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

Abstract

PURPOSE: To clinically assess a new PET/MRI technology in which the PET-component features a new PET- detector and time-of-flight (TOF) technology. Thus, we compared SUVmax/mean of neoplastic lesions and physiological structures between TOF- and non-TOF-PET/MRI imaging. We qualitatively evaluated image quality derived from TOF-PET/MRI, non-TOF-PET/MRI reconstruction and FD-PET/CT. Lastly we did clinical measurements to evaluate the PET- detector sensitivity in order to better understand the background of our clinical results.
MATERIALS AND METHODS: Twenty-seven oncological patients were prospectively enrolled and evaluated with FDG-PET/CT and PET/MRI (15 M/ 12 F; mean age 56 ±10 y). Time between injection and PET/CT was 62.4 ±7.6 min, consecutive start of imaging of PET/MRI was 104.6 min±18.2 after injection. To assess the differences between TOF and non-TOF, all PET--images of the PET/MRI were reconstructed twice -with and without TOF. To compare lesion and tissue characterization between both reconstructions, malignant lesions as well as physiological structures were compared. 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 (except the subcutaneous fat, spleen and blood pool) 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.
CONCLUSION: 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.