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Schlagwörter:
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Zusammenfassung:
First prototype clinical PET/MRI scanners are readily available to be tested in patient studies. In addition to provide a unique possibility for multifunctional imaging with temporally and spatially matched data, PET/MRI also provides anatomical information that can be used for attenuation correction with no radiation exposure to the subjects. When both, PET and MRI, are necessary for a clinical diagnosis, the ability to perform simultaneous PET and MRI in one machine, results in a reduced scan time. Three PET/MRI systems have already been delivered to clinical centers and they are showing promising results in first patient studies. For quantitative PET imaging attenuation correction is obligatory. In current PET/MRI setups, there is no possibility to perform a transmission scan. Thus, the attenuation map needs to be derived from the MRI image instead. Based on the MRI image, we computed the attenuation map of the patient using an adaptation of our correction method which uses a database of MRI-CT template images that are registered to the patient image. The MR-based attenuation corrected PET images were quantitatively compared to the PET/CT images. Here we describe three studies in the field of neuro-oncology and a patient with cerebral stroke. The main aim of the PET/MRI examinations was the exclusion of metastases for the determination of further therapy strategies. Furthermore, the exact co-registration of PET and MRI data as well as the good soft tissue contrast from the MR images supports the radiotherapy planning. One patient suffered from pharyngeal carcinoma received a [18F]FDG-PET/CT examination for tumor staging. Incidentally, PET/CT revealed a hypo-dense area of the temporal right lobe, obviously revealing an old cerebral infraction. In addition to a better soft tissue contrast, MRI offers advanced diagnostic options like MRI spectroscopy and MRI angiography. These two imaging options showed a reduced choline area and peripheral stenosis of the right arteria cerebri media, adding additional data for the diagnosis along to the reduced FDG uptake in this area. Finally, we performed a full set of phantom scans according to the NEMA protocol to investigate the PET imaging performance. Detailed studies assessing potential mutual interferences between PET and MRI showed only minor, for in vivo imaging, not relevant effects.
