AUTOMATED SYNTHESIS OF RADIOPHARMACEUTICALS FOR POSITRON EMISSION TOMOGRAPHY - AN APPARATUS FOR LABELING WITH [C-11] METHYL-IODIDE (MIASA)

A fully automated apparatus for the routine synthesis and formulation of short-lived C-11 (t(1/2) = 20 min) labelled radio-pharmaceuticals for positron emission tomography (PET) has been developed. [C-11]Carbon dioxide is converted to [C-11]methyl iodide, which can be used to label a wide variety of substrates by methylation at C, N, O, or S electron rich centres. The apparatus, MIASA (methyl iodide automated synthesis apparatus), was designed to operate as part of an automated labelling system in a shielded 'hot' laboratory. The apparatus was designed without the site constraints of typical instrumentation used in hot cells, although it is compact where necessary. Ample use of indicators and sensors, together with compact design of the reaction flasks for small dead space and efficient evaporation, led to good reliability and performance. The design of the hardware and software is described in this paper, together with a preparation of 3-N-[C-11]methyl-spiperone as a sterile injectable solution in physiological saline.