Laser‐induced interstitial thermotherapy of liver metastases in an interventional 0.5 Tesla MRI system: Technique and first clinical experiences

Laser‐induced interstitial thermotherapy (LITT) surveyed by magnetic resonance imaging (MRI) has been shown to be effective in various applications. The laser treatment of colorectal liver metastases usually requires a separate device (e.g., ultrasound or CT) to position the laser applicator. In this study, we used an interventional 0.5 T MRI system, allowing both the navigation to the target tissue and on‐line thermometry. Laser irradiation was performed using a near‐infrared laser source combined with a cooled laser light guide. We treated 20 patients exhibiting a total of 58 colorectal liver metastases. Clinically relevant complications did not occur. No residual tumor was observed after laser irradiation in all metastases with a diameter below 2 cm. Metastases with a mean diameter between 2 and 3 cm demonstrated total necrosis in 71%, while in larger tumors this proportion decreased to 46% (diameter, 3–4 cm) and 30% (diameter, >4 cm), respectively. We conclude that LITT, guided by the employed interventional MRI system, is feasible and safe. The results suggest a more aggressive treatment, especially for larger metastases. J. Magn. Reson. Imaging 2001;13:729–737. © 2001 Wiley‐Liss, Inc.