Linda DeMello1,
  Rajan Rakheja1, Christopher B. Glielmi2, Christian
  Geppert3, Hersh Chandarana4, Kent Friedman1
 1Radiology,
  New York University School of Medicine, New York, United States; 2MR
  R&D Collaborations, Siemens Healthcare, New York, United States; 3MR
  R&D Collaborations, Siemens Medical Systems, New York, United States; 4Radiology,
  NYU Langone Medical Center, New York, United States
This study was performed to compare the accuracy of spatial registration of PET/CT and PET/MR in patients with FDG-avid metastatic lesions. Thirteen patients underwent PET/CT followed by PET/MR, and the spatial coordinates of the visually estimated centers of nineteen metastatic lesions were measured. Total distance between the isocenters was calculated, along with averages and standard deviations. Morphologic PET/MR sequences showed significantly more accurate spatial registration than PET/CT, likely secondary to simultaneous acquisition of PET and MR data. However, EPI-based DWI sequences demonstrated significant misregistration compared to PET/CT, likely due to respiratory motion and the inherent spatial distortion of DWI.