Dosimetric consequences of radiopharmaceutical infiltrations

Frank P. Castronovo, Kenneth A. Mc Kusick, H. William Strauss

Research output: Contribution to journalArticlepeer-review

7 Scopus citations


RATIONALE AND OBJECTIVES. Little is known about the time-related biologic behavior of radiopharmaceutical misinjections. Such inadvertent tissue infiltration of such injections may not only adversely affect a scheduled test or cause some discomfort, but potentially could produce tissue damage. Radiopharmaceutical infiltrations were assessed in a rat model.METHODS Particulate and nonparticulate radiopharmaceuticals were injected subcutaneously or intradermally into an anesthetized shaved rat model. The rate of release of the nine infiltrations per radiopharmaceutical per injection type were measured from computer data acquired with a gamma camera up to 24 hours after administration. These data were used for dosimetry determinations. RESULTS. When injected subcutaneously, the particulate radiopharmaceutical, technetium 99m (Tc) albumin microspheres, exhibited essentially no movement, and the soluble agents showed a biexponential release pattern. The rate of release was similar for Tc methylene diphosphonate (Tc MDP) and for Ga citrate (Ga), whereas thallous chloride (Tl) exhibited the slowest release pattern. The average effective half-lives (T av-eff) were 78.3 minutes, 76.1 minutes, and 268.4 minutes, respectively. When injected intradermally, the nonparticulates exhibited a triexponential release pattern; MDP showed a more rapid release (T av-eff, 50 minutes) and Tl showed the slowest (T av-eff, 491.2 minutes). Absorbed doses were calculated using conventional medical internal radiation dose (MIRD) methodology for small unit density spheres. The absorbed dose was greatest for a Tl infiltration. A Tl infiltrate of 1 mCi per gm of tissue is capable of producing radiation-absorbed doses greater than 500 rads. Additional studies were performed with heat, hyduronidase, and volume dilution in an attempt to accelerate the rate of release of Tl. Local heat application proved to be more efficient than volume change or hyaluronidase application. CONCLUSION. These data indicate an insignificant skin radiation burden from the majority of nonparticulate infiltrated radiodiagnostic agents. Thallium 201, however, has the potential to produce significant radiation burdens when infiltrated at high specific activity. Actual human infiltration release rates may differ because of variants in blood flow and assumed infiltration volume relative to the animal model.

Original languageEnglish
Pages (from-to)59-64
Number of pages6
JournalInvestigative Radiology
Issue number1
StatePublished - Jan 1994
Externally publishedYes


  • Infiltration
  • Radiopharmaceutical
  • Rat model
  • Thallium 201 thallous chloride


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