Radiology Reporting Trends for Indeterminate Low T1 Signal Intensity Bone Lesions Described on Spine MRI

PURPOSE: Low T1 signal intensity bone lesions are commonly encountered on MR imaging and lack consensus for management. This study evaluated radiology follow-up recommendations for indeterminate T1 hypointense vertebral lesions described in image reports. METHODS: We retrospectively reviewed 538 spine MRIs in which vertebral lesions were reported as “indeterminate.” Report recommendations and cancer history were recorded. Exams were excluded if there was prior metastatic bone disease, clearly aggressive features or described stability. RESULTS: 259 lesions met study criteria. 67% had no cancer history, 22% had active or remote early stage cancer and 11% had metastatic disease. 77% of reports advised further evaluation or follow-up. 53% recommended MRI, 16% recommended CT, 9% suggested nuclear imaging and 8% advised follow-up without specifying modality. 9% invoked multiple imaging modalities for further evaluation. Only 49% gave specific follow-up timing recommendations which varied from 2-4 weeks to 6-12 months. Follow-up was recommended in 76% without known cancer, 84% with local cancer and 72% with metastatic disease. Follow-up timing trended sooner in the setting of known malignancy (2.9-3.4 months) than those without cancer (5 months). 17 cases with initial non-contrast evaluation underwent repeat contrast-enhanced MRI within 30 days. Three malignant lesions were identified, all in individuals with known or concurrently diagnosed extra-skeletal metastatic disease. CONCLUSION: Radiology reporting of low T1 signal intensity bone lesions is very heterogenous. When lesions were mentioned, most reports recommended follow-up imaging. There was substantial variation in modality and over 50% of cases did not provide a specific follow-up interval. Malignancy history did not strongly influence the frequency of follow-up recommendation, but it did appear to influence follow-up timing. At present there are no multi-disciplinary guidelines to standardize reporting and management of low T1 signal intensity vertebral lesions.