Imaging performance of a DEPFET pixel Bioscope system in Tritium autoradiography

A Bioscope system based on a 64 x 64-matrix of DEPFET pixels has been developed for real-time digital autoradiography in biomedical applications. It provides very good energy and spatial resolution at the same time. The DEPFET pixel cells consist of p-channel JFETs integrated into the high-ohmic it-silicon substrate, This leads to it very low noise performance at room temperature. Two dedicated ASIC chips have been developed for steering and readout of the pixel matrix. The measured system noise of (69 +/- 4)e(-) at 35 degrees C is mostly due to sensor leakage current and can be largely reduced by cooling or a faster readout. The spatial resolution is examined by measurements with a laser as well as with a dedicated test chart and is determined to be (6.7 +/- 0.7) mu m for 6 keV-X-ravs and 4.3 +/- 0.8 mu m for 22 keV-X-rays. The measurements are compared to simulation results with different reconstruction algorithms. Due to the thin entrance window at the detector backside and the low noise performance, a detection of low-energy beta-emitters such as 3 H is possible, Measurements with H-3-labeled biological samples were taken, The ability of the DEPFET pixel Bioscope to separate different radiolabels in the same sample is demonstrated by a measurement with H-3 and C-14. (c) 2005 Elsevier B.V. All rights reserved.