BACKGROUND Onco-neurosurgical practice still relies heavily on pre-operatively acquired images to guide intra-operative decision-making for safe tumor removal, a practice with inherent pitfalls such as registration inaccuracy due to brain shift, and lack of real-time (functional) feedback. Exploiting the opportunity for real-time imaging of the exposed brain can improve intra-operative decision-making, neurosurgical safety and patient outcomes. Previously, we described functional Ultrasound (fUS) as a high-resolution, depth-resolved imaging technique able to detect functional regions and vascular morphology during awake resections. Here, we present for the first time fUS as a fully integrated, MRI/CT-registered imaging modality in the OR. MATERIAL AND METHODS fUS relies on high-frame-rate (HFR) ultrasound, making the technique sensitive for very small motions caused by vascular dynamics (µDoppler) and allowing measurements of changes in cerebral blood volume (CBV) with micrometer-millisecond precision. This opens up the possibility to 1) detect functional response, as CBV-changes reflect changes in metabolism of activated neurons through neurovascular coupling and 2) visualize in-vivo vascular morphology of tumor and healthy tissue. During a range of anesthetized and awake onco-neurosurgical procedures we acquired images of brain and spinal cord using conventional linear ultrasound probes connected to an experimental acquisition unit. Building on Brainlab’s ‘Cranial Navigation’ and ‘Intra-Operative Ultrasound’ modules, we could co-register our intra-operative Power Doppler Images (PDIs) to patient-registered MRI/CT-data. Using the ‘IGTLink’ research interface, we could access and store real-time tracking data for informed volume reconstructions in post-processing. RESULTS Intra-operative fUS could be registered to MRI/CT-images in real-time, showing overlays of PDIs at imaging depths of >5 centimeters. During meningioma resections, these co-registered PDIs revealed fUS’ ability to visualize the tumor’s feeding vessels and surrounding healthy vasculature prior to durotomy, with a level of detail unprecedented by conventional MRI-sequences. Comparing post-operatively reconstructed 3D-vascular maps of pre- and post-durotomy acquisitions, further confirmed the dural dependency of the vascular network feeding the tumor. During awake resections, fUS revealed distinct functional areas as activated during motor and language tasks. CONCLUSION fUS is a new real-time, high-resolution and depth-resolved imaging technique, combining characteristics uniquely beneficial for a potential image-guided resection tool. The successful integration of fUS in the onco-neurosurgical OR demonstrated by our team, is an essential step towards clinical integration of fUS, as well as the technique’s validation against modalities such as MRI and CT.

中文翻译：

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P09.03 将功能性超声 (fUS) 完全集成到肿瘤神经外科手术室：迈向具有多模态潜力的新型实时、高分辨率图像引导切除工具

背景 肿瘤神经外科实践仍然在很大程度上依赖于术前获得的图像来指导术中安全切除肿瘤的决策，这种实践具有固有的缺陷，例如由于脑移位导致的配准不准确，以及缺乏实时性（功能性）回馈。利用暴露大脑的实时成像机会可以改善术中决策、神经外科安全和患者预后。以前，我们将功能超声 (fUS) 描述为一种高分辨率、深度分辨的成像技术，能够在清醒切除期间检测功能区域和血管形态。在这里，我们首次将 fUS 作为手术室中完全集成的 MRI/CT 注册成像模式。材料和方法 fUS 依赖于高帧率 (HFR) 超声，使该技术对由血管动力学（μDoppler）引起的非常小的运动敏感，并允许以微米-毫秒的精度测量脑血容量（CBV）的变化。这开辟了以下可能性：1) 检测功能反应，因为 CBV 变化反映了通过神经血管耦合激活神经元代谢的变化，以及 2) 可视化肿瘤和健康组织的体内血管形态。在一系列麻醉和清醒的肿瘤神经外科手术过程中，我们使用连接到实验采集单元的传统线性超声探头采集大脑和脊髓的图像。在 Brainlab 的“颅内导航”和“术中超声”模块的基础上，我们可以将我们的术中能量多普勒图像 (PDI) 与患者注册的 MRI/CT 数据共同注册。使用“IGTLink”研究界面，我们可以访问和存储实时跟踪数据，以便在后处理中进行知情的体积重建。结果 术中 fUS 可以实时配准到 MRI/CT 图像，显示在大于 5 厘米的成像深度处 PDI 的叠加。在脑膜瘤切除术中，这些共同注册的 PDI 揭示了 fUS 能够在硬脑膜切开术之前可视化肿瘤的供血血管和周围的健康脉管系统，其细节水平是传统 MRI 序列前所未有的。比较硬脑膜切开术前后采集的术后重建 3D 血管图，进一步证实了供给肿瘤的血管网络对硬脑膜的依赖性。在清醒切除期间，fUS 揭示了在运动和语言任务期间被激活的不同功能区域。结论 fUS 是一种新的实时、高分辨率和深度分辨成像技术，结合了对潜在的图像引导切除工具独特有益的特性。我们团队证明 fUS 在肿瘤神经外科手术中的成功整合是 fUS 临床整合的重要一步，也是该技术针对 MRI 和 CT 等方式的验证。