Intracranial vasculature 3D printing: review of techniques and manufacturing processes to inform clinical practice

Patient-Specific Vascular Flow Phantom for MRI- and Doppler Ultrasound Imaging

OBJECTIVE

Intraoperative Doppler ultrasound imaging of human brain vasculature is an emerging neuro-imaging modality that offers vascular brain mapping with unprecedented spatiotemporal resolution. At present, however, access to the human brain using Doppler Ultrasound is only possible in this intraoperative context, posing a significant challenge for validation of imaging techniques. This challenge necessitates the development of realistic flow phantoms outside of the neurosurgical operating room as external platforms for testing hardware and software. An ideal ultrasound flow phantom should provide reference-like values in standardized topologies such as a slanted pipe, and allow for measurements in structures closely resembling vascular morphology of actual patients. Additionally, the phantom should be compatible with other clinical cerebrovascular imaging modalities. To meet these criteria, we developed and validated a versatile, multimodal MRI- and ultrasound Doppler phantom.

METHODS

Our approach incorporates the latest advancements in phantom research using tissue-mimicking material and 3D-printing with water-soluble resin to create wall-less patient-specific lumens, compatible for ultrasound and MRI.

RESULTS

We successfully produced three distinct phantoms: a slanted pipe, a y-shape phantom representing a bifurcating vessel and an arteriovenous malformation (AVM) derived from clinical Digital Subtraction Angiography (DSA)-data of the brain. We present 3D ultrafast power Doppler imaging results from these phantoms, demonstrating their ability to mimic complex flow patterns as observed in the human brain. Furthermore, we showcase the compatibility of our phantom with Magnetic Resonance Imaging (MRI).

CONCLUSION

We developed an MRI- and Doppler Ultrasound-compatible flow-phantom using customizable, water-soluble resin prints ranging from geometrical forms to patient-specific vasculature.

GRAVEN: a database of teaching method that applies gestures to represent the neurosurgical approach's blood vessels and nerves

BACKGROUND

In this era of rapid technological development, medical schools have had to use modern technology to enhance traditional teaching. Online teaching was preferred by many medical schools. However due to the complexity of intracranial anatomy, it was challenging for the students to study this part online, and the students were likely to be tired of neurosurgery, which is disadvantageous to the development of neurosurgery. Therefore, we developed this database to help students learn better neuroanatomy.

MAIN BODY

The data were sourced from Rhoton's Cranial Anatomy and Surgical Approaches and Neurosurgery Tricks of the Trade in this database. Then we designed many hand gesture figures connected with the atlas of anatomy. Our database was divided into three parts: intracranial arteries, intracranial veins, and neurosurgery approaches. Each section below contains an atlas of anatomy, and gestures represent vessels and nerves. Pictures of hand gestures and atlas of anatomy are available to view on GRAVEN ( www.graven.cn ) without restrictions for all teachers and students. We recruited 50 undergraduate students and randomly divided them into two groups: using traditional teaching methods or GRAVEN database combined with above traditional teaching methods. Results revealed a significant improvement in academic performance in using GRAVEN database combined with traditional teaching methods compared to the traditional teaching methods.

CONCLUSION

This database was vital to help students learn about intracranial anatomy and neurosurgical approaches. Gesture teaching can effectively simulate the relationship between human organs and tissues through the flexibility of hands and fingers, improving anatomy interest and education.

Modified patient-specific surgical-guide-assisted precise treatment of unilateral comminuted zygomaticomaxillary complex fractures: A 5-year retrospective study

Our study aimed to evaluate modified patient-specific surgical-guide-assisted precise treatment of unilateral comminuted zygomaticomaxillary complex (ZMC) fractures. The retrospective non-randomized study was conducted in a single hospital in China. All patients diagnosed with unilateral comminuted ZMC fractures between January 1, 2018 and December 31, 2022 were retrospectively reviewed. All patients underwent preoperative spiral computed tomography (CT). CT data were processed using software to DICOM format and transferred to Proplan CMF3.0 for preoperative virtual surgical planning and postoperative evaluation. All data were extracted from standardized electronic medical records. All statistical analyses were performed using SPSS version 20.0. The chi-square test and t-test were used for statistical analyses. The 54 included patients were divided into two comparable, equal cohorts of 27 patients, and followed up for at least 6 months. Fracture reduction was assisted using the modified patient-specific surgical guides in the guide group (23 males, four females; mean age 37.74 ± 12.07 years) and without the modified patient-specific surgical guides in the control group (20 males, seven females; mean age 37.44 ± 13.58 years). In the guide group, the mean eminence deviation between the affected and unaffected sides was 1.01 ± 0.92 mm, and the mean width deviation between the affected and unaffected sides was 1.29 ± 1.32 mm. In the control group, the mean eminence deviation between the affected and unaffected sides was 1.99 ± 1.69 mm, and the mean width deviation between the affected and unaffected sides was 2.68 ± 2.01 mm. The differences in facial protrusion (p = 0.001) and width (p = 0.003) symmetry between the affected and healthy sides of the two groups were statistically significant (p < 0.05). In conclusion, applying the modified patient-specific surgical guides to unilateral comminuted zygomaticomaxillary complex fracture reduction has the advantages of greater predictability and effectiveness, and improved bilateral ZMC symmetry. It should be noted that this approach would be especially beneficial for less-experienced surgeons.

Stereolithographic (SLA) 3D Printing for Preprocedural Planning in Endovascular Aortic Repair of a Thoracic Aneurysm

BACKGROUND

When treating aortic aneurysm patients with complex anatomical features, preprocedural planning aided by 3D-printed models offers valuable insights for endovascular intervention. This study highlights the use of stereolithographic (SLA) 3D printing to fabricate a phantom of a challenging aortic arch aneurysm with a complex neck anatomy.

CLINICAL CASE

A 75-year-old female presented with a 58 mm descending thoracic aortic aneurysm (TAA) extending to the distal arch, involving the left subclavian artery (LSA) and the left common carotid artery (LCCA). The computed tomography (CT) scans underwent scrutiny by radiology and vascular teams. Nevertheless, the precise spatial relationships of the ostial origins proved to be challenging to ascertain. To address this, a patient-specific phantom of the aortic arch was fabricated utilizing an SLA printer and a biomedical resin. The thoracic endovascular aortic repair (TEVAR) procedure was simulated using fluoroscopy on the phantom to enhance procedural preparedness. Subsequently, the patient underwent a right carotid-left carotid bypass and a right carotid-left subclavian bypass. After a 24-hour interval, the patient underwent the TEVAR procedure, during which a 37 mm × 150 mm stent graft (CTAG, WL Gore and Associates, Flagstaff, AZ, USA) and a 40 mm × 200 mm stent graft (CTAG, WL Gore and Associates, Flagstaff, AZ, USA) were deployed, effectively covering the LSA and LCCA. Notably, the aneurysm exhibited complete sealing, with no indications of endoleaks or graft infoldings. At the 12-month follow-up, the patient remains in good health, with no evidence of endoleaks or any other surgery-related complication.

CONCLUSION

This report showcases the successful use of a 3D-printed endovascular phantom in guiding the decision-making process during the preparation for a TEVAR procedure. The simulation played a pivotal role in selecting the appropriate stent graft, ensuring an intervention protocol optimized based on the patient-specific anatomy.

3D printed arrowroot starch-gellan scaffolds for wound healing applications

Skin, the largest organ in the body, blocks the entry of environmental pollutants into the system. Any injury to this organ allows infections and other harmful substances into the body. 3D bioprinting, a state-of-the-art technique, is suitable for fabricating cell culture scaffolds to heal chronic wounds rapidly. This study uses starch extracted from Maranta arundinacea (Arrowroot plant) (AS) and gellan gum (GG) to develop a bioink for 3D printing a scaffold capable of hosting animal cells. Field emission scanning electron microscopy (FE-SEM) and X-ray diffraction analysis (XRD) prove that the isolated AS is analogous to commercial starch. The cell culture scaffolds developed are superior to the existing monolayer culture. Infrared microscopy shows the AS-GG interaction and elucidates the mechanism of hydrogel formation. The physicochemical properties of the 3D-printed scaffold are analyzed to check the cell adhesion and growth; SEM images have confirmed that the AS-GG printed scaffold can support cell growth and proliferation, and the MTT assay shows good cell viability. Cell behavioral and migration studies reveal that cells are healthy. Since the scaffold is biocompatible, it can be 3D printed to any shape and structure and will biodegrade in the requisite time.

The Integration of 3D Virtual Reality and 3D Printing Technology as Innovative Approaches to Preoperative Planning in Neuro-Oncology

Our study explores the integration of three-dimensional (3D) virtual reality (VR) and 3D printing in neurosurgical preoperative planning. Traditionally, surgeons relied on two-dimensional (2D) imaging for complex neuroanatomy analyses, requiring significant mental visualization. Fortunately, nowadays advanced technology enables the creation of detailed 3D models from patient scans, utilizing different software. Afterwards, these models can be experienced through VR systems, offering comprehensive preoperative rehearsal opportunities. Additionally, 3D models can be 3D printed for hands-on training, therefore enhancing surgical preparedness. This technological integration transforms the paradigm of neurosurgical planning, ensuring safer procedures.

Medical 3D Printing Using Desktop Inverted Vat Photopolymerization: Background, Clinical Applications, and Challenges

Medical 3D printing is a complex, highly interdisciplinary, and revolutionary technology that is positively transforming the care of patients. The technology is being increasingly adopted at the Point of Care (PoC) as a consequence of the strong value offered to medical practitioners. One of the key technologies within the medical 3D printing portfolio enabling this transition is desktop inverted Vat Photopolymerization (VP) owing to its accessibility, high quality, and versatility of materials. Several reports in the peer-reviewed literature have detailed the medical impact of 3D printing technologies as a whole. This review focuses on the multitude of clinical applications of desktop inverted VP 3D printing which have grown substantially in the last decade. The principles, advantages, and challenges of this technology are reviewed from a medical standpoint. This review serves as a primer for the continually growing exciting applications of desktop-inverted VP 3D printing in healthcare.

Imaging of intracranial aneurysms in animals: a systematic review of modalities

Intracranial aneurysm (IA) animal models are paramount to study IA pathophysiology and to test new endovascular treatments. A number of in vivo imaging modalities are available to characterize IAs at different stages of development in these animal models. This review describes existing in vivo imaging techniques used so far to visualize IAs in animal models. We systematically searched for studies containing in vivo imaging of induced IAs in animal models in PubMed and SPIE Digital library databases between 1 January 1945 and 13 July 2022. A total of 170 studies were retrieved and reviewed in detail, and information on the IA animal model, the objective of the study, and the imaging modality used was collected. A variety of methods to surgically construct or endogenously induce IAs in animals were identified, and 88% of the reviewed studies used surgical methods. The large majority of IA imaging in animals was performed for 4 reasons: basic research for IA models, testing of new IA treatment modalities, research on IA in vivo imaging of IAs, and research on IA pathophysiology. Six different imaging techniques were identified: conventional catheter angiography, computed tomography angiography, magnetic resonance angiography, hemodynamic imaging, optical coherence tomography, and fluorescence imaging. This review presents and discusses the advantages and disadvantages of all in vivo IA imaging techniques used in animal models to help future IA studies finding the most appropriate IA imaging modality and animal model to answer their research question.

Development of a 3D Printed Brain Model with Vasculature for Neurosurgical Procedure Visualisation and Training

BACKGROUND

Simulation-based techniques using three-dimensional models are gaining popularity in neurosurgical training. Most pre-existing models are expensive, so we felt a need to develop a real-life model using 3D printing technology to train in endoscopic third ventriculostomy.

METHODS

The brain model was made using a 3D-printed resin mold from patient-specific MRI data. The mold was filled with silicone Ecoflex™ 00-10 and mixed with Silc Pig^® pigment additives to replicate the color and consistency of brain tissue. The dura mater was made from quick-drying silicone paste admixed with gray dye. The blood vessels were made from a silicone 3D-printed mold based on magnetic resonance imaging. Liquid containing paprika oleoresin dye was used to simulate blood and was pumped through the vessels to simulate pulsatile motion.

RESULTS

Seven residents and eight senior neurosurgeons were recruited to test our model. The participants reported that the size and anatomy of the elements were very similar to real structures. The model was helpful for training neuroendoscopic 3D perception and navigation.

CONCLUSIONS

We developed an endoscopic third ventriculostomy training model using 3D printing technology that provides anatomical precision and a realistic simulation. We hope our model can provide an indispensable tool for young neurosurgeons to gain operative experience without exposing patients to risk.

Patient-specific brain arteries molded as a flexible phantom model using 3D printed water-soluble resin

Visualizing medical images from patients as physical 3D models (phantom models) have many roles in the medical field, from education to preclinical preparation and clinical research. However, current phantom models are generally generic, expensive, and time-consuming to fabricate. Thus, there is a need for a cost- and time-efficient pipeline from medical imaging to patient-specific phantom models. In this work, we present a method for creating complex 3D sacrificial molds using an off-the-shelf water-soluble resin and a low-cost desktop 3D printer. This enables us to recreate parts of the cerebral arterial tree as a full-scale phantom model ([Formula: see text] cm) in transparent silicone rubber (polydimethylsiloxane, PDMS) from computed tomography angiography images (CTA). We analyzed the model with magnetic resonance imaging (MRI) and compared it with the patient data. The results show good agreement and smooth surfaces for the arteries. We also evaluate our method by looking at its capability to reproduce 1 mm channels and sharp corners. We found that round shapes are well reproduced, whereas sharp features show some divergence. Our method can fabricate a patient-specific phantom model with less than 2 h of total labor time and at a low fabrication cost.

Full color 3D printing of anatomical models

INTRODUCTION

We propose an effective method for manufacturing human anatomical specimens in response to the shortage of cadaver specimens and the poor simulation results of anatomical specimen substitutes.

METHODS

Digital human data with high precision were used to create digital models and corresponding mapped textures. Different materials were chosen to print the digital models with full-color and multimaterial 3D-printing technology on the basis of the histological characteristics of the anatomical structures. Anatomy experts and surgeons were then invited to compare the 3D printed models with authentic anatomical specimens in terms of morphological appearance, anatomical detail, and textural properties.

RESULTS

The skull, brain, hand muscles, blood vessels and nerves of the hand, and the deep structure of the head and face were printed. The skull model used hard material, and the brain and hand muscles models used flexible and hard materials combined. The blood vessels, nerves of the hand, and the superficial and deep structure of the head and face used transparent materials, revealing the small vessels and nerves in the interior. In all the models there were no significant differences from anatomical specimens in morphological appearance and anatomical detail. They also affected vision and touch in the same way as authentic specimens in the textural properties of color, roughness, smoothness, and fineness.

CONCLUSION

Full-color and multi-material 3D printed anatomical models have the same visual and tactile properties as anatomical specimens and could serve to complement or supplement them in anatomy teaching to compensate for the shortage of cadavers. This article is protected by copyright. All rights reserved.

The Role of 3D Printing in Planning Complex Medical Procedures and Training of Medical Professionals-Cross-Sectional Multispecialty Review

Medicine is a rapidly-evolving discipline, with progress picking up pace with each passing decade. This constant evolution results in the introduction of new tools and methods, which in turn occasionally leads to paradigm shifts across the affected medical fields. The following review attempts to showcase how 3D printing has begun to reshape and improve processes across various medical specialties and where it has the potential to make a significant impact. The current state-of-the-art, as well as real-life clinical applications of 3D printing, are reflected in the perspectives of specialists practicing in the selected disciplines, with a focus on pre-procedural planning, simulation (rehearsal) of non-routine procedures, and on medical education and training. A review of the latest multidisciplinary literature on the subject offers a general summary of the advances enabled by 3D printing. Numerous advantages and applications were found, such as gaining better insight into patient-specific anatomy, better pre-operative planning, mock simulated surgeries, simulation-based training and education, development of surgical guides and other tools, patient-specific implants, bioprinted organs or structures, and counseling of patients. It was evident that pre-procedural planning and rehearsing of unusual or difficult procedures and training of medical professionals in these procedures are extremely useful and transformative.

Properties and Characteristics of Three-Dimensional Printed Head Models Used in Simulation of Neurosurgical Procedures: A Scoping Review

BACKGROUND

Intracranial surgery can be complex and high risk. Safety, ethical and financial factors make training in the area challenging. Head model 3-dimensional (3D) printing is a realistic training alternative to patient and traditional means of cadaver and animal model simulation.

OBJECTIVE

To describe important factors relating to the 3D printing of human head models and how such models perform as simulators.

METHODS

Searches were performed in PubMed, the Cochrane Library, Scopus, and Web of Science. Articles were screened independently by 3 reviewers using Covidence software. Data items were collected under 5 categories: study information; printers and processes; head model specifics; simulation and evaluations; and costs and production times.

RESULTS

Forty articles published over the last 10 years were included in the review. A range of printers, printing methods, and substrates were used to create head models and tissue types. Complexity of the models ranged from sections of single tissue type (e.g., bone) to high-fidelity integration of multiple tissue types. Some models incorporated disease (e.g., tumors and aneurysms) and artificial physiology (e.g., pulsatile circulation). Aneurysm clipping, bone drilling, craniotomy, endonasal surgery, and tumor resection were the most commonly practiced procedures. Evaluations completed by those using the models were generally favorable.

CONCLUSIONS

The findings of this review indicate that those who practice surgery and surgical techniques on 3D-printed head models deem them to be valuable assets in cranial surgery training. Understanding how surgical simulation on such models affects surgical performance and patient outcomes, and considering cost-effectiveness, are important future research endeavors.

MRI-Based and Histologically Verified 3D Modeling of Spatial Distribution of Intra-Arterially Transplanted Cells in Rat Brain

Visualization of transplanted stem cells in the brain is an important issue in the study of the mechanisms of their therapeutic action. MRI allowing visualization of single transplanted cells previously labeled with superparamagnetic iron oxide particles is among the most informative methods of non-invasive intravital imaging. Verification of MRI data using pathomorphological examination at the microscopic level helps to avoid errors in data interpretation. However, making serial sections of the whole brain and searching for transplanted cells under the microscope is laborious and time-consuming. We have developed a method for 3D modeling of the distribution of transplanted cells in the brain allowing navigating through various brain structures and identifying the areas of accumulation of transplanted cells, which significantly increases the efficiency and reduces the time of histological examination.

Design of a 3D printed coronary artery model for CT optimization

INTRODUCTION

To design a custom phantom of the coronary arteries to optimize CT coronary angiography (CCTA) protocols.

METHODS

Characteristics of the left and right coronary arteries (mean Hounsfield Unit (HU) values and diameters) were collected from consecutive CCTA examinations (n = 43). Four different materials (two mixtures of glycerine, gelatine and water, pig hearts, Ecoflex™ silicone) were scanned inside a Lungman phantom using the CCTA protocol to find the closest model to in vivo data. A 3D printed model of the coronary artery tree was created using CCTA data by exporting a CT volume rendering into Autodesk Meshmixer™ software. The model was placed in an acid bath for 5 h, then covered in Ecoflex™, which was removed after drying. Both the Ecoflex™ and pig heart were later filled with a mixture of contrast (Visipaque 320 mg I/ml), NaCl and gelatin and scanned with different levels of tube current and iterative reconstruction (ASiR-V). Objective (HU, noise and size (vessel diameter) and subjective analysis were performed on all scans.

RESULTS

The gelatine mixtures had HU values of 130 and 129, Ecoflex™ 65 and the pig heart 56. At the different mA/ASiR-V levels the contrast filled Ecoflex™ had a mean HU 318 ± 4, noise 47±7HU and diameter of 4.4 mm. The pig heart had a mean HU of 209 ± 5, noise 38±4HU and a diameter of 4.4 mm. With increasing iterative reconstruction level the visualisation of the pig heart arteries decreased so no measurements could be performed.

CONCLUSION

The use of a 3D printed model of the arteries and casting with the Ecoflex™ silicone is the most suitable solution for a custom-designed phantom.

IMPLICATIONS FOR PRACTICE

Custom designed phantoms using 3D printing technology enable cost effective optimisation of CT protocols.

Additive Fabrication of a Vascular 3D Phantom for Stereotactic Radiosurgery of Arteriovenous Malformations

In this study, an efficient methodology for manufacturing a realistic three-dimensional (3D) cerebrovascular phantom resembling a brain arteriovenous malformation (AVM) for applications in stereotactic radiosurgery is presented. The AVM vascular structure was 3D reconstructed from brain computed tomography (CT) data acquired from a patient. For the phantom fabrication, stereolithography was used to produce the AVM model and combined with silicone casting to mimic the brain parenchyma surrounding the vascular structure. This model was made with tissues-equivalent materials for radiology. The hollow vascular system of the phantom was filled with a contrast agent usually employed on patients for CT scans. The radiological response of the phantom was tested and compared with the one of the clinical case. The constructed model demonstrated to be a very accurate physical representation of the AVM and its vasculature and good morphological consistency was observed between the model and the patient-specific source anatomy. These results suggest that the proposed method has potential to be used to fabricate patient-specific phantoms for neurovascular radiosurgery applications and medical research.

Three-Dimensional Modeling in Training, Simulation, and Surgical Planning in Open Vascular and Endovascular Neurosurgery: A Systematic Review of the Literature

BACKGROUND

The expanding use of three-dimensional (3D) printing in open vascular and endovascular neurosurgery presents a promising new tool in resident learning as well as operative planning. Recent studies have investigated the accuracy, efficacy, and practicality of 3D-printed models of patient-specific disease.

OBJECTIVE

To review the literature exploring 3D modeling in neurovascular and endovascular surgery for training, simulation, and surgical preparation.

METHODS

A systematic search of the PubMed database was conducted using keywords relating to 3D printing and neurovascular or endovascular surgery. Articles were manually screened to include those that focused on resident training, surgical simulation, or preoperative planning. Information on fabrication method, materials, cost, and validation measures was collected.

RESULTS

A total of 27 articles were identified that met inclusion criteria. Twenty-one studies used 3D printing to produce aneurysm models, 5 produced arteriovenous malformation models, and 1 produced aneurysm and arteriovenous malformation models. Stereolithography was the most common fabrication method used, with acrylonitrile butadiene styrene and VeroClearTangoPlus (Stratasys) being the most frequently used materials. The mean manufacturing cost per model was U.S. $624.83. Outcomes included model measurement accuracy, concordance of intraoperative devices with those selected preoperatively, and qualitative feedback.

CONCLUSIONS

Models generated by 3D printing are anatomically accurate and aid in resident learning as well as operative planning in open vascular and endovascular neurosurgery. As advancements in printing methods are made and manufacturing costs decrease, this tool may supplement training on a wider scale in a field in which direct exposure to cases is limited.

Building a Functional Salivary Gland for Cell-Based Therapy: More than Secretory Epithelial Acini

A few treatment options exist for patients experiencing xerostomia due to hyposalivation that occurs as a result of disease or injury to the gland. An opportunity for a permanent solution lies in the field of salivary gland replacement through tissue engineering. Recent success emboldens in the vision of producing a tissue-engineered salivary gland composed of differentiated salivary epithelial cells that are able to differentiate to form functional units that produce and deliver saliva to the oral cavity. This vision is augmented by advances in understanding cellular mechanisms that guide branching morphogenesis and salivary epithelial cell polarization in both acinar and ductal structures. Growth factors and other guidance cues introduced into engineered constructs help to develop a more complex glandular structure that seeks to mimic native salivary gland tissue. This review describes the separate epithelial phenotypes that make up the gland, and it describes their relationship with the other cell types such as nerve and vasculature that surround them. The review is organized around the links between the native components that form and contribute to various aspects of salivary gland development, structure, and function and how this information can drive the design of functional tissue-engineered constructs. In addition, we discuss the attributes of various biomaterials commonly used to drive function and form in engineered constructs. The review also contains a current description of the state-of-the-art of the field, including successes and challenges in creating materials for preclinical testing in animal models. The ability to integrate biomolecular cues in combination with a range of materials opens the door to the design of increasingly complex salivary gland structures that, once accomplished, can lead to breakthroughs in other fields of tissue engineering of epithelial-based exocrine glands or oral tissues.