Types of Dosimeters

LiF TLD badges and rings (if needed) are used to measure the radiation dose that a worker may receive while attending patients undergoing therapeutic or diagnostic procedures with radionuclides or while working with x-ray generating devices (e.g., fluoroscope unit). The LiF crystal stores radiation energy.  When it is heated the energy is released as visible light and allows a determination of exposure. The badges can read exposures as low as 1 mrem.

Note: Dosimeters cannot detect very low levels of beta particle radiation (average energies below 70 KeV).

Collection of Dosimeters

All badges and rings are collected by the designated department or location contact to be processed by a contractor. They are to be given to the contact within the first 5 days of the new monitoring period. Many badges are exchanged monthly; some are exchanged every 3-4 months.

Each clinical location or department pays for the cost of its dosimetry service and also pays non-returned dosimeter fees.

Required Monitoring

Monitoring is required for any worker who might exceed 10 percent of the occupational limit (500 mrem), or any worker in a radiation area (> 5 mrem/hour or >50 uSv/hour).  Years of monitoring history demonstrate that most SHC, SCH and VAPAHCS exposures are non-detectable, and therefore monitoring is not required for many locations. Examples of areas where monitoring is typically required might include nuclear medicine or interventional radiology. Examples of areas where monitoring is typically not required are dental x-ray or chest x-ray units.

How to Wear

Badges are to be worn at the collar. Fetal badges are to be worn near the waist. If using a lead apron, the fetal badge is worn at the waist under the apron. If lead aprons are used, wear the whole body badge outside of the apron at the collar and clip the fetal badge under the apron. Finger rings are worn on the hand where the highest exposure is expected, underneath gloves, to avoid contamination.

Note: If you are issued a badge, you must wear it whenever you are working near radiation. These badges provide legal records of accumulated radiation exposure for a lifetime; therefore, it is imperative that they are used when issued.

Precautions and Storage

Do not wear dosimeters for non-work exposures such as while at the dentist’s office or when traveling by air.

Store badges in a safe location when not in use, away from sun, heat, sources of radiation or potential damage. Protect badges from impact, puncture, or compression. Unless traveling between different off-site clinics, badges must be kept at work. Do not store badges in a car and risk damage and lost readings.

Do not store Extremity (finger) rings in lab coat pockets. Storing rings in the lab coat pocket may expose the rings to radiation measured by the whole body badge. Rings are to measure hand exposures only.

A missing or invalid dosimeter reading creates a gap in your radiation dose record and affects the monitoring program’s ability to provide accurate exposure readings. For a missing dosimeter a Lost/Damaged Dosimeter Report Form is required.

Dosimetry Requests

Dosimetry requests can be made on this website.

Records of Prior Exposure

Each individual having a previous or on-going radiation exposure history with another institution is required to submit an Authorization to Obtain Radiation Exposure History form.

Lost Dosimetry

If you have lost your dosimeter, a lost monitor report is required.

Frequently missing dosimeter readings creates a gap in your radiation dose record and gives the impression of a lackadaisical monitoring program. If a dosimeter is lost frequently, and if it is not required due to the exposure environment, it will be cancelled.

Late Dosimetry

Dosimeters are considered “late” when they have not been returned to the dosimetry location’s contact within 5 days after the end of the wear period (e.g., if issued a monthly dosimeter on the 1st of October, return the worn dosimeter to the contact by the 5th of November). Dosimetry accounts will be charged a late fee in addition to the usual dosimeter costs for dosimeters not returned within 90 days.

Late dosimeters may not be read as accurately as dosimeters returned on time. A control badge accompanies the badges while in transit to and from the dosimetry vendor. Its purpose is to record background radiation during the use period and to record any radiation received by the badges during shipment. The exposure recorded by the control badge is subtracted from the exposure on the badges worn by the workers. The net exposure is the value found on the exposure reports. When a badge is returned late it cannot be processed with the control badge and a correct exposure may not be reported.

Late dosimeters may also affect the whole location for the dosimeter because the location contact may delay return of the entire group of badges while waiting for individuals who turn badges in late. This delays the processing and reporting of results to other users.

If a significant exposure occurs, an early report is very desirable. If a badge is returned late, higher work exposures cannot be investigated in a timely manner. Returning a dosimeter late is the same as not wearing one.

Frequently late dosimeters gives the impression of a lackadaisical monitoring program and may be cancelled if it is not required due to the exposure environment.

Failure to Use Dosimeter as Required

Failure of an employee to use a required badge may result in appropriate disciplinary action. When badges are required, it is both the individual and the supervisor’s responsibility to ensure that they are worn.

Bioassays

Bioassays determine the quantities, and in some cases, the locations of radioactive material in the human body, whether by direct measurement, called in vivo counting, or by analysis and evaluation of materials excreted from the human body. Individuals who handle large amounts of easily ingested radionuclides may be required to participate in a bioassay monitoring program. Bioassays may also be ordered by the RSO after a spill, an unusual event, or a procedure that might result in an uptake.