Design of an MRI Compatible Steerable Guide for MRI-Guided Laser Interstitial Thermal Therapy

Laser interstitial thermal therapy (LITT) may generate precise ablative lesions under real-time magnetic resonance imaging (MRI) for the treatment of epilepsy and brain tumors. The Visualase Thermal Therapy System (Medtronic, Inc, MN, USA) is a minimally-invasive LITT platform that delivers laser light through a fiber-optic cable ensheathed in a cooling catheter. Currently, the system may create ablation lesions of a 1cm sphere along a linear trajectory. However, lesions larger than 1cm in diameter, small irregularly shaped lesions, or targets surrounded by critical structures may require multiple probe placements for complete treatment. In this paper, the design and prototype of a novel ‘Steerable Guide for the Visualase LITT system’ is presented. The system enables deployment of the laser fiber along a controlled curved trajectory and may treat lesions up to 5cm in diameter through a single insertion. Catheter insertion experiments were performed in tissue-mimicking phantoms to investigate the safety and accuracy of system. The system was able to achieve a curved trajectory with up to 25 mm tip displacement and allowed the optical fiber to be inserted along the curved trajectory. The average and standard deviation of tip position error between predicted and actual position was 0.33mm and 0.22mm, respectively.