ALARA & Personnel Radiation Monitoring/Dosimetry

Individuals who are occupationally exposed to radiation and who potentially could receive, in 1 year, radiation exposure more than 10 percent of the regulatory limits, individuals who work in a room using fluoroscopy, CT, or X-ray, or when an individual enters a High Radiation Area (could receive more than 100 millirem in 1 hour). The JH Radiation Control Unit (RCU) may assign dosimeters to individuals who work in a radiation environment where the exposure will be less than 10 percent of the regulatory limit. The dosimeter records your personal exposure; do not allow other individuals to wear it.

Those using only H-3, C-14, S-35, or P-33 will not be provided with badges, as radiation from these low-energy beta emitters cannot be recorded on the badge monitor.

Individuals may request a dosimeter by completing a personnel radiation monitor request form. The form has an area to list the exposure you may have received at other facilities. The completed form can be submitted to the RCU, in person, by email ([email protected]) or fax (410-955-7183).

In many cases, you will receive a dosimeter the day you send the completed request to RCU. At that time, you will receive a spare dosimeter to wear for the remaining monitoring period. After the initial wear period, you will receive a new dosimeter each month or quarter, depending on your work environment. The new dosimeters will be delivered to your dosimeter coordinator.

Some situations may require additional dosimeters to be worn. You may request additional dosimeters from RCU. RCU will discuss your situation with you and issue the proper additional dosimeters and offer guidance on the appropriate wearing of the dosimeters.

An occupationally exposed pregnant woman who chooses to declare her pregnancy may do so at any time by notifying the Radiation Control Unit. See policy HSE914.  

Participation in the fetal protection program is entirely voluntary.  Once RCU is notified, the pregnant individual will be contacted and given further guidance on completing the process. ​ In a declared pregnancy, RCU will:

• Evaluate the dose received by the embryo/fetus throughout the pregnancy due to the woman’s occupational exposure; and
• Assist the pregnant worker in limiting that dose to 0.5 rem (500 mrem or 5 mSv). ​The 0.5 rem limit applies to the sum of internal and external doses received by the embryo/fetus due to occupational exposure of the mother and is equivalent to 10% of the annual whole body dose limit for occupationally exposed adults.  In addition, substantial variation above a uniform monthly dose rate should be avoided so that all the 0.5 rem allowed dose does not occur in a short period during the pregnancy.

The new dosimeters will be delivered to your dosimeter coordinator’s location. At that time, replace the dosimeter you are currently wearing with the new one. Return the older dosimeter to your dosimeter coordinator, who will return that dosimeter to RCU for processing.

Your dosimeter should be stored at your work location, preferably on your lab coat or if your area has one, a badge board. The dosimeter should not be stored in your car as the temperature fluctuation in a vehicle may affect the dosimeter’s accuracy. In addition, your dosimeter is to record your occupational exposure at your work location. Do not wear the dosimeter when you are receiving radiation exposure as a patient. Do not travel with your dosimeter, as this will result in exposure to luggage scanners. Notify RCU if any of these occur to receive a replacement dosimeter.

As indicated before, dosimeters should not be left in a car. In addition, dosimeters should not be submerged in any liquid or left next to any radiation source or waste. If this does occur, please notify RCU immediately for a replacement and proper processing of the affected dosimeter.

The dosimeter should be worn with the open window facing the radiation source, and should not be obstructed by clothing. The dosimeter is issued to document exposure to the head and trunk of the body. In most cases, the dosimeter should be worn at the waist or chest level. For those requiring ring badges, they should be worn with the name on the badge facing the palm of your hand. A disposable glove may be put on after your ring dosimeter is in place. This will not affect any readings but will prevent contamination of the ring dosimeter. Unless your work requires it, a dosimeter should not be worn on the extremities. When wearing a lead apron, wear the dosimeter on the outside of the apron at the collar. Note, fetal dosimeters are an exception, as they should be worn under your lead apron.

For additional information regarding how to correctly wear your dosimeter, please see this Landauer guidance.

You can cancel your dosimeter by notifying your dosimeter coordinator or RCU. You are responsible for returning all badges to your dosimeter coordinator or RCU. There is a charge for unreturned dosimeters.

Notify your dosimeter coordinator or RCU so a replacement dosimeter can be issued. There is a charge for lost dosimeters. You are required to return damaged dosimeters to Radiation Control.

If you think you may have received a high dose of radiation, notify RCU immediately. RCU will discuss the circumstances of your possible radiation exposure, issue another dosimeter and send the suspected high dosed dosimeter for processing.

RCU will send the radiation exposure report to the dosimeter coordinator approximately 30 – 45 days after the end of the wear period. The dosimeter coordinator will distribute or make available the exposure reports to the department(s) or individual(s). You may also email a request for your exposure report from RCU.

• How to Read Your Dosimetry Report from LANDAUER
• Sample report

If your badge is returned to RCU promptly at the end of each wear period, you should receive a report 30 – 45 days after each wear period. In addition, you can request your exposure history at any time by emailing RCU, [email protected].

Your radiation exposure records are stored electronically indefinitely. If you leave Johns Hopkins and require your occupational exposure history, it can be requested by your new employer.