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Creating a 3D Brain Model Using CT-Converted STL Files

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Angel Sosa

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If you are able to read this sentence, you not only have your English teacher to thank (as the popular bumper sticker suggests), but also your brain. The human brain — all of 3 pounds (1,350 grams) — consumes over 10% of the human body's total energy, yet most of its weight is water and makes up very little of the body's total mass. 

 

Demonstration of a 3D brain model.

 

The recent explosion of 3D printing technologies in the field of neurosurgery has made creating a 3D brain model using CT-converted STL files easier than ever. This popularity has led to a number of medical authorities to further explore the technology's current utility and future potential. In a recent article titled "3D printing in neurosurgery: A systematic review," it was found that 3D printing techniques are not only practical, but also a viable means of creating anatomically correct models that can be applied to medical simulations, training, surgical planning, and secondary devices. 3D-printed models have also enabled neurosurgeons to explore structures in a way that is non-invasive. Amazingly, 3D models can be created using existing technologies, such as two-dimensional MRI, CT, and X-ray scans. These files are then converted into 3D printer-ready STL files using a program such as democratiz3D® from embodi3D®, a free tool that makes converting CT scans in 3D-printable files as easy as possible.  

 

Before you can make use the awesome medical 3D printing services offered by embodi3D®, you must become a registered embodi3D® member. It's absolutely free to join — sign up today! Once you've signed up, be sure to check out the tutorial demonstrating how easy it is to create your own 3D models. 

 

 

#1. 3D Printing a Brain Model with Stroke from an STL File

 

 

This excellent 3D model of the brain circulation shows all the intracranial vessels. Stroke is a generic term that describes the clinical event of a sudden onset of neurologic deficit secondary to cerebrovascular disease. Stroke has 4 main etiologies, including cerebral infarction (80%), intraparenchymal hemorrhage (15%), nontraumatic subarachnoid hemorrhage (5%), and venous infarction (approximately 1%). Clinically, ischemic infarction is the most common etiology and will be the main topic of this introduction. The principal cause of cerebral infarction is atherosclerosis and its sequelae.

 

Middle Cerebral Artery (MCA) distribution typically involves the majority of the lateral surface of the hemisphere, including the frontal, temporal, and parietal lobes. In addition, the majority of the lenticulostriate arteries arise from the M1 segment and supplies the basal ganglia.

 

Anterior Cerebral Artery (ACA)  supplies the medial anteroinferior frontal lobe, the anterior 2/3 of the medial hemisphere surface, and a variable amount of territory over the cerebral convexity. The corpus callosum is also typically supplied primarily by the ACA branches: Callosal perforating, pericallosal, and posterior splenial branches.

 

Posterior Cerebral Artery  (PCA) vascular territory, including the occipital lobes, inferior temporal lobes, and medial posterior 1/3 of  the interhemispheric brain. Patients with PCA ischemia most commonly present with visual complaints. Large vessel/atherosclerotic strokes represent ~ 40% of strokes. The carotid bifurcation is the most common site of atherosclerotic plaque.

 

Circle of Willis

- A1-segment: Anterior cerebral artery from carotid bifurcation to anterior communicating artery gives rise to the medial lenticulostriate arteries.

- A2-segment: Part of anterior cerebral artery distal to the anterior communicating artery.

- P1-segment: Part of the posterior cerebral artery proximal to the posterior communicating artery. The posterior communicating artery is between the carotid bifurcation and the posterior cerebral artery)

- P2-segment: Part of the posterior cerebral artery distal to the posterior communicating artery.

- M1-segment: Horizontal part of the middle cerebral artery which gives rise to the lateral lenticulostriate arteries which supply most of the basal ganglia.
- M2-segment: is the part in the sylvian fissure and the M3-segment is the cortical segment.

 

- Horizontal M1-segment
Gives rise to the lateral lenticulostriate arteries which supply part of head and body of caudate, globus pallidus, putamen and the posterior limb of the internal capsule.
Notice that the medial lenticulostriate arteries arise from the A1-segment of the anterior cerebral artery.

- Sylvian M2-segment  
Branches supply the temporal lobe and insular cortex (sensory language area of Wernicke), parietal lobe (sensory cortical areas) and inferolateral frontal lobe

- Cortical M3-segment
Branches supply the lateral cerebral cortex

 

 

 

 

 

 

#2. A Brain Model Created from a High-Resolution MRI Scan

 

 

 

This 3D model shows each of the cerebral hemispheres (the frontal lobe, the parietal lobe, the temporal lobe, and the occipital lobe, limbic lobe), sulcus, Silvian fissure and Rolandic fissure. 

Surgical education has undergone a recent paradigm shift toward simulation-based training as opposed to the traditional experience-based training program. This change reflects the need for a safe teaching environment separated from the risk-inherent operating room, thus enabling teaching faculty to focus on training during simulations and patient care during operations. Other factors have also contributed to the shift including instituted training restrictions that have limited patient interactions, which are essential for procedural learning. The capabilities of 3D printing are well suited for the development of these physical simulators, which is evident from the literature.

 

 

 

#3. An MRI of the Brain

 

 

This excellent MRI image of the brain shows all the anatomy structures with great detail. Current surgical planning for the resection of brain tumors involves using MRI technology to differentiate between tumor and surrounding brain tissue. Nonetheless, even when this distinction is clear, it can be difficult for surgeons to appreciate the relationships between adjacent anatomical landmarks during the procedure. 3D printing technology has enabled MRI data to be translated into patient-specific models depicting the associations between tumor, skull, vasculature, and surrounding nonpathologic brain tissue. Therefore, surgeons can recognize the location and extent of the tumor relative gyral/sulcal patterns and skull features. Models have then been further utilized to simulate realistic surgical approaches under microscopic observation. Spottiswoode et al. additionally included printed regions of functional MRI (fMRI) activation determined from presurgical mapping paradigms in the model to demarcate areas of eloquent cortex that should be avoided in resection.

 

 

 

 

 

 

#4. A Brain CTA (nrrd file)

 

 

This is an illustrative case of a normal CT angiography obtained with contrast administration.

 

 

 

 

#5. A Fronto-Parietal Brain Tumor from an MRI

 

 

Printed head models have also had a role in the planning and development of novel treatments for brain tumors. Phantoms that replicate the properties of the skull and cerebral tissue were produced to evaluate the potential for MRI-guided focused ultrasound to be used in the noninvasive thermocoagulation of brain tumors.

 

 

 

 

#6. A 55-Year-Old Male's Brain (from an MRI Scan)

 

 

The neocortex is the most phylogenetically developed structure of the human brain as compared with the brains of other species. The complex pattern of folding allows an increased cortical surface to occupy a smaller cranial volume. The pattern of folding that forms the sulcal and gyral patterns remains highly preserved across individuals. This enables a nomenclature for the cortical anatomy.

 

 

 

 

#7. A Post-Traumatic Brain Injury

 

Pneumocephalus refers to the presence of intracranial gas, and in the vast majority of cases the gas is air. The term encompasses gas in any of the intracranial compartments, and is most commonly encountered following trauma or surgery. Gas on CT will have a very low density (~ -1000HU) but care needs to be taken in ensuring that it is not fat which although of much higher density (-90HU) also appear completely black on routine brain windows. 

 

 

#8. A 3d printable model of the brain: An example

 

This brain model was printed for a customer in white PLA. It turned out great!

 

 

#9. Dilated Ventricles with Colpocephaly

 

Colpocephaly is a congenital brain abnormality in which the occipital horns - the posterior or rear portion of the lateral ventricles (cavities) of the brain -- are larger than normal because white matter in the posterior cerebrum has failed to develop or thicken. 

 

 

 

 

#10. Full Sized Brain with marked cerebellar atrophy 

 

Diffuse atrophy of the cerebellum refers to a progressive and irreversible reduction in cerebellar volume. It is a relatively common finding and found in a wide variety of clinical scenarios. 

 

 

 

 

References

 

1. Randazzo, M., Pisapia, J. M., Singh, N., & Thawani, J. P. (2016). 3D printing in neurosurgery: a systematic review. Surgical neurology international, 7(Suppl 33), S801.

 

2. Radiology assistant web.

 

3 Radiopaedia.org

 

4. Osborn´s Brain Imaging.

 

5. Medscape

 

 

 

 

 

 

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