Visualization of the infratemporal fossa: enhancing anatomical learning through three-dimensional modeling

Woohyun Cho; Hye Jin Kim; Mi-Sun Hur; Han-Soo Lee; Kwan Hyun Youn

doi:10.5115/acb.24.127

Abstract

The infratemporal fossa and pterygopalatine fossa are critical pathways for blood vessels and nerves leading to the orbit, nasal cavity, and oral cavity. Anatomical observation of these areas is challenging for learners due to their complex connections with surrounding structures and their deep location within the body. Since it is not easy to understand this area in three dimensions with only textbook images, there is a need to produce three-dimensional (3D) content. Most existing 3D data have reconstructed the digital imaging and communication in medicine files from computed tomography images with high accuracy; however, the surrounding structures often obstruct the view. For this reason, this project utilized Cinema4D (R18) software to refine the modeled bones and to create 3D models of muscles, blood vessels, and nerves that accurately represent their anatomical shapes and pathways. To facilitate easier access for learners via PC, the content was converted into PDF format. This enables the educational materials to be more easily viewed and the main structures more clearly observed using a computer-based viewer.

Introduction

The infratemporal fossa, a region characterized by narrow spaces densely packed with delicate structures, poses challenges for observation, thus highlighting the necessity for educational tools to aid in learning. Historically, anatomical models such as écorché figures, handcrafted models, and plastinated specimens were created in analog formats. With advancements in technology, a variety of digital content has been developed. Previous research at Columbia University focused on the creation of two-dimensional (2D) illustrations depicting the infratemporal fossa and pterygopalatine fossa. These illustrations segregated each area into layers, enabling animated slide-based presentations to facilitate students’ anatomical learning [1]. However, the limitations of 2D representations compared to three-dimensional (3D) models were evident. Therefore, this study proposes that 3D models of the infratemporal fossa, overcoming the limitations of flat images, are expected to serve as more effective 3D educational tools.

Recently improved 3D models offer significant advantages over previously developed traditional 3D anatomical models. The previous models demonstrate limited interactivity and static representations of anatomical structures. However, the currently available 3D models allow the magnification of details and the selective adjustment of transparency. An early example of the utility of 3D content in human anatomy was demonstrated in 1989 by the National Library of Medicine [2] in the United States, which developed prototype 3D data for male and female bodies. This data has been continuously improved and utilized as technology advances, thereby accelerating the rapid development of 3D anatomical content.

The educational effectiveness of utilizing 3D models was validated through a case study at the University of Montpellier, where computer 3D rendering images were produced to enhance learning in zygomatic bone anatomy [3]. The developed educational content was experimentally assessed among medical students. Students were divided into two groups: one that received 3D anatomical instruction and another that did not. After attending lectures, both groups underwent testing, and the performance of the undergraduates was compared. It was reported that students who received 3D anatomical guidance performed significantly better than those who only attended lectures. Additionally, generally all participants reported that, although initially requiring instructor assistance with the software, the new educational content significantly enhanced their interest in learning anatomy.

In the dental field, the structures around the foramen ovale, which are closely related to the structures of the infratemporal fossa, are clinically significant for procedures such as nerve block anesthesia, mandibular fracture repair, tumor resections, and treatments for trigeminal neuralgia. To meet these needs, this study aimed to create anatomically appropriate 3D models that allow users direct access and observation of desired areas. Most existing human 3D models, reconstructed from DICOM files, offer high accuracy but obstruct the view of vascular and nerve structures due to surrounding anatomy. Utilizing Cinema4D (R18; Maxon), this research focused on producing visually clearer representations of the fine structures traversing the infratemporal fossa, developing a 3D model that is easier for trainees to observe. Additionally, to facilitate access for users who find general 3D programs challenging, the final 3D model was converted into a PDF file using Adobe Acrobat DC (Adobe) for distribution.

Materials and Methods

3D production of the infratemporal fossa

3D design for production of the infratemporal fossa

This study aims to understand the morphology of the maxillary artery and inferior alveolar nerve traversing the infratemporal fossa in three dimensions and to present this information in a visually accessible manner. During the production process, anatomical textbooks and atlases were referenced, serving as important guides for the creation of the 3D model. Descriptions of the infratemporal fossa in most textbooks were similar, with illustrations typically depicting the external and internal structures of the infratemporal fossa. However, variations in representation across different publications necessitated multiple perspectives for 3D modeling, including views from above, below, front, and back. Existing resources rarely offered illustrations from these various viewpoints. Consequently, where information was lacking, further anatomical details about the infratemporal fossa were investigated, and coronal section data from head specimens were used to estimate the thickness of the pterygoid muscles. Additionally, observations of cadavers in anatomy labs were conducted with the assistance of anatomists to supplement the data.

In this study, before producing the skull in 3D space, actual bone specimens and skull models were consulted. To clearly display the mandibular nerve, the skull was sectioned sagittally, and parts that obstructed the view of the vessels and nerves in the infratemporal fossa, such as the upper portion of the squamous part of the temporal bone, the roof of the orbit (frontal bone), and the posterior aspect of the mastoid process, were edited out. Additionally, to construct the pterygoid muscles, virtual blueprints were created based on 2D images and researched data. To represent an average form, images from anatomical textbooks and atlases that clearly depicted the maxillary artery and mandibular nerve were selected at six works, aligned to the same positions, simplified, and organized for clarity [4 -9].

3D modeling tools and production process

In this study, the Cinema4D (R18) program developed by Germany’s Maxon company was utilized as a tool for creating models of the skull, muscles, blood vessels, and nerves. Although the Mimics program (version 21.0; Materialisem), which specializes in quantifying real data, was considered, it was deemed unsuitable for displaying typical anatomical structures. Therefore, using Cinema4D allowed for the initial creation of blood vessels and nerves, which are often obscured by surrounding structures, and later adjustments to achieve more typical and ideal forms. Additionally, to make the data more familiar and effectively recognizable to students learning anatomy, the color norms from anatomical illustrations were followed in the 3D models, with arteries rendered in red and nerves in yellow (Tables 1 and 2).

3D PDF production process

Implementation of 3D PDF

When importing a WRL file into Adobe Acrobat, the 3D PDF file can be viewed using Tetra4D (Tech Soft 3D). The table of contents within the PDF maintains the same order as the modeling tree in the 3D program. The order of the contents is arranged as follows: cranium, wing muscle, maxillary artery, mandibular nerve, sphenomandibular ligament, and articular disc (Figs. 1, 2).

Results

3D modeling

A 3D model for the comprehensive study of the infratemporal fossa was created (Fig. 3). In Cinema4D, the default image in the software shows the cranium, pterygoid muscles, maxillary artery, mandibular nerve, articular disc, and sphenomandibular ligament all together, with the mandible rendered as semi-transparent. Users can select the desired anatomical regions from the modeling list and examine them from various perspectives. The model allows for manipulations such as hiding or revealing structures and zooming in or out.

3D PDF file

The 3D PDF file shows the state with the cranium, pterygoid muscles, maxillary artery, mandibular nerve, articular disc, sphenomandibular ligament, and the additionally sectioned zygomatic bone all included (Fig. 4). Although it is of lower quality compared to Cinema4D, it is easier to handle and retains the advantages of 3D. Each structure can be more easily selected or removed from the table of contents, and colors and transparency can be adjusted. In the current state shown in Fig. 4A, the mandible is rendered with transparency.

Discussion

This study aimed to develop an improved learning tool to overcome the limitations of existing anatomical resources in describing the infratemporal fossa. By utilizing 3D technology, we created detailed models of the cranium and pterygoid muscles, including vascular and neural structures, to aid students in understanding complex microstructures that are difficult to observe. Traditional 3D anatomical applications often display blood vessels and nerves either too generally or excessively, obscuring structural clarity. To address this, we used sectioned crania to enhance the view of the infratemporal fossa and organized the maxillary artery from its origin to its terminal branches and the anterior and posterior trunks of the mandibular nerve for clear differentiation. As a result, it was easier to trace the overall paths of the maxillary artery and mandibular nerve. This approach significantly aided in the intuitive understanding of the fundamental concepts of the infratemporal fossa, including its roof, lateral wall, and medial wall.

Due to the limitations of using traditional 2D resources and cadavers for anatomical study, most anatomy textbooks and atlases only provide views of the external and internal surfaces. This has made it challenging to accurately depict the paths of blood vessels and nerves as they are altered by structures such as bones, muscles, and ligaments.

To date, anatomical tables that render cadavers in 3D based on computed tomography and magnetic resonance imaging data have been developed. Current trends indicate that the 3D industry is leveraging artificial intelligence and big data, and technologies like augmented reality (AR), virtual reality, and merged reality created from 3D images are expected to play a crucial role in the future of medicine [10].

Additionally, from an illustrator's perspective, the advantage of 3D modeling is the ability to easily observe structures from viewpoints that are typically difficult to access. This makes 3D modeling a valuable resource for enhancing the visual quality of 2D illustrations. The 3D infratemporal fossa PDF developed in this study is designed to be easily accessible without the need for specialized 3D software, reducing the need for large rendering files. Users can quickly and easily view the 3D model on a personal computer and add annotations as needed. Although there are limitations, such as a reduction in modeling quality when converted to PDF, the format offers a user-friendly interface and excellent accessibility.

Furthermore, we propose modifying and developing the 3D modeled infratemporal fossa into AR data using game engines that support Integrated Development Environments, and distributing it as an application. This can serve as an educational tool for anatomy lectures and for students learning anatomy. This approach aims to provide a better method for studying the infratemporal fossa and to utilize the 3D model as a valuable foundational resource.