Augmented Reality Registration System for Visualization of Skull Landmarks.

BACKGROUND: Augmented reality (AR) is an emerging technology in neurosurgery with the potential to become a strategic tool in the delivery of care and education for trainees. Advances in technology have demonstrated promising use for improving visualization and spatial awareness of critical neuroanatomic structures. In this report, we employ a novel AR registration system for the visualization and targeting of skull landmarks. METHODS: A markerless AR system was used to register 3-dimensional reconstructions of suture lines onto the head via a head-mounted display. Participants were required to identify craniometric points with and without AR assistance. Targeting error was measured as the Euclidian distance between the user-defined location and the true craniometric point on the subjects' heads. RESULTS: All participants successfully registered 3-dimensional reconstructions onto the subjects' heads. Targeting accuracy was significantly improved with AR (3.59 ± 1.29 mm). Across all target points, AR increased accuracy by an average of 19.96 ± 3.80 mm. Posttest surveys revealed that participants felt the technology increased their confidence in identifying landmarks (4.6/5) and that the technology will be useful for clinical care (4.2/5). CONCLUSIONS: While several areas of improvement and innovation can further enhance the use of AR in neurosurgery, this report demonstrates the feasibility of a markerless headset-based AR system for visualizing craniometric points on the skull. As the technology continues to advance, AR is expected to play an increasingly significant role in neurosurgery, transforming how surgeries are performed and improving patient care.

Morphometric Study of the Posterior Fossa: Identification of Practical Parameters for Tailored Selection of Surgical Routes to the Petroclival Region.

Introduction The petroclival region is an integral part of the skull base. It can harbor different pathologies and provides access to the petroclival junction and cerebellopontine angle. We present the results of the morphometric analysis of the posterior fossa and a prediction model to enable skull base surgeons to choose an optimal surgical corridor considering patient's bony anatomy. Methods Ninety patients (14 to assess interobserver reliability) with temporal bone computed tomography were selected. Exclusion criteria included patients <18 years of age, radiographic evidence of trauma, infection, or previous surgery. The images were analyzed using OsiriX MD (Bernex, Switzerland). We recorded clival length, vertical angle, and surface area, and petroclival angle, petrous apex, and translabyrinthine corridors volume. Results The average age was 49.5 years (55%) for males. The mean clival length and surface areas were 44.2 mm (standard deviation [SD] ± 4.1) and 8.1 cm 2 (SD ± 1.3). The mean petrous apex and translabyrinthine corridors volumes were 2.2 cm 3 (SD ± 0.6) and 10.1 cm 3 (SD ± 3.7). The mean petroclival angle at the internal auditory canal (IAC) was 154.9 degrees (SD ± 9). The clival length correlated positively with clival surface area (rho = 0.6, p <0.05), petrous apex volume (rho = 0.3, p < 0.05), and translabyrinthine volume (rho = 0.3, p < 0.05). Conclusion The petroclival region is complex and with high variability of surgical significance. The use of preoperative measurements of the clival length and petroclival angle as part of surgical planning that could help the surgeon to choose an optimal surgical corridor by overcoming the anatomical variability elements.

Structural Differences in Meibum From Donors After Hematopoietic Stem Cell Transplantations.

PURPOSE: Meibum is considered to be a key component of tears that serve to protect the eye, and conformational changes in meibum have not been studied extensively within the population of patients who had hematopoietic stem cell transplantation (HSCT). The aim of this study was to determine possible lipid conformational changes in the meibum of patients who had HSCT. METHODS: Participants who had HSCT were randomly sampled for this prospective comparative study. Control participants did not have dry eye or had not undergone allogeneic or autologous stem cell transplantation. Fourier-transform infrared spectroscopy was used to measure meibum phase transition. RESULTS: Meibum was collected from both eyes of 36 donors without dry eye (Mc) and from 22 patients who had undergone HSCT (MHSCT). There were no significant differences between the phase transition parameters based on gender or race. The following were the significant differences (P < 0.0001) between the parameters for Mc compared with MHSCT : lipid order (% trans) at 33.4°C increased from 40 (1) to 54 (2), cooperativity decreased from 7.9 (0.4) to 5.4 (0.3), the phase transition temperature (C) increased from 30.3 (0.4) to 34.2 (0.9), and the magnitude of the phase transition (cm) increased from 4.0 (0.1) to 4.7 (0.5) (standard error of the mean). CONCLUSIONS: Conformational and thermodynamic differences were observed between Mc and MHSCT. The changes observed in the lipid conformation of meibum from patients receiving HSCTs suggest that meibum composition changes after stem cell transplantation, and clinicians should consider treating the meibomian glands to improve the ocular surface.

Role of dietary fatty acids in liver injury caused by vinyl chloride metabolites in mice.

BACKGROUND: Vinyl chloride (VC) causes toxicant-associated steatohepatitis at high exposure levels. Recent work by this group suggests that underlying liver disease may predispose the liver to VC hepatotoxicity at lower exposure levels. The most common form of underlying liver disease in the developed world is non-alcoholic fatty liver disease (NAFLD). It is well-known that the type of dietary fat can play an important role in the pathogenesis of NAFLD. However, whether the combination of dietary fat and VC/metabolites promotes liver injury has not been studied. METHODS: Mice were administered chloroethanol (CE - a VC metabolite) or vehicle once, 10weeks after being fed diets rich in saturated fatty acids (HSFA), rich in poly-unsaturated fatty acids (HPUFA), or the respective low-fat control diets (LSFA; LPUFA). RESULTS: In control mice, chloroethanol caused no detectable liver injury, as determined by plasma transaminases and histologic indices of damage. In HSFA-fed mice, chloroethanol increased HSFA-induced liver damage, steatosis, infiltrating inflammatory cells, hepatic expression of proinflammatory cytokines, and markers of endoplasmic reticulum (ER) stress. Moreover, markers of inflammasome activation were increased, while markers of inflammasome inhibition were downregulated. In mice fed HPUFA all of these effects were significantly attenuated. CONCLUSIONS: Chloroethanol promotes inflammatory liver injury caused by dietary fatty acids. This effect is far more exacerbated with saturated fat, versus poly-unsaturated fat; and strongly correlates with a robust activation of the NLRP3 inflammasome in the saturated fed animals only. Taken together these data support the hypothesis that environmental toxicant exposure can exacerbate the severity of NAFLD/NASH.