Dosimetry

A well-functioning dosimetry program is essential for compliance with applicable federal and state regulations. The UMB radiation dosimetry program is described in detail in Procedures 3.1/3.1.1.

ALARA

Federal and state regulations require that radiation exposure (individual radiation exposure as well as collective dose equivalent) must be kept “As Low As Reasonably Achievable.” The UMB ALARA Program is described in detail in the Radiation Safety Program Manual and Procedure 1.6.

In accordance with state regulations, COMAR G.26(b)(9), the University of Maryland, Baltimore, has established a table of investigational levels for occupational dose that, when exceeded, will initiate investigations and considerations of action by the Radiation Safety Officer.

ALARA I and II Limits

Dose Equivalent

Level 1

Level II

Total effective Dose Equivalent

> 125 mrem/quarter

> 375 mrem/quarter

Eye Dose Equivalent

> 375 mrem/quarter

> 1125 mrem/quarter

Skin or Extremity, Shallow Dose Equivalent

> 1250 mrem/quarter

> 3750 mrem/quarter

Total Effective Dose Equivalent (Declared Pregnant Worker)

> 10 mrem/month

> 50 mrem/month

ALARA I Limits: If the individual dose is equal to or greater than the Level I limits but less than the Level II limits, the Radiation Safety Officer will:

  • Ensure a notice is sent to the individual informing them of the exposure.
  • Conduct a review of the circumstances surrounding the exposure.
  • Report the results at the first RSC meeting after the quarter when the dose was recorded.

ALARA II Limits: If the individual dose is equal to or greater than the Level II limits, the Radiation Safety Officer will:

  • Investigate in a timely manner.
  • If warranted, take action to prevent or reduce ongoing exposures.
  • Present to the RSC at its first meeting after completion of the investigation a report of the investigation, any actions taken, and a copy of the individual’s MDE exposure form or its equivalent.
  • Ensure the details of these reports are included in the RSC minutes.

Types of External Dosimeters

Thermoluminescent Dosimeter (TLD Badge) 

  • This badge responds accurately to gamma, X-ray, and neutron radiation.
  • It also responds accurately to beta emitters with a maximum energy greater than 0.25 MeV. It 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.
  • These badges are exchanged on a quarterly basis.
  • These badges should be worn on the chest, collar, or waist, depending on the requested placement.

Optically Stimulated Luminescence Dosimeter (OSL badge)

  • These badges detect photon and beta radiation. They respond accurately to beta emitters with a maximum energy greater than 0.57 MeV.
  • Unlike other badges, these badges can be re-read to re-evaluate unusual exposures.
  • These badges are exchanged on a quarterly or monthly basis.
  • These badges are designated as collar or torso badges. For those who only have a collar badge, it should be worn outside of the lead apron at the collar. For those who are double badged, the collar badge should be worn outside of the lead apron at the collar, and the torso badge should be worn around the chest or waist underneath the lead apron.

 

Ring Dosimeter

  • This badge detects exposures to the extremities and skin from external sources of gamma, X-ray, and beta radiation. It accurately responds to beta emitters with a maximum energy greater than 0.25 MeV.
  • They are required when working with more than 0.5 mCi of P-32, or 1 mCi of I-125, Cr-51, or X-ray diffraction units.
  • Designed to wear underneath disposable gloves.
  • These badges are exchanged on a quarterly or monthly basis.
  • Wear the ring on the finger that will potentially receive the highest shallow-dose equivalent, with the TLD on the palm side of your hand toward the radiation source.

Who is Required to Wear Dosimeters?

The large majority of employees and students at the University are not exposed to ionizing radiation and thus are not covered by the dosimetry program. The below requirements are for those individuals who may be exposed to ionizing radiation at the Medical Center or research laboratories on campus.

The following table of occupational dose limits was set by the Maryland Department of Environment (Section D.201a of COMAR 26.12.01.01).

Adult External Occupational Dose Limits

Dose Term

Dose Limit

Total Effective Dose Equivalent (TEDE)

5 rem (5,000 mrem)/year

Total Organ Dose Equivalent (TODE)

50 rem (50,000 mrem)/year

Lens Dose Equivalent (LDE)                       (dose to the lens of the eye)

15 rem (15,000 merm)/year

Shallow Dose Equivalent (SDE)                      (dose to the skin of the whole body or to the skin of any extremity)

50 rem (50,000 mrem)/year

 

Individuals who are required to wear OSL or TLD dosimeters (COMAR Sec. D.502a):

  • Adults who potentially may receive, in one year, from sources external to the body, a dose in excess of 10 percent of the limits in the above table.
  • Declared pregnant women who potentially may receive during the entire pregnancy, from radiation sources external to the body, a deep dose equivalent in excess of 100 mrem (1 mSv).
  • Individuals entering a high or very high radiation area.

Individuals who are required to wear ring dosimeters:

  • All hospital employees whose hand(s) may become exposed to radiation fields by radiation-producing machines or radioactive materials are required to use ring dosimetry.
  • Research personnel whose hand(s) may become exposed to radiation fields by radiation-producing machines or whose hands may handle, at one time, more than 0.5 mCi of P-32, or 1.0 mCi of I-125 or Cr-51 are required to use ring dosimetry.

Pregnant Workers

The Fetal Protection Program is described in detail in Procedure 1.4.

  • To be considered under the Pregnant Worker policy, a woman must declare her pregnancy in writing and provide other relevant information (i.e., approximate date of conception or delivery). Please go to the following link for the declaration form: http://afcf.umaryland.edu/ehs/public/pregnantworker/
  • EHS will provide counseling if desired.
  • The worker will be assigned a monthly fetal monitoring dosimeter.
  • In the event of elevated exposures, the RSO may seek reassignment of duties.
  • Please read the following: Instruction Concerning Prenatal Radiation Exposure.

Requesting Dosimeters

In order to receive a dosimeter:

Exposure Reports

The Radiation Safety Officer reviews exposures on a regular basis. Subsequently, high or unusual exposures are reported to the Radiation Safety Committee. Per regulations, all monitored individuals receive an annual exposure report. 

Internal Dosimetry Program

The method and frequency of internal monitoring is based on an assessment of the radiological hazards of the work to be performed and the nature and half-life of the radionuclide. The internal dosimetry program applies to:

  • Anyone utilizing 1 mCi or more of unsealed radioiodine.
  • Individuals who are involved in operations that use more than 100 mCi or more of tritium in an uncontained form other than metallic foil.
  • Individuals who are involved in an accident or spill who become personally contaminated.