Dosimetry

In working with radioactive materials, careful monitoring of the amount of ionizing radiation delivered to one’s body allows one to verify that safe practices are being followed.

Types Of External Dosimetry


Genesis Thermoluminescent Dosimeter (TLD Badge)

  • Used for determining deep-dose equivalent from external sources of gamma radiation and x-ray exposure or beta radiation with maximum energy greater than 0.7 MeV with minimum reportable dose of 10 mrem.
  • Will not record beta radiation of H-3, C-14 or S-35, because these betas are too weak to penetrate the paper wrapping on the film. On the other hand, these betas are too weak to penetrate the outer layer of skin as well.
  • Exchanged every quarter (3 months).

Ring Dosimeter

  • Measures exposures to the extremities and skin from external sources of gamma radiation and x-ray exposure or beta radiation with maximum energy greater than 0.7 MeV with a minimum reportable dose of 20 mrem.
  • Required when working with more than 1 mCi of P-32, I-125, Cr-51 or x-ray diffraction unit.
  • Design to wear inside of disposable gloves
  • Comes in Small, Medium, Large, and XL

Wearing The Dosimeters

  • Shall be at ALL TIMES when working with or around radiation sources. This includes the waste areas for radionuclides or radioactive material.
  • Place the Genesis Whole Body Dosimeter on the chest, collar or waist depending on the requested placement and with the front of the badge holder forward. Those performing Fluoroscopy procedures are encouraged to wear two radiation dosimeters, one at the collar worn outside of the lead, and one at the chest worn underneath the lead apron.
  • Wear the TLD Ring Dosimetry on the finger which will potentially receive the highest shallow-dose equivalent. (This may not be your ring finger.) Wear the ring monitor with the TLD on the palm side of your hand toward the radiation source.
  • Never wear another individual’s monitoring device; always were your own badge.

Requesting Dosimeters

  • Complete Badge Application Form in order to receive a dosimeter. This form must be completed before RSD can issue a dosimeter.
  • When an occupational worker is using radioactive materials or radiation producing devices in two separate job assignments or units (e.g. Nuclear Medicine and PET Center) a radiation monitor (film or ring) must be issued for each unit. Other individual monitoring devices may be required for monitoring exposures to the eyes or to airborne radioactive material.

Return Process

At the end of each wear period, the monitors will be processed for exposure. Simply return the TLD badge and ring dosimeter to the Unit Coordinator who will then forward the monitors to Radiation Safety Department for processing. It is important that you return all dosimeters whether used or non-used at the end of each wear period.

The radiation dosimeters must be received by Radiation Safety Department no later than the 10th of the month following the wear period end date to ensure it is returned to Mirion for processing. Late badges and non-returned badges are considered a regulatory non-compliance violation and may result in unfavorable disciplinary action. You must return all the radiation dosimeters (Genesis Whole Body Badge or TLD Rings), not only to comply with regulatory guidelines and commitments but in order to receive credit for the chips and filter components that are removed for recycling. The shipping containers that the Unit Coordinators received containing the monthly or quarterly radiation dosimeters are designed to be reused for returning the dosimeters to Radiation Safety Department.

Reporting

Radiation Safety Department receives quarterly dosimetry exposure reports from Mirion for Authorized Users and Occupational Workers to ensure that exposure dose limits are within our established Occupational ALARA Program at WVU and WVUH. Each Unit Coordinator is sent a copy of the report for posting and reviewing. Explanations and remarks regarding this report can be found on the reverse side of each report.

Note: There is about a one month delay before the report is available.

An individual who has questions regarding their exposure report is encouraged to contact RSD. In addition to the monthly and/or quarterly exposure reports, an annual radiation exposure report is prepared by Mirion and distributed by RSD.

ALARA Compliance

A personalized ALARA memo is generated by Mirion notifying each occupational worker whose exposure in that quarter exceeds the ALARA (As Low As Reasonably Achievable) Program Level 1 and Level 2. The memo indicates the exposure and level exceeded and is sent to the participant/radiation user to review. According to our “ALARA Program” Investigational Level 1 exposure notice requires no action related specifically to the exposure. The Level 2 exposure notice is investigated by the RSO to determine the cause of the unusual exposure and may require additional action from the appropriate administrator. The occupational worker is required to complete a questionnaire and return it to the RSO as part of the investigation.

Investigational Levels



Exposure Limits



Fetal Monitor Service

A woman who is planning or is pregnant can decide whether she wants to formally declare her pregnancy to take advantage of lower dose limits for the embryo/fetus. It is up to the pregnant radiation employee to decide whether or not she will formally declare her pregnancy to her supervisor in writing and/or the Radiation Safety Officer.

If she chooses not to declare her pregnancy, only the individual monitoring limits for an adult radiation employee will be in effect. General consideration is to limit the radiation dose received by the pregnant woman and the embryo/fetus and to avoid substantial variation in dose.

Therefore, it is recommended that a radiation employee who utilizes radioactive materials and/or radiation producing devices in her job assignment should inform her supervisor in writing of their desire to declare their pregnancy.

All data of a private nature will be protected from unauthorized disclosure. The supervisor shall endorse that the declared pregnant woman contact Radiation Safety Department to obtain information on risks to the embryo/fetus from occupational radiation exposure and review methods that may be used to keep doses low.

A monthly fetal radiation monitoring device will be assigned to the radiation employee to monitor the embryo/fetal dose rate to be worn on the waist in addition to the individual monitoring device. If the declared pregnant woman is wearing a lead apron, the fetal badge should be worn underneath the apron. This change in monitoring, as well as the associated dose restrictions, remains in effect until it is withdrawn in writing or verbally communicates to Radiation Safety Department stating that she is no longer pregnant.

For protection of the embryo/fetus of a declared pregnant woman, the dose to the fetus shall remain less than 0.5 rem (5 mSv) during the entire pregnancy. The fetus is very sensitive to high doses of ionizing radiation, especially during months one thru three of gestation. Each month a summary exposure report is generated and displays the estimated dose from conception to declaration, rolling exposure history by month for both mother and child, and accumulated fetal totals for the gestation period. Routine exposure reports for badges returned for processing have separate reporting as well.

The declaration can be withdrawn at any time. No explanation is required.

Declared Pregnancy Form Information for Pregnant Radiation Employee Regulation Guide 8.13 Prenatal Radiation Exposure