Answer to Question #9608 Submitted to "Ask the Experts"

Category: Radiation Workers

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


How much radiation exposure would a typical ICU (intensive care unit) nurse be exposed to from a patient having a routine bone scan with an average activity of 650 MBq of 99mTc?


Thank you for your question. It depends on time and distance, but the dose rate would be about 0.01 mSv at one meter.

According to National Council on Radiation Protection and Measurements Report 124 (NCRP 1996), the dose rate at the surface of a patient receiving 740 MBq of 99mTc methylene disphosphonate is about 0.06-0.09 mSv h-1, about 0.02-0.03 mSv h-1 at bedside, and about 0.01 mSv h-1 at a meter. This would be within several minutes of having the injection of the radionuclide because after a few hours, this would diminish significantly.

Being close to the patient within the first hour or two after the patient had the scan would give a person nearby the most dose. If you spent 15 minutes per hour for each of the two hours at bedside with the patient, you'd receive about 0.01-0.015 mSv total.

For comparison, one day's worth of natural background radiation is 0.01 mSv, a chest x ray is about 0.1 mSv, and a cross-country plane flight is about 0.05-0.06 mSv.

Kelly Classic
Certified Medical Health Physicist

National Council on Radiation Protection and Measurements. Sources and magnitude of occupational and public exposures from nuclear medicine procedures. Bethesda, MD: NCRP; NRCP Report No. 124; 1996.

Ask the Experts is posting answers using only SI (the International System of Units) in accordance with international practice. To convert these to traditional units we have prepared a conversion table. You can also view a diagram to help put the radiation information presented in this question and answer in perspective. Explanations of radiation terms can be found here.
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