HIGH MAGNETIC-SUSCEPTIBILITY COATINGS FOR VISUALIZATION OF OPTICAL FIBERS ON A SPECIALIZED INTERVENTIONAL MRI SYSTEM

The aim of this study was to develop methods of visualising optical fi bres on MRI scans for monitoring interstitial laser therapy. Scans wer e per formed on a specialised MRI extremity scanner at 0.17 T. Optical fibres of 0.4 mm diameter used for delivering laser energy were coate d with iron particles from a superferromagnetic contrast agent. MR ima ges of the fibres were acquired using gradient echo sequences (TR/TE = 300/10, 1 mm in-plane, 3 mm slice) and assessed for fibre visibility. Coated fibres could be resolved as lines 2 +/- 1 mm wide using the gr adient echo sequence. Uncoated fibres were invisible on the sequences used for in vivo therapy monitoring due to partial volume averaging. I t is concluded that optical fibre visualisation by MRI may be improved by coating with ferromagnetic particles. Biocompatibility requires fu rther assessment, but direct coating appears to be a promising method for fibre visualisation in MR-guided laser therapy.