3.3 Determination of Exposure

3.3.1 Dosimeters

Personal dosimeters used to record occupational radiation exposures are supplied and processed through a commercial dosimeter service.  The administration and management of the personnel monitoring program is provided by EHS.  Personal dosimeters are available upon request and are assigned to individuals based upon regulatory requirements and their potential for occupational exposure to penetrating radiation.  Dosimeters are normally exchanged on a monthly basis.  Copies of dosimetry reports are provided for each dosimeter account and are maintained on file at EHS. Temporary dosimeters are available for interim issue until a permanent dosimeter assignment is established, or in the case of a lost or damaged dosimeter.  Contact 335-8501 if you have questions concerning dosimeters or dosimeter reporting.

Documented completion of EHS radiation safety training applicable to job function is required as a prerequisite to obtaining a personal dosimeter.  A listing of EHS radiation safety training courses available online can be accessed from EHS’s training web page or contact EHS for more information regarding applicable training for your job function.  Dosimeter service request forms are also available from our web site.  

Returning Dosimeters

Monthly dosimeters must be received by EHS by no later than the 10th day of the month following the wear period.  If dosimeters are received late or lost three or more times during a 12-month period, one of two things will happen, depending on your status as a dosimeter participant:

  1. Required Participants – The department of an individual who is required to have dosimetry based on his/her job duties will be assessed an administrative fee.  This will continue for each subsequent lost or late dosimeter until the participant has less than three late or missing dosimeters during the preceding 12 month period.
  2. Elective Participants - Dosimeter service will be canceled following the third late or lost dosimeter.  Individuals wishing to reinstate dosimeter services, are required to contact EHS and pay an administrative reinstatement fee.

Types of Dosimeters

Whole Body and Collar Dosimeters provide measurement of penetrating and non-penetrating radiation exposure.  Penetrating radiation is designated on reports as “DDE” for deep dose equivalent and includes exposure to the whole body (head, trunk, active blood-forming organs, and reproductive organs).  Non-penetrating radiation is designated as “SDE” for shallow dose equivalent, and includes exposure to the skin and extremities.  Lens of the eye dose equivalent is designated as “LDE.”

Whole body dosimeters are to be worn on the torso in the region likely to receive the highest radiation exposure.  If a protective lead apron is worn, wear the whole body dosimeter underneath your lead apron.  Collar dosimeters are to be worn at the collar and external to a thyroid shield or lead apron.

Ring dosimeters provide measurement of radiation exposure to the extremities (hands and forearms).  The ring dosimeter is to be worn under your disposable glove and on the hand most likely to receive the highest radiation dose.  The label side of the dosimeter should face the side of the highest potential exposure.

Wrist dosimeters are also available to monitor exposure to the extremities.  The wrist dosimeter is to be worn under your disposable glove and on the hand most likely to receive the highest radiation dose.

3.3.2 Specific-Use Dosimeter Requirements

Bone Densitometer Operators  

Personnel operating newly purchased X-ray bone densitometers are required to wear whole body dosimeters for the first six months of the new unit’s operation.  Operators may discontinue dosimeter use after six months if minimal operator exposure has been demonstrated for the new densitometer.

Diagnostic Radiology and Fluoroscopy Personnel 

Diagnostic Radiology personnel directly involved in radiographic procedures are recommended to wear a whole body dosimeter.  Individuals operating fluoroscopic equipment are required by regulation to wear a whole body dosimeter under their lead apron.  A collar dosimeter worn outside the lead apron at collar level and ring dosimeters is also recommended.

Nuclear Medicine Personnel  

Personnel directly involved in radiopharmaceutical dosage administration and/or radiochemistry procedures are required to wear both a whole body and ring dosimeter. 

Nursing Services Personnel

Whole body dosimeters are required for Nursing Services personnel routinely involved in certain radiopharmaceutical and/or brachytherapy patient care.  Nursing Services personnel utilizing lead aprons during fluoroscopy or other X-ray procedures should wear the whole body dosimeter under the lead apron at waist or chest level.

Positron Emission Tomography Personnel  

Personnel directly involved in radiopharmaceutical dosage administration, radiochemistry procedures, and service or maintenance to the cyclotron are required to wear both a whole body and a ring dosimeter.  A second ring dosimeter is recommended for individuals who routinely prepare and/or administer radiopharmaceuticals.  The label side of the ring should face the palm side of the hand.

Radiation Oncology Personnel  

Whole body dosimeters are required to be worn by radiation oncology therapists, dosimetrists, medical physicists and physicians.  Additionally, ring dosimeters are required to be worn by individuals directly involved in brachytherapy source preparation and administration. The label side of the ring should face the palm side of the hand.

3.3.3 Bioassays

Thyroid and/or urine bioassays are performed for personnel for whom internal exposure to radioactive materials is considered most likely.  Bioassays are normally performed for: 

  • Individuals who prepare and administer radiopharmaceutical dosages of I-131.
  • Individuals performing iodination procedures with I-125 or I-131.
  • Individuals using quantities of radioactive materials above the bioassay threshold level, as determined by EHS.
  • Declared pregnant radiation workers working with unsealed radioactive material.
  • Individuals with an accidental or suspected intake of radioactive material.

3.3.4 Accidental Exposure Assessment

Anyone suspecting that they have had an intake of radioactive material through any pathway (e.g., ingestion, inhalation, or skin absorption) should contact EHS immediately at 335-8501 so that an evaluation can be performed.