A routine, automated synthesis of oxygen-15-labeled butanol for positron tomography

The use of labeled butanol for autoradiographic and positron tomographic measurement of cerebral blood flow has been well established using radiocarbon labels. The advantages of the short half-life of oxygen-15 (15O) in doing sequential flow studies are also recognized. An automated procedure has been developed for the routine rapid and sequential synthesis of 15O-labeled butanol in amounts and with purity suitable for use in positron tomography. Butanol can now replace 15O-labeled water, which is commonly used for routine applications. The 14N(d,n)15O reaction is used, with 8 MeV deuterons on a nitrogen target containing 0.2% oxygen. Labeled oxygen is reacted with tri-n-butyl-borane by passing the gas over an alumina support which holds the reagent. Washing with water through small C18-bonded phase silica cartridges eliminates labeled water and the majority of boron-containing impurities. Injectable labeled butanol is collected at 2.5 min after the end of bombardment. The yield is 6 mCi per microampere of saturated bombardment, measured at the end of synthesis. Injectable product up to 250 mCi can be obtained at 10-min intervals.