Sean Reynolds MD, Presenter: Nothing to Disclose

Janusz Karol Kikut MD, Abstract Co-Author: Nothing to Disclose

The Tc-99m chelating radiopharmaceutical Sestamibi adheres to disposable syringes with a reported 10-50% of the prescribed dose remaining in the syringe after injection. Nuclear Stress laboratories develop their MPI activity dosing schedules empirically to bring consistent diagnostic quality exams for the utilized imaging systems. This does not account for variable syringe residual and potentially results in unnecessary absorbed radiation dose to patients or compromised image quality. Adsorption to the rubber gasket of the plunger is a postulated culprit. 2-part syringe designs without rubber gaskets are available. We compared syringes with and without rubber gaskets to determine the effect on residual activity in the syringe following patient administration. We compared the results against MDP which has no significant demonstrated adherence to the rubber gasket syringe components.

35 consecutive doses of Tc-99m-Sestamibi and 30 doses of Tc-99m-MDP were prepared by nuclear pharmacy (Pharmalogic Holdings, Boca Raton, FL) in 3 mL Luer-lock syringes with rubber gaskets (Mod# 309657 BD, Franklin Lakes, NJ). These were assayed in a well-counter (CRC-15R, Capintec, Inc. Ramsey NJ) before and after patient administration. The same procedure was performed with with 11 doses of Tc-99m-Sestamibi in 3 mL Luer-lock gasketless syringes (Air-Tite, Inc., Virginia Beach, VA). A scintigraphic image of a post-injection 3-part syringe was obtained to localize tracer retention in the syringe.

Tc-99 MDP showed a mean residual dose 6.3% (range 0.78-14.9) consistent with that reported by others as dead space of the Luer-lock tip. Tc-99m-Sestambi syringes with rubber gaskets had residual 23% (range 8.5-35.3). Tc-99m-Sestambi in gasketles syringes had residual 7.2% (range 3.0-10.4). A scintigraphic image of the three part syringe showed a majority of the residual activity bound to the rubber gasket of the plunger.

There was significant adsorption of Sestamibi to rubber gaskets in the 3-part syringes. The gasketless 2-part syringe design reduces the Sestamibi syringe residual to the level of dead-space activity in the Luer-lock tip.

Using 2- part plastic syringes without rubber gaskets for the T99m Sestambi doses reduces the high and variable syringe residual to that of relatively small and constant dead space activity allowing more controlled implementation of ALARA principles.

Reynolds, S, Kikut, J, T99m Sestambi Dispensed in 2-part Plastic Syringes Shows Negligible Syringe Retention and Allows Improved Implementation of ALARA Principles.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14045456.html