Understanding the Relationship Between Real-Time Thermal Imaging and Thermal Damage Estimate During Magnetic Resonance-Guided Laser Interstitial Thermal Therapy.

OBJECTIVE: Magnetic resonance-guided laser interstitial thermal therapy is a minimally invasive procedure that uses intraoperative magnetic resonance thermometry (MRT) to generate a thermal damage estimate (TDE) of the ablative area. This study aimed to compare areas produced by the MRT heat map with the system-generated TDE produced by Visualase software.

METHODS: All ablations were performed using the Visualase laser ablation system. MRT heat map and TDE were quantified using MATLAB version R2014a. TDE was compared with the summed area of green, yellow, and red areas (heat map 63.9 [HM63.9]) and the summed area of light blue, green, yellow, and red areas (heat map 50.4 [HM50.4]) produced by the MRT heat map.

RESULTS: Fifty-six patients undergoing magnetic resonance-guided laser interstitial thermal therapy were examined. Mean TDE produced was 236 mm2 (SEM = 9.5). Mean HM63.9 was 231 mm2 (SEM = 8.7), and mean HM50.4 was 370 mm2 (SEM = 12.8). There was no significant difference between TDE and HM63.9 (P = 0.51). There was a significant difference between TDE and HM50.4 (P < 0.001) and between HM63.9 and HM50.4 (P < 0.001).

CONCLUSIONS: The system-generated TDE consistently remains contained within the boundaries of the MRT heat map. At standard factory settings, TDE and the area produced within the periphery of HM63.9 are similar in magnitude. The light blue portion of the MRT heat map may serve as an additional means of predicting when critical structures may be at risk during laser ablation if exposed to further thermal stress.