Real time β-imaging with silicon hybrid pixel detectors: investigations into amino acids uptake and genetics

We present some additional results obtained with the BETAview system, a digital system for real time β-imaging based on semiconductor pixel detectors and on a single photon counting read-out chip. In this paper, we describe the system assembled with a Si detector, 300 μm thick, segmented into 64×64 square pixels with 170 μm pitch. The solid state pixel array detector is bump-bonded pixel by pixel to a low threshold, single particle counting electronics, the photon counting chip (PCC) developed by the Medipix1Collaboration for biomedical applications. Each cell (corresponding to a detector pixel) of the front-end chip has a maximum count rate of 2 MHz, a minimum nominal threshold of 1400 e¯ (corresponding to about 5 keV in Si) and contains a 15-bit counter. The detector sensitive area is about 1 cm2, but several detectors could be assembled in arrays. The measured background counts were about 3.5·10-2 cps/cm2, which implies a very high sensitivity of the device. The detection threshold used in this experiment was 15 keV. In this paper we show the results obtained in the real time monitoring of two biological dynamic processes: an amino acid uptake and the thermal denaturation process of oligonucleotides. Specifically, we have followed over time the accumulation of a marked amino acid ([14C]L-Leucine) into Octopus vulgaris eggs cells. After about 20 min from the beginning of the uptake process, the radioactively marked eggs become clearly visible over the background culture radioactive medium. We also describe the successful performance of the β-imaging system in genetic studies involving the real time reconstruction of denaturation and kinetics curves for two different 32P-radiolabeled nucleotides