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Performance of a chip for hybrid pixel detectors with two counters for X-ray imaging
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Radiation Sciences.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Radiation Sciences.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Radiation Sciences.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Radiation Sciences.
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2004 (English)In: Proceedings of the 5th International Workshop on Radiation Imaging Detectors / [ed] Gostilo, Vladimir, 2004, Vol. 531, 215-220 p.Conference paper, Published paper (Refereed)
Abstract [en]

A semiconductor hybrid pixel detector for dynamic X-ray imaging is developed. The detector, called DIXI, consists of a semiconductor sensor mounted onto a readout chip. A detector module with a silicon sensor is currently being assembled with the use of anisotropic conductive film as interconnection between the sensor and the readout chip. The basic building block of the detector is in size and consists of 992 square pixel cells arranged in 31 columns and 32 rows. The pixels have a side of . The readout chip is capable of performing photon counting and has an externally adjustable threshold. The readout chip has been characterised by charge injection in the absence of a sensor. The threshold dispersion is measured to 365 e for hole collection. Even if the chip was not originally designed for electron collection a threshold dispersion of 1650 e has been achieved. Two counters are implemented in every single pixel cell and the threshold can be changed from one image to the next in order to select different parts of the X-ray spectrum.

Place, publisher, year, edition, pages
2004. Vol. 531, 215-220 p.
National Category
Physical Sciences
Identifiers
URN: urn:nbn:se:uu:diva-92121DOI: 10.1016/j.nima.2004.06.008OAI: oai:DiVA.org:uu-92121DiVA: diva2:165086
Conference
5th International Workshop on Radiation Imaging Detectors, 7 - 11 Sep 2003, Riga, Latvia
Available from: 2004-09-07 Created: 2004-09-07 Last updated: 2013-09-13Bibliographically approved
In thesis
1. Modeling the Performance of a Hybrid Pixel Detector for Digital X-ray Imaging
Open this publication in new window or tab >>Modeling the Performance of a Hybrid Pixel Detector for Digital X-ray Imaging
2004 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The development of digital detectors for X-ray imaging in medical diagnostics receives an increasing amount of attention. The detector under development at the Department of Radiation Sciences at Uppsala University is a hybrid pixel detector, which consists of a semiconductor sensor mounted onto a readout chip. The readout chip is capable of performing photon counting and has an externally adjustable threshold.

A simulation tool for the detector and a model applying the linear-systems transfer theory to X-ray hybrid pixel detectors have been developed. Also a characterization of the readout chip has been done. In order to estimate the potential of the detector for diagnostic radiology, we investigate the image quality using the spatial frequency dependent detective quantum efficiency (DQE). By means of the detector simulations, the influence of threshold setting, noise sources, level of exposure and charge sharing on the DQE have been studied. By means of the linear-systems theory, a single analytical expression is provided to obtain the DQE of a hybrid pixel detector.

The method developed in this thesis will make it possible to optimize a detector design according to a particular medical application. It will also permit modifications and new features to be included without having to construct a full detector system.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2004. 45 p.
Series
Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1104-232X ; 1012
Keyword
Radiation sciences, Hybrid pixel detector, X-ray imaging, simulations, cascaded linear-systems, Strålningsvetenskap
National Category
Radiology, Nuclear Medicine and Medical Imaging
Identifiers
urn:nbn:se:uu:diva-4545 (URN)91-554-6035-6 (ISBN)
Public defence
2004-09-30, Polhemsalen, Ångströmlaboratoriet, Läggerhyddsv. 1, Uppsala, 13:30
Opponent
Supervisors
Available from: 2004-09-07 Created: 2004-09-07Bibliographically approved
2. DIXI – a Hybrid Pixel Detector for X-ray Imaging
Open this publication in new window or tab >>DIXI – a Hybrid Pixel Detector for X-ray Imaging
2004 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Medical X-ray imaging is an important tool in diagnostic radiology. The ionising-radiation dose to the patient is justified by the clinical benefit of the examination. Nonetheless, detectors that operate at even lower doses and provide more information to the radiologist are desired. A hybrid pixel detector has the potential to provide a leap in detector technology as it incorporates a more advanced signal-processing capability than currently used detectors.

The DIXI digital detector is a hybrid pixel detector developed for X-ray imaging. It consists of a readout chip and a semiconductor sensor. The division in two parts makes it possible to optimise each part individually. The detector is divided into square pixels with a size of 270 x 270 μm2. DIXI has the ability to count single photons and every readout pixel has two embedded counters to allow the acquisition of two images close in time. A discriminator enables the selection of photons with energies above a preset threshold level.

The readout chip Angie has been developed and its performance has been evaluated in terms of noise, threshold variation and capability to perform energy weighted counting. Silicon sensors have been fabricated, and a control system for DIXI has been designed and built. An electroless process for deposition of Ni/Au bumps on the chip and sensor has been optimised as a preparation for the assembly of a complete detector, which is being assembled by flip-chip bonding using anisotropic conductive film.

A simulation library for the DIXI detector has been set up and results on the image quality are reported for different exposures and working conditions. A theoretical model for hybrid pixel detectors based on the cascaded linear system theory has been developed. The model can be used to investigate and optimise the detector for different detector configurations and operating conditions.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2004. 65 p.
Series
Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1104-232X ; 1018
Keyword
Radiation sciences, hybrid pixel detector, photon-counting, X-ray, imaging, simulation, Strålningsvetenskap
National Category
Radiology, Nuclear Medicine and Medical Imaging
Identifiers
urn:nbn:se:uu:diva-4572 (URN)91-554-6050-X (ISBN)
Public defence
2004-10-15, Polhemsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 13:30
Opponent
Supervisors
Available from: 2004-09-24 Created: 2004-09-24 Last updated: 2013-09-13Bibliographically approved

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Bingefors, NilsBrenner, RichardFransson, KjellGustafsson, Leif

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