Principles of Computer Numerical Controlled Machining Applied to Cranial Microsurgery

Abstract

Over the last decade, a plethora of tools have been developed for neuroscientists to interface with the brain. Implementing these tools requires precise removal of sections of the skull to access the brain. These delicate cranial microsurgical procedures need to be performed on sub-millimeter thick bone without damaging the underlying tissue and therefore, require significant training. Automating some of these procedures would not only enable more precise microsurgical operations, but also democratize use of advanced neurotechnologies. Here, we describe the 'Craniobot', a cranial microsurgery platform that combines automated skull surface profiling with a computer numerical controlled (CNC) milling machine to perform a variety of cranial microsurgical procedures in mice. The Craniobot utilizes a low force contact sensor to profile the skull surface and uses this information to perform micrometer-scale precise milling operations within minutes. We have used the Craniobot to drill pilot holes to anchor cranial implants, perform skull thinning, and open small to large craniotomies. The Craniobot is built using off-the-shelf components for under $1000 and is controlled using open-source CNC programming software.

An open-source automated surgical instrument for microendoscope implantation

“…It can also reduce training time and unnecessary manpower. Recently, high precision automated surgical stereotaxic tools for craniotomies have been developed (Coffey et al, 2013; Ghanbari et al, 2018; Pak et al, 2015). These tools provided low-cost and easy-to-adopt solutions for a variety of surgeries such as cranial window/hole drilling, skull thinning.…”

“…Consequently, this will lead to higher inter-subject variability. Although there are commercially available automated stereotaxic instruments (Pak et al, 2015) and open-source robotic instruments for craniotomy (Coffey et al, 2013; Ghanbari et al, 2018; Pak et al, 2015), these instruments cannot be readily adapted for tissue aspiration purposes.…”

Cortex-wide neural interfacing via transparent polymer skulls

“…See-Shells can be implanted using simple modifications to well established chronic cranial window implantation procedures 49,50 , with the major change being the removal of large sections of the skull above the dorsal cerebral cortex. In this study, we utilized a robot that uses surface profiling to guide a computer numerical controlled (CNC) mill to perform the craniotomy 51 . Automation enabled reliable removal of the bone without damage to the underlying dura and brain and also allowed precise positioning of the implant relative to bregma.…”

“…A rodent stereotaxic instrument (David Kopf Instruments Inc.) was modified to have CNC milling capabilities by incorporating a programmatically controlled 3-axis motorized manipulator (MTS25-Z8, Thorlabs) 51 . A handheld mill (Rampower, Ram Products Inc.) fitted with a 200 μm diameter end mill (Harvey tools Inc.) was mounted on the 3-axis manipulator using a custom adaptor plate.…”

“…The CNC milling machine incorporated in the stereotaxic instrument was used to perform automated craniotomies in C57BL/6, Thy1-YFP and Thy1-GCaMP6f mice along a predefined path slightly smaller than the perimeter of the See-Shell (Supplementary Fig. 1a) as described previously 51 . The milling was stopped at depths of 107.85 ± 16.79 µm in C57BL/6 (n = 7 mice), 57.14 ± 16.25 µm in Thy1-GCaMP6f (#024276, Jackson Laboratories) (n = 14 mice), and 70 µm in three Thy1-YFP mice (#003709, Jackson Laboratories).…”