Lesion detection and workflow optimization in whole body diffusion MR imaging using trimodality PET/CT+MR in the oncology setting.

Objectives To evaluate whole-body MR protocol to determine the value PET/CT+MR “tri-modality” imaging provides in addition to conventional PET/CT with respect to small lesion detection, and how this affects clinical decision-making.

Methods This IRB-approved, HIPAA-compliant study was performed on 10 consenting patients who presented to our clinic and were receiving diagnostic PET/CT. 30 min. after injection of FDG and prior to PET/CT acquisition, subjects were scanned on a 3T MRI scanner The subject was transported between MR and PET/CT using a pneumatically actuated "tri-modality table" to facilitate MR-PET/CT image co-registration. The researchers were not blinded to the other modality in this feasibility study.

Results All FDG-avid visceral organ lesions and lymphadenopathy seen on PET/CT demonstrated restricted diffusion on the DWI images (fig 1). With respect to workflow we were able to complete both the DWI and T1 sequences within the allotted scan window, without disturbing the normal workflow of PET/CT. Co-registration between the PET/CT and MR images using the tri-modality table was very robust requiring minimal correction (rigid-body co-registration) in post-processing.

Conclusions Rapid trimodality whole body DWI MRI shows a good correlation with FDG avid lesions in the oncological setting, and DWI may help improve clinical confidence in small PET/CT equivocal lesions, although a larger cohort is needed to confirm this. Whole body DWI can be performed within the uptake period of a conventional diagnostic PET/CT. Tri-modality PET/CT+MR demonstrated excellent co-registration between imaging modalities.