Stereotactic Laser Ablation of High-Grade Gliomas

Ammar H. Hawasli, M.D., Ph.D.; Albert H. Kim, M.D., Ph.D.; Gavin P. Dunn, M.D., Ph.D.; David D. Tran, M.D., Ph.D.; Eric C. Leuthardt, M.D.

Disclosures

Neurosurg Focus. 2014;37(6):e1 

In This Article

Stereotactic LITT

Stereotactic LITT is a minimally invasive treatment for intracranial lesions. This method stems from similar minimally invasive ablation techniques pioneered by general surgeons.[19,35,40,68] Stereotactic laser ablation produces high temperatures that lead to tissue coagulation, necrosis, and cellular apoptosis.[2–4,7,32,60,73] Research in animals has shown that ablation produces a histologically proven immediate disruption of the blood-brain barrier (BBB) and subsequent neovascularization, which can be observed as enhancement on MRI sequences.[3,4,6,7,47,73] Stereotactic laser ablation techniques for intracranial lesions have historically been limited by the inability to monitor ablation progress or temperature intraoperatively. Online intraprocedural treatment monitoring is critical for stereotactic LITT to assess real-time tissue temperature and avoid treatment beyond the target zone. Fortunately, recent technological advances in intraoperative MRI now enable accurate intraoperative thermal monitoring. Intraprocedural repetitive measurements of T1-weighted 2D fast low-angle shot sequences or similar methodologies provide the temporally sensitive thermometry measurements necessary to create controlled and conformal lesions (Fig. 1A).[28,32–34]

Figure 1.

Stereotactic laser ablation of brain tumors. A: Example of intraoperative thermometry monitoring during LITT of an insular brain tumor. In the left and center panels, green lines indicate target periphery. Yellow, blue, and black lines indicate the edge of low-, medium-, and high-dose margins. The right panel shows an example of cumulative temperature measurements during LITT. Reproduced with permission from Neurosurgery. Hawasli AH et al: Magnetic resonance imaging-guided focused laser interstitial thermal therapy for intracranial lesions: single-institution series. Neurosurgery 73(6):1007–1017, 2013. B: Image of Neuroblate probe with side-emitting laser. C: Image of Visualase probe with uniform laser emission.

Additionally, stereotactic laser ablation has been further streamlined by clinicians and industry innovators to make laser ablation an optimal and safe procedure.[23,28,45,49] There are currently 2 frequently used stereotactic LITT technologies for intracranial ablations: Neuroblate (Monteris Medical) and Visualase. Although both technologies serve to provide the same ultimate results (i.e., target ablation), each has its own advantages. One version of Neuroblate has a side-firing probe that can be rotated, advanced, and retracted by an MRI-compatible driver for conformal treatments and a large radius of treatment, at the potential cost of treatment time (Fig. 1B). The standard Visualase system (Fig. 1C) and an alternative Neuroblate version use a diffuse-tip probe that generates a uniform ellipsoid ablation zone around the center of the probe. This method saves time at the expense of target conformality. Depending on whether it is a diffuse-tip probe or a side-firing probe, the effective treatment radius ranges from approximately 1 to 2 cm. Thus, because the probe can be moved back and forth along its implanted axis, the "treatment" column can be as large as 3 cm (or larger with the side-firing type). This impacts the size of lesions that can be treated. Tumors less than 3 cm in maximal diameter can be readily treated with single-trajectory LITT. As the tumor gets larger, or the anatomical dimensions become less globoid, treatment may require more than one trajectory. Also, as the size becomes greater than 3 cm, it is important to consider the mass effect of the tumor, which can occasionally be transiently exacerbated by LITT. To date, LITT has been used to treat both primary and metastatic brain tumors, radiation necrosis, and epilepsy foci with varying degrees of success.[57] Here, we review the literature on the use of LITT for HGGs and discuss a possible role for this procedure in clinical settings for both newly diagnosed and recurrent HGGs.

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