Recovery of 201Tl by ion exchange chromatography from proton bombarded thallium cyclotron targets

Production of pharmaceutical grade [201Tl]Thallous chloride using 30 MeV cyclotron

Multiple patient doses of [201Tl]TlCl has been produced using electrodeposited enriched 203Tl in 30 MeV cyclotron (Cyclone-30) with 28 MeV proton energy at 50 μA beam current for 8 h. Ion Exchange Column Chromatography (IECC) and liquid-liquid extraction has been employed for semi-automated radiochemical separation and purification of produced [201Tl]TlCl. The produced [201Tl]TlCl was used in coronary artery disease (CAD) patients.

Production and in vivo imaging of (203)Pb as a surrogate isotope for in vivo (212)Pb internal absorbed dose studies

(212)Pb is a clinically relevant therapeutic alpha emitter isotope. A surrogate, (203)Pb, if prepared with sufficiently high specific activity could be used to estimate (212)Pb in vivo absorbed doses. An improved production procedure of (203)Pb with a simple, new separation method and high specific radioactivity for imaging is reported. We determined the in-vivo biodistribution of (203)Pb in mice by SPECT/CT. This highlights application possibilities of (203)Pb for further in vivo and clinical uses (radiolabeled (212)Pb-peptide co-injection, dosimetry calculation).

Thallium Transfer from Hydrochloric Acid Media into Pure Ionic Liquids

Pure hydrophobic ionic liquids are known to extract metallic species from aqueous solutions. In this work we have systematically investigated thallium (Tl) extraction from aqueous hydrochloric acid (HCl) solutions into six pure fluorinated ionic liquids, namely imidazolium- and pyrrolidinium-based ionic liquids with bis(trifluoromethanesulfonyl)imide and bis(fluorosulfonyl)-imide anions. The dependence of the Tl extraction efficiency on the structure and composition of the ionic liquid ions, metal oxidation state, and initial metal and aqueous acid concentrations have been studied. Tl concentrations were on the order of picomolar (analyzed using radioactive tracers) and millimolar (analyzed using inductively coupled plasma mass spectrometry). The extraction of the cationic thallium species Tl(+) is higher for ionic liquids with more hydrophilic cations, while for the TlX(z)(3-z) anionic species (where X = Cl(-) and/or Br(-)), the extraction efficiency is greater for ionic liquids with more hydrophobic cations. The highest distribution value of Tl(III) was approximately 2000. An improved mathematical model based on ion exchange and ion pair formation mechanisms has been developed to describe the coextraction of two different anionic species, and the relative contributions of each mechanism have been determined.

A rapid improved method for gamma-spectrometric determination of 202Tl impurities in [201Tl]-labelled radiopharmaceuticals

Despite the cyclotron production method and the efficiency of the radiochemical procedures adopted, the long-lived radio-isotopic impurity 202Tl is always present in [201Tl]-labelled radio-pharmaceuticals, together with other short-lived impurities like, 200Tl. Rapid determination of the 202Tl impurity, can be achieved using HPGe gamma spectrometry and a detector shielded by a 5 mm thick envelope of lead. In this way, dead-time correction errors, Compton and X-ray background, are very efficiently avoided and suppressed. The same method could be applied routinely in nuclear medicine, to determine the radioisotopic purity of 201Tl by means of an ionisation chamber dose calibrator.