Читать книгу Intracranial Gliomas Part III - Innovative Treatment Modalities - Группа авторов - Страница 38

The Visualase^® thermal therapy system utilizes a diffusing fiberoptic tip probe constructed using a proprietary epoxy formulation, 15 W laser output, and water cooling [28]. The device software computes and displays changes in the target as treatment progresses and predicts the extent of the thermal damage area using the Arrhenius model. Use of higher laser energy (15 vs. 12 W) and a diffusing instead of directional probe allows faster treatment time with Visualase^® in comparison to NeuroBlate^®. However, the diffusing probe provides a cylinder-like area of thermal damage, which in many instances does not correspond to the geometrically complex shape of brain tumors; such a mismatch creates problems for conformal and selective management of the lesion. Additionally, software of the Visualase^® system does not calculate TDT lines, which may create problems for treatment planning, assessment of the therapeutic results, and predicting the outcome in cases of HGG.

Fig. 1. Schematics showing layout of MRI suite adapted for the NeuroBlate^® procedure. The NeuroBlate^® electronics rack and workstation are situated in the MRI control room adjacent to the imaging suite. The cooling line, fiberoptic cable, and temperature probe cable are passed into the imaging suite through a wave guide. Inset A: Modified Navigus^® device. Inset B: Intraoperative MRI interface platform and probe driver. Inset C: Close-up of probe driver. Inset D: Tip of laser probe showing laser beam emerging out of the sapphire capsule. Reproduced from Sloan et al. [13].

Fig. 2. Illustrative time course of MR thermometry as presented by NeuroBlate^® software. Predictive thermal damage threshold (TDT) lines are generated: yellow (thermal dose equivalent 43°C for 2 min), blue (thermal dose equivalent 43°C for 10 min), and white (thermal dose equivalent 43°C for 60 min). The region of thermometry monitoring (green area; not shown in the lower row of images) and the temperature reference points (small light blue squares, identified by violet arrows on the first panel), are demonstrated. Three panels in each row represent 3 successive “slices” perpendicular to the probe axis: the left panel is the most distal (nearest to the end of the sapphire capsule of the probe); the center panel is at the plane of laser exit from the probe; and the right panel is the slice proximal to the laser exit. Of note, the lowest thermal dose demarcation (yellow) appears first and begins to enlarge with continued lasing (middle and lower rows of images). A temperature (in °C) color key is shown at the bottom. Reproduced from Sloan et al. [13].