Separation Of Nuclear Isomers Research Articles

Radionuclide generator-based production of therapeutic\xa0177Lu from its long-lived isomer 177mLu

BackgroundIn this work, a lutetium-177 (177Lu) production method based on the separation of nuclear isomers, 177mLu & 177Lu, is reported. The 177mLu-177Lu separation is performed by combining the use of DOTA & DOTA-labelled peptide (DOTATATE) and liquid-liquid extraction.MethodsThe 177mLu cations were complexed with DOTA & DOTATATE and kept at 77 K for periods of time to allow 177Lu production. The freed 177Lu ions produced via internal conversion of 177mLu were then extracted in dihexyl ether using 0.01 M di-(2-ethylhexyl) phosphoric acid (DEHPA) at room temperature. The liquid-liquid extractions were performed periodically for a period up to 35 days.ResultsA maximum 177Lu/177mLu activity ratio of 3500 ± 500 was achieved with [177mLu]Lu-DOTA complex, in comparison to 177Lu/177mLu activity ratios of 1086 ± 40 realized using [177mLu]Lu-DOTATATE complex. The 177Lu-177mLu separation was found to be affected by the molar ratio of lutetium and DOTA. A 177Lu/177mLu activity ratio up to 3500 ± 500 was achieved with excess DOTA in comparison to 177Lu/177mLu activity ratio 1500 ± 600 obtained when lutetium and DOTA were present in molar ratio of 1:1. Further, the 177Lu ion extraction efficiency, decreases from 95 ± 4% to 58 ± 2% in the presence of excess DOTA.ConclusionThe reported method resulted in a 177Lu/ 177mLu activity ratio up to 3500 after the separation. This ratio is close to the lower end of 177Lu/177mLu activity ratios, attained currently during the direct route 177Lu production for clinical applications (i.e. 4000–10,000). This study forms the basis for further extending the liquid-liquid extraction based 177mLu-177Lu separation in order to lead to a commercial 177mLu/177Lu radionuclide generator.

Laser isotope separation (review)

Part II of the review (sec. 6–11) deals with isotope separation by the method of selective dissociation of polyatomic molecules in a strong pulse CO2 laser field (sec. 6), on the basis of selective photochemical reactions of electronically excited atoms and molecules (sec. 7) and vibrationally excited molecules (sec. 8), and by the method of selective deflection of atoms by laser radiation (sec. 9). The review ends with a discussion of economic and engineering aspects of laser isotope separation (sec. 10) and of several problems (sec. 11) related directly to laser isotope separation (separation of nuclear isomers, preparation of very pure substances, and selective detection of single atoms and molecules).

Separation of Nuclear Isomers in the Electric Field

Segre, Halford and Seaborg1 demonstrated the isomeric filiation of bromine 80 by a chemical method on the basis of the Szilard-Chalmers process. We have carried out experiments in which the isomeric filiation is proved by a physical method, collecting the isomers when partly separated by means of an electric field using electrodes in a non-electrolytic solution.

On the Separation of Nuclear Isomers

The fact that nuclear isomers can be separated chemically cannot be explained on the basis of the recoils involved. However, with $K$ capture, or with internal conversion accompanying the isomeric transition, there is a mechanism for the separation. The positive charge built up by the Auger effect during the electronic readjustment is enough to cause molecular dissociation. To illustrate this, the probabilities for Auger effect and for x-rays for all shells of the Br atom were calculated and compared, and they show that the excess charge in this case becomes as high as 4.7e. The effect on homopolar binding is examined by using a hydrogen molecule model. It is found that excess charges considerably less than 4.7e should cause dissociation in the Br case.