Using 3D Printing to Create Personalized Brain Models for Neurosurgical Training and Preoperative Planning

doi:10.1016/j.wneu.2016.02.081

World Neurosurgery

Volume 90, June 2016, Pages 668-674

https://doi.org/10.1016/j.wneu.2016.02.081 Get rights and content

Background

Three-dimensional (3D) printing holds promise for a wide variety of biomedical applications, from surgical planning, practicing, and teaching to creating implantable devices. The growth of this cheap and easy additive manufacturing technology in orthopedic, plastic, and vascular surgery has been explosive; however, its potential in the field of neurosurgery remains underexplored. A major limitation is that current technologies are unable to directly print ultrasoft materials like human brain tissue.

Objective

In this technical note, the authors present a new technology to create deformable, personalized models of the human brain.

Methods

The method combines 3D printing, molding, and casting to create a physiologically, anatomically, and tactilely realistic model based on magnetic resonance images. Created from soft gelatin, the model is easy to produce, cost-efficient, durable, and orders of magnitude softer than conventionally printed 3D models. The personalized brain model cost $50, and its fabrication took 24 hours.

Results

In mechanical tests, the model stiffness (E = 25.29 ± 2.68 kPa) was 5 orders of magnitude softer than common 3D printed materials, and less than an order of magnitude stiffer than mammalian brain tissue (E = 2.64 ± 0.40 kPa). In a multicenter surgical survey, model size (100.00%), visual appearance (83.33%), and surgical anatomy (81.25%) were perceived as very realistic. The model was perceived as very useful for patient illustration (85.00%), teaching (94.44%), learning (100.00%), surgical training (95.00%), and preoperative planning (95.00%).

Conclusions

With minor refinements, personalized, deformable brain models created via 3D printing will improve surgical training and preoperative planning with the ultimate goal to provide accurate, customized, high-precision treatment.

Introduction

Neurosurgery is a high-risk field with potentially fatal consequences for the patient. It holds the greatest proportion of malpractice claims among all physician specialties.¹ Neurosurgical training programs are held to increasingly greater standards to demonstrate and document trainee competence. At the same time, strict work hour regulations in Europe and North America have decreased drastically the time available to acquire the necessary surgical motor skills and technical judgment.² One possible strategy to enhance surgical education within this tightly regulated time window is to increase hands-on training through surgical simulators that closely mimic the operating room experience.3, 4, 5, 6

Currently, residential training and surgical planning rely almost exclusively on 2-dimensional (2D) computed tomography and magnetic resonance images. Surgical preparedness could be advanced through 3-dimensional (3D) simulators with the goal of providing the spatial awareness and tactile experience of how the brain feels, moves, and responds during a surgical procedure.⁷ With physiologically, anatomically, and tactilely realistic models, surgeons could practice complex procedures and preoperatively optimize treatment plans, a desirable goal, which is out of reach with 2-dimensional images alone.4, 8 Recent prototype studies in orthopedic surgery, vascular surgery, and neurosurgery demonstrate how surgical models can improve patient consent,⁹ help optimize surgical and endovascular procedures,¹⁰ and enhance the surgical training experience.¹¹

With rapid advances in additive manufacturing and 3D printing,¹² graspable, 3D models of any organ can now be created directly from 2D computer tomography scans or magnetic resonance images.¹³ Although 3D-printed medical models are physiologically and anatomically accurate, they are typically undeformable and tactilely unrealistic.¹⁴ With current 3D printing technologies, it is virtually impossible to reproduce the ultrasoft nature of the human brain and mimic its tactile properties. A major challenge in printing soft structures is that the material deforms significantly during the fabrication process, even under its own weight.¹⁵

Here we propose a novel method to create a physiologically, anatomically, and tactilely accurate model of the human brain. We adopted a 3-step manufacturing process that uses the undeformable 3D-printed brain model as a template for molding and casting.¹⁶ We created a negative silicone mold of this template, and cast a soft, deformable brain model from a surrogate material that closely mimics the rheological features of the human brain.¹⁷ To explore the realism this model, we performed nanoindentation tests on slices of our brain model and compared them with nanoindentation tests on sagittal slices of mammalian brains.¹⁸ To evaluate the usefulness of the model, we perform a multicenter survey of neurosurgeons and surgical residents in Europe and the United States. We close by discussing their feedback and by identifying potential applications of the model.

Section snippets

Magnetic Resonance Imaging

Magnetic resonance images of a healthy 25-year-old female brain were acquired at the Stanford University Center for Cognitive and Neurobiological Imaging via a 3-Tesla scanner (GE MR750, Milwaukee, Wisconsin, USA) with a 32-channel radiofrequency receive head coil (Nova Medical, Inc., Wilmington, Massachusetts, USA)¹⁹ (Figure 1).

Brain Surface Model

Volumetric image segmentation and cortical reconstruction were performed by the use of FreeSurfer (Harvard University, Cambridge, Massachusetts, USA), an image analysis

Results

The proposed method successfully produced a physiologically, anatomically, and mechanically realistic personalized brain model. The model is based on magnetic resonance images, which were successfully converted into a printable stereolithography file using FreeSurfer. The FreeSurfer analysis revealed the specific brain dimensions with a volume of 1228.8 cm³, a surface area of 1766.9 cm², an average cortical thickness of 0.263 cm, and left and right gyrification indices of 2.937 and 3.011. These

Discussion

Effective surgical training and careful preoperative planning are significant to the success of any neurosurgical procedure. In this technical note, we explored the potential of current 3D printing technologies and created a personalized brain model to improve the surgical training experience and the preoperative planning process on an individualized patient-specific basis. Taken together, the material cost for a personalized brain model is $50, and the entire fabrication process takes 24

Conclusions

3D printing enables the creation of personalized, deformable brain models with realistic physiological and anatomical features, which improve patient education, neurosurgical training, and preoperative planning.

Acknowledgments

The authors thank Allan L. Reiss for providing the MRI scans, Maria A. Holland for creating STL files from the medical images, Marc E. Levenston for providing access to a 3d printer, and Timothy C. Ovaert and Rijk de Rooij for guidance with nanoindentation testing. The authors acknowledge support by the Stanford BioX program IIP 2014.

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: Conflict of interest statement: The authors declare no conflict of interest.

View full text

Technical NoteUsing 3D Printing to Create Personalized Brain Models for Neurosurgical Training and Preoperative Planning

Background

Objective

Methods

Results

Conclusions

Introduction

Section snippets

Magnetic Resonance Imaging

Brain Surface Model

Results

Discussion

Conclusions

Acknowledgments

World Neurosurg

World Neurosurg

World Neurosurg

World Neurosurg

J Mech Behav Biomed Mater

Neuroimage

World Neurosurg

World Neurosurg

Neurosurgery tops and malpractice risks

Neurosurgery

Impact of the Accreditation Council for Graduate Medical Education work-hour regulations on neurosurgical resident education and productivity

J Neurosurg

Fundamentals of neurosurgery: virtual reality tasks for training and evaluation of technical skills

World Neurosurg

Establishing a surgical skills laboratory and dissection curriculum for neurosurgical residency training

J Neurosurg

Utility of multimaterial 3D Printers in creating models with pathological entities to enhance the training experience of neurosurgeons

J Neurosurg

3D printing of patient-specific anatomy: a tool to improve patient consent and enhance imaging interpretation by trainees

Br J Neurosurg

Technical Note
Using 3D Printing to Create Personalized Brain Models for Neurosurgical Training and Preoperative Planning