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

Abstract

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