Evaluation of Novel Methods for Motion Correction in Simultaneous PET/MR

Due to comparatively long measurement times in PET/MR imaging, patient movement during the acquisition is likely. This leads to artefacts which have a negative impact on the visual assessment and quantitative validity of the image data and, in the worst case, lead to misinterpretations. Simultaneous PET/MR systems allow the registration of movements and enable correction of the PET data. In order to assess the effectiveness of the motion correction methods, it is necessary to carry out measurements on phantoms that are reproducibly moved. An experimental setup was developed for specific movements. An MR-compatible robotic system was used to generate rigid movements of a brain-like phantom acquired on a Siemens mMR. Different tools, either from the manufacturer or open-source software, were used to estimate and correct for motion. Different motion estimates were compared with the robot-induced motion. Results of motion correction of the PET data were evaluated by determining the segmented volume of a flask. The flask was a hotspot visible in both PET and MR, used to simulate a lesion. The experimental setup is suitable for the generation of reproducible movement patterns. The results showed the motion-corrected PET images have a decreased volume as expected. The evaluated motion correction methods produced corrected PET images that were less affected by motion.