Environmental, Health and Safety Services

Nuclear Medicine Introduction


Radioactive material is used in various designated areas within the campus Teaching Hospital (VTTH) and Equine Medical Center (EMC) to support diagnostic and therapeutic procedures.

Radioisotopes currently in use at Virginia Tech are:

Technetium 99m is used for internal imaging of dogs, cats, and horses and emits readily detectable gamma rays. This radioisotope has a very short half-life of six hours (i.e. half of the radioactivity will be gone in six hours). This means that within three days, the radioactivity will decay to background radiation levels as Tc99m changes to Tc99 yielding soft beta rays.

Iodine 123 is used for thyroid imaging of dogs and cats. This radioisotope has a short half-life of 13.3 hours and emits gamma rays while decaying. Within six days the radioactivity will decay to background radiation levels.

Iodine 131 is used for thyroid treatment for dogs and cats in both patient and research status. The half life of this isotope is 8 days emitting beta and gamma radiation and, therefore, requires different safety precautions than either Tc 99 or I 123 previously mentioned. The radiation levels, when using I 131, are expected to be at background amounts within 80 days of administration of doses.

Strontium 90 is used as a treatment tool for ocular lesions and is located only at VTTH. The half-life of Sr90 is a little over 29 years (approximately 10622 days). The beta emitting decay changes Sr90 to Yttrium 90 which actually works as the mechanism for treatment. The decay rate will affect the ability to regulate treatment dose and therefore must be taken into consideration periodically.


All university personnel using radioisotopes or involved with their use must be authorized, trained, and included in the dosimetry program. These requirements follow the standard university protocol for all radiation material use.