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Autoradiolysis describes the degradation of radioactively labeled compounds due to the activity of the labeled compounds themselves. It scales with activity concentration and is of importance for high activity and microfluidic PET tracer synthesis. This study shows that microfluidic devices can be shaped to reduce autoradiolysis by geometric exclusion of positron interaction. A model is developed and confirmed by demonstrating in-capillary storage of non-stabilized [18F]FDG (2-[18F]Fluoro-2-deoxy- d -glucose) at max. 23 GBq/ml while maintaining > 90 % radiochemical purity over 14 h.

The presented paper describes a magnetic field sensor system for the real-time monitoring of magnetic resonance (MR) image encoding in the presence of gradient and main magnetic field imperfections. For this purpose, a novel simplified design for nuclear magnetic resonance (NMR) probes has been developed. The design fulfills the requirements of providing below ppm measurement accuracy in combination with long readout times. To this end, NMR is performed with a nanoliter water volume, which together with the radiofrequency (RF) solenoid coil is cast into an Epoxy holder. Based on the Larmor relation (i.e. the proportionality between the NMR resonance frequency and the local B 0 ), time varying magnetic field information is extracted from the phase evolution of the detected RF signals. Susceptibility matching techniques are applied to homogenize the B 0 field across the NMR sample and in this way to extend the readout time of the NMR probes. The presented design of NMR probe is significantly simpler compared to previous presented ones by De Zanche et al. in the sense that it omits the glass capillary plus additional matching fluidics. The optimization of the susceptibility for the Epoxy is described and results of the probe characterization measurements are presented. The feasibility of magnetic field monitored MRI is demonstrated for ultra-fast single- and multishot data acquisition schemes.

We present a chemical sensor based on a microfabricated array of eight silicon cantilevers actuated at their resonance-frequency and functionalized by polymer coatings. The operating principle relies on transduction of chemical or physical processes into a mechanical response. After exposure to analyte vapor, analyte molecules diffuse into the cantilever coating, which begins to swell. Jointly with the mass increase, a change of interfacial stress between coating and cantilever occurs, resulting in a bending of the cantilevers. Our setup allows the simultaneous detection of cantilever oscillation and bending of eight cantilevers by time-multiplexed optical beam deflection readout. The ac component of the cantilever response is demodulated, and the cantilever resonance-frequency is tracked by a custom-built phase-locked loop. By filtering out the ac component (oscillation), the dc signal (bending) is extracted, yielding information on mass as well as surface stress changes simultaneously. Detection results of water, primary alcohols, alkanes and perfumes are presented.

A novel chemical sensor based on a micromechanical array of silicon cantilevers is presented. Chemical reactions are transduced by sensitization of cantilevers with coatings such as metals, self-assembled monolayers, or polymers into a mechanical response. This is read out using an optical beam-deflection technique by a sequential readout scheme. Reference cantilever sensors permit subtraction of background signals (differential measurement). Coating of each cantilever sensor with a different sensitive layer allows operation of the array-device as a new form of chemical nose. Detection of hydrogen, primary alcohols, natural flavors, and water vapor is demonstrated. We show that the magnitude of sensor response is proportional to the amount of analyte present.