Combining PET and MRI Scanning

Positron emission tomography (PET) technology enables clinicians to visualize cellular activity and metabolism but it lacks resolving morphology. Magnetic resonance (MR) technology is excellent for imaging soft tissue as well as functional and morphological details but it has lower then PET sensitivity for cellular activity. When these two powerful tools are combined, clinicians may be able to see early cellular changes that can be accurately mapped onto MR images and shorten the time between diagnosis and treatment. The clinical availability of simultaneous PET and MRI systems offers medical imaging a range of potential benefits in oncologic, neurological, and cardiovascular applications.

Today, three large-imaging companies have PET/MRI whole-body scanners in their portfolios, although all three are significantly different. Recently, GE Healthcare had present for FDA approval the first integrated, simultaneous, time-of-flight (TOF) capable, whole body SIGNA PET/MR. This system had been installed at Stanford University, University of California San Francisco, and University of Zurich.

The SIGNA PET/MR features GE’s new, exclusive MR-compatible silicon photomultiplier detector (SiPM) technology which is up to three times more sensitive than conventional PET technology. It also features fast coincidence timing resolution enabling TOF reconstruction with which the arrival times of each coincident pair of photons are more precisely detected, and the time difference between them is used to localize the PET signal accurately. TOF leads to improved PET image quality with higher structural detail and improved signal-to-noise ratio.

Simultaneous PET-MRI may improve clinical outcomes through improved diagnostic accuracy, therapy planning, and disease monitoring.