Perpendicular Trajectory Research Articles

Augmented reality guidance improves accuracy of orthopedic drilling procedures

In several orthopedic procedures, the accurate use of surgical power tools is critical to avoid damage to surrounding tissues. As such, various guidance techniques and safety measures were developed. Augmented reality (AR) guidance shows promise but requires validation. We evaluated a new approach using an inside-out infrared tracking solution for the HoloLens to compensate for its limited tracking performance. Eighteen participants with varying levels of experience (student, trainee, expert) each drilled twelve trajectories (six perpendicular, six oblique) in equidimensional wooden logs. Three different techniques were evaluated: freehand drilling; proprioception-guided drilling towards the contralateral index finger; and AR-guided drilling using a tracked drill and a virtual overlay of the log with predefined guidance vectors. The angular errors between planned and performed trajectories were compared using a mixed-design ANOVA. The results demonstrated that guidance technique (p < 0.001) and drilling direction (p < 0.001) significantly affected drilling accuracy, while experience (p = 0.75) did not. AR outperformed both other techniques, particularly for oblique trajectories (p < 0.001). For perpendicular trajectories, it only outperformed proprioception guidance (p = 0.04). Target plots revealed an important scatter perpendicular to the longitudinal axis of the log during freehand and proprioception-guided drilling, especially for oblique trajectories. This inaccuracy disappeared during AR-guided drilling. As such, we were able to conclude that AR guidance using inside-out infrared tracking reduced angular uncertainty during directional drilling, resulting in improved drilling accuracy. This improvement was particularly noticeable for complex trajectories and angles. The benefits of AR guidance were observed across all experience levels, highlighting its potential for orthopedic applications. We believe this study opens the way for the methodical evaluation of AR guidance in specific orthopedic use cases.

Development of an adjustable patient-specific rigid guide to improve the accuracy of external ventricular catheter placement.

The most common method for external ventricular drain (EVD) placement is the freehand approach, which has reported inaccuracy rates of 12.3%-44.9%, especially in the case of altered ventricular anatomy. Current assistive devices require added time or equipment or do not account for shifted ventricles. To improve the accuracy of emergent EVD placement in the setting of altered ventricular anatomy, the authors designed a patient-specific EVD (PS-EVD) guide. The PS-EVD guide has a tripod base and a series of differently angled inserts that lock in place at multiple rotational positions, allowing for numerous insertion angles. For testing, the authors designed a 3D-printed phantom skull with a gelatin brain analog containing ventricles simulating normal and altered ventricular anatomy. Low-resolution CT scans of the phantom were used to calculate the insertion angle in relation to the standard perpendicular entry. The corresponding insert at the correct rotational position within the base unit was positioned over the entry point on the phantom, and the catheter was inserted. Accuracy was evaluated with repeat CT scans. With normal ventricular anatomy, as well as abnormally shifted ventricles, proper use of the PS-EVD guide led to accurate catheter insertion into the ventricle in trials, as confirmed on coronal and sagittal CT images, including cases in which a perpendicular trajectory, such as with the Ghajar guide, was insufficient. The PS-EVD guide allows consistent and accurate EVD placement in phantom skulls with both normal and altered ventricular anatomy. Further trials comparing this device to the freehand approach are required.

B-Lift curves and involute curves in Lorentzian 3-space

The involute of a curve is often called the perpendicular trajectories of the tangent vectors of a unit speed curve. Furthermore, the B-Lift curve is the curve acquired by combining the endpoints of the binormal vectors of a unit speed curve. In this study, we investigate the correspondences between the Frenet vectors of a curve’s B-lift curve and its involute. We also give an illustration of a helix that resembles space in Lorentzian 3-space and show how to visualize these curves by deriving the B-Lift curve and its involute.

The TIGR triangle of the pineal region: a virtual reality anatomic study.

In this morphometric study, we describe the anatomy of the TIGR triangle, which is bordered by the tentorial surface of the cerebellum, the internal cerebral vein and vein of Galen complex, and the vein of Rosenthal. These structures define the window, or deep keyhole, to access the pineal region in non-midline supracerebellar infratentorial approaches. The posterior fossa anatomy of 16 patients was studied in virtual reality (VR), and the TIGR triangles were defined and measured with special attention on its angular orientation in the posterior fossa. The angular expanse of the posterior fossa was measured and recorded as the transverse-sigmoid junction (TSJ) angle. Because a perpendicular corridor through an anatomic aperture provides the best exposure, we studied the starting point along the TSJ angle that offers the best exposure of TIGR. In the 31 posterior fossa sides included in the study, the perpendicular trajectory through the TIGR triangle was on average 27.13° CI 95% (range: 5.97°-48.53°) from the midline. When comparing the SCIT variants, both the paramedian and lateral approaches provided near-perpendicular trajectory through the TIGR triangle in a majority of specimens. However, the modified paramedian approach, with starting point defined as TSJ angle/3, provided the most perpendicular path through the TIGR triangle. We studied the size, spatial orientation, and morphology of the TIGR triangle. Our data indicated that the best exposure of TIGR is through a modified paramedian SCIT approach, in which the starting point one third of the way from midline to the TSJ.

Assessment of surface irregularities created by controlled liquid droplet on the surface of stainless steel AISI 304L

Surfaces created by the erosive action of water droplets have not been sufficiently explored because of their stochastic structure, which depends on hydraulic parameters. This article details the complex analysis of surfaces created by the controlled distribution of water droplets on the surface of AISI 304L using an ultrasonically stimulated water jet. The traverse speed of the jet controlled the distribution of the water droplets. The surface topology was modified in an interleaved mode when the trajectories were parallel for all samples. Additionally, the second layer treated the other half of the preprepared samples with a perpendicular trajectory with respect to the parallel trajectory. The 3D surface reconstruction was performed using a noncontact MicroProf FRT measuring instrument. Several profile roughness parameters (Ra, Rz, Rv, Rp, Rsk, and Rku), areal surface roughness parameters (Sa, Sz, Sp, Sv, Ssk, Sku, Sdr, Sk, Spk, and Svk) and surface isotropy values were measured for the surfaces generated using variations in the traverse speed of the jet. The measurement results show a decreasing trend of surface roughness upon an increase in the traverse speed, and a better surface finish was also measured for the cross-hatch trajectory compared to the linear trajectory. The results also show that the generated surfaces have deeper valleys with truncated peaks, which are suitable for use in a wide range of technical and medical applications. This study shows the potential utilization of controlled liquid droplet impingement for surface preparation in various application domains.

Energy loss of charged particles in anisotropic 2D materials using the oscillator model

We apply the oscillator model to study the energy loss processes of external charged particles interacting with a 2D material characterized by an anisotropic conductivity tensor. We model the material as a monolayer of harmonic oscillators, with anisotropic electronic vibration modes. We focus on the cases of parallel and perpendicular trajectories of the external particle, and we obtain analytical expressions for the stopping power and total energy loss in terms of reduced variables. This allows us to analyze in detail the interaction and to adapt the model to the considered material using adequate values for the physical parameters involved.

Launching Plasmons in a Two-Dimensional Material Traversed by a Fast Charged Particle.

We use a dielectric-response formalism to compute the induced charge density and the induced potential in a conductive two-dimensional (2D) material, traversed by a charged particle that moves on a perpendicular trajectory with constant velocity. By analyzing the electric force on the material via the Maxwell stress tensor, we showed that the polarization of the material can be decomposed into a conservative part related to the dynamic image force, and a dissipative part describing the energy and momentum transfer to the material, which is ultimately responsible for launching the plasma oscillation waves in the material. After showing that the launching dynamics is fully determined by the Loss function of the material, we used a conductivity model suitable for the terahertz to the midinfrared frequency range, which includes both the intraband and interband electron transitions in the material, to compute the real-space and time animations of the propagating plasma waves in the plane of the material. Finally, we used a stationary phase analysis to show that the plasmon wave crests go into an overdamped regime at large propagation distances, which are comparable to the distances where retardation effects are expected to emerge due to hybridization of the plasmon dispersion with the light line at long wavelengths.

Volume-Based Radiofrequency Thermocoagulation for Pediatric Insulo-Opercular Epilepsy: A Feasibility Study.

Stereotactic ablation surgeries including radiofrequency thermocoagulation (RFTC) and laser interstitial thermal therapy are recent less invasive treatment methods for insular epilepsy. Volume-based RFTC after stereoelectroencephalography was first proposed by a French group as a more effective method for seizure relief in insular epilepsy patients than stereoelectroencephalography-guided RFTC. To describe the feasibility and technical details about volume-based RFTC in patients with insulo-opercular epilepsy. We successfully treated 3- and 6-year-old patients with medically refractory insulo-opercular epilepsy with volume-based RFTC, in which the target volume of coagulation was flexibly designed by combining multiple spherical models of 5-mm diameter which is smaller than reported previously. The insula was targeted by oblique trajectory from the frontoparietal area in one case, and the opercular cortex was targeted by perpendicular trajectories from the perisylvian cortex in the other case. The use of the small sphere model required more trajectories and manipulations but enabled more exhaustive coagulation of the epileptogenic zone, with 70% to 78% of the planned target volume coagulated without complications, and daily seizures disappeared after RFTC in both patients. Volume-based RFTC planned with small multiple sphere models may improve the completeness of lesioning for patients with insulo-opercular epilepsy. Careful planning is necessary to reduce the risks of vascular injuries.

Arthroscopic Patellar Osteochondral Transplantation

The undersurface location of the patellar articular cartilage presents unique challenges to osteochondral defect treatment. Current osteochondral grafting techniques and instrumentation require arthrotomy and patellar eversion to access the defect with the necessary perpendicular trajectory. We describe an all-arthroscopic patellar osteochondral grafting technique, with transpatellar retrograde reaming for recipient socket creation and graft fixation, to treat focal patellar cartilage defects.

Interaction of charged particles with a graphene monolayer modeled as a set of electronic oscillators

We assess the applicability of the oscillator model to evaluate the energy loss of a fast charged particle incident on graphene. We study the cases of a parallel and perpendicular trajectory of the particle. We focus on two frequency regimes for graphene’s electron response: the optical regime, which is dominated by two types of oscillators with non-dispersing frequencies in the ultraviolet regime, and the terahertz (THz) regime, which is dominated by a strongly dispersing sheet plasmon mode in doped graphene. In the latter regime, we invoke the kinematic resonance condition for a parallel trajectory, and we propose a method for averaging the energy loss for a perpendicular trajectory. We show that the oscillator model provides analytical expressions, which give results in generally good agreement with a dielectric-response approach to the same problem, even in the THz regime.

Subaxial Cervical Pedicular Screw Insertion via the Nonanatomic Axis: Technical Notes and Preliminary Clinical Report.

Retrospective study. To report the technical details of subaxial cervical pedicular screw insertion via the nonanatomic axis (nAA-CPS) and evaluate its clinical safety and accuracy. The nAA-CPS technique was performed in 21 patients. Preoperative and intraoperative management-related details are described, and a manipulation protocol is presented. Clinical outcomes were used to assess the safety and accuracy of screws was evaluated using postoperative computed tomography (CT) according to the pedicle perforation grading system, and the nonanatomic pedicle transverse angle (nPTA) and nonanatomic pedicle axis length (nPAL) were assessed based on pre- and postoperative CT images. According to "one constant entry point (EP) and two perpendicular trajectory angles" protocol, nAA-CPS was performed without much interference from the muscles. No intraoperative or postoperative neurovascular complications related to the technique were observed. Of the 112 inserted screws, 78 (69.64%) were assessed as grade 0, 24 (21.43%) as grade 1, 4 (3.57%) as grade 2 and 6 (5.36%) as grade 3. The overall rate of correct position (grades 0 and 1) was 91.07% (102/112), and the rate of malposition was 8.93% (10/112), including five screws implanted medially and the other five laterally. The nPTA was highly consistent on pre- and postoperative CT (P < .05), while postoperative nPAL was significantly shorter than preoperative nPAL (P > .05). Clinically, the accuracy and safety of nAA-CPS was similar to the traditional CPS technique. The protocol, derived from previous radiological studies and workshops, greatly helped standardize clinical manipulation; thus, nAA-CPS is a promising alternative to the traditional CPS.

Oscillator model applied to 2D materials: Energy loss of relativistic charged particles

In this work we present a fully relativistic formulation for the energy loss of an external charged particle interacting with a 2D material. We model this material as a monolayer of atoms represented by harmonic oscillators, with isotropic or anisotropic electronic vibration modes. We develop the model for a wide range of incident energies and considering both parallel and perpendicular trajectories.

Endoscopic Fenestration of Cavum Septum Pellucidum Cysts to the Third Ventricle: Technical Note.

Cavum septum pellucidum (CSP) and cavum vergae (CV) cysts are common incidental findings on imaging studies. However, they may rarely present with symptoms related to the obstruction of the foramen of Monro by the cyst leaflets. There is no consensus regarding the management of symptomatic CSP and CV cysts. We present an original transcavum interforniceal endoscopic fenestration technique. The step-by-step surgical procedure and two illustrative cases are presented. A 31-yr-old male and a 24-yr-old woman presented with symptomatic CSP and CV cysts. For both patients, neuronavigation was used to plan the procedure. An endoscope was introduced into the cyst through a right frontal burr-hole. After an examination of the endoscopic anatomy, a communication between the cyst and the third ventricle was performed using an endoscopic forceps. In both cases, directly after the fenestration, cerebrospinal fluid (CSF) passed through the communication, and the collapse of the cyst was appreciated. Symptoms were relieved in both patients, and neuropsychological assessment improved. Postoperative imaging showed a reduction in the cyst bulge, and patent foramen of Monro. Endoscopic fenestration of CSP and CV cysts to the third ventricle through an interforniceal navigated approach is a feasible and efficient surgical procedure. Theoretical advantages include a single tract through noneloquent brain, a perpendicular trajectory to the membrane for fenestration, and a large CSF space beyond the fenestration point.

The importance of the number of points, transect location and interpolation techniques in the analysis of bathymetric measurements

Determining the bathymetric properties of a river, lake or reservoir is important for many reasons because it identifies location of sections with sedimentation or erosion which indicate the key processes and biophysical habitat status. This study used observational data of a 5 km section of the Danube River (transformed into a reservoir after 1972) to determine the best GIS interpolation method and the optimal number of sampling points to get an accurate description of the riverbed. Nine interpolation methods were used to generate bathymetric maps of the Danube course, between km 955 and km 950, in the area of Iron Gates reservoir, using a variable number of points (n = 1943; n = 4328; n = 17139), obtained by single beam echo sounder. Six methods of deterministic interpolation have been used: Inverse Distance Weighting (IDW) – criteria automatically determined (CAD) and manually determined (MD); Local Polynomial Interpolation (LPI) – criteria automatically determined (CAD) and manually determined (MD); Radial Basis Function (RBF) – fully regularized spline CRS; Radial Basis Function RBF – spline with tension SWT, and three geo-statistics methods: Ordinary Kriging – OK, Simple Kriging – SK, Universal Kriging – UK. Cross-validation and bathymetric Digital Elevation Models (DEM s) analysis were used to evaluate the accuracy of the estimated data and maps. The two interpolation methods, Inverse Distance Weighting (IDW-MD) and Simple Kriging (SK), provide satisfactory results, even in the case of a small number of points (n = 1943). If the number of measured points grows and a section grid (perpendicular/longitudinal) is developed, the DEM s bathymetric accuracy improves significantly, especially in the case of complex morphology, even if the positive and negative forms of the bed lead to sudden changes in the measured values. The obtained results revealed differences between the interpolation methods used, particularly in the case of a small number of points measured per perpendicular trajectories, but by the addition of points on longitudinal paths, a significant improvement of the bathymetric maps is obtained.

A new technique of ultrasound guided percutaneous renal biopsy by perforated probe and perpendicular needle trajectory.

The percutaneous biopsy of native kidneys according to the classical methodology is performed under real time ultrasound guidance with the needle introduction along a trajectory of about 30°, aimed to the lower pole of the kidney. Recently, a variant of the classical technique has been introduced by which a perforated ultrasound probe is used to guide the needle along a perpendicular trajectory to the terminal section of the lower kidney pole where the front and back margins of the cortical kidney tissue join each other without renal sinus interposition so to offer to the needle a 3-4 cm thick cortical tissue front which allows to obtain a cortical tissue sample suitable for histological examination even with a single needle pass, while at the same time limiting the possibility of damaging the smaller kidney calices of the lower group whose lesion causes hematuria. In this paper, we present a large survey (50 patients) to compare to data from the literature obtained by using similar needle gauge and with a similar follow-up period after biopsy. The result of this comparison confirms the efficacy of this variant of the classical technique because in front of a statistically lower number of needle passes, it allowed to obtain 100% of samples suitable for histological analysis, in absence of major complications and with a statistically lower post-biopsy hemoglobin drop in comparison to that observed in a group of 44 patients biopsied with a greater number of needle passes, in the only study of the literature which is directly comparable to our study in relation to needle gauge and duration of monitoring.

Influential factors affecting black carbon trends at four sites of differing distance from a major highway in Las Vegas.

Elevated air pollution levels adjacent to major highways are an ongoing topic of public health concern worldwide. Black carbon (BC), a component of particulate matter (PM) emitted by diesel and gasoline vehicles, was measured continuously via a filter-based light absorption technique over ~ 16 months at four different stations positioned on a perpendicular trajectory to a major highway in Las Vegas, NV. During downwind conditions (winds from the west), BC at 20 m from the highway was 32 and 60% higher than concentrations at 100 and 300 m from the roadway, respectively. Overall highest roadside (20-m site) BC concentrations were observed during the time period of 4 a.m.-8 a.m. under low-speed variable winds (3.02 μg/m3) or downwind conditions (2.84 μg/m3). The 20-m site BC concentrations under downwind conditions are 85% higher on weekday periods compared to weekends during the time period of 4 a.m.-8 a.m. Whereas total traffic volume was higher on weekdays versus weekends and differed by approximately 3% on weekdays versus weekends, similarly, the detected heavy-duty fraction was higher on weekdays versus weekends and differed by approximately 21% on weekdays versus weekend. Low wind speeds predominated during early morning hours, leading to higher BC concentrations during early morning hours despite the maximum traffic volume occurring later in the day. No noticeable impact from the airport or nearby arterial roadways was observed, with the 300-m site remaining the lowest of the four-site network when winds were from the east. Multivariate linear regression analysis revealed that heavy-duty traffic volume, light-duty traffic volume, wind speed, weekday versus weekend, surface friction velocity, ambient temperature, and the background BC concentration were significant predictors of roadside BC concentrations. Comparison of BC and PM2.5 downwind concentration gradients indicates that the BC component contributes substantially to the PM2.5 increase in roadside environments. These results suggest that BC is an important indicator to assess the contribution of primary traffic emissions to near-road PM2.5 concentrations, providing opportunities to evaluate the feasibility and effectiveness of mitigation strategies.

Revisiting the rules for freehand ventriculostomy: a virtual reality analysis.

OBJECTIVE Frontal ventriculostomy is one of the most frequent and standardized procedures in neurosurgery. However, many first and subsequent punctures miss the target, and suboptimal placement or misplacement of the catheter is common. The authors therefore reexamined the landmarks and rules to determine the entry point and trajectory with the best hit rate (HtR). METHODS The authors randomly selected CT scans from their institution's DICOM pool that had been obtained in 50 patients with normal ventricular and skull anatomy and without ventricular puncture. Using a 5 × 5-cm frontal grid with 25 entry points referenced to the bregma, the authors examined trajectories 1) perpendicular to the skull, 2) toward classic facial landmarks in the coronal and sagittal planes, and 3) toward an idealized target in the middle of the ipsilateral anterior horn (ILAH). Three-dimensional virtual reality ventriculostomies were simulated for these entry points; trajectories and the HtRs were recorded, resulting in an investigation of 8000 different virtual procedures. RESULTS The best HtR for the ILAH was 86% for an ideal trajectory, 84% for a landmark trajectory, and 83% for a 90° trajectory, but only at specific entry points. The highest HtRs were found for entry points 3 or 4 cm lateral to the midline, but only in combination with a trajectory toward the contralateral canthus; and 1 or 2 cm lateral to the midline, but only paired with a trajectory toward the nasion. The same "pairing" exists for entry points and trajectories in the sagittal plane. For perpendicular (90°) trajectories, the best entry points were at 3-5 cm lateral to the midline and 3 cm anterior to the bregma, or 4 cm lateral to the midline and 2 cm anterior to the bregma. CONCLUSIONS Only a few entry points offer a chance of a greater than 80% rate of hitting the ILAH, and then only in combination with a specific trajectory. This "pairing" between entry point and trajectory was found both for landmark targeting and for perpendicular trajectories, with very limited variability. Surprisingly, the ipsilateral medial canthus, a commonly reported landmark, had low HtRs, and should not be recommended as a trajectory target.

Interdisciplinary endoscopic assisted surgery of a patient with a complete transorbital intracranial impalement through the dominant hemisphere

Transorbital injuries are common and represent about 24% to 45% of all penetrating head injuries in adults and children [1]. However, only <1% of the cases show a skullor brainpenetrating route with consecutive intracranial injuries [1, 2]. The direction and orbital entry route depends on the velocity of the impalement and the trajectory of the foreign body. In low-velocity injuries, the foreign body may be directed by the configuration of the orbital walls and enters most likely through the superior and inferior orbital fissures or the orbital canal [3]. In cases of higher-velocity impalements, the orbital wall may directly fracture following a perpendicular trajectory line. Here, we describe the first case in the literature of a complete impalement injury through the dominant hemisphere entering the inner orbital angle, fracturing the medial aspects of the skull base and leaving the skull contralaterally through the occipital bone, treated successfully in interdisciplinary cooperation via a combined transnasal–transcranial approach.

Visual error augmentation enhances learning in three dimensions

Because recent preliminary evidence points to the use of Error augmentation (EA) for motor learning enhancements, we visually enhanced deviations from a straight line path while subjects practiced a sensorimotor reversal task, similar to laparoscopic surgery. Our study asked 10 healthy subjects in two groups to perform targeted reaching in a simulated virtual reality environment, where the transformation of the hand position matrix was a complete reversal--rotated 180 degrees about an arbitrary axis (hence 2 of the 3 coordinates are reversed). Our data showed that after 500 practice trials, error-augmented-trained subjects reached the desired targets more quickly and with lower error (differences of 0.4 seconds and 0.5 cm Maximum Perpendicular Trajectory deviation) when compared to the control group. Furthermore, the manner in which subjects practiced was influenced by the error augmentation, resulting in more continuous motions for this group and smaller errors. Even with the extreme sensory discordance of a reversal, these data further support that distorted reality can promote more complete adaptation/learning when compared to regular training. Lastly, upon removing the flip all subjects quickly returned to baseline rapidly within 6 trials.

The presigmoid approach to anterolateral pontine cavernomas

Anterolateral cavernomas of the pons have been surgically removed via a variety of approaches, commonly retrosigmoid or transventricular. The goal in this study was to evaluate the presigmoid approach as an alternative. Clinical data were reviewed in 9 patients presenting with anterolateral pontine cavernomas between 1999 and 2007. All patients were treated via a presigmoid approach, which provided a nearly perpendicular trajectory to the anterolateral pons. The brainstem was entered through a "safe zone" between the trigeminal nerve and the facial/vestibulocochlear nerve complex. Complete resection was achieved in all cases. No patient experienced recurrent events during follow-up (1-24 months). The patients' modified Rankin Scale score improved within 1 year of surgery (1.7 ± 0.4) compared with baseline (2.6 ± 0.2; p < 0.05). Only one patient experienced a new deficit (decreased hearing), which was corrected with a hearing aid. The presigmoid approach is recommended for the resection of anterolateral pontine cavernomas. With this approach, the need for cerebellar retraction is nearly eliminated. The lateral "presigmoid" entry point creates a trajectory that allows complete resection of even deep lesions at this level, or anterior to the internal acoustic meatus.