Effectiveness of various syringe shields in minimizing radiation exposure

Introduction: Nuclear medicine technologists have an increased risk of radiation exposure due to patient procedures and the radiopharmaceuticals they handle every day. Practicing ALARA (As Low As Reasonably Achievable) through the use of syringe shields can aid in reducing this radiation risk. There are many different styles of syringe shields that are available and in use today. Over the years, our department has acquired newer syringe shields but staff continue to utilize some of the older syringe shields. The purpose of this study is to evaluate and compare the various types of syringe shields in our department to determine the effectiveness of each at minimizing radiation exposure.

Methods: Four different types of 3cc syringe shields were evaluated: 1) 1mm tungsten Pro-Tec II with lead glass and a locking screw, 2) 2mm tungsten Pro-Tec III with lead glass and a spring loaded clip, 3) 2mm tungsten Bullet syringe (no glass) with twist lock, and 4) 3mm tungsten Bullet syringe (no glass) with a locking screw. The syringe shields were tested using a 34.7 mCi 99mTc dose. The syringe shields were laid on the collimator and syringe counts, along with a background count, were all collected for 30-seconds using a gamma camera equipped with a low energy high resolution collimator and a 15% 99mTc window. The syringe shields that have glass were acquired twice, once with the glass side facing down and again with glass side facing up. Neither decay nor dead time was taken into account in this study. Instantaneous radiation exposure rates were also collected for 30-seconds using two RaySafe dosimeters in direct contact with the sides of each syringe shield to include both glass and non-glass readings, as necessary.

Results: Data obtained from the gamma camera for the Pro-Tec II, Pro-Tec III, twist lock Bullet, and locking screw Bullet syringe shields revealed 690K (531K with glass side down), 229K (388K with glass side down), 83K, and 78K counts per minute, respectively. The RaySafe dosimeter readings demonstrated that the above syringe shields had exposure rates of 0.78mSv/h from non-glass side and 5.4mSv/hr from glass side, 0.48mSv/h from each the non-glass and glass sides, 0.19mSv/h from each side, and 0.10mSv/h from each side, respectively.

Conclusions: Of the four syringe shields used in this study, the Bullet syringe shields performed the best with the locking screw design reducing both counts and exposure slightly better than the twist lock design. The bullet syringes were the newer syringe shields, while the Pro-Tec shields were the older in our department. The Pro-Tec syringe shields, especially the Pro-Tec II, did not provide as much protection against radiation as compared to the newer Bullet shields.