Characterisation of a single photon counting pixel system for imaging of low-contrast objects

Mikulec, B., Campbell, M., Dipasquale, G., Schwarz, C. and Watt, J. (2001) Characterisation of a single photon counting pixel system for imaging of low-contrast objects. In: 1st International Workshop on Radiation Imaging Detectors, Sundsvall, Sweden, 13-17 Jun 1999, pp. 352-359. (doi: 10.1016/S0168-9002(00)01037-8)

Abstract

In the framework of the Medipix1 collaboration the PCC, a single photon counting pixel chip, has been developed with the aim of improving the contrast resolution in medical imaging applications. The PCC consists of a matrix of 64×64 square pixels with 170 μm side length, each pixel comprising a 15-bit counter and a pulse-height discriminator. The chip has been bump bonded to equally segmented 200 μm thick SI-LEC GaAs detectors showing a very high absorption energy for X-rays used in diagnostics. An absolute calibration of the system with a radioactive source and a synchrotron beam are described resulting in the value of the test input capacitance of ∼24.7 fF. Using this value a full characterisation of the system from electrical measurements is presented. The entire system can reach a minimum threshold of ∼2100e− with ∼250e− rms noise. One of the characteristic features of the PCC is the possibility to adjust the thresholds of all pixels on a pixel-by-pixel basis with 3-bit precision. The threshold distribution after adjustment is ∼120e− rms. The spatial resolution of the system has been measured to be 3.6 lp/mm. A comparison of a tooth image taken with the PCC and with a screen-CCD-system demonstrates its imaging capabilities.

• Item Type: Conference Proceedings
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Watt, Dr John
• Authors: Mikulec, B., Campbell, M., Dipasquale, G., Schwarz, C., and Watt, J.
• Subjects: Q Science > QC Physics
• College/School: College of Science and Engineering > School of Physics and Astronomy
• Journal Name: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
• ISSN: 01689002