WP1. Integrated detector based on high quality epitaxial GaAs.
Detectors made from semi-insulating GaAs have been bonded to integrating and photon counting read-out chips. High purity VPE GaAs layers have been produced. The properties of the layers have been tested in prototype detectors.
WP2. Pixel array based on a CdZnTe sensor bonded to a CMOS readout chip.
Semi-insulating GaAs and CdTe detectors have also been bonded to integrating and photon counting read-out chips. We have shown that GaAs and CdZnTe detectors can be reliably bump bonded to readout chips with a pitch of 38 um and even down to 25 um.
WP3. Silicon CCD coated with a high efficiency pixel aligned scintillator.
Initial tests produced scintillating layers of BGO by laser ablation. However it turned out to be difficult to etch pixel structures in these layers. An alternate method was then introduced: A grid structure was etched in silicon and the grid was subsequently filled by a scintillating material. The results obtained with this structure are promising. The structure has been given the name Scintillating Guides Screen. A patent has been applied for.
Objectives and content
Digital X-ray imaging systems are now replacing X-ray film in a number of fields. The main reasons are time savings since digital images do not require photographic development and that image processing can be introduced to assist the viewer in the interpretation of the image. The main limitation in the current systems is that the sensor cost is high related to the effectiveness. This proposal concerns research in order to reduce the cost and increase the sensitivity of the sensor.
The most important application areas for digital X-ray imaging are in medicine and dentistry since the new technique leads to a reduction of the X-ray dose to the patient. In dental radiography the use of the technology to be developed will give a potential to decrease X-ray doses needed for diagnostics to 1 - 3 % of the dose required when using conventional film or to 5 - 15 % of the doses needed with the best available digital imaging systems today. The user can also save up to 10 % of the working time due to the immediate imaging available with this technology. Another advantage is that the use of chemicals for film development in reduced.
The technology of this project is also known to be relevant for general imaging in industrial applications. Improved image quality, faster response and reduced radiation are important advantages of the system.
The objective in this project is to develop an X-ray imaging sensor with a quantum efficiency for X-ray photons close to 100% and at a cost not significantly higher than the cost for the currently used CCD sensors. The three most promising concepts for development of such a sensor are:
- Integrated detector based on high quality epitaxial GaAs. - Pixel array based on a CdZnTe sensor bonded to a CMOS readout chip. - Silicon CCD coated with a high efficiency pixel aligned scintillator.
The project will start with work on all three concepts and proceed up to a point where a final decision is made and full scale prototype system for intraoral imaging is produced.
The consortium comprises a manufacturer of equipment for medical imaging, REGAM, a manufacturer of equipment for imaging in industrial and security applications, METOREX, a semiconductor manufacturer, IMC, a manufacturer of equipment for growth of semiconductor materials, AIXTRON, and three universities U.Freiburg, U.Glasgow and KTH with long experience in semiconductor processing.
Funding SchemeCSC - Cost-sharing contracts
79104 Freiburg (In Breisgau)
164 40 Kista
G12 8QQ Glasgow