The next generation of x-ray?

Gary Boas, gboas@eggship-media.com

Researchers are developing x-ray detectors that could offer improved contrast over traditional detectors and thus help reduce the possibility of radiation injury in medical imaging.

Thor-Erik Hansen and colleagues at the SINTEF Group’s Micro- and Nanotechnology Laboratory (MiNaLab) in Oslo, and at other SINTEF departments located both in Oslo and Trondheim, had been using traditional dual-energy x-ray technology for various materials characterization projects. They found, though, that the resolution was at times insufficient for detecting certain materials. Also, the scintillating detectors with photodiode readout used in their systems proved limited with respect to speed and radiation hardness.

New x-ray technology will use “edge-illuminated detectors” that can detect a greater range of particle energies and offer improved contrast over traditional x-ray systems.

The researchers are therefore developing technology in which they are replacing the dual-energy systems with fast x-ray spectroscopy. The new system will be based on “edge-illuminated detectors” that can detect a greater range of particle energies than the previously used technology. Here, when x-ray photons encounter the edge of the detector chip, they dislodge a number of electrons proportional to their energy level. The detector subsequently counts and sorts the photons based on their energy level.

The detector element will be a silicon chip covering the 5- to 200-keV range, with a typical response time of 15 ns.

Because the technology offers improved contrast, it can be used to distinguish materials with very similar densities. Hansen noted a number of applications that could benefit from its use, including materials characterization and identification, security and industrial tomography. Medical imaging applications would benefit further, he said, because the doses of x-ray energy required are lower than usual.

The system is in the early stages of development. The first step, Hansen explained, is to build a module including the x-ray optics, detector chip and application-specific integrated circuit readout, and to assemble it with cooling. This module will facilitate line scanning in spectroscopy.