Evaluation and clinical quantification of neoplastic lesions and physiological structures in TOF-PET/MRI and non-TOF/MRI - a pilot study

Objectives To compare the SUVmax/mean of neoplastic lesions and physiological structures between TOF- and non-TOF-PET/MRI. Furthermore, we qualitatively evaluated image quality derived from TOF-, non-TOF-PET/MRI reconstruction and FDG-PET/CT. Lastly we did clinical measurements to evaluate the PET-detector sensitivity in order to better understand the background of our clinical results.

Methods Twenty seven oncological patients were prospectively enrolled and evaluated with FDG-PET/CT and PET/MRI. To assess the differences between TOF and non-TOF, all PET-images of the PET/MRI were reconstructed twice -with and without TOF and then compared both in physiological structures and neoplastic lesions. Furthermore, PET image quality, artifacts, image sharpness, noise and lesion detectability were assessed as well. Count rates between both systems were also compared.

Results All malignant lesions and the majority of physiologic tissue showed a good correlation concerning SUV (max and mean) measurements between PET/CT, non-TOF and TOF reconstructions. The general image quality was rated statistically significant superior in non-TOF (p<0.001) and TOF-reconstruction in PET/MRI (p<0.01) compared to PET/CT. Furthermore, TOF-PET/MRI was rated superior concerning image quality (p<0.05) compared to non-TOF PET/MRI. The ratio of emitted/received events between both systems (PET/CT and PET/MRI) was 2.78.

Conclusions PET/MRI with TOF is reliable concerning SUV quantification and image quality. The technical promise of an improved sensitivity of the new PET-detector in this PET/MRI device could be confirmed in a clinical setting.