Detectability of Spinal Metastasis in Known Malignancies: A Comparative Study between 1Tesla MRI and F18 Sodium Fluoride PET- CT

Background:  The development of spinal metastasis is a seminal event in the progression of common malignancies and their early detection plays a critical role in deciding the treatment protocol and assessing prognosis. There is no consensus in the literature regarding the preferred imaging modality. The study was undertaken with the objective to compare the efficacy of Magnetic Resonance Imaging (MRI) as against 18F Sodium Fluoride (Positron Emission Tomography- Computed Tomography) PET-CT in detection of spinal metastatic lesions. Methods: A total of 32 patients with biopsy-proven malignancy and clinical and laboratory suspicion of metastases were taken up for this study. All patients underwent spinal MRI and whole body 18F Sodium Fluoride PET-CT scan using standard techniques. The MR images and 18-F Sodium Fluoride PET-CT scans was read independently by an experienced Radiologist and an experienced Nuclear Physician respectively, who were blind to the results of the other study. Results: A total of 1056 vertebrae of 32 patients were examined by both PET CT and MRI. On MRI 148 total lesions were detected whereas on PET CT scan 199 lesions were found. Analyzing the data by using Mc Nemar’s chi square statistics assuming 18F NaF as case and MRI as control, it is found that p value is 0.000. That means statistically ‘highly significant difference’ were seen in detection of vertebral metastasis by PET CT than MRI as PET CT picked up more number of lesions. Conclusion: Combined 18F NaF PET CT scan showed superior to MRI in the detection of spinal metastatic lesions. Consequently18F NaF PET CT has a better impact on clinical management compared to MRI, which will help in staging and reducing the morbidity associated with advanced malignancy.