Speaker
Description
Purpose: Nuclear medicine is a functional imaging technique. It uses a radiotracer
injected into an organism to map its displacement, through the emission and the
annihilation of a positron. It doesn’t give information on anatomical features. When an
external hardware is used, such as a coil in a PET/MRI system, attenuation will impact the
resulting image. A classical solution in the context of PET/MRI is to bring the external
hardware to a CT system, to obtain an attenuation map: the main limitations of this
approach are the requirement of that second imaging modality, as well as the inherent
extrapolation from the CT energies (70-140 keV) to the PET energies (511 keV). The
approach presented here relies entirely on a PET acquisition, circumventing the need for
another imaging technique as well as the extrapolation.
Method: Using a germanium MR-compatible phantom, two PET acquisitions are obtained,
one with a cylindrical aqueous external attenuator and one without it. By comparing their
sinogram, it is possible to extract a track or an eclipse caused by the external hardware,
corresponding to the lines of incidence affected by the hardware. This approach is
methodologically simple and easily reproducible.
Results: Looking only at the ratio of the sinograms, it was possible to determine accurately
the distance of the external hardware and of its radius. The results were compared with
physical measurements and MRI acquisitions done at the same time as the PET
acquisition. All the measured and determined values are in statistical agreement.
Future Work: Future works include an analysis of more complex structures, especially
those with many attenuators. Other enquiries of interest include the exact position in
Cartesian space, as well as the use of non-convex shapes.
| Keyword-1 | PET/MRI |
|---|---|
| Keyword-2 | Attenuation |