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 |