Beckman Laser Institute, University of California at Irvine, East Irvine, California, USA.
Department of Biomedical Engineering, University of Texas at Austin, Austin, Texas, USA.
Lasers Surg Med. 2022 Oct;54(8):1107-1115. doi: 10.1002/lsm.23591. Epub 2022 Aug 10.
Erbium:yttrium-aluminum-garnet (Er:YAG) laser ablation can effectively resect water-bearing tissues. Application of Er:YAG 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 Er:YAG 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 Er:YAG tissue resection with minimal lateral thermal spread.
Mice underwent stereotactic laser surgery with the proposed Yb/Er:YAG 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 Er:YAG 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/Er:YAG neurosurgery where a continuous wave Tm fiber-laser was used for coagulation.
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/Er:YAG laser surgery yielded lower thermal spread compared with Tm/Er:YAG laser surgery, maximizing the efficiency in both hemostasis (blood flow stoppage) and maximizing tissue ablation efficiency with minimal residual thermal damage zone.
In this study, a vascular specific coagulation scheme with Yb/Er:YAG dual-wavelength surgery is presented for neurosurgery. Additionally, Yb/Er:YAG study results are compared with that of a tissue coagulation approach in Tm/Er:YAG 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.
掺铒石榴石（Er:YAG）激光烧蚀可有效切除含水性组织。Er:YAG 切除在神经外科中的应用受到术中术野不可预测性出血的限制。最近，一种结合双波长激光手术系统的治疗诊断一体化系统已被证明可用于体内肿瘤组织的切除，该系统使用掺铥（Tm）光纤激光进行凝固，用 Er:YAG 进行切除，并结合光相干断层扫描（OCT）引导。然而，由于缺乏血管特异性，使用 Tm 光纤激光进行凝固时，通常会出现 100 微米量级的侧向热扩散。在这项研究中，我们利用血管特异性掺镱（Yb）光纤激光在活体神经外科中增强光凝作用，提高 Er:YAG 组织切除的精度，同时最大限度地减少侧向热扩散。
在活体小鼠中进行立体定向激光手术，使用我们提出的 Yb/Er:YAG 双波长血管特异性神经外科手术。使用 OCT 系统（波长范围 1310±70nm）和 OCT 衍生的血管造影图像记录皮质图像，以确认血管的凝固，并指导后续的 Er:YAG 切除步骤。激光手术后，处死小鼠，进行苏木精和伊红染色和尼氏染色的组织学分析，以比较侧向热扩散与我们之前报道的使用连续波 Tm 光纤激光进行凝固的 Tm/Er:YAG 神经外科手术。
Yb 光纤激光的凝固方案可阻止在小鼠大脑中遇到的不同大小的血管中的血流。Yb/Er:YAG 激光手术后的鼠脑切片组织学分析表明，与 Tm/Er:YAG 激光手术相比，热扩散更小，最大限度地提高了止血（血流停止）和最大限度地提高组织消融效率的效率，同时最大限度地减少残留的热损伤区。
在这项研究中，我们提出了一种血管特异性的 Yb/Er:YAG 双波长手术用于神经外科。此外，还将 Yb/Er:YAG 研究结果与之前报道的 Tm/Er:YAG 手术中的组织凝固方法进行了比较，以突出改进的凝固、减少非特异性热损伤和限制侧向热扩散。实验结果表明，所开发的双波长激光系统可以有效地切除神经组织，具有高定位性、亚微米级的最小侧向热扩散，同时保持无血手术视野。
