A Shielded, Automated Injector for Energetic Beta-Emitting Radionuclides

Abstract

Objective: Systemic radiation therapy may require the clinical use of relatively high levels (tens of millicuries) of energetic pure, beta-emitting radionuclides such as ³²P, ⁸⁹Sr and ⁹⁰Y. To deliver such amounts of radioactivity to the patient presents a unique radiation hazard to the staff in nuclear pharmacy, radiation oncology and nuclear medicine due to the brake, or bremsstrahlung, radiation produced in the injection volume and syringe.

Methods: We designed a portable shield and automated delivery system which can be operated remotely to perform intravenous or intraperitoneal administration of a given amount of radioactivity and in a fixed period of time.

Results: By encasing a 60-cc syringe in 1.4 cm of acrylic and covering that layer with 6 mm of lead, we could reduce the exposure rate to approximately 0.12 mR hr^-1 mCi^-1 at 5 cm from the side of the device containing a ⁹⁰Y source. Corresponding exposure rates were 0.027 and 0.001 mR hr^-1 mCi^-1, at 20 and 100 cm respectively, from the side of the injection syringe. For a 50-mCi clinical injection, we estimated exposure rates of approximately 6 mR hr^-1 at 5 cm from a ⁹⁰Y source enclosed in this prefabricated, portable syringe holder.

Conclusions: We recommend that clinics, using high-energy beta emitters for radiotherapy, fabricate acrylic and lead holders for syringes used in the protocols to reduce their staffs’ exposure.