Stereotactic Guided Laser-Induced Interstitial Thermotherapy (SLITT) in Gliomas with Intraoperative Morphologic Monitoring in an Open MR-Unit

Abstract

Stereotactic guided laser-induced interstitial thermotherapy (SLITT) represents a minimal invasive method to produce necrosis in cerebral tumor tissue by local heating. The dose/response relationship relies on experimental studies and few clinical data performed in high field MR systems. A better understanding of the energy-dose/tissue response in human brain tumors is important to optimize this treatment modality. Twenty-four patients with gliomas were treated with SLITT, with a total of 30 laser procedures performed. Under local anesthesia 600 microns laser-fibers were inserted by stereotactic-guided technique into the center of the tumor. In a low field open MR system (0.2 T) the denaturation of the tumor using a neodymium YAG laser (1064 nm) was monitored by 3D-turbo FLASH T1-weighted sequences. Laser energy was applied in steps of 400 to 1200 Joules. Development of necrosis at a mean total energy dose of 2979 Joules could be monitored in all procedures. Two different thermal lesion architectures were observed. First signal changes were monitored after a mean of 1108 Joules and 1393 Joules, respectively. Mean max. total lesion size was 21.2 mm. The higher the total energy the larger was the thermolesion, but no linear relationship could be seen. Tumor tissue response showed no dependency on tumor grading. Monitoring of stereotactic guided laser-induced thermolesions in the low-power MR OPEN is feasible and safe. Although lesion size basically is energy dependent, it should be applied individually, since the thermal response in brain tumors varies due to different optical properties, even in the same tumor gradings.

Renaissance of laser interstitial thermal ablation

“…A wide range of tumor sizes have been treated. Some studies 28,29,42,43,45,48 have reported short-term follow-up, demonstrating decreased perilesional edema and tumor size. Longer-term follow-up and the existence of a control population would be useful to establish the efficacy of LITT.…”

“…Complications include wound infection, 29 neurological deficits, 7,24,27,29,34,46 vascular injuries, 27,46 and cerebral edema. 5,27 Although pooled results from these studies 5,7,24,27,29,34,46 should be interpreted with caution, given the widely varied methodologies, the overall rate of complications, which themselves range from mild to severe, was 28.6% (range 20%-50% per study). Transient or permanent neurological complications were observed in 11.1% of all patients.…”

Magnetic resonance–guided laser interstitial thermal therapy: report of a series of pediatric brain tumors

“…However, some studies have found that tissue damage caused by thermal ablation can be tissue-type dependent. 42 Moreover, tumors with similar histological grades have been shown to have variable responses to LITT, 16,[30][31][32] which makes it very challenging to standardize tumor-specific laser protocols. As explained earlier, the software links the temperature limits and the voxels in the image.…”

Nonthermal irreversible electroporation for intracranial surgical applications

“…Methods of tissue destruction include phototherapy, 2 radiofrequency lesioning, 7,40 cryoablation, 53 microwave ablation, 41,52 high-intensity focused ultrasonography, 19,32,55 and laser interstitial thermotherapy. 3,31,49 Mechanisms of tissue destruction include changes in local temperature resulting in coagulation necrosis 18,50 (radiofrequency lesioning, laser interstitial thermotherapy, and high-intensity focused ultrasonography) and cell membrane rupture 18 (cryoablation), generation of free-radicals (phototherapy), and in situ tissue fixation (microwaves). 41 Each of these techniques has selective advantages when used in the brain.…”