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Pre-clinical combined MR-PET scanner that could lead to improved radia tion therapy and cardiology treatments.

Scientists across Europe have gotten one step closer to many imaging specialists: a clinical PET-MR machine.

HYPERImage, funded by the European Union, leading research universities and Philips, has a budget of around 7 million euros to advance medical imaging.

While not functional yet, the experimental PET-MRI device does suggest that the technology in development works, and that the team has overcome some of the most important technical hurdles in combining two normally mutually hostile systems: state-of-the art time-of-flight PET with a powerful 3 Tesla MR magnet.

What the scientists did was create PET detectors "compatible with the strong magnetic fields associated with MR," he says, while also developing methods for PET attenuation correction, where scattering of gamma rays can create inaccurate readings.

This is hard for a number of reasons. First, magnetic fields can play havoc with PET's sensitive detectors.

"Magnetics distort electronics," Tobias Schaeffter, Ph.D., a professor of imaging sciences at King's College London who worked on the project and whose colleagues have been researching PET-MR devices for the last ten years, tells DOTmed News. This means common vacuum-based photomultiplier tubes, at the core of a PET machine, would be impossible to use, as they would get scrambled. That's why for the device, the scientists installed silicon photomultipliers with integrated digital read-out electronics, which are impervious to the magnetics.

But the interferences run both ways: the PET's electronics could also affect the MR device, creating misleading images.

To solve this problem, they housed the digital PET modules inside a tiny Faraday cage, which traps the potentially distorting RF waves.

The current version is a stacked system, consisting of the PET detector, crystals for gamma ray reading and integrated electronics, all caged inside an 8 cm long, 4 cm high box. The boxes can be scaled to increase power.

Source: Philips

You can discuss more about PET and related topics in our PET Group.