Whole-body magnetic resonance imaging for detection of malignant disease: A head-to-head-comparison with whole-body 18F-FDG-PET/CT as the reference standard

Introduction: The combined use of 18 F-FDG-PET and computed tomography (CT) scans is an integrated part of diagnosing and staging patients with suspected malignancy or other pathologies. Magnetic resonance imaging (MRI) has proven its use as a non-ionizing imaging alternative for identifying potential malignancy in specific organs. Objective: To investigate the clinical value of whole-body MRI in detection of suspicious lesions, we compared 1.5T MRI findings to those obtained from a whole-body 18 F-FDG-PET/CT scan, the latter serving as the reference standard. Finally, the findings were compared with histology if available. Materials and methods: Twenty-five patients (9 women and 16 men, mean age ± SD: 64.5 ± 11.8 years; range: 34±85 years) with suspected malignancy or other pathologies were enrolled. All patients were scanned using both modalities. Imaging included the head, torso and extremities. Images were scored blinded by experienced readers: two radiologists and two nuclear medicine physicians. Statistical tests included weighted kappa for measuring interobserver reliability and Wilcoxon signed-rank test for detection differences between paired observations. Results and discussion: Interobserver reliability between each pair of specialists was fair-to-strong (Weighted kappa). Statistically significant differences between the findings of the two modalities were found in the colon (p=0.016), soft tissues of the extremities (p=0.002) and skeleton of the extremities (p=0.008). Twelve patients had histology available. WB-MRI and whole-body 18 F-FDG-PET/CT found 10 of these cases (sensitivity: 83.3%, 95% CI: 55.2%-95.3%). Conclusion: The diagnostic value of WB-MRI equaled whole-body 18 F-FDG-PET/CT. The MRI approach could therefore be considered in patients unsuitable for 18 F-FDG-imaging e.g. younger patients, during pregnancy or dysregulated diabetics.