Medipix: From particles to patients

A redesign of a chip originally used in the LHC has provided high-quality imaging technology for medical applications


In the 1990s, researchers on the Large Hadron Collider were assembling the last pieces of detector electronics, designed to capture high-resolution images of particle collisions quickly and with no background noise.  

CERN researchers, led by Michael Campbell, were quick to realise that this technology could be used in other imaging applications. Campbell and his colleagues conceived the Medipix project to bring high-quality imaging technology to research communities beyond high-energy physics. In collaboration with institutes around the world, the Medipix team redesigned the chip used in the LHC and produced the Medipix chip. The chip consists of an integrated circuit connected to a sensitive element, which together form a small particle detector. Both the sensors and the microchips are divided into tiny sensitive elements (pixels) - similar to those in a digital camera - that detect individual photons.

Today, the Medipix collaboration has 17 member institutes. Over the years the team has produced the Medipix1 chip, the Medipix2 chip, with improved resolution; Timepix, a modified version of Medipix2 with the additional functionality of time measurements; and Medipix3, which not only counts photons but also determines their energy levels.

The Medipix chip has seen many practical applications. As the name implies, medical imaging is one of the most important. Radiography and computer tomography (CT) use X-ray photons to study the human body. The Medipix chip, with its single-photon counting technique, is well suited to these fields. To date, it has been used in X-ray CT, in prototype systems for digital mammography, in CT images for mammography and in beta and gamma autoradiography of biological samples.  

The Medipix project has improved hybrid-pixel technology to the point that the chip is being used to develop future systems within high-energy physics. The Medipix design team is currently working on using Timepix as a prototype to upgrade the detector for LHCb (one of the LHC experiments).

The path of technology transfer is often circular. The dissemination of a technology stimulates advancement which in turn nourishes the initial technology.

Other fields of applications include electron microscopy, background radiation monitoring, dosimetry and education.

The educational potential of the portable and user-friendly Medipix chip and its accompanying USB readout system was quickly recognized by Becky Parker, a teacher from the Simon Langton Grammer School in Kent, UK. Parker’s students developed a space-based cosmic ray detector using the Timepix chip, which won a science competition run by the British National Space Centre and is set to launch on a satellite in 2012.

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