Purpose: The present study compares the diagnostic value of (18)F-fluorodeoxyglucose (FDG) positron emission tomography (PET) and MRI to combined/registered (18)F-FDG PET/MRI for staging and restaging in paediatric oncology.
Methods: Over 8 years and 2 months, 270 (18)F-FDG PET and 270 MRI examinations (mean interval 5 days) were performed in 132 patients with proven (n = 117) or suspected (n = 15) malignant disease: solid tumours (n = 64), systemic malignancy (n = 53) and benign disease (n = 15). A total of 259 suspected tumour lesions were analysed retrospectively during primary diagnosis and 554 lesions during follow-up. Image analysis was performed separately on each modality, followed by analysis of combined and registered (18)F-FDG PET/MRI imaging.
Results: A total of 813 lesions were evaluated and confirmed by histopathology (n = 158) and/or imaging follow-up (n = 655) after 6 months. In the separate analysis of (18)F-FDG PET and MRI, sensitivity was 86 %/94 % and specificity 85 %/38 %. Combined/registered (18)F-FDG PET/MRI led to a sensitivity of 97 %/97 % and specificity of 81 %/82 %. False-positive results ((18)F-FDG PET n = 69, MRI n = 281, combined (18)F-FDG PET/MRI n = 85, registered (18)F-FDG PET/MRI n = 80) were due to physiological uptake or post-therapeutic changes. False-negative results ((18)F-FDG PET n = 50, MRI n = 20, combined (18)F-FDG PET/MRI n = 11, registered (18)F-FDG PET/MRI n = 11) were based on low uptake or minimal morphological changes. Examination-based evaluation during follow-up showed a sensitivity/specificity of 91 %/81 % for (18)F-FDG PET, 93 %/30 % for MRI and 96 %/72 % for combined (18)F-FDG PET/MRI.
Conclusion: For the detection of single tumour lesions, registered (18)F-FDG PET/MRI proved to be the methodology of choice for adequate tumour staging. In the examination-based evaluation, MRI alone performed better than (18)F-FDG PET and combined/registered imaging during primary diagnosis. At follow-up, however, the examination-based evaluation demonstrated a superiority of (18)F-FDG PET alone.