The infiltrated radiopharmaceutical injection: dosimetric considerations

Area of Science:

• Nuclear Medicine
• Radiopharmaceutical Dosimetry
• Biomedical Engineering

Background:

• Radiopharmaceutical extravasation is a clinical concern.
• Understanding absorbed dose from extravasated agents is crucial for patient safety.
• Limited data exists on the biologic behavior and dosimetry of subcutaneous radiopharmaceutical infiltrations.

Purpose of the Study:

• To determine the biologic behavior of selected radiopharmaceuticals following subcutaneous injection in a rat model.
• To assess the subsequent absorbed dose and radiation burden from these infiltrations.
• To evaluate the radiobiological risk associated with extravasated radiopharmaceuticals.

Main Methods:

• Subcutaneous injection of 99mTc-microspheres, 99mTc-MDP, 67Ga-citrate, and 201Tl-chloride in Sprague-Dawley rats.
• In vivo imaging and computer analysis immediately after injection and at intervals up to 24 hours.
• Calculation of radiation burdens for a uniform 5g infiltrate mass.

Main Results:

• Particulate 99mTc-microspheres showed minimal diffusion from the injection site.
• Non-particulate agents exhibited a biexponential release pattern.
• Calculated radiation burdens (rad/mCi) were 59.4 for 99mTc-microspheres, 13.6 for 99mTc-MDP, 32.9 for 67Ga-citrate, and 92.2 for 201Tl-chloride.

Conclusions:

• The diffusion characteristics of radiopharmaceuticals vary significantly after subcutaneous injection.
• Radiation burdens from extravasated agents, when distributed in a 5g mass, are below the threshold for severe skin reactions.
• These findings aid in understanding and managing potential risks associated with radiopharmaceutical extravasation.