Abstract for presentation at 38th Annual Scientific Meeting of the Australian and New Zealand Society of Nuclear Medicine 2008

Installation of C-11 Pro Synthesizer™ - The RAPID Experience

  • Charmaine Jeffery, Department of Medical Technology and Physics, Sir Charles Gairdner Hospital, Australia
  • Dr Laurence Morandeau, Department of Medical Technology and Physics, Sir Charles Gairdner Hospital, Australia
  • Sun Chan, Department of Medical Technology and Physics, Sir Charles Gairdner Hospital, Australia
  • Peter Gibbons, Department of Medical Technology and Physics, Sir Charles Gairdner Hospital, Australia
  • Chris Jones, Department of Medical Technology and Physics, Sir Charles Gairdner Hospital, Australia
  • Dr Roger Price, Department of Medical Technology and Physics, Sir Charles Gairdner Hospital, Australia
  • Stan Poniger, Austin Health, Australia
  • Dr Henry Tochon-Danguy, Austin Health, Australia

    • Background:
    The Radiopharmaceutical Production and Development (RAPID) team at SCGH recently acquired a C-11 Pro automated radiotracer synthesizer (iPhase Technologies, Austin Health) to produce 11C-Pittsburgh Compound B (11C-PIB). 11C-PIB is a promising PET imaging agent for the early detection of Alzheimer's disease, and as such, is being utilised in the Australian Imaging Biomarker and Lifestyle (AIBL) Flagship Study of Aging (Australian Imaging Biomarkers and Lifestyle - About Us, 2006). The RAPID module is the first unit installed outside Austin Health. Several unforeseen problems were encountered during installation and validation, which arose from the supporting infrastructure, despite pre-installation modifications to RAPID facilities being completed to iPhase specifications. These problems and subsequent solutions are discussed, to allow other purchasers of the C-11 Pro to benefit from the RAPID experience.

    Problems and Solutions:
    #1 - Target leak and blown target window. Target leaks were observed, due to Teflon O-rings becoming brittle after irradiation and not sealing effectively, which required the target window housing to be tightened after several uses. Damage to the target windows resulted from target parameters that gave a target pressure of 23bars during irradiation (loaded to 15bars, 35uA current). The cyclotron manufacturer (IBA) advised that 20bars is the maximum operating pressure for these windows, thus the target is now loaded to a maximum of 11.3bars and run at 30uA.
    #2 - Slow transfer of irradiated gas from cyclotron and poor trapping of 11CO2 on Carbosphere column of C-11 Pro synthesizer. Transferral of irradiated gas took >5mins, due to a bypass regulator (set at 2bars) installed on the gas transfer line by IBA. Installation of a needle valve prior to the C11-Pro gas inlet allowed regulation of the flow rate. Selective trapping of 11CO2 from the irradiated gas onto the Carbosphere column was low (<40%, c.f. 90% at Austin). The larger gas volume exiting the RAPID target (c.f. Austin) was eluting 11CO2 whilst still transferring gas. Installing a larger Carbosphere column increased trapping efficiency (up to 75%) by reducing the amount of 11CO2 eluted. Faster gas transfer also improved trapping efficiency.
    #3 - 12CO2 contamination. The reduction of 11CO2 to 11CH3OH was poor, using 0.1M LiAlH4 (100μL). Total reduction of 11CO2 was achieved by changing to 1M LiAlH4; however, poor labelling of the precursor in the reactor loop was still observed over many syntheses. 12CO2 contamination was suspected - a new target gas bottle was installed, and the target cleaned with 2M HNO3, to no effect. The target gas was sampled from various points and analysed by gas chromatography (GC) to pinpoint the 12CO2 source. The contamination came from hydrocarbon and moisture traps plumbed into the target gas line, which were supposed to reduce 122     levels to less than 1ppb. Due to faulty installation, they were releasing more 12CO2 than can be measured in normal air (>>350ppm).

    Conclusions:
    The C-11 Pro has been successfully installed and is now routinely and reliably producing 11C-PIB, with 33 patients scanned by early February 2008. Several challenges that presented at the time of installation have been overcome, with input from RAPID and iPhase Technologies. From our experience, the RAPID team recommends:
    · installing an appropriate flow regulator device to the gas transfer lines
    · installing target windows tightly
    · utilising operating conditions that result in a target pressure of less than 20bars during irradiation (with 18/9 IBA cyclotron)
    · analysing the target gas that arrives at the synthesizer for 12C-carbon dioxide by GC prior to installation, or other possible contaminants

    References:
    Australian Imaging Biomarkers and Lifestyle - About Us. (2006). Retrieved February, 19, 2008, from http://www.aibl.nnf.com.au/page/about

    Conference Organiser - ICMS Pty Ltd