The 980-nm diode laser for brain surgery: histopathology and recovery period.
ABSTRACT The 980-nm diode laser has been under investigation for neurosurgery because of a local peak in the absorption spectra of water around this wavelength. This work was carried out to examine the extent of thermal changes and the recovery process of laser-induced brain lesions. In order to study the quality of the lesions, a conventional monopolar electrocoagulation technique was applied comparatively. An in vivo stereotaxic neurosurgical procedure was performed on Wistar rats. Bilateral brain lesions of the same size (2-3 mm diameter) were created with a diode laser and via electrocoagulation. Subjects were sacrificed 0, 2 and 7 days after surgery in order to observe the healing process of the necrotic tissue. The surgical after-effects of both types of lesions were identified through immunohistochemical staining with CD68 macrophage marker and haematoxylin eosin (H&E). CD68 was found to be more efficient than H&E in determining the thermally altered areas. Histological examinations showed that the 980-nm diode laser system has a remarkable ablating ability with minimal thermal damage of nearby tissue.
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ABSTRACT: In this study, a thulium (Tm:YAP) laser system was developed for brain surgery applications. As the Tm:YAP laser is a continuous-wave laser delivered via silica fibers, it would have great potential for stereotaxic neurosurgery with highest local absorption in the IR region. The laser system developed in this study allowed the user to set the power level, exposure time, and modulation parameters (pulse width and on-off cycles). The Tm:YAP laser beam (200-600 mW, 69-208 W/cm(2)) was delivered from a distance of 2 mm to cortical and subcortical regions of ex-vivo Wistar rat brain tissue samples via a 200-μm-core optical fiber. The system performance, dosimetry study, and ablation characteristics of the Tm:YAP laser were tested at different power levels by maximizing the therapeutic effects and minimizing unwanted thermal side-effects. The coagulation and ablation diameters were measured under microscope. The maximum ablation efficiency (100 × ablation diameter/coagulation diameter) was obtained when the Tm:YAP laser system was operated at 200 mW for 10 s. At this laser dose, the ablation efficiency was found to be 71.4% and 58.7% for cortical and subcortical regions, respectively. The fiber-coupled Tm:YAP laser system in hence proposed for the delivery of photothermal therapies in medical applications.Lasers in Medical Science 04/2011; 26(5):699-706. · 2.00 Impact Factor