Answer to Question #11614 Submitted to "Ask the Experts"

Category: Medical and Dental Patient Issues — Diagnostic X Ray and CT

The following question was answered by an expert in the appropriate field:

Q

I had an abdominal and pelvic computed tomography (CT) scan and asked the hospital what the effective dose was that I received. They said 1,097 milligray-centimeters (mGy-cm). I asked what that was in terms of millisieverts (mSv), and they stated it's the same—so 1,097 mSv. Could I really have received that high of a dose?

I've been having extreme anxiety over this and called the hospital twice. I keep getting told the same thing. I'm afraid I made my cancer risk really high.

I'm 31 years old and scared. Please help me understand.

A

I would be frightened, too, if I was told that I had received a dose of 1,097 mSv from a CT scan. But your radiation exposure was nowhere near that high. Based on having an abdominal/pelvic CT scan with a dose-length product of 1,097 mGy-cm, your effective dose is approximately 16 mSv. The cancer risk from this exposure, if it exists, is minimal.

As I indicated above, the dose they quoted is called the dose-length product or DLP. It is the radiation dose measured in an acrylic phantom (abbreviated as CTDIvol), using the same machine parameters that were used for your study, multiplied by the length of the scan in cm. This is commonly reported on CT scanners; however, it is not the same as the effective dose.

Whomever you spoke to at the hospital was clearly misinformed. The next time you need this type of information, I suggest speaking to the hospital's diagnostic medical physicist, medical health physicist, or radiation safety officer. (Depending on the facility, these could all be the same person—ask for the radiation safety officer first.)

Kent Lambert, CHP, FHPS

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