Nuclear Medicine Iodine I-131

VTH Policy # Bio410a

Implementation Date: 11/13/2014

Date of Last Revision: 5/2/2023

Next Review Due: 5/1/2025


Reviewed by VTH Administrative Team: 6/2019

Reviewed by VTH Board: N/A


Reviewed by Legal Counsel: N/A

Reviewed by Biosecurity Subcommittee: 6/2019; 5/2/2023

Subject to modification by the Biosecurity Subcommittee of the CVM Occupational Health and Safety Committee without approval.

Printable PDF: Nuclear Medicine Iodine I-131 Policy


Iodine 131 (I-131), is a radioactive isotope that is used in nuclear medicine studies and is ordered through a licensed pharmaceutical company. This isotope is handled by animal imaging technicians. Students may not handle isotopes or inject patients.


In the Iodine 131 lab (RB 13 LAC), the room is divided by a piece of yellow and red tape on the floor. One side is considered “hot” or has the potential for radioactivity.  There is a sign designating which side of the room is hot.  Proper radiation precautions should be practiced in this area.

I-131 has a long half-life. Items brought into the Iodine ward have the potential to be quarantined for up to 3 months until at background radiation levels.

Procedure (if applicable)

      1. A consent form must be signed by the client before I-131 is ordered.  This form should be acquired through medical records.
      1. PPE must be worn. Gloves, booties and protective eye wear are available in the lab.
      1. Evaluate the patient but do not remove from the cage.
      1. Put a glove over the end of the stethoscope when auscultating and discard gloves in the silver lead lined receptacle.
      1. Record in the patient record located on the cart on the “cold” side of the room, the food consumption, water consumption, urine and bowel movements. Indicate any other observations. date, time and initial all entries.
      1. The exam table is the most likely hot area in the room and should not be used for anything but injecting the patient. Never place anything hot on the cart with the logbook.
      1. When handling disposable material, a Geiger counter shall be used to measure radioactivity of the material.  If cold, the material may be disposed of in the regular trash.   If hot, the material shall be disposed of in the silver lined trash receptacle.
      1. If the litter box is full, scrape the used litter into the lead lined pails. Fresh litter is in the corner where the cages are.

      2. Sweep any spilled litter into a corner to prevent tracking of hot litter through the room.

      3. Refresh the water and feed the patient per clinician’s instructions.

      4. If a patient needs to be touched or petted (no bodily contact), change gloves immediately after handling.  Put hot gloves in the silver lead lined trash receptacle.

      5. Before leaving the I-131 ward, shoes and hands must be surveyed with the Geiger counter.

      6. If shoes register above background, they should be placed in a plastic bag, labelled with name, date, time and contact information and left in the I-131 ward. If readings on the hands are above background, clean the affected area with soap and flush with water until cold status is reached. If hands cannot be cleared, contact Radiation Safety on campus at 217-333-2755.


      8. Patients are routinely released after a minimum of 5 days. An Animal Imaging technician will survey the patient and release the patient after it attains legal level of radioactivity. A radioactive label is attached to the animal’s collar and is to be kept there until the date indicated on the radioactive stickers.

      9. Upon clearing the survey, the animal will be released to their tagged SAC cage.

    Any questions about I-131 therapy procedures should be directed to an imaging technician at 217 333-5330.

      Definitions (if applicable)

      Cleared - Radioactivity levels have reached cold status and no additional biosecurity measures need to be taken.

      Cold – A term that refers to radioactivity below 100 CPM.

      CPM – Counts Per Minute, a measurement of the rate of events registered by a radiation monitoring device (e.g. Geiger Counter)

      Geiger counter – An instrument used for measuring ionizing radiation. It detects radiation such as alpha particles, beta particles and gamma rays.

      Half-life- is the amount of time required for a quantity to fall to half its value as measured at the beginning of the time period. The term "half-life" can be used to describe any quantity which allows an exponential decay (i.e. the time required for half of the unstable, radioactive atoms in a sample to undergo radioactive decay). The half-life for I-131 is 8 days.

      Hot – A term that refers to radioactivity.

      Iodine 131 (I-131) – Iodines are among the most widely used radionuclides. Iodine-131 is used extensively in nuclear medicine. Iodine -131 collects in the thyroid gland making iodine especially useful for diagnosing and treating thyroid problems.

      Personal Protective Equipment (PPE) - Personal protective equipment may include items such as gloves, safety glasses and shoes, earplugs or muffs, hard hats, respirators, or coveralls, vests and full body suits.

      Veterinary Teaching Hospital (VTH): The collective clinical services of the Large Animal Clinic, Midwest Equine, the Small Animal Clinic, and the Veterinary Medicine South Clinic.


      KeywordsIodine, 1-131, diagnose, radioactive, isotope, CPM, geiger, radioactivity, level, half-life, counter, survey, therapy, students, handle   Doc ID123946
      OwnerJenny C.GroupUofI College of Veterinary Medicine Teaching Hospital
      Created2023-02-09 09:28 CSTUpdated2023-10-09 11:47 CST
      SitesUniversity of Illinois College of Veterinary Medicine Teaching Hospital
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