Visualization Techniques for Precise Alignment in VR: A Comparative Study

Martin-Gomez, Alejandro; Eck, Ulrich; Navab, Nassir

doi:10.1109/vr.2019.8798135

Cited by 28 publications

(10 citation statements)

References 15 publications

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“…Improving the haptic feedback might lead to even improved reliability of VRbased measures in future. In this preliminary study, only claims for orbitary scenarios were raised and similar research alignment tasks have resulted in comparable performance 37 . Nevertheless, it can be mentioned that the discussed VR application only constitutes a platform for any kind of clinical or research 3D data.…”

Section: Discussionmentioning

confidence: 99%

Validation of virtual reality orbitometry bridges digital and physical worlds

Maloca

Faludi

Żelechowski

et al. 2020

Sci Rep

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Clinical science and medical imaging technology are traditionally displayed in two dimensions (2D) on a computer monitor. In contrast, three-dimensional (3D) virtual reality (VR) expands the realm of 2D image visualization, enabling an immersive VR experience with unhindered spatial interaction by the user. Thus far, analysis of data extracted from VR applications was mainly qualitative. In this study, we enhance VR and provide evidence for quantitative VR research by validating digital VR display of computed tomography (CT) data of the orbit. Volumetric CT data were transferred and rendered into a VR environment. Subsequently, seven graders performed repeated and blinded diameter measurements. the intergrader variability of the measurements in VR was much lower compared to measurements in the physical world and measurements were reasonably consistent with their corresponding elements in the real context. The overall VR measurements were 5.49% higher. As such, this study attests the ability of VR to provide similar quantitative data alongside the added benefit of VR interfaces. VR entails a lot of potential for the future research in ophthalmology and beyond in any scientific field that uses three-dimensional data. Orbital tumors can either be primary, arising from structures within the orbit, or secondary, due to metastatic spread of a primary tumor elsewhere 1-3. A myriad of clinical findings suggest the presence of an orbital mass, namely proptosis, diplopia, pain, conjunctival congestion and varying degrees of visual loss 4,5. Diagnosis relies on adequate clinical examination and orbital imaging like magnetic resonance imaging (MRI) and/or computed tomography (CT) 6. Despite the great progress in medical imaging, the diagnosis of orbital lesions based on neuroimaging features may lack characteristic imaging features. Often, the diagnosis of specific orbital disorders such as Graves' disease associated orbitopathy, orbital inflammation, orbital lymphoma, lacrimal gland epithelial tumor, metastatic carcinoma, and vascular orbital lesions is ambiguous 7-10. Confirmation of the diagnosis frequently relies on a biopsy which can be technically challenging and prone to complications due to the dense arrangement of tissue or inaccessibility of many of these lesions 11. Visualization of orbital lesions is still based on pre-surgery image assessment of two-dimensional (2D) data visualization on a computer monitor or on intraoperative exploration 12,13. There are increasing possibilities for presentation and interaction with virtual reality 14. In this context, virtual reality (VR) has recently been optimized as an enhanced medical image display method and showed to safeguard visual comfort 15,16. The main objective of this study was to extend current medical image display and validate the level of spatial precision in orbitometry of CT data, representing the physical world, compared to precision in three-dimensional (3D) virtual reality for the first time. This is especially important when new ways are explored to use ...

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Section: Discussionmentioning

confidence: 99%

Validation of virtual reality orbitometry bridges digital and physical worlds

Maloca

Faludi

Żelechowski

et al. 2020

Sci Rep

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“…As such, we are investigating various rendering techniques to optimize holographic alignment similar to studies previously done in VR. 37 We are also working to better understand the vergence-accommodation conflict whereby holograms are always accommodated (or focused) at a fixed distance due to the nature of the display system but visualized at a variety of distances based on the position of the user. 38 The convergence of two eyes toward the display point conflicts with the accommodation of each individual eye, which seeks to minimize blur at the focal point through lens adjustment.…”

Section: Discussionmentioning

confidence: 99%

“…Much of the work focuses on better understanding factors related to the visual perception and interpretation of holograms. As such, we are investigating various rendering techniques to optimize holographic alignment similar to studies previously done in VR 37 . We are also working to better understand the vergence‐accommodation conflict whereby holograms are always accommodated (or focused) at a fixed distance due to the nature of the display system but visualized at a variety of distances based on the position of the user 38 .…”

Section: Discussionmentioning

confidence: 99%

Patient posture correction and alignment using mixed reality visualization and the HoloLens 2

et al. 2021

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Purpose The purpose of this study was to develop and preliminarily test a radiotherapy system for patient posture correction and alignment using mixed reality (MixR) visualization. The write‐up of this work also provides an opportunity to introduce the concepts and technology of MixR for a medical physics audience who may be unfamiliar with the topic. Methods A MixR application was developed for on optical‐see‐through head‐mounted display (HoloLens 2) allowing a user to simultaneously and directly view a patient and a reference hologram derived from their simulation CT scan. The hologram provides a visual reference for the exact posture needed during treatment and is initialized in relation to the origin of a radiotherapy device using marker‐based tracking. The system further provides marker‐less tracking that allows the user tofreely navigate the room as they view and align the patient from various angles. The system was preliminarily tested using both a rigid (pelvis) and nonrigid (female mannequin) anthropomorphic phantom. Each phantom was aligned via hologram and accuracy quantified using CBCT and CT. Results A fully realized system was developed. Rigid registration accuracy was on the order of 3.0 ± 1.5 mm based on the performance of three users repeating alignment five times each. The lateral direction showed the most variability among users and was associated with the largest off‐sets (approximately 2.0 mm). For nonrigid alignment, the MixR setup outperformed a setup based on three‐point alignment and setup photos, the latter of which showed a difference in arm position of 2 cm and a torso roll of 6–7°. Conclusions MixR visualization is a rapidly emerging domain that has the potential to significantly impact the field of medicine. The current application is an illustration of this and highlights the advantages of MixR for patient setup in radiation oncology. The key feature of the system is the way in which it transforms nonrigid registration into rigid registration by providing an efficient, portable, and cost‐effective mechanism for reproducing patient posture without the use of ionizing radiation. Preliminary estimates of registration accuracy indicate clinical viability and form the foundation for further development and clinical testing.

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“…To help with the alignment task, the surgeon could furthermore choose between four different shaders. The shaders were adapted from Gomez at al 26 and included an opaque shader, a transparent shader, a wireframe shader, and the Fresnel shader which rendered areas of strong curvature in the object, and an outline shader which rendered the object outline ( Fig. 4 ).…”

Section: Methodsmentioning

confidence: 99%

Augmented Reality for Retrosigmoid Craniotomy Planning

Leuze

Neves

Martin-Gomez

et al. 2021

J Neurol Surg B Skull Base

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While medical imaging data have traditionally been viewed on two-dimensional (2D) displays, augmented reality (AR) allows physicians to project the medical imaging data on patient's bodies to locate important anatomy. We present a surgical AR application to plan the retrosigmoid craniotomy, a standard approach to access the posterior fossa and the internal auditory canal. As a simple and accurate alternative to surface landmarks and conventional surgical navigation systems, our AR application augments the surgeon's vision to guide the optimal location of cortical bone removal. In this work, two surgeons performed a retrosigmoid approach 14 times on eight cadaver heads. In each case, the surgeon manually aligned a computed tomography (CT)-derived virtual rendering of the sigmoid sinus on the real cadaveric heads using a see-through AR display, allowing the surgeon to plan and perform the craniotomy accordingly. Postprocedure CT scans were acquired to assess the accuracy of the retrosigmoid craniotomies with respect to their intended location relative to the dural sinuses. The two surgeons had a mean margin of davg = 0.6 ± 4.7 mm and davg = 3.7 ± 2.3 mm between the osteotomy border and the dural sinuses over all their cases, respectively, and only positive margins for 12 of the 14 cases. The intended surgical approach to the internal auditory canal was successfully achieved in all cases using the proposed method, and the relatively small and consistent margins suggest that our system has the potential to be a valuable tool to facilitate planning a variety of similar skull-base procedures.

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Visualization Techniques for Precise Alignment in VR: A Comparative Study

Cited by 28 publications

References 15 publications

Validation of virtual reality orbitometry bridges digital and physical worlds

Validation of virtual reality orbitometry bridges digital and physical worlds

Patient posture correction and alignment using mixed reality visualization and the HoloLens 2

Augmented Reality for Retrosigmoid Craniotomy Planning

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