FIG 4.

Interreader variability in the interpretation of PET/MR imaging–based NI-RADS. Axial T1WI postgadolinium sequence (A) and axial fused PET/MR imaging (B) in a patient with a history of maxillary sinus SCC status post subtotal maxillectomy and radiation. On the initial posttreatment PET/MR imaging, enhancing tissue in the pterygopalatine fossa (arrow) does not have corresponding FDG uptake. This primary site finding was scored a 2 by 1 reader (for discordant PET and MR imaging findings) and as a 1 by the other reader (for expected treatment related change). The patient has no evidence of recurrence on follow-up imaging nor clinical evidence of recurrence. In these scenarios, although agreement may not be perfect, the linked NI-RADS management decision of “short interval follow-up” allows these patients to be correctly risk-stratified.