Laser-induced thermotherapy for liver metastases in an open 0.2 T MR system.

Objective: To test the feasibility and safety of the laser-induced thermoth erapy (LITT) for liver metastases in open MR imaging system operating at 0. 2 Tesla. Method: Laser therapy using the Nd:YAG laser was performed on 25 p atients with a total of 41 liver metastases. An open low-field MRI scanner was used for puncture, positioning of the laser applicator, and monitoring the therapy. A true FISP sequence was used to trade the puncture in close t o real-time. Localization diagnostics and temperature monitoring were aided by T-1-weighted gradient echo sequences in the breath-holding technique. I n the first follow up after 24-48 hours, a contrast-enhanced T1-weighted gr adient-echo sequence was performed in an MRI scanner at 1.5 T. The pre-, in tra- and postinterventional volumes of the liver metastases as well as the thermolesions and the thermonecroses were determined. Results: LITT in an o pen MRI system was technically feasible in all patients with no clinically relevant complications. The mean volumes of-the thermolesions measured duri ng intervention in low-field MRI were lower than the volumes of the thermon ecroses measured after intervention in high-field MRI. Conclusion: The tech nique presented here of laser-induced thermotherapy for liver metastases in an open MRI system is technically feasible and safe.