Patent Number: 
Section: claims

1. A method for the generation of 223Ra of pharmaceutically tolerable purity comprisingi) preparing a generator mixture comprising 227Ac, 227 Th, and 223Ra in a first aqueous solution comprising a first mineral acid;ii) loading said generator mixture onto a diglycolamide DGA separation medium;iii) eluting said 223Ra from said DGA separation medium using a second mineral acid in a second aqueous solution to give an eluted 223Ra solution; andiv) stripping the DGA separation medium of said 227Ac and 227Th by flowing a third mineral acid in a third aqueous solution through the DGA separation medium in a reversed direction, wherein said 223Ra of pharmaceutically tolerable purity comprises less than 45 Bq 227Ac per 1 MBq 223Ra. 2. The method as claimed in claim 1 wherein at least 99.5% of the 227Ac loaded onto the resin in step ii) is regenerated in step iv). 3. The method as claimed in claim 1 wherein at least 95% of the 227Th loaded onto the resin in step ii) is regenerated in step iv). 4. The method of claim 1 additionally comprising the step of:y) storing said mixture of 227Ac and 227Th for a period sufficient to allow ingrowth of 223Ra by radioactive decay, whereby to re-form a generator mixture comprising 227Ac, 227Th, and 223Ra. 5. The method as claimed in claim 1 wherein the generator mixture has an 227Ac activity of at least 1 GBq. 6. The method as claimed in claim 1 wherein the generator mixture is stored as a salt and contacted with a separation medium only when separation of 223Ra is required. 7. The method of claim 6 wherein said contacting occurs for no more than 1 day every 1 to 8 weeks. 8. The method as claimed in claim 1 wherein the DGA separation medium is a DGA resin. 9. The method as claimed in claim 1 wherein the DGA separation medium comprises N,N,N′,N′-tetrakis-2-ethylhexyldiglycolamide binding groups. 10. The method as claimed in claim 1 wherein said first mineral acid is an acid selected from the group consisting of H2SO4, HNO3, and HCl. 11. The method of claim 10 wherein said first mineral acid is HCl. 12. The method as claimed in claim 1 wherein said second mineral acid is an acid selected from the group consisting of H2SO4, HNO3, and HCl. 13. The method of claim 12 wherein said second mineral acid is HCl. 14. The method as claimed in claim 1 wherein the eluted 223Ra solution has a contamination level of no more than 45 Bq 227Ac per 1 MBq 223Ra. 15. The method as claimed in claim 1 wherein the steps of loading the generator mixture onto the DGA separation medium and eluting the eluted 223Ra solution provide a separation ratio of 223Ra to 227Ac of at least 10,000:1. 16. The method as claimed in claim 1 wherein said third mineral acid is an acid selected from the group consisting of H2SO4, HNO3, and HCl. 17. The method of claim 16 wherein said third mineral acid is HCl.