Specific Activity of 11C-Labelled Radiotracers: A Big Challenge for PET Chemists

Considerations in the Development of Reversibly Binding PET Radioligands for Brain Imaging

“…Several hundred GBq of carbon-11 can be prepared through this reaction on modern biomedical cyclotrons. Radioligands are produced with specific activities typically in the range 180–370 GBq/μmol [305, 306]. With rigorous precautions in production and labeling methodology, radioligands with impressively higher specific activities of up to about 5550 GBq/μmol may be obtained [305].…”

“…Radioligands are produced with specific activities typically in the range 180–370 GBq/μmol [305, 306]. With rigorous precautions in production and labeling methodology, radioligands with impressively higher specific activities of up to about 5550 GBq/μmol may be obtained [305]. The chemical form obtained from the cyclotron irradiation may be [ 11 C]carbon dioxide [307] or [ 11 C]methane [308, 309], depending on whether the nitrogen gas target is doped with oxygen or hydrogen, respectively (Fig.…”

Pitfalls and Limitations of SPECT, PET, and Therapeutic Radiopharmaceuticals

“…The theoretical maximum specific activity of 11 C (ie, if every atom is radioactive) is 341 TBq/μmol, but the specific activity of a 11 C-labeled compound is typically several orders of magnitude lower. For example, as discussed by Gomez-Vallejo et al, 60 37 GBq of carrier-free 11 C carbon dioxide precursor is equivalent to 0.1 nmol; incorporation of 1 or 100 nmol of nonradioactive carbon dioxide decreases the resultant specific activity by a factor of 10 or 1000.…”

“…By contrast, if 11 C methane is converted to 11 C methyl iodide, the resultant specific activity tends to be higher by a factor of 10. 60 However, results can still vary between production runs, and there are many complicating factors, including target components and the purity of gases and reagents.…”

Synthesis and in vivo evaluation of 11C‐labeled (1,7‐dicarba‐closo‐dodecaboran‐1‐yl)‐N‐{[(2S)‐1‐ethylpyrrolidin‐2‐yl]methyl}amide

“…18 A methodology is well established in our laboratory. [ 11 C]CH 4 was directly generated in an IBA Cyclone 18/9 cyclotron by irradiation of a gas N 2 /H 2 mixture with 18 MeV protons.…”