Does the Novel Integrated PET/MRI Offer the Same Diagnostic Performance as PET/CT for Oncological Indications?

BACKGROUND We compared PET/MRI with PET/CT in terms of lesion detection and quantitative measurement to verify the feasibility of the novel integrated imaging modality for oncological applications. METHODOLOGY/PRINCIPAL FINDINGS In total, 285 patients referred to our PET/CT center for oncological indications voluntarily participated in this same-day PET/CT and PET/MRI comparative study. PET/CT images were acquired and reconstructed following routine protocols, and then PET/MRI was performed at a mean time interval of 28±11 min (range 15-45 min). PET/MRI covered the body trunk with a sequence combination of transverse T1WI 3D-volumetric interpolated breath-hold, T2WI turbo spin echo with fat saturation, diffusion-weighted imaging with double b values (50 and 800 s/mm2), and simultaneous PET acquisition over 45 min/5 bed positions. The maximum standardized uptake value (SUVmax) was assessed by manually drawn regions of interest over fluorodeoxyglucose-positive lesions. Among 285 cases, 57 showed no abnormalities, and 368 lesions (278 malignant, 68 benign and 22 undetermined) were detected in 228 patients. When stand-alone modalities were evaluated, PET revealed 31 and 12 lesions missed by CT and MRI, respectively, and CT and MRI revealed 38 and 61 more lesions, respectively, than PET. Compared to CT, MRI detected 40 more lesions and missed 8. In the integrated mode, PET/CT correctly detected 6 lesions misdiagnosed by PET/MRI, but was false-negative in 30 cases that were detected by PET/MRI. The overall diagnosis did not differ between integrated PET/MRI and PET/CT. SUVmax for lesions were slightly higher from PET/MRI than PET/CT but correlated well (ρ = 0.85-0.91). CONCLUSIONS/SIGNIFICANCE The novel integrated PET/MRI performed comparatively to PET/CT in lesion detection and quantitative measurements. PET from either scanner modality offered almost the same information despite differences in hardware. Further study is needed to explore features of integrated PET/MRI not addressed in this study.