Tumour uptake of 11C-thymidine labeled in the methyl position was assessed after intravenous injection in 13 patients with head and neck tumours. This activity was compared to other tracers such as C15O, 13NH3 and C15O2. In every single case a 'positive' tumour image after injection of 11C-thymidine was obtained. Time-activity curves showed the initial activity to be followed by a rapid decrease over the first 10-15 min with an apparent plateau thereafter. A similar level of uptake was found in normal salivary gland regions and myocardium, while higher activities were noted in liver and kidney parenchyma. It is suggested that both blood flow and cellular metabolism can influence 11C-thymidine imaging in this class of human tumours.
A no-carrier added synthesis of [11C]thymidine from cyclotron produced [11C]methyl iodide is presented. The bis-silylated derivative of the lithium salt of 5-bromo-2'-deoxyuridine is treated with [11C]methyl iodide in THF at -50 degrees C giving 20-30 mCi [11C]thymidine in a 40-70% radiochemical yield. Purification is performed by reversed phase chromatography on a C18 column. The whole procedure takes 25 min and the specific activity is about 20-30 mCi/mumol at the end of the synthesis.
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