Augmented Reality-Assisted Craniotomy for Parasagittal and Convexity En Plaque Meningiomas and Custom-Made Cranio-Plasty: A Preliminary Laboratory Report

Background: This report discusses the utility of a wearable augmented reality platform in neurosurgery for parasagittal and convexity en plaque meningiomas with bone flap removal and custom-made cranioplasty. Methods: A real patient with en plaque cranial vault meningioma with diffuse and extensive dural involvement, extracranial extension into the calvarium, and homogeneous contrast enhancement on gadolinium-enhanced T1-weighted MRI, was selected for this case study. A patient-specific manikin was designed starting with the segmentation of the patient’s preoperative MRI images to simulate a craniotomy procedure. Surgical planning was performed according to the segmented anatomy, and customized bone flaps were designed accordingly. During the surgical simulation stage, the VOSTARS head-mounted display was used to accurately display the planned craniotomy trajectory over the manikin skull. The precision of the craniotomy was assessed based on the evaluation of previously prepared custom-made bone flaps. Results: A bone flap with a radius 0.5 mm smaller than the radius of an ideal craniotomy fitted perfectly over the performed craniotomy, demonstrating an error of less than ±1 mm in the task execution. The results of this laboratory-based experiment suggest that the proposed augmented reality platform helps in simulating convexity en plaque meningioma resection and custom-made cranioplasty, as carefully planned in the preoperative phase. Conclusions: Augmented reality head-mounted displays have the potential to be a useful adjunct in tumor surgical resection, cranial vault lesion craniotomy and also skull base surgery, but more study with large series is needed

Head-Mounted Projector for Manual Precision Tasks: Performance Assessment

The growing interest in augmented reality applications has led to an in-depth look at the performance of head-mounted displays and their testing in numerous domains. Other devices for augmenting the real world with virtual information are presented less frequently and usually focus on the description of the device rather than on its performance analysis. This is the case of projected augmented reality, which, compared to head-worn AR displays, offers the advantages of being simultaneously accessible by multiple users whilst preserving user awareness of the environment and feeling of immersion. This work provides a general evaluation of a custom-made head-mounted projector for the aid of precision manual tasks through an experimental protocol designed for investigating spatial and temporal registration and their combination. The results of the tests show that the accuracy (0.6±0.1 mm of spatial registration error) and motion-to-photon latency (113±12 ms) make the proposed solution suitable for guiding precision tasks

Key Ergonomics Requirements and Possible Mechanical Solutions for Augmented Reality Head-Mounted Displays in Surgery

In the context of a European project, we identified over 150 requirements for the development of an augmented reality (AR) head-mounted display (HMD) specifically tailored to support highly challenging manual surgical procedures. The requirements were established by surgeons from different specialties and by industrial players working in the surgical field who had strong commitments to the exploitation of this technology. Some of these requirements were specific to the project, while others can be seen as key requirements for the implementation of an efficient and reliable AR headset to be used to support manual activities in the peripersonal space. The aim of this work is to describe these ergonomic requirements that impact the mechanical design of the HMDs, the possible innovative solutions to these requirements, and how these solutions have been used to implement the AR headset in surgical navigation. We also report the results of a preliminary qualitative evaluation of the AR headset by three surgeons

Key Ergonomics Requirements and Possible Mechanical Solutions for Augmented Reality Head-Mounted Displays in Surgery

In the context of a European project, we identified over 150 requirements for the development of an augmented reality (AR) head-mounted display (HMD) specifically tailored to support highly challenging manual surgical procedures. The requirements were established by surgeons from different specialties and by industrial players working in the surgical field who had strong commitments to the exploitation of this technology. Some of these requirements were specific to the project, while others can be seen as key requirements for the implementation of an efficient and reliable AR headset to be used to support manual activities in the peripersonal space. The aim of this work is to describe these ergonomic requirements that impact the mechanical design of the HMDs, the possible innovative solutions to these requirements, and how these solutions have been used to implement the AR headset in surgical navigation. We also report the results of a preliminary qualitative evaluation of the AR headset by three surgeons

Architecture of a Hybrid Video/Optical See-through Head-Mounted Display-Based Augmented Reality Surgical Navigation Platform

In the context of image-guided surgery, augmented reality (AR) represents a ground-breaking enticing improvement, mostly when paired with wearability in the case of open surgery. Commercially available AR head-mounted displays (HMDs), designed for general purposes, are increasingly used outside their indications to develop surgical guidance applications with the ambition to demonstrate the potential of AR in surgery. The applications proposed in the literature underline the hunger for AR-guidance in the surgical room together with the limitations that hinder commercial HMDs from being the answer to such a need. The medical domain demands specifically developed devices that address, together with ergonomics, the achievement of surgical accuracy objectives and compliance with medical device regulations. In the framework of an EU Horizon2020 project, a hybrid video and optical see-through augmented reality headset paired with a software architecture, both specifically designed to be seamlessly integrated into the surgical workflow, has been developed. In this paper, the overall architecture of the system is described. The developed AR HMD surgical navigation platform was positively tested on seven patients to aid the surgeon while performing Le Fort 1 osteotomy in cranio-maxillofacial surgery, demonstrating the value of the hybrid approach and the safety and usability of the navigation platform

Evaluation of a Wearable AR Platform for Guiding Complex Craniotomies in Neurosurgery

Today, neuronavigation is widely used in daily clinical routine to perform safe and efficient surgery. Augmented reality (AR) interfaces can provide anatomical models and preoperative planning contextually blended with the real surgical scenario, overcoming the limitations of traditional neuronavigators. This study aims to demonstrate the reliability of a new-concept AR headset in navigating complex craniotomies. Moreover, we aim to prove the efficacy of a patient-specific template-based methodology for fast, non-invasive, and fully automatic planning-to-patient registration. The AR platform navigation performance was assessed with an in-vitro study whose goal was twofold: to measure the real-to-virtual 3D target visualization error (TVE), and assess the navigation accuracy through a user study involving 10 subjects in tracing a complex craniotomy. The feasibility of the template-based registration was preliminarily tested on a volunteer. The TVE mean and standard deviation were 1.3 and 0.6 mm. The results of the user study, over 30 traced craniotomies, showed that 97% of the trajectory length was traced within an error margin of 1.5 mm, and 92% within a margin of 1 mm. The in-vivo test confirmed the feasibility and reliability of the patient-specific template for registration. The proposed AR headset allows ergonomic and intuitive fruition of preoperative planning, and it can represent a valid option to support neurosurgical tasks

Can Liquid Lenses Increase Depth of Field in Head Mounted Video See-Through Devices?

Wearable Video See-Through (VST) devices for Augmented Reality (AR) and for obtaining a Magnified View are taking hold in the medical and surgical fields. However, these devices are not yet usable in daily clinical practice, due to focusing problems and a limited depth of field. This study investigates the use of liquid-lens optics to create an autofocus system for wearable VST visors. The autofocus system is based on a Time of Flight (TOF) distance sensor and an active autofocus control system. The integrated autofocus system in the wearable VST viewers showed good potential in terms of providing rapid focus at various distances and a magnified view

A Case-Control Study on the Role of an Antiviral Treatment with Interferon and Ribavirin after Conventional Chemotherapy in Diffuse Large B-Cell Lymphomas with Hepatitis C Virus (HCV) InfectionBlood (ASH Annual Meeting Abstracts), Nov 2008; 112: 3054

Antiviral therapy (AVT) with interferon +/– ribavirin can induce neoplastic regression without chemotherapy (CT) in low-grade non-Hodgkin’s lymphomas (in particular, immunocytomas and nodal/extranodal marginal lymphomas) with associated HCV infection (HCV+). High grade, diffuse large B-cell non- Hodgkin’s lymphomas (DLBCL) are HCV+ in about 12% of cases in Italian population. These patients show peculiar clinical characteristics, such as older age, liver damage, presence of monoclonal gammopathy (often with no clinically relevant cryoglobulinemic and/or rheumatoid activity), increased rate of autoimmune disorders and extranodal localizations. Their clinical outcome, however, is generally considered not significantly different, in terms of response rate, progression free survival (PFS) and overall survival (OS), from that of subjects with HCV negative (HCV–) DLBCL when treated with standard or even high dose CT and if significant signs of liver dysfunction are absent. In the present study we aimed to determine the possible role of AVT, performed after a standard CT treatment, in HCV+ DLBCL. We evaluated 40 HCV+ DLBCL patients (male/female ratio 25/15; median age 63 years, range 39–71) who received AVT after first complete (27 patients) or partial (13 patients) remission was achieved by frontline standard CT. Classic or modified CHOP+/– rituximab regimens were generally employed. Twenty-two patients (55%) showed a higher (3–4) IPI score and twenty patients (50%) evidenced increased ALT/AST values. A favourable HCV genotype (type 2–3) and a low viral load ( 70/kg. A small number of patients received interferon-alpha with or without ribavirin. The planned duration of AVT ranged from 3 to 12 months and was modulated according to viral genotype and molecular response (genotype 2: 3 months, if viral clearance obtained after 1 month, otherwise continued for 6 months; other genotypes: 3 months of treatment with following suspension if viral clearance not obtained, otherwise continued for 12 months). Sequential treatment (CT followed by AVT) was generally well tolerated. Six patients, however, interrupted AVT before three months, mainly because of general malaise or myelotoxicity. HCV clearance was obtained in 22 patients (55%). A case-control comparison was made with a similar cohort of 40 HCV+ DBLCL patients, who did not receive AVT, matched for age, sex, IPI score, liver function, type of prior CT and response, viral load and HCV genotype. Three-year PFS was not statistically different between the two groups (52.5% vs 57.5%, p n.s.), while a trend in favour of AVT treated patients was observed in terms of three-year OS (67.5%% vs 57.5%, p=0.055). A weak correlation between viral clearance and longer OS duration was also observed (p=0.048). Interestingly, during the follow up period, severe hepatic failure developed in 5 (12.5%) out of patients who had not received AVT and in only one (2.5%) of those treated with AVT. Seventy-nine percent of relapsed patients not treated with AVT received salvage CT, compared to 100% of AVT treated patients. Our currently available data indicate that a sequential treatment with CT followed by AVT is feasible in HCV+ DLBCL and may induce complete virus clearance in more than half of these patients. We hypothesize that a better control of the viral infection, rather than a direct or indirect antineoplastic activity of AVT, could have positive effects on the clinical outcome of patients with HCV+ DLBCL and, possibly, on their survival, i.e. by allowing the possibility of further salvage therapies and reducing that of hepatic failure