Radiation levels from Ra-223 Chloride unit doses and shielding requirements

Objectives Radium-223 Chloride (Xofigo, Algeta) is an alpha emitting therapeutic radiopharmaceutical used to treat metastatic bone cancer primarily from prostate cancers. Ra-223 decays by a series of multiple α, β, and γ emissions. The manufacturer states that radiation emitted from the patient unit dose is low, so no additional shielding is required for administration. The objective was to determine the radiation levels from Ra-223 unit doses and the most effective syringe shield for Ra-223.

Methods The radiation levels from 2 unit doses of Ra-223, with an activity of 93.6uCi/5ml (dose 1) and 132.0uCi/7.2ml (dose 2), were evaluated. Two thermoluminescent dosimeters (TLD) were placed on each unit dose syringe, exposed for 30 minutes, removed and sent to Landauer Inc. for radiation measurement. Dose 1 was placed in a Biodex Beta Syringe Shield and 2 TLDs were positioned on the outside of the shield for 30 minutes. Dose 2 was placed in a Tc-99m Tungsten Syringe Shield and 2 TLDs were positioned on the outside of the shield for 30 minutes. TLDs were then removed and sent to Landauer Inc. Two additional TLDs were used as controls.

Results The radiation levels from the unshielded 93.6uCi Ra-223 unit dose and the unshielded 132.0uCi Ra-223 unit dose were 1110 mrem/hr and 670 mrem/hr and 1110 mrem/hr and 760 mrem/hr, respectively, indicating significant radiation levels. The radiation levels from the 93.6uCi Ra-223 dose in a Biodex Beta Shield and the 132.0uCi Ra-223 dose in a Tc-99m tungsten syringe shield were both background indicating effective shielding for both syringe shields.

Conclusions The radiation levels from two clinical Ra-223 unit doses were evaluated. Significant radiation levels of 1110 mrem/hr were obtained for both unit doses. A Biodex Beta Syringe Shield and Tc-99m Tungsten Syringe Shield were both effective at reducing radiation levels to background. Although radiation levels from unit doses are relatively low, radiation emitted from the Ra-223 dose should be shielded to adhere to the ALARA principle.