Combined multimodal co-registration of PET/CT and MRI images increases diagnostic accuracy in squamous cell carcinoma staging

OBJECTIVES: The purpose of our study was to assess the diagnostic value of multi-modal imaging through co-registration of short tau inversion recovery (STIR) and diffusion-weighted imaging (DWI) MRI with 18FDG-PET/CT in T and N staging of head and neck tumours. MATERIALS AND METHODS: 25 patients with head and neck squamous cell carcinoma who had undergone MRI and PET/CT before treatment were retrospectively evaluated. The sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of PET/CT, MRI and their combined use were assessed in T and N staging. Histopathology and follow-up imaging results were used as the gold standard. RESULTS: In assessing trans-compartmental extensions, PET-MRI showed 93 % sensitivity, 88 % specificity, 94 % PPV, and 88 % NPV, as compared to the 94 and 53 % sensitivity, 75 and 75 % specificity, 89 and 82 % PPV, and 86 and 43 % demonstrated by MRI and PET, respectively. In the identification of pathological lymph nodes, PET-MRI showed 92 % sensitivity, 89 % specificity, 96 % PPV, and 89 % NPV, whereas PET/CT displayed 72 % sensitivity, 89 % specificity, 95 % PPV and 53 % NPV. The corresponding figures for DWI and STIR sequences were 84 and 100 % sensitivity, 67 and 56 % specificity, 88 and 86 % PPV, and 60 and 100 % NPV, respectively. CONCLUSIONS: Multi-modal imaging assessment of co-registered MRI and PET/CT images provides more accurate results for trans-compartmental extensions in T and N staging than the individual techniques alone.