Validation of a rhinologic virtual surgical simulator for performing a Draf 3 endoscopic frontal sinusotomy

A Narrative Review on 3-Dimensional Visualization Techniques in Neurosurgical Education, Simulation, and Planning

BACKGROUND

High-fidelity visualization of anatomical organs is crucial for neurosurgical education, simulation, and planning. This becomes much more important for minimally invasive neurosurgical procedures. Realistic anatomical visualization can allow resident surgeons to learn visual cues and orient themselves with the complex 3-dimensional (3D) anatomy. Achieving full fidelity in 3D medical visualization is an active area of research; however, the prior reviews focus on the application area and lack the underlying technical principles. Accordingly, the present study attempts to bridge this gap by providing a narrative review of the techniques used for 3D visualization.

METHODS

We conducted a literature review on 3D medical visualization technology from 2018 to 2023 using the PubMed and Google Scholar search engines. The cross-referenced manuscripts were extensively studied to find literature that discusses technology relevant to 3D medical visualization. We also compiled and ran software applications that were accessible to us in order to better understand them.

RESULTS

We present the underlying fundamental technology used in 3D medical visualization in the context of neurosurgical education, simulation, and planning. Further, we discuss and categorize a few important applications based on the 3D visualization techniques they use.

CONCLUSIONS

The visualization of virtual human organs has not yet achieved a level of realism close to reality. This gap is largely due to the interdisciplinary nature of this research, population diversity, and validation complexities. With the advancements in computational resources and automation of 3D visualization pipelines, next-gen applications may offer enhanced medical 3D visualization fidelity.

Virtual reality surgical planning for endoscopic endonasal approaches to the craniovertebral junction

PURPOSE

To demonstrate the utility of virtual reality (VR) for preoperative surgical planning of endoscopic endonasal craniovertebral junction (CVJ) surgery.

MATERIALS AND METHODS

Five patients who had undergone endoscopic endonasal surgery of the craniovertebral junction with preoperative virtual reality surgical planning were identified and described.

RESULTS

The anterior approach to the CVJ has been traditionally accomplished transorally. However, recently the transnasal endoscopic approach to this location has been described. Multiple anatomical studies have been conducted using the nasopalatine, nasoaxial, and rhinopalatine lines (NPL, NAxL, RPL) in an attempt to preoperatively delineate the inferior limits of endoscopic dissection. The use of advanced surgical simulation using immersive virtual reality is an innovative approach for analyzing CVJ anatomy and developing a surgical plan. VR simulation through the use of interactive and highly accurate patient specific models allows for the creation of three-dimensional (3D) digital reconstructions via the fusion of CT and MRI studies. Incorporation of simulation technology has been shown to increase surgeon proficiency while simultaneously decreasing complication rates. The described case series demonstrates the novel utility of VR planning for designing the endoscopic surgical approach to the CVJ.

CONCLUSIONS

VR technology allows for the creation of anatomically accurate 3D models that can be used for preoperative planning of endoscopic endonasal surgery. Such models help in the development of safe surgical plans by predicting inferior and lateral planes of dissection and assisting in the identification of critical structures.

Fully automated preoperative segmentation of temporal bone structures from clinical CT scans

Middle- and inner-ear surgery is a vital treatment option in hearing loss, infections, and tumors of the lateral skull base. Segmentation of otologic structures from computed tomography (CT) has many potential applications for improving surgical planning but can be an arduous and time-consuming task. We propose an end-to-end solution for the automated segmentation of temporal bone CT using convolutional neural networks (CNN). Using 150 manually segmented CT scans, a comparison of 3 CNN models (AH-Net, U-Net, ResNet) was conducted to compare Dice coefficient, Hausdorff distance, and speed of segmentation of the inner ear, ossicles, facial nerve and sigmoid sinus. Using AH-Net, the Dice coefficient was 0.91 for the inner ear; 0.85 for the ossicles; 0.75 for the facial nerve; and 0.86 for the sigmoid sinus. The average Hausdorff distance was 0.25, 0.21, 0.24 and 0.45 mm, respectively. Blinded experts assessed the accuracy of both techniques, and there was no statistical difference between the ratings for the two methods (p = 0.93). Objective and subjective assessment confirm good correlation between automated segmentation of otologic structures and manual segmentation performed by a specialist. This end-to-end automated segmentation pipeline can help to advance the systematic application of augmented reality, simulation, and automation in otologic procedures.

Application of holographic augmented reality for external approaches to the frontal sinus

BACKGROUND

External approaches to the frontal sinus such as osteoplastic flaps are challenging because they require blind entry into the sinus, posing risks of injury to the brain or orbit. Intraoperative computed tomography (CT)-based navigation is the current standard for planning the approach, but still necessitates blind entry into the sinus. The aim of this work was to describe a novel technique for external approaches to the frontal sinus using a holographic augmented reality (AR) application.

METHODS

Our team developed an AR system to create a 3-dimensional (3D) hologram of key anatomical structures, based on CT scans images. Using Magic Leap AR goggles for visualization, the frontal sinus hologram was aligned to the surface anatomy in 6 fresh cadaveric heads' anatomic boundaries, and the boundaries of the frontal sinus were demarcated based on the margins of the fused image. Trephinations and osteoplastic flap approaches were performed. The specimens were re-scanned to assess the accuracy of the osteotomy with respect to the actual frontal sinus perimeter.

RESULTS

Registration and surgery were completed successfully in all specimens. Registration required an average of 2 minutes. The postprocedure CT showed a mean difference of 1.4 ± 4.1 mm between the contour of the osteotomy and the contour of the frontal sinus. One surgical complication (posterior table perforation) occurred (16%).

CONCLUSION

We describe proof of concept of a novel technique utilizing AR to enhance external approaches to the frontal sinus. Holographic AR-enhanced surgical navigation holds promise for enhanced visualization of target structures during surgical approaches to the sinuses.