Er:YAG laser brain surgery with vascular specific coagulation.

ABSTRACT

BACKGROUND AND OBJECTIVE: Erbiumyttrium-aluminum-garnet (ErYAG) laser ablation can effectively resect water-bearing tissues. Application of ErYAG resection in neurosurgery is complicated by unpredictable bleeding in surgical field. Recently, an integrated theranostic system combining a dual-wavelength laser surgery system using a thulium (Tm) fiber-laser for coagulation and ErYAG for resection, combined with optical coherence tomography (OCT) guidance was demonstrated for the in vivo resection of tumor tissue. However, lateral thermal spread in the range of 100s of micrometers is common due to lack of vascular specificity using a Tm fiber-laser for coagulation. In this study, a vascular specific ytterbium (Yb) fiber-laser is utilized for enhanced photocoagulation during in vivo neurosurgery improving the precision of ErYAG tissue resection with minimal lateral thermal spread. METHODS: Mice underwent stereotactic laser surgery with the proposed Yb/ErYAG dual wavelength vascular specific neurosurgery in vivo. An OCT system (wavelength range 1310 ± 70 nm) and OCT derived angiography  images were used to record cortical images to confirm the coagulation of blood vessels and guide subsequent ErYAG resection steps. After the laser surgery, mice were killed, and histological analysis was carried out using hematoxylin and eosin staining and Nissl staining to compare the lateral thermal spread with our previously reported Tm/ErYAG neurosurgery where a continuous wave  Tm fiber-laser was used for coagulation. RESULTS: Coagulation scheme using a Yb fiber-laser allowed stoppage of blood flow in disparately sized blood vessels encountered in the mice brain. Histological analysis of murine brain slices post Yb/ErYAG laser surgery yielded lower thermal spread compared with Tm/ErYAG laser surgery, maximizing the efficiency in both hemostasis (blood flow stoppage) and maximizing tissue ablation efficiency with minimal residual thermal damage zone. CONCLUSION: In this study, a vascular specific coagulation scheme with Yb/ErYAG dual-wavelength surgery is presented for neurosurgery. Additionally, Yb/ErYAG study results are compared with that of a tissue coagulation approach in Tm/ErYAG surgery previously reported to highlight improved coagulation, reduced nonspecific thermal damage and limited lateral thermal spread. Experimental results suggest that the developed dual-wavelength laser system can effectively resect neural tissues with high localization, minimal lateral thermal spread at the micrometer level while maintaining a bloodless surgical field.