Comparing Different Registration and Visualization Methods for Navigated Common Femoral Arterial Access-A Phantom Model Study Using Mixed Reality.

Mixed reality (MxR) enables the projection of virtual three-dimensional objects into the user's field of view via a head-mounted display (HMD). This phantom model study investigated three different workflows for navigated common femoral arterial (CFA) access and compared it to a conventional sonography-guided technique as a control. A total of 160 punctures were performed by 10 operators (5 experts and 5 non-experts). A successful CFA puncture was defined as puncture at the mid-level of the femoral head with the needle tip at the central lumen line in a 0° coronary insertion angle and a 45° sagittal insertion angle. Positional errors were quantified using cone-beam computed tomography following each attempt. Mixed effect modeling revealed that the distance from the needle entry site to the mid-level of the femoral head is significantly shorter for navigated techniques than for the control group. This highlights that three-dimensional visualization could increase the safety of CFA access. However, the navigated workflows are infrastructurally complex with limited usability and are associated with relevant cost. While navigated techniques appear as a potentially beneficial adjunct for safe CFA access, future developments should aim to reduce workflow complexity, avoid optical tracking systems, and offer more pragmatic methods of registration and instrument tracking.

A New Method for Common Femoral Arterial Access Using a Mixed Reality-Assisted Technique on a Phantom Model.

PURPOSE: The purpose of this study was to investigate the technical feasibility and usability of a mixed reality (MiR)-assisted common femoral arterial (CFA) access technique using a sonography-assisted registration method. MATERIALS AND METHODS: A total of 60 CFA punctures were performed on a phantom model by 2 observers. Thirty punctures were performed using MiR (MiR group) and 30 punctures were performed using a conventional sonography-guided access procedure (control group). In the MiR group, a virtual object was created based on a computed tomography (CT) angiography scan of the model and registered to the physical patient in an MiR environment utilizing a software prototype that allowed registration based on a sonography scan. Positional error assessment encompassed 4 measurements using cone beam CT scans: (1) distance of the needle tip to the centerline, (2) distance of the needle entry site from the mid-level of the ostium of the profound femoral artery, (3) angle of entry of the needle in coronal, and (4) sagittal planes. Technical success rates as well as positional errors were compared between both groups. In addition, the usability of the system was assessed according to the system usability scale (SUS). RESULTS: Technical success was 96.7% and 100% in the MiR and control groups, respectively. The median distance between the needle tip and the centerline was 3.0 (interquartile range [IQR]: 2.0-4.6) in the MiR group and 3.2 mm (IQR: 2.3-3.9) (p=0.63) in the control group. Similarly, the median distance from the needle entry site to the mid-level of the ostium of the profound femoral artery was 3.0 mm (IQR: 2.0-5.0) in the MiR group and 4.5 mm (IQR: 2.0-7.8) (p=0.18) in the control group. The median coronal angles of needle entry were 7.5° (IQR: 6-11) and 6° (IQR: 2-12) (p=0.13), and the median sagittal angles were 50° (IQR: 47-51) and 51° (IQR: 50-55) (p<0.01) in the MiR and control groups, respectively. The mean SUS score provided by both observers was 51.3. CONCLUSION: The feasibility of an MiR-assisted CFA access technique could be demonstrated on a phantom model. Further studies are needed to investigate the technique beyond phantom model experiments and in different anatomical settings. CLINICAL IMPACT: This study demonstrates the technical feasibility of a Mixed-Reality-assisted common femoral arterial access procedure on a phantom model. The positional accuracy was comparable to a conventional sonography-guided technique. However, there are several limitations that need to be resolved prior to potential implementation into clinical practice. Further studies are needed to investigate its performance beyond phantom model experiments and the prototypical application requires further technical refinement to increase its usability.

"Mixed Reality" in patient education prior to abdominal aortic aneurysm repair.

Background: To investigate the usability of Mixed-Reality (MR) during patient education in patients scheduled for abdominal aortic aneurysm (AAA) repair. Patients and methods: Consecutive patients scheduled for elective AAA repair were block-randomized in either the Mixed-Reality group (MR group) or the conventional group (control group). Patients of both groups were educated about open and endovascular repair of their respective AAA. The MR group was educated using a head-mounted display (HMD) demonstrating a three-dimensional virtual reconstruction of the respective patient's vascular anatomy. The control group was educated using a conventional two-dimensional monitor to display the patient's vasculature. Outcomes were informational gain as well as patient satisfaction with the educational process. (DRKS-ID: DRKS00025174). Results: 50 patients were included with 25 patients in either group. Both groups demonstrated improvements in scores in the Informational Gain Questionnaire (IGQ) when comparing pre- and post-education scores. (MR group: 6.5 points (±1.8) versus 7.9 points (±1.5); Control group: 6.2 points (±1.8) versus 7.6 points (±1.6); p<0.01) There was no significant difference between the MR group and the control group either in informational gain (MR group: 1.4±1.8; Control group: 1.4±1.8; p=0.5) nor in patient satisfaction scores (MR group: mean 18.3 of maximum 21 points (±3.7); Control group: mean 17 of 21 points (±3.6); p=0.1) Multiple regression revealed no correlation between the use of MR and informational gain or patient satisfaction. Usability of the system was rated high, and patients' subjective assessment of MR was positive. Conclusions: The use of MR in patient education of AAA patients scheduled for elective repair is feasible. While patients reported positively on the use of MR in education, similar levels of informational gain and patient satisfaction can be achieved with MR and conventional methods.

Mixed reality for the assessment of aortoiliac anatomy in patients with abdominal aortic aneurysm prior to open and endovascular repair: Feasibility and interobserver agreement.

OBJECTIVES: The objective is to evaluate the feasibility and interobserver agreement of a Mixed Reality Viewer (MRV) in the assessment of aortoiliac vascular anatomy of abdominal aortic aneurysm (AAA) patients. METHODS: Fifty preoperative computed tomography angiographies (CTAs) of AAA patients were included. CTAs were assessed in a mixed reality (MR) environment with respect to aortoiliac anatomy according to a standardized protocol by two experienced observers (Mixed Reality Viewer, MRV, Brainlab AG, Germany). Additionally, all CTAs were independently assessed applying the same protocol by the same observers using a conventional DICOM viewer on a two-dimensional screen with multi-planar reconstructions (Conventional viewer, CV, GE Centricity PACS RA1000 Workstation, GE, United States). The protocol included four sets of items: calcification, dilatation, patency, and tortuosity as well as the number of lumbar and renal arteries. Interobserver agreement (IA, Cohen's Kappa, κ) was calculated for every item set. RESULTS: All CTAs could successfully be displayed in the MRV (100%). The MRV demonstrated equal or better IA in the assessment of anterior and posterior calcification (κMRV: 0.68 and 0.61, κCV: 0.33 and 0.45, respectively) as well as tortuosity (κMRV: 0.60, κCV: 0.48) and dilatation (κMRV: 0.68, κCV: 0.67). The CV demonstrated better IA in the assessment of patency (κMRV: 0.74, κCV: 0.93). The CV also identified significantly more lumbar arteries (CV: 379, MRV: 239, p < 0.01). CONCLUSIONS: The MRV is a feasible imaging viewing technology in clinical routine. Future efforts should aim at improving hologram quality and enabling accurate registration of the hologram with the physical patient.

[Mixed Reality in Vascular Surgery - a Scoping Review]. / Mixed Reality in der Gefäßchirurgie ­ ein Scoping Review.

BACKGROUND: "Mixed reality" (MR) allows the projection of virtual objects into the user's field of view through a head-mounted display (HMD). In the interventional and surgical treatment of vascular diseases MR applications could be of future benefit. The following scoping review aims to provide orientation on the current application of the aforementioned technologies in the field of vascular surgery and to define research goals for the future. METHODS: A systematic literature search was performed in PubMed (MEDLINE) using the search terms "aorta", "intervention", "endovascular intervention", "vascular surgery", "aneurysm", "endovascular", "vascular access", each in combination with "mixed reality" or "augmented reality". The search was performed according to PRISMA (Preferred Reporting Items for Systematic reviews and Meta-Analyses) guidelines for scoping reviews. RESULTS: From 547 references 8 relevant studies were identified. The search results could be classified into two categories: (1) MR aimed at information management and improving periprocedural ergonomics (n = 3) and (2) MR aimed at intraoperative navigation (n = 5). The registration of the physical patient with the virtual object and the tracking of instruments in the MR environment for intraoperative navigation is currently the focus of scientific interest and could be demonstrated on phantom and animal models with technical success. However, the methods presented so far are associated with high infrastructural costs and important limitations. CONCLUSION: The use of MR in the field of vascular surgery is promising. For the future, alternative, pragmatic registration methods with appropriate quantification of the positional error should be aimed at. The developed software and hardware solutions should be adapted to the requirements of vascular surgery. Electromagnetic instrument tracking appears to be a useful complementary technology for the implementation of MR-assisted navigation.

Mixed-Reality-Assisted Puncture of the Common Femoral Artery in a Phantom Model.

Percutaneous femoral arterial access is daily practice in a variety of medical specialties and enables physicians worldwide to perform endovascular interventions. The reported incidence of percutaneous femoral arterial access complications is 3-18% and often results from suboptimal puncture location due to insufficient visualization of the target vessel. The purpose of this proof-of-concept study was to evaluate the feasibility and the positional error of a mixed-reality (MR)-assisted puncture of the common femoral artery in a phantom model using a commercially available navigation system. In total, 15 MR-assisted punctures were performed. Cone-beam computed tomography angiography (CTA) was used following each puncture to allow quantification of positional error of needle placements in the axial and sagittal planes. Technical success was achieved in 14/15 cases (93.3%) with a median axial positional error of 1.0 mm (IQR 1.3) and a median sagittal positional error of 1.1 mm (IQR 1.6). The median duration of the registration process and needle insertion was 2 min (IQR 1.0). MR-assisted puncture of the common femoral artery is feasible with acceptable positional errors in a phantom model. Future studies should aim to measure and reduce the positional error resulting from MR registration.

Spatial stratification of various Lyme disease spirochetes in a Central European site.

To determine whether the genospecies composition of Lyme disease spirochetes is spatially stratified, we collected questing Ixodes ricinus ticks in neighboring plots where rodents, birds, and lizards were present as reservoir host and compared the prevalence of various genospecies. The overall prevalence of spirochetes in questing ticks varied across the study site. Borrelia lusitaniae appeared to infect adult ticks in one plot at the same frequency as did Borrelia afzelii in the other plots. The relative density of questing nymphal and adult ticks varied profoundly. Where lizards were exceedingly abundant, these vertebrates seemed to constitute the dominant host for nymphal ticks, contributing the majority of infected adult ticks. Because lizards support solely B. lusitaniae and appear to exclude other genospecies, their narrow genospecies association results in predominance of B. lusitaniae in sites where lizards are abundant, while limiting its spread to the host's habitat range. To the extent that Central European B. lusitaniae strains are nonpathogenic, the presence of numerous lizards should locally decrease risk of infection for people. Evaluation of regional risk of infection by Lyme disease spirochetes should take the spatial effect of hosts into consideration, which stratify the distribution of specifically infected ticks on a small scale.