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@INPROCEEDINGS{Buchholz:825285,
      author       = {Buchholz, Martin and Brandt, Marie and Vanasschen,
                      Christian and Spahn, Ingo and Coenen, Heinrich Hubert},
      title        = {{I}sotopic radiolabelling of the {MR}-contrast agent
                      {G}d-{DOTA} with {G}d-147/149},
      reportid     = {FZJ-2016-07749},
      year         = {2015},
      abstract     = {Objectives Due to the new multimodal capabilities of in
                      vivo imaging techniques, the supply of 147/149Gd appears
                      interesting for SPECT or autoradiographic imaging with the
                      aim to evaluate (new) MRI contrast agents. Although the
                      production of 147/149Gd by irradiation of Sm and Eu has been
                      published[1,2], an in vivo application of radiogadolinium
                      has hitherto not been reported. Also the isolation of
                      147,149Gd from the more effective target material Eu was not
                      described. Therefore, a bulk separation from the Eu target
                      material was developed, followed by the authentic labeling
                      of Gd-DOTA and a stability assessment of the complex in
                      human blood serum (HBS). Methods A described separation of
                      Sm2O3 and Gd2O3 with a Na-Hg amalgam[2] was systematically
                      adapted for the new target material Eu2O3. The influence of
                      extraction time, europium mass, amalgam mass and inert
                      atmosphere was assessed. The resulting Eu/Gd mixture was
                      absorbed on a DGA normal resin for the removal of excess
                      sodium with 1 M HNO3. The lanthanides were eluted
                      quantitatively with 0.1 M HCl, the resulting solution
                      reduced to dryness and taken up in 0.5 ml pure water.
                      Carrier-added and n.c.a.147/149Gd-DOTA was synthesized
                      within 20 min at 90°C in a 0.1 M NaOAc buffer at pH 4-6 and
                      the reaction monitored by radio-TLC. The stability of the
                      complex in HBS was investigated at 37°C over a time period
                      of 6 days. Results A $99.92\%$ reduction of the Eu
                      contamination down to 0.4 mg was achieved with the optimized
                      Na-Hg amalgam extraction without loss of 147/149Gd. This was
                      sufficient for first in vivo proof of principle tests with
                      147/149Gd-DOTA due to the strong chemical analogy of the
                      neighboring lanthanides Gd and Eu. Removal of excess sodium
                      was accomplished by a DGA resin enabling the application in
                      an animal model. Carrier-added and n.c.a. 147,149Gd-DOTA
                      were prepared with yields $>99\%.$ Additionally, over a time
                      period of 6 days no decomposition or ion leaching was
                      observed in HBS. Conclusions Bulk Eu was removed by amalgam
                      extraction from c.a. as well as n.c.a 147/149Gd which was
                      successfully used to label DOTA. This shows the possibility
                      of an authentic labeling of (new) MRI contrast agents,
                      allowing their in vitro or in vivo evaluation with
                      autoradiography or SPECT. Acknowledgements The authors
                      gratefully acknowledge the IKP-4 of FZJ for beam time and
                      all cyclotron operators. References [1] Denzler F.-O. et al.
                      (1997), Appl. Radiat. Isot., 48, 319. [2] Buchholz M. et al.
                      (2014), Appl. Radiat. Isot., 91, 8},
      month         = {May},
      date          = {2015-05-26},
      organization  = {21st International Symposium on
                       Radiopharmaceutical Sciences, Columbia
                       (USA), 26 May 2015 - 31 May 2015},
      subtyp        = {Plenary/Keynote},
      cin          = {INM-5},
      cid          = {I:(DE-Juel1)INM-5-20090406},
      pnm          = {573 - Neuroimaging (POF3-573)},
      pid          = {G:(DE-HGF)POF3-573},
      typ          = {PUB:(DE-HGF)6},
      url          = {https://juser.fz-juelich.de/record/825285},
}