Topic: Musculoskeletal
Presentation Time: Sunday, 10:39 a.m.
V. Zampa1, U. Albisinni2, I. Bargellini1, F. Odoguardi1, R. Cioni1, C. Bartolozzi1; 1Pisa/IT, 2Bologna/IT
Presentation Number: B-461
Purpose: To evaluate the role of dynamic Gadolinium-enhanced MRI (D-MRI) in the nidus detection of osteoid osteoma (OO) and in the assessment of the results after radiofrequency (RF) thermal ablation.
Materials and Methods: Twenty-three patients with histologically proven OO underwent MRI before and 6 months after percutaneous CT-guided RF ablation. MRI protocol included a conventional study (C-MRI: SE-T1w, GRE-T2w and FSE-IR) and D-MRI (FastSPGR-T1w) after Gd injection. MRI images were evaluated by two blinded readers to assess bone edema and joint effusion on C-MRI, and degree of nidus contrast uptake on D-MRI.
Results: Pre-procedural C-MRI revealed specific abnormal findings in all cases, with clear nidus delineation only in 9; at D-MRI, early and high contrast uptake allowed accurate nidus identification in 20/23 cases. After treatment, 8 patients reported persistent pain. In these cases, where persistent edema and nidus contrast uptake was identified, patients underwent further treatment. In asymptomatic patients and in patients reporting residual discomfort not requiring medical therapy after treatment, D-MRI did not demonstrate residual nidus contrast uptake, and C-MRI showed reduction of bone edema and joint effusion, allowing definition of success. Moreover, in 6 cases of successful treatment, C-MRI showed an area of apparently normal bone marrow delineated by a rim (hypointense in T1-w and slightly hyperintense in T2-weighted images), recalling osteonecrosis in the site of previous RF ablation.
Conclusion: D-MRI allows nidus detection in OO. After RF ablation, MRI enables accurate assessment of results, and D-MRI is able to differentiate a persisting active nidus from bone edema.