Diagnostic Criteria Regarding Morphology, Extent, and Metastases
| Parameter | Unenhanced MRI | Enhanced MRI | 18F-FDG PET |
| Morphology | |||
| Solid | Restricted diffusion | Enhancement | Avidity* |
| Cystic | Hyperintensity on T2 and DWI (T2 shine-through) | No enhancement | No central avidity; exception: single paraspinal abscess |
| Homogeneous | Uniform T2 and DWI signal | Uniform enhancement | Not applicable |
| Heterogeneous | Varying T2 and DWI signal | Varying enhancement | Not applicable |
| Necrosis, areas of decreased/ absent enhancement | Heterogeneity/hyperintensity on T2 and DWI (T2 shine-through) | Decreased or absence of enhancement | No avidity, and fluid noted on CT or MRI |
| Tumor margins | Well-defined = distinct; ill-defined = indistinct | Well-defined = distinct; ill-defined = indistinct | Not applicable since all margins on PET are ill defined |
| Tumor extent | |||
| Infiltration of adjacent organs | Tumor/avidity extending beyond organ of origin and infiltrating adjacent structures | Tumor/avidity extending beyond organ of origin and infiltrating adjacent structures | Tumor/avidity extending beyond organ of origin and infiltrating adjacent structures |
| Extension across midline | Tumor/avidity extending beyond margin of contralateral vertebral body | Tumor/avidity extending beyond margin of contralateral vertebral body | Tumor/avidity extending beyond margin of contralateral vertebral body |
| Encasement of vessels | Tumor/avidity surrounding vessel and extending > 270°; for PET, MRI or CT was used for anatomic correlation | Tumor/avidity surrounding vessel and extending > 270°; for PET, MRI or CT was used for anatomic correlation | Tumor/avidity surrounding vessel and extending > 270°; for PET, MRI or CT was used for anatomic correlation |
| Tumor thrombosis | Enlarged vein with altered signal on T2 and DWI | Enlarged vein with focus of intraluminal enhancement | Focal linear avidity within vein, either enlarged or contiguous with solid tumor tissue |
| Metastases | |||
| Solid organ (liver, spleen, kidney, or pancreas) | Hyperintensity on T2 and DWI | Lesion enhancement and washout on delayed images | Avidity obviously greater than background within organ* |
| Bone marrow | Hyperintensity on T2 and DWI | Tumor enhancement | Avidity, either diffuse or focally within lesion* |
| Lymph node | Short axis > 1 cm with loss of normal kidney bean shape | Short axis > 1 cm with loss of normal kidney bean shape | Avidity within lymph node despite size* |
| Final diagnosis | Most appropriate diagnosis based on imaging features | Most appropriate diagnosis based on imaging features | Most appropriate diagnosis based on imaging features |
↵* If equivocal, then region of interest was placed within lesion of concern, and mean SUVmax was compared with mediastinal blood pool or hepatic background. Mean SUVmax > 2.5 was considered suggestive of tumor involvement or metastatic disease.
DWI = diffusion-weighted imaging.