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Improved specific radioactivity of the PET radioligand [ 11 C]FLB 457 by use of the GE medical systems PETtrace MeI microlab
Author(s) -
Sandell Johan,
Langer Oliver,
Larsen Peter,
Dolle Fréderic,
Vaufrey Françoise,
Demphel Stéphane,
Crouzel Christian,
Halldin Christer
Publication year - 2000
Publication title -
journal of labelled compounds and radiopharmaceuticals
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.432
H-Index - 47
eISSN - 1099-1344
pISSN - 0362-4803
DOI - 10.1002/(sici)1099-1344(20000330)43:4<331::aid-jlcr320>3.0.co;2-h
Subject(s) - chemistry , methyl iodide , iodide , radioligand , radiochemistry , nuclear chemistry , iodine , medicinal chemistry , receptor , inorganic chemistry , organic chemistry , biochemistry
[ 11 C]FLB 457 is a high affinity dopamine D 2 receptor radioligand that is used for visualisation and quantitation of extrastriatal dopamine D 2 receptors with positron emission tomography (PET). In this study, we report a comparison regarding the specific radioactivity of [ 11 C]FLB 457 obtained by two different methods of synthesising [ 11 C]methyl iodide. In addition, the synthesis of unlabelled FLB 457 and the corresponding desmethyl‐precursor, starting from commercially available material, is reported. The first method used for [ 11 C]methyl iodide synthesis was reduction of [ 11 C]CO 2 with lithium aluminium hydride in tetrahydrofuran to [ 11 C]CH 3 OH, followed by conversion into [ 11 C]CH 3 I= with hydrogen iodide. The second, recently developed method uses gas phase halogenation of [ 11 C]CH 4 with iodine. [ 11 C]FLB 457 was labelled with [ 11 C]methyl triflate produced on‐line from [ 11 C]methyl iodide. With the first method a specific radioactivity for [ 11 C]FLB 457 of 2100 Ci/mmol (78 GBq/μmol) (n=13) at 40 min after end of bombardment (EOB) was achieved. Using the gas phase method a specific radioactivity of 3400 Ci/mmol (126 GBq/μmol) (n=7) at 40 min EOB could be obtained. The use of the gas phase method also resulted in shorter time for set‐up compared to the regular method since no wet chemistry is involved in the preparation of [ 11 C]methyl iodide. Copyright © 2000 John Wiley & Sons, Ltd.