Evaluation of MRI Safety of Ru-106 Eye Applicators.

INTRODUCTION

Ruthenium-106 brachytherapy is a primary treatment for uveal melanoma (UM), the most common intra-ocular malignancy in adults. This study evaluated the safety of Ru-106 applicators at 3 Tesla (T) MRI and their impact on image quality.

METHODS

Magnetic attraction and eddy currents were tested on a 20-mm-diameter Ru-106 applicator using a nylon string and a porcine eye. Safety criteria were defined by ocular oncologists, comparing magnetic field interactions to the forces exerted on the eye during surgery. Five UM patients were scanned at 3T MRI with the applicator in situ using both conventional anatomical sequences and scans optimised to reduce metal artefacts.

RESULTS

Minimal magnetic interactions were observed. Eddy currents caused slight lagging during fast movements and temporary detachment of the applicator of the porcine eye in conditions that were considered unrealistic for clinical scans. Significant susceptibility artefacts compromised image quality of the affected eye.

CONCLUSION

Patients with Ru-106 applicators can be safely used in 3T MRI with some simple precautions. MR image quality of the eye was poor due to major susceptibility artefacts; however, imaging of extra-ocular anatomy is feasible.