No abstract

Für die 18F‐Markierung von Radiopharmaka benötigt man annähernd wasserfreie [18F]Fluorid‐Lösungen, doch um [18F]F− von Anionaustauscherharzen zu waschen, werden üblicherweise wässrige K2CO3‐Lösungen verwendet. Ersetzt man K2CO3 durch starke organische Basen wie die Phosphazenbase P2Et (deren konjugierte Säure hier abgebildet ist), so lässt sich hoch reaktives [18F]F− ohne eine azeotrope Wasserverdampfung zurückgewinnen.

The formulated [(18)F]FPRGD2 was obtained without any operator manipulation with a d.c. yield of 13% ± 3% (n = 13) in 130 min, a radiochemical purity >98% and a specific activity of 140 ± 40 TBq/mmol.

Doing without water: The 18F labeling of radiopharmaceuticals requires nearly anhydrous solutions of [18F]fluoride. Aqueous K2CO3 is generally used to elute [18F]fluoride from an anion‐exchange resin. Replacing aqueous K2CO3 with strong organic bases, such as the phosphazene base P2Et (conjugate acid shown), enabled the recovery of highly reactive [18F]fluoride and avoided the azeotropic evaporation of water, which is very difficult on a microchip device.

BackgroundKinetic modeling of physiological function using imaging techniques requires the accurate measurement of the time-activity curve of the tracer in plasma, known as the arterial input function (IF). The measurement of IF can be achieved through manual blood sampling, the use of small counting systems such as beta microprobes, or by derivation from PET images. Previous studies using beta microprobe systems to continuously measure IF have suffered from high background counts.MethodsIn the present study, a light-insensitive beta microprobe with a temporal resolution of up to 1 s was used in combination with a pump-driven femoral arteriovenous shunt to measure IF in rats. The shunt apparatus was designed such that the placement of the beta microprobe was highly reproducible. The probe-derived IF was compared to that obtained from manual sampling at 5-s intervals and IF derived from a left ventricle VOI in a dynamic PET image of the heart.ResultsProbe-derived IFs were very well matched to that obtained by "gold standard" manual blood sampling, but with an increased temporal resolution of up to 1 s. The area under the curve (AUC) ratio between probe- and manually derived IFs was 1.07 ± 0.05 with a coefficient of variation of 0.04. However, image-derived IFs were significantly underestimated compared to the manually sampled IFs, with an AUC ratio of 0.76 ± 0.24 with a coefficient of variation of 0.32.ConclusionsIF derived from the beta microprobe accurately represented the IF as measured by blood sampling, was reproducible, and was more accurate than an image-derived technique. The use of the shunt removed problems of tissue-background activity, and the use of a light-tight probe with minimal gamma sensitivity refined the system. The probe/shunt apparatus can be used in both microprobe and PET studies.