visualizing the brain and craniotomized skull for virtual surgical planning

用于 NHP 神经外科计划的 MRI 自动 3D 大脑和颅骨建模

Nonhuman primates (NHPs) are invaluable models for translational medical research because they are evolutionarily and behaviorally similar to humans. NHPs have gained particular importance in neural engineering preclinical studies because their brains are highly relevant models of neural function and dysfunction1,2,3,4,5,6,7,8. Some powerful brain stimulation and recording techniques, such as optogenetics, calcium imaging, and others, are best served with direct access to the brain through cranial windows9,10,11,12,13,14,15,16,17,18,19,20,21,22,23. In NHPs, cranial windows are often achieved with a chamber and an artificial dura to protect the brain and support long-term experimentation8,10,12,17,18,24,25,26,27. Likewise, headposts often accompany chambers to stabilize and align the head during experiments14,15,25,26,28,29,30. The effectiveness of these components is heavily dependent on how well they fit into the skull. A closer fit to the skull promotes bone integration and cranial health by decreasing the likelihood of infection, osteonecrosis, and implant instability31. Conventional design methods, such as manually bending the headpost during surgery25,29 and estimating the skull curvature by fitting circles to coronal and sagittal slices of magnetic resonance (MR) scans9,12 can introduce complications due to imprecision. Even the most precise of these create 1-2 mm gaps between the implant and the skull, providing space for granulation tissue to accumulate29. These gaps additionally introduce difficulty placing screws in surgery9, compromising the stability of the implant. Customized implants have more recently been developed to improve osseointegration and implant longevity9,29,30,32. Additional costs have accompanied advancements in custom implant design because of the reliance on computational models. The most accurate methods require sophisticated equipment such as computerized tomography (CT) machines in addition to MR Imaging (MRI) machines30,32,33 and&#160;even computer numerical control (CNC) milling machines for developing implant prototypes25,29,32,34. Gaining access to both MRI and CT, particularly for use with NHPs, may not be feasible for labs in need of custom-fitted implants like cranial chambers and headposts.
As a result, there is a need in the community for inexpensive, accurate, and non-invasive techniques of neurosurgical and experimental planning that facilitate the design and validation of implants prior to use. This paper describes a method of generating virtual 3D brain and skull representations from MR data for craniotomy location planning and the design of custom cranial chambers and headposts that fit the skull. This streamlined procedure provides a standardized design that can benefit experimental outcomes and the welfare of the research animals. Only MRI is required for this modeling because both bone and soft tissue are depicted in MRI. Instead of using a CNC milling machine, models can be 3D printed inexpensively, even when multiple iterations are required. This also allows for the final design to be 3D printed in biocompatible metals such as titanium for implantation. Additionally, we describe the fabrication of an artificial dura, which is placed inside the cranial chamber upon implantation. These components can be validated pre-surgically by fitting all parts onto a life-size, 3D-printed model of the skull and brain.

作者聚焦：简化的大脑和颅骨建模以增强 NHP 研究中的神经外科计划

非人灵长类动物的神经植入物设计工具箱

Our research offers an efficient and automated method for brain and skull modeling, which is beneficial for neurosurgical planning and designing custom implants. It facilitates a simultaneous extraction of brain and skull models using a single software platform, which eliminates a requirement for extra imaging processes like commuted tomography scans. Virtual brain and skull modeling for medical imaging such as MRI or CT scans has been increasingly adopted for NHP neurosurgical planning in recent years.These models, used alongside 3D design software and 3D printing, enable the creation of customized implants tailored to specific experiments and animals. Many non-human primate neuroscience experiments require the use of chronic cranial chambers and head posts. The use of generic implants introduces gaps between the implant and the skull, which can result in higher rates of infection, osteonecrosis, and implant instability, therefore compromising experiments and the wellbeing of the animal.Our custom implants reduce gaps and subsequent issues. Our protocol provides researchers with a more accurate and time-effective neurosurgical planning procedure. It increases surgical planning efficacy, and reduces complications associated with NHP neuroscience experiments, thus improving scientific results overall.

可视化大脑和开颅颅骨，用于虚拟手术计划

首先，使用 1T MRI 机器获取颅骨和大脑的 T-3 快速磁化准备梯度 ECHO 或 MP-RAGE 文件。在命令窗口中输入 MP-RAGE 文件的名称，并验证 MRI 图像是否正确显示。按照命令行说明隔离颅骨。选择一个阈值，该阈值可有效将颅骨与其他组织分离而不会丢失颅骨物质，然后按 Y 确认此值。使用类似的方法进行脑隔离。在出现提示时输入大脑的阈值，并根据需要进行调整，以确保大脑与颅骨和其他组织明显分开。按 Y 确认所选值。要确定开颅坐标，请选择一个 Z 坐标系，然后在所选 Z 坐标系上为开颅中心选择一个点。在显示大脑和头骨的图中，放置点以覆盖感兴趣区域，以便精确表示头骨。要将文件导入 CAD 软件以进行自定义腔室设计，请打开软件，然后转到文件，单击打开，然后从目录中选择 STL Reduction 文件。之后，单击选项，然后在“导入为”菜单中，选择“曲面主体”，然后单击“确定”。现在，在 CAD 软件中查看腔室的头骨表面，确保所选区域的边缘在头骨表示中清晰可见。要在创建的平面上绘制腔室裙边形状，请绘制腔室的内圆并将其围绕上平面上的点居中。使用弧线和线条的混合，构建腔室裙板的外部边界以最大化面积，然后挤压到两个表面的下部。接下来，按照腔室轮廓的形状，从上平面到两个复制曲面的上部执行拉伸切割。删除导入曲面的两个剩余副本，以露出腔室裙板和内圈。使用移动或复制功能将裙边直接移至腔室顶部下方，确保精确向下平移。然后，将物体从腔室顶部的底部挤压到裙边以连接它们。使用拉伸、凸台或底座，选取腔室顶部的底面，并创建与围绕中心轴中心的环具有相同的内半径和外半径的草图。将挤出方向设置为最高到主体，以腔室裙为目标。要设计头柱，请保存大脑和头骨 STL 文件，以便进行潜在的 3D 打印。使用 STL 尺寸缩小提取腔室周围的头骨区域，以创建头柱足迹以导入设计软件。然后，选择 Y 以激活 STL 大小缩减。在图像上选择显示大脑和头骨的点，确保在灰色头骨区域紧密均匀分布。将缩小尺寸的文件作为曲面主体导入 CAD 软件，以设计自定义头柱封装。然后，使用拉伸、凸台或底座选择新平面，并使用圆弧和线绘制头柱封装。使用圆弧在封装周围绘制平滑边缘，并将草图拉伸到输入的曲面。从头柱封装的平面到复制曲面执行拉伸切割。随后，删除原始曲面及其副本。现在，创建一个平行于参考平面的新平面，向上或向下平移，以悬停在头柱底部上方至少一毫米处。使用评估选项卡中的测量工具获取精确的翻译长度。然后，从这个新平面到前柱底部进行圆形拉伸，为前柱顶部创建一个居中平台。使用移动或复制对齐头柱顶部和底部。将头柱顶部指定为要移动的主体，并在约束菜单中设置三个配合。确保最后一个配对曲面的轮廓边缘同心配接。然后，将头柱后腿上的一条垂直线与头柱顶部背面的水平线垂直配对。验证每个连接的方向，并根据需要调整菜单中的配接方向。

Research

JoVE Journal

Bioengineering

Visualizing the Brain and Craniotomized Skull for Virtual Surgical Planning

A Neural Implant Design Toolbox for Nonhuman Primates

This paper describes an in-house method of 3D brain and skull modeling from magnetic resonance imaging (MRI) tailored for nonhuman primate (NHP) ...

科研

生物工程