Ten years of ALARA experience in commercial nuclear pharmacy

The objective of this study was to review ten years of extremity exposure in a growing nuclear pharmacy company and determine those practices that have been most effective in keeping exposures ALARA. The focus of this study was specifically on extremity exposure since whole body exposures have not been as significant. Methods: More than 400 dispensing employees are monitored weekly for extremity exposure. Currently, these employees handle and dispense more than 9,000 Curies (333,000 GBq) of activity ready for use in nuclear medicine procedures each week. The quarterly and annual extremity exposure histories were examined and compared with the introduction of different initiatives to limit these exposures. Changes in the total activity per unit dose were considered as well as the introduction of different compounding practices during this time. An attempt was made to also determine specifically which activities contribute most to the extremity exposure of a dispenser. Procedural changes were reviewed as well as engineering controls such as new shielding materials and designs. Results: A significant conversion of cardiac doses occurred during the time period evaluated. Tc-99m heart agents became the preferred radiopharmaceutical replacing a significant portion of Tl-201 that had been used previously. Tl-201 is still used often in conjunction with a Tc-99m agent. The significance of the switch is the high percentage of dispensed doses for cardiac studies and the higher activities of the Tc-99m agents. A combination of procedural changes and engineering controls (primarily tungsten shielding devices) have been effective in preventing the extremity exposure increase one might expect based on higher activities dispensed per unit dose and the higher energy of Tc-99m compared to Tl-201. One procedural change, the mandatory use of tongs for handling unshielded syringes of radiopharmaceuticals, resulted in a 17% reduction in the average exposure to the extremities. Engineering controls were more difficult to precisely quantify since they were introduced for specific dispensing activities and other variables were in play. However, the extremity exposures did not increase at a rate equivalent to the rate of activity increase and number of dispensed units. The determination of which activities contribute most to the extremity exposure is inconclusive at this time. Conclusions: Using a diligent strategy of improved dispensing procedures and new and innovative engineering controls it is possible to maintain extremity exposures ALARA even in an environment of increased numbers of dispensed units and higher activities. More definitive study is needed to properly assess the contribution of different dispensing activities to the overall extremity exposure