Answer to Question #12398 Submitted to "Ask the Experts"

Category: Medical and Dental Equipment and Shielding — Equipment

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

Q

Is there an ASTM or International Electrotechnical Commission (IEC) spec that identifies the maximum allowable amount of radiation that escapes from medical diagnostic equipment? Not towards the patient, but through the machine covers into the atmosphere. 

Must medical diagnostic equipment be manufactured with shielded covers to prevent escaping radiation?

A

For x-ray equipment sold in the United States, the Food and Drug Administration regulations apply. See the performance standards for ionizing radiation emitting products.

The following passages are relative to your question:

(k) Leakage radiation from the diagnostic source assembly. The leakage radiation from the diagnostic source assembly measured at a distance of 1 meter in any direction from the source shall not exceed 0.88 milligray (mGy) air kerma (vice 100 milliroentgen (mR) exposure) in 1 hour when the x-ray tube is operated at the leakage technique factors. If the maximum rated peak tube potential of the tube housing assembly is greater than the maximum rated peak tube potential for the diagnostic source assembly, positive means shall be provided to limit the maximum x-ray tube potential to that of the diagnostic source assembly. Compliance shall be determined by measurements averaged over an area of 100 square cm with no linear dimension greater than 20 cm.

(l) Radiation from components other than the diagnostic source assembly. The radiation emitted by a component other than the diagnostic source assembly shall not exceed an air kerma of 18 microGy (vice 2 mR exposure) in 1 hour at 5 cm from any accessible surface of the component when it is operated in an assembled x-ray system under any conditions for which it was designed. Compliance shall be determined by measurements averaged over an area of 100 square cm with no linear dimension greater than 20 cm.

On the international level this is covered in the IEC standard 60601-1-3 Medical electrical equipment–Part 1–3. Collateral standard: General requirements for radiation protection in diagnostic x-ray equipment.

I am not aware of any ASTM standard regarding leakage radiation.

Joel Gray, PhD, FAAPM

Typically, medical diagnostic x-ray equipment is manufactured with lead shielding in the x-ray tube housing to keep external radiation levels within the limits stated above.

Kennith "Duke" Lovins, CHP

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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