Volumetric trends associated with MRI-guided laser-induced thermal therapy (LITT) for intracranial tumors.

Background: MR-guided Laser Induced Thermal Therapy (LITT) is a procedure for intracranial tumors. Minimal data exists regarding post-procedure lesion volume changes.

Objectives: We aim to analyze changes in lesion volume during the post-LITT period using polygonal tracing with fusion. Additionally, we investigated the role of lesion histopathology on LITT parameters and volume dynamics.

Methods: Sixteen patients with intracranial neoplasms received LITT. Using OsiriX DICOM Viewer, three raters computed lesion volumes at the following: pre-ablation (PreA), immediate post-ablation (IPA), 24 hours post-ablation (24PA), and first follow-up post-ablation (FPA), which ranged from 4 to 11 weeks post-ablation. Statistical analyses for volume changes between time points and inter-rater reliability were performed. Additionally, comparisons were made between metastatic versus non-metastatic and small versus large lesions in terms of operative parameters and volume changes.

Results: There was an acute increase in volume at IPA with a decrease in size by 24PA. ANOVA among inter-rater datasets showed no significant difference at any time point (highest F(1,15)  = 0.225, P > 0.80, for IPA). GLM repeated measures, for Intra-Rater analysis, demonstrated statistically significant differences across time points (lowest F(1,15)  = 13.297, P = 0.003). IPA volumes were larger than those at PreA, 24PA, and FPA (average volume increase [95% CI]: 281% [157-404%], 167% [134-201%], 187% [154-219%], respectively; all P < 0.004). Correlation analysis showed lower inter-rater reliability at IPA versus other time points (all P < 0.03). Larger lesions (>2.5 cm³ ) versus smaller (<2.5 cm³ ) did not demonstrate a difference in percent volume increase. Operative parameters and volume dynamics were not different between metastatic and non-metastatic groups.

Conclusions: The response of intracranial lesions to LITT demonstrates a peak in volume at the IPA time point with decreased IPA inter-rater reliability. We recommend that conclusions about intracranial lesion size post-LITT be made at least 24 hours post-LITT rather than immediately after LITT.