Abstract

There is a renewed interest in MR-guided laser interstitial thermal therapy (LITT) as a minimally invasive alternative to craniotomy for local treatment of various brain tumors and epilepsy. LITT allows for focused delivery of laser energy monitored in real time by MRI, for precise ablation of the lesion. Although highly promising, the long-term effects of laser ablation as a viable treatment option for neurological disorders have yet to be rigorously studied and quantified. In this work, we present a quantitative framework for monitoring per-voxel thermal-induced changes post-LITT over time on multi parametric MRI. We demonstrate that voxel-by-voxel quantification of MRI markers over time can enable a careful and accurate (a) characterization of early LITT-related changes (if and when they are exaggerated and when they subside), and (b) identification and monitoring of MRI markers that potentially allow for better quantification of response to LITT therapy. The framework was evaluated on two distinct cohorts of patients (GBM, epilepsy), who were monitored post-LITT at regular time-intervals via multi-parametric MRI. On a cohort of six GBM studies we found that (a) it may be important for the initial treatment-related changes to subside to more reliably capture MRI markers relating to tumor recurrence, and (b) T1w MRI and T2-GRE may better differentiate changes that may correspond to tumor recurrence from patients with no recurrence, as compared to T2w-MRI, and FLAIR. Similarly, our preliminary analysis of four epilepsy studies suggests that (a) early LITT changes (attributed to swelling, edema) appear to subside within 4-weeks post-LITT, and (b) ADC may be more reflective of early treatment changes (up to 1 month), while T1w may be more reflective of early delayed treatment changes (1 month, 3 months), while T2-w and T2-FLAIR appeared to be more sensitive to late treatment related changes (6-months post-LITT) compared to the other MRI protocols under evaluation.

Highlights

  • There has been a recent interest in the potential utility of Magnetic Resonance Imaging (MRI)-guided Laser-induced interstitial thermal therapy (LITT) to treat brain tumors, such as glioblastoma multiforme (GBM) [1,2,3] and more recently, to treat epilepsy [4]

  • We realize that the MRI changes for epilepsy and GBM are inherently different as different tissues are targeted during treatment, the purpose of this study is to provide a quantitative framework for monitoring changes in MR markers over time that can be used to capture LITT related changes over time

  • We detail our findings while evaluating our framework in the context of these objectives: (1) evaluating temporal profiles of changes in MRI markers to quantify changes post-LITT over-time, (2) identifying post-LITT MRI markers that are more sensitive to capturing treatment changes over time, and (3) evaluate when early LITT induced changes dissipate over time

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Summary

Introduction

There has been a recent interest in the potential utility of Magnetic Resonance Imaging (MRI)-guided Laser-induced interstitial thermal therapy (LITT) to treat brain tumors, such as glioblastoma multiforme (GBM) [1,2,3] and more recently, to treat epilepsy [4]. LITT potentially provides an advantage over other more invasive treatment options due to real-time image guidance, and the avoidance of larger incisions. Since LITT is based on thermal destruction of the target, it is not constrained by a maximum dose limit, and may be used opportunistically multiple times post- treatment if required [5]. To our knowledge currently there is relatively little information regarding the specific in vivo imaging characteristics of LITT-induced changes within and around the ablation zone for GBM patients

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