Answer to Question #2353 Submitted to "Ask the Experts"

Q

I have been an x-ray tech for 30 years and have recently had several CT scans. I would like to know the amount of exposure I received and what the acceptable doses are. In addition to the C-sp, L-sp, hip, pelvis, sacrum/coccyx, and several chest x rays, I was subjected to head, abdomen (w/wo contrast), and pelvis CTs. The exposures for the CTs were 120 kV @ 230 mAs × 38 exposures, 120 kV @ 90 mAs × 2, 120 kV @ 250 mAs × 63, and 120 kV @ 1250 mAs × 3. I weigh 135 pounds and am concerned that, had I been monitored, it might compromise my livelihood as a technician. Thank you for your time and expertise in answering my question. If this is not something you can help with, perhaps you can tell me how or where I can get this information.

A

To obtain accurate radiation doses from CT procedures, one really needs to speak to a medical physicist at the institution where the CTs were done. Doses vary from machine to machine and according to the parameters employed in a given procedure (kV and mAs values, as you provided, and which organs were within the scanned regions). Approximate values were provided by the International Commission on Radiological Protection (ICRP) in their ICRP Publication 62. I sometimes quote these to people to give an idea of typical doses; perhaps they will be helpful to you (doses from the other x-ray procedures you mentioned will add to this total, but are generally a good bit lower than CT doses).

Head CT: Effective dose 180 mrem (1.8 mSv), bone marrow dose 270 mrem (2.7 mSv), thyroid dose 190 mrem (1.9 mSv)

Abdominal CT: Effective dose 760 mrem (7.6 mSv), bone marrow dose 560 mrem (5.6 mSv), uterus dose 800 mrem (8 mSv), ovaries dose 800 mrem (8 mSv)

Pelvic CT: Effective dose 710 mrem (7.1 mSv), bone marrow dose 560 mrem (5.6 mSv), uterus dose 2600 mrem (26 mSv), ovaries dose 2300 mrem (23 mSv)

For comparison, most of us receive around 300 mrem (3 mSv) of radiation (effective dose) each year from natural radiation in the environment. Radiation workers are permitted to receive 5,000 mrem (50 mSv) (effective dose) each year; medical and environmental exposures are specifically exempted from this total.


Michael G. Stabin, PhD, CHP