A MRI-Based Toolbox for Neurosurgical Planning in Nonhuman Primates

Summary

The method outlined below aims to provide a comprehensive protocol for the preparation of nonhuman primate (NHP) neurosurgery using a novel combination of three-dimensional (3D) printing methods and MRI data extraction.

Abstract

In this paper, we outline a method for surgical preparation that allows for the practical planning of a variety of neurosurgeries in NHPs solely using data extracted from magnetic resonance imaging (MRI). This protocol allows for the generation of 3D printed anatomically accurate physical models of the brain and skull, as well as an agarose gel model of the brain modeling some of the mechanical properties of the brain. These models can be extracted from MRI using brain extraction software for the model of the brain, and custom code for the model of the skull. The preparation protocol takes advantage of state-of-the-art 3D printing technology to make interfacing brains, skulls, and molds for gel brain models. The skull and brain models can be used to visualize brain tissue inside the skull with the addition of a craniotomy in the custom code, allowing for better preparation for surgeries directly involving the brain. The applications of these methods are designed for surgeries involved in neurological stimulation and recording as well as injection, but the versatility of the system allows for future expansion of the protocol, extraction techniques, and models to a wider scope of surgeries.

Introduction

Primate research has been a pivotal step in the progression of medical research from animal models to human trials^1,2. This is especially so in the study of neuroscience and neural engineering as there is a large physiological and anatomical discrepancy between rodent brains and those of nonhuman primates (NHP)^1,2,3. With emerging genetic technologies such as chemogenetics, optogenetics, and calcium imaging that require genetic modification of neurons, neural engineering research studying neural function in NHP’....

Protocol

All animal procedures were approved by the University of Washington Institute for Animal Care and Use Committee. Two male rhesus macaques (monkey H: 14.9 kg and 7 years old, monkey L: 14.8 kg and 6 years old) were used.

1. Image acquisition

1. Transport the monkey to a 3T MRI scanner and place the animal in an MR-compatible stereotaxic frame (Table of Materials).
2. Record the standard T1 (flip angle = 8°, repetition time/echo time = 7.5/3.69 s, matrix size = 432 x 432 x 80, acquisition duration = 103.7 s, Multicoil (Table of Materials), number of averages = 1, slice thickness = 1 mm) a....

Results

The manipulation and analysis of MRIs as a preoperative craniotomy planning measure has been used successfully in the past^2,5,10,16. This process, however, has been greatly enhanced by the addition of the 3D modeling of the brain, skull, and craniotomy. We were able to successfully create an anatomically accurate physical model of the brain that reflected the area of interest for our studies (<.......

Discussion

This article describes a toolbox for preparation for neurosurgeries in NHPs using physical and CAD models of skull and brain anatomy extracted from MR scans.

While the extracted and 3D printed skull and brain models were designed specifically for the preparation of craniotomy surgeries and head post implantations, the methodology lends itself to several other applications. As described before, the physical model of the skull allows for pre-bending of the head post before surgery, which creates.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
3D Printing Software (GrabCAD Print)	Stratasys	Version 1.36	Used for High quality 3D printing
3D Printing Software (Simplify 3D)	Simplify3D	Version 4.1	Used for PLA 3D printing
Agarose	Benchmark Scientific	A1700	Used for making gel brains
Black Nail Polish	L.A. Colors	CNP637	Used for gel molding
Cannula (ID 450 um, OD 666 um)	Polymicro Technologies	1068150625	Used to inject dye into gel brain
Catheter Connector	B Braun	PCC2000	Perifix for 20-24 Gage epidural catheters; Units per Cs 50
Dremel 3D Digilab 3D45 printer	Dremel	F0133D45AA	Used for prototyping in PLA
ECOWORKS	Stratasys	300-00104	Used to dissolve QSR support structures
Erlymeyer flask	Pyrex	4980	Used for gel molding
Ethyl cyanoacrylate	The Original Super Glue Corp.	15187	Used to make combined cannula
Graduated cylinder		3023	Used for gel molding
HATCHBOX PLA 3D Printer Filament	HATCHBOX	3DPLA-1KG1.75-RED/3DPLA-1KG1.75-BLACK	1kg Spool, 1.75mm, Red/Black
Locust Bean Gum	Modernist Pantry	1018	Gumming agent for gel brain mixtures
MATLAB	MathWorks	R2019b	Used for skull extraction
McCormick Yellow Food Color	McCormick		Used for dye injection
Microwave	Panasonic	NN-SD975S	Used for agarose curing
MR Imaging Software (3D Slicer)	3D Slicer	Version 4.10.2	Used for 3D model generation
MR Imaging Software (Mango with BET plugin)	Reasearch Imaging Institute	Version 4.1	Used for brain extraction
Philips Acheiva MRI System	Philips	4522 991 19391	Used to image non-human primates
Phosphate Buffered Solution	Gibco	70011-044	10X diluted with DI water to 1X
Pump	WPI	UMP3T-1	Used for dye injection
Pump driver	WPI	UMP3T-1	Used for dye injection
Refrigerator	General Electric		Used to preserve agarose gel
Scientific Spatula	VWR	82027-494	Used to extract gel molds
SolidWorks	Dassault Systemes	2019
Stratasys ABS-M30 filament	Stratasys	333-60304	Used for high quality 3D printing
Stratasys F170 3D printer	Stratasys	123-10000	Used for high quality 3D printing
Stratasys QSR support	Stratasys	333-63500	Used to create supports with ABS model
Syringe	SGE	SGE250TLL	Used for dye injection