Purpose Minimally invasive techniques for treatment of malignant brain lesions when surgically unresectable continue to emerge. We describe neurointerventional surgery with MR-guided laser-induced interstitial thermotherapy of glioblastomas & metastases using intra-operative MRI for placement of laser and real-time mapping of brain temperature changes.

Methods Thermotherapy (burning) of glioblastoma (n=4) or metastatic adenocarcinoma (n=2) of six subjects (54–70 years) was performed using AutoLITT system (Monteris Medical, Inc.) on a 1.5 T or 3 T system (Magnetom Espree or Verio, Siemens). During each session, a biopsy needle trajectory was first planned using post-contrast T1-w 3D data. A needle guide was secured onto the skull and used with imaging guidance to insert the needle tip through a burr hole into the center of the lesion. The final location of the needle was verified from T2-w images obtained along and perpendicular to the needle axis. The tumor was manually segmented on the 3D data and temperature reference points were marked on the healthy tissue in the tumor vicinity. Subsequently, the needle was replaced by a CO₂-cooled laser probe that emits energy in one side direction with simultaneous internal cooling to avoid unintentional thermal damage in other directions. Temperatures maps were generated by proton resonance frequency shift-based phase mapping technique using a gradient-echo (TR/TE/α=81/19.1/30°, FOV =256×256 mm, matrix =128×128, bandwidth=100 Hz/pixel, three 5 mm slices aligned perpendicular to the fiber, 7.8 s/slice) sequence for data acquisition. Laser energy was imparted while continuously monitoring temperature evolution in the region for areas exceeding the threshold for thermal damage of brain tissue (43°C). The interventionalists then repositioned the laser fiber in any rotation (5° increments) or depth (>1 mm increments) to allow multiple targets for maximal therapy along the trajectory. Success of the procedure was verified by repeat immediate and follow-up structural imaging over days to several months.

Results Thermal ablation of 6 lesions of various sizes (16×13×16 mm to 50×30×40 mm) and locations ranging from sub-cortical white matter to peri-ventricular gray matter was possible in all cases (see example in Abstract O-030 figure 1). Mild local edema without significant mass effect was observed post-operatively in all cases and one intra-ventricular hemorrhage resolved spontaneously. Two subjects developed temporary motor deficits 2 weeks after the procedures and the symptoms resolved significantly at 2 months for both subjects.

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Abstract O-030 Figure 1

A glioblastama (arrow) in the left thalamus as visible from a post-contrast T1-w image (left) obtained before and a T2-w image (right) obtained 2 days after thermotherapy shown burn as hyperintensity.

Conclusion Laser thermotherapy of malignant brain lesions, specifically those that are surgically unresectable, can be performed successfully with a reasonable procedural complication risk using MRI to monitor localization and real-time extent of laser treatment.

Competing interests J Sunshine: Siemens Medical. G Sandhu: None. A Sloan: Monteris Medical. M Griswold: Siemens Medical.