Direct Visual Feedback Research Articles

Diaphragm Tracking System That Superimposes Planned Diaphragm Contours on Kilovolt Cine Images During Multiple Breath-Hold Volumetric Modulated Arc Therapy for Abdominal Tumors.

We recently published a phantom validation of our diaphragm tracking system, DiaTrak, on an Elekta linear accelerator with an integrated cone-beam computed tomography (CBCT) unit for multiple breath-hold volumetric modulated arc therapy of abdominal tumors, where the diaphragm position was compared between digitally reconstructed radiography (DRR) and kilovolt (kV) projection streaming images by template matching. In the present report, the visual feedback of the diaphragm position was added to the reported system. DICOM-RT diaphragm contour data were additionally exported from a treatment planning system to the DiaTrak PC. Following phantom localization by registering the CBCT to the planning CT images, a projected diaphragm contour was overlaid on each DRR image, whereas another two projected diaphragm contours were superimposed on each kV projection cine image every 180 ms after shifting ±5 mm (set as breath-hold tolerance) in the craniocaudal direction during gantry rotation. It was visually confirmed that the projected diaphragm surface was observed within the two contour lines on the kV cine window. The diaphragm registration errors of the localized phantom were also calculated based on image cross-correlation between the DRR and the projection cine images every 180 ms. It was found that the mean diaphragm registration error was -0.29 mm with a standard deviation of 0.32 mm during the gantry rotation. In conclusion, a new interface for the 5 mm tolerance check was proposed to provide direct visual feedback, thereby giving a sense of assurance to the attending radiotherapy technologists. The calculated diaphragm registration errors were relatively small compared to the tolerance of 5 mm, and therefore it is considered clinically acceptable.

Understanding the Interaction of Transcranial Direct Current Stimulation and Visual Feedback During an Ankle Movement Task.

Transcranial direct current stimulation (tDCS) has been demonstrated to facilitate motor performance in healthy individuals; however, results are variable. The neuromodulatory effects of tDCS during visuomotor tasks may be influenced by extrinsic visual feedback. However, this interaction between tDCS and visual feedback has not been explored for the lower limb. Hence, our objective was to explore if tDCS over the primary lower limb motor cortex differentially facilitates motor performance based on the availability of visual feedback. Twenty-two neurotypical adults performed ankle plantarflexion and dorsiflexion movements while tracking a sinusoidal target. Spatiotemporal, spatial, and temporal error were calculated between the ankle position and target. Participants attended two sessions, a week apart, with (Stim) and without (No-Stim) anodal tDCS. Sessions were divided into two blocks containing randomized visual feedback conditions: full, no, and blindfold. During Stim sessions, the first block included the application of tDCS to the lower limb M1. Spatiotemporal and spatial error increased as feedback faded (p < .001). A two-way repeated-measures analysis of variance showed a significant interaction between tDCS and visual feedback (p < .05) on spatiotemporal error. Post hoc analyses revealed a significant improvement in spatiotemporal error when visual feedback was absent (p < .01). Spatial and temporal errors were not significantly affected by stimulation or visual feedback. Our results suggest that tDCS enhances spatiotemporal ankle motor performance only when visual feedback is not available. These findings indicate that visual feedback may play an important role in demonstrating the effectiveness of tDCS.

One-Insertion Stereotactic Brain Biopsy Using In Vivo Optical Guidance-A Case Study.

Stereotactic neurosurgical brain biopsies are afflicted with risks of inconclusive results and hemorrhage. Such complications can necessitate repeated trajectories and prolong surgical time. To develop and introduce a 1-insertion stereotactic biopsy kit with direct intraoperative optical feedback and to evaluate its applicability in 3 clinical cases. An in-house forward-looking probe with optical fibers was designed to fit the outer cannula of a side-cutting biopsy kit. A small aperture was made at the tip of the outer cannula and the edges aligned with the optical probe inside. Stereotactic biopsies were performed using the Leksell Stereotactic System. Optical signals were measured in millimeter steps along the preplanned trajectory during the insertion. At the region with the highest 5-aminolevulinic acid (5-ALA)-induced fluorescence, the probe was replaced by the inner cannula, and tissue samples were taken. The waiting time for pathology diagnosis was noted. Measurements took 5 to 10 minutes, and the surgeon received direct visual feedback of intraoperative 5-ALA fluorescence, microcirculation, and tissue gray-whiteness. The 5-ALA fluorescence corroborated with the pathological findings which had waiting times of 45, 50, and 75 minutes. Because only 1 trajectory was required and the patient could be prepared for the end of surgery immediately after sampling, this shortened the total surgical time. A 1-insertion stereotactic biopsy procedure with real-time optical guidance has been presented and successfully evaluated in 3 clinical cases. The method can be modified for frameless navigation and thus has great potential to improve safety and diagnostic yield for both frameless and frame-based neurosurgical biopsy procedures.

Diarylethene Photoswitches and 3D Printing to Fabricate Rewearable Colorimetric UV Sensors for Sun Protection

AbstractDespite education campaigns linking sun overexposure and skin cancer, it remains one of the leading preventable cancer diagnoses. Skin cancer risk is correlated with overexposure to UV light in sunlight and can be prevented by avoiding exposure. While sun protection can be achieved using sunscreen and clothing, people must be made aware of their risk to facilitate behavior change. Herein, new rewearable UV sensors which overcome the single‐use limitations of other products are presented. These sensors utilize diarylethene photoswitches, which develop a colored appearance upon exposure to UV and are reset to colorless by green light (&lt;10 min). These photoswitches are incorporated into a range of materials, enabling the use of advanced manufacturing to develop highly desirable consumer products. 3D stereolithographic printing is used to prototype sensors, with complex geometries and appealing aesthetics, that can be worn by users. The UV sensitivity of these devices is tuned by incorporating chromophores, meeting the needs of diverse skin types. The colorimetric response allows for direct visual feedback to the user, or quantification using photography, allowing for dosimetry of UV exposure. These new reusable devices aim to reduce people's exposure to UV, while reducing the waste generated by single‐use devices.

S2876 To the Duodenum, and Beyond! Using the BougieCap for Duodenal Stricture Dilation

Introduction: Benign duodenal strictures are typically caused by peptic ulcer disease, caustic ingestion, surgical anastomoses, or inflammatory bowel disease. Treatment of benign strictures usually involves endoscopic dilation using through-the-scope (TTS) balloon dilators with or without fluoroscopy. TTS balloon dilators allow visualization during dilation, but they do not provide haptic feedback. The BougieCap dilator is a newer device that attaches to the endoscope and allows direct visual and haptic feedback during dilation. While it is generally used for dilation of esophageal strictures, this report describes its use for dilation of a benign duodenal stricture. Case Description/Methods: A 75-year-old male with stage IV non-small cell lung cancer on immunotherapy was found to have biliary dilation on imaging. He subsequently underwent endoscopic ultrasound which incidentally revealed a duodenal stricture at the junction of the first and second portions of the duodenum. The stricture was unable to be traversed with the linear echoendoscope or an adult upper endoscope. TTS balloon dilation from 8 to 12 mm was performed, however, the adult upper endoscope was still unable to traverse the stricture. Biopsies of the stricture were obtained and were negative for malignancy and gastric biopsies did not reveal any evidence of Helicobacter pylori infection. Approximately 4 months later, the patient developed progressive nausea and vomiting. Upper endoscopy again showed the duodenal stricture which was unable to be traversed. The decision was made to use the BougieCap device for dilation. The stricture was then sequentially dilated from 10 to 12 mm using the BougieCap with direct visualization of mucosal disruption during dilation as expected (Figure). The adult upper endoscope was then able to traverse the stricture easily. There were no procedural complications or adverse effects and the patient reported improvement in his symptoms. Discussion: Benign duodenal strictures are typically treated with endoscopic dilation using TTS balloon dilators, although this method is limited by the lack of haptic feedback or complete visualization in some cases. In this case, TTS balloon dilation was ineffective for initial stricture dilation, thus the BougieCap was used for more precise dilation under direct visualization. While the BougieCap is generally used for esophageal stricture dilation, it may also serve as a safe and effective method to dilate refractory benign duodenal strictures.Figure 1.: Endoscopic image of BougieCap dilation of the duodenal stricture.

Teaching Pronunciation with Direct Visual Articulatory Feedback: Pedagogical Considerations for the Use of Ultrasound in the Classroom

Teaching Pronunciation with Direct Visual Articulatory Feedback: Pedagogical Considerations for the Use of Ultrasound in the Classroom

Controllable Shrinking Fabrication of Solid-State Nanopores.

Nanopores have attracted widespread attention in DNA sequencing and protein or biomarker detection, owning to the single-molecule-scale detection accuracy. Despite the most use of naturally biological nanopores before, solid-state nanopores are widely developed with strong robustness, controllable sizes and geometries, a wide range of materials available, as well as flexible manufacturing. Therefore, various techniques typically based on focused ion beam or electron beam have been explored to drill nanopores directly on free-standing nanofilms. To further reduce and sculpt the pore size and shape for nano or sub-nano space-time sensing precision, various controllable shrinking technologies have been employed. Correspondingly, high-energy-beam-induced contraction with direct visual feedback represents the most widely used. The ability to change the pore diameter was attributed to surface tension induced original material migration into the nanopore center or new material deposition on the nanopore surface. This paper reviews typical solid-state nanopore shrinkage technologies, based on the careful summary of their principles and characteristics in particularly size and morphology changes. Furthermore, the advantages and disadvantages of different methods have also been compared completely. Finally, this review concludes with an optimistic outlook on the future of solid-state nanopores.

15. Utilization of Augmented Reality Smart Glasses for the Provision of Remote Surgical Training in the Resource-Constrained Setting

Background: Surgical mission trips constitute an important strategy by which the global surgery campaign addresses inequities in surgical disease worldwide. Travel restrictions related to the COVID-19 pandemic, however, impose a challenging limit on the reach and impact of surgical mission work. In this study, we demonstrate the utility of a remote surgical mentorship program equipped with cutting-edge augmented reality (AR) technology for sustaining global surgery capacity building efforts within the constraints of the COVID-19 pandemic. Methods: Our remote surgical training program connects mentor and mentee surgeons via an AR-enabled digital headset and integrated smartphone application. The Vuzix® Smart Glasses system allows mentee surgeons to transmit a point-of-view livestream of activity in the operating room while receiving direct audio and visual feedback from their remote mentor in realtime. To facilitate their engagement, mentor and mentee surgeons interact using an integrated smartphone application that enables case scheduling, clinical documentation, and performance evaluation. Performance is assessed on the basis of three validated assessment tools that are well-established in the surgical education literature: the Objective Structured Assessment of Technical Skills, the Self-Confidence Scale, and the Student Evaluation of Educational Quality Survey. This survey is administered via the mobile application to both mentor and mentee surgeons at the time of their onboarding as well as after every subsequent three-month training quarter for the duration of the year-long program. Results: To date, 83 mentor and mentee surgeons across 33 countries and 6 continents are enrolled and actively participating in our remote training program. Baseline survey data suggest a mentee surgeon cohort that stands to benefit greatly from inclusion in our training program. A majority of mentee surgeons report incomplete knowledge and anxiety in association with their specialty prior to initiating training. Conclusion: The COVID-19 pandemic has created an urgent need for sustainable remote surgical capacity building strategies. Our remote surgical training program powered by AR-enabled telecommunication and smartphone technology constitutes a promising solution towards this end.

Skin-inspired electrochemical tactility and luminescence

Animal skin is deformable, yet capable of consistently sensing external stimuli (mechanical, thermal, chemical) without morphological and functional deterioration. This high deformability and signal stability are ensured because the receptors and the signal transmission systems are based on the electrochemical change in the embedded cells. Further, in the skin of various nocturnal animals and deep-sea creatures, electrochemical changes triggered by mechanical stimuli lead to bioluminescence, which can be effective or direct visual feedback that responses to environmental stress in the biological system. In this regard, recently, researches to artificially imitate electrochemical mechanisms of tactile sensation and luminescence in the skin have made remarkable advances in the field of electronic skin (e-skin). This perspective article introduces recent pivot advances in the ion-based tactile sensors and electrochemiluminescent skins, and suggests the technological challenges, then the article ends with perspectives to the skin-inspired ionic artificial devices.

3D-printed Handheld Models Do Not Improve Recognition of Specific Characteristics and Patterns of Three-part and Four-part Proximal Humerus Fractures.

Reliably recognizing the overall pattern and specific characteristics of proximal humerus fractures may aid in surgical decision-making. With conventional onscreen imaging modalities, there is considerable and undesired interobserver variability, even when observers receive training in the application of the classification systems used. It is unclear whether three-dimensional (3D) models, which now can be fabricated with desktop printers at relatively little cost, can decrease interobserver variability in fracture classification. Do 3D-printed handheld models of proximal humerus fractures improve agreement among residents and attending surgeons regarding (1) specific fracture characteristics and (2) patterns according to the Neer and Hertel classification systems? Plain radiographs, as well as two-dimensional (2D) and 3D CT images, were collected from 20 patients (aged 18 years or older) who sustained a three-part or four-part proximal humerus fracture treated at a Level I trauma center between 2015 and 2019. The included images were chosen to comprise images from patients whose fractures were considered as difficult-to-classify, displaced fractures. Consequently, the images were assessed for eight fracture characteristics and categorized according to the Neer and Hertel classifications by four orthopaedic residents and four attending orthopaedic surgeons during two separate sessions. In the first session, the assessment was performed with conventional onscreen imaging (radiographs and 2D and 3D CT images). In the second session, 3D-printed handheld models were used for assessment, while onscreen imaging was also available. Although proximal humerus classifications such as the Neer classification have, in the past, been shown to have low interobserver reliability, we theorized that by receiving direct tactile and visual feedback from 3D-printed handheld fracture models, clinicians would be able to recognize the complex 3D aspects of classification systems reliably. Interobserver agreement was determined with the multirater Fleiss kappa and scored according to the categorical rating by Landis and Koch. To determine whether there was a difference between the two sessions, we calculated the delta (difference in the) kappa value with 95% confidence intervals and a two-tailed p value. Post hoc power analysis revealed that with the current sample size, a delta kappa value of 0.40 could be detected with 80% power at alpha = 0.05. Using 3D-printed models in addition to conventional imaging did not improve interobserver agreement of the following fracture characteristics: more than 2 mm medial hinge displacement, more than 8 mm metaphyseal extension, surgical neck fracture, anatomic neck fracture, displacement of the humeral head, more than 10 mm lesser tuberosity displacement, and more than 10 mm greater tuberosity displacement. Agreement regarding the presence of a humeral head-splitting fracture was improved but only to a level that was insufficient for clinical or scientific use (fair to substantial, delta kappa = 0.33 [95% CI 0.02 to 0.64]). Assessing 3D-printed handheld models adjunct to onscreen conventional imaging did not improve the interobserver agreement for pattern recognition according to Neer (delta kappa = 0.02 [95% CI -0.11 to 0.07]) and Hertel (delta kappa = 0.01 [95% CI -0.11 to 0.08]). There were no differences between residents and attending surgeons in terms of whether 3D models helped them classify the fractures, but there were few differences to identify fracture characteristics. However, none of the identified differences improved to almost perfect agreement (kappa value above 0.80), so even those few differences are unlikely to be clinically useful. Using 3D-printed handheld fracture models in addition to conventional onscreen imaging of three-part and four-part proximal humerus fractures does not improve agreement among residents and attending surgeons on specific fracture characteristics and patterns. Therefore, we do not recommend that clinicians expend the time and costs needed to create these models if the goal is to classify or describe patients' fracture characteristics or pattern, since doing so is unlikely to improve clinicians' abilities to select treatment or estimate prognosis. Level III, diagnostic study.

Visuomotor integration deficits are common to familial and sporadic preclinical Alzheimer's disease.

We investigated whether subtle visuomotor deficits were detectable in familial and sporadic preclinical Alzheimer’s disease. A circle-tracing task—with direct and indirect visual feedback, and dual-task subtraction—was completed by 31 individuals at 50% risk of familial Alzheimer’s disease (19 presymptomatic mutation carriers; 12 non-carriers) and 390 cognitively normal older adults (members of the British 1946 Birth Cohort, all born during the same week; age range at assessment = 69–71 years), who also underwent β-amyloid-PET/MRI to derive amyloid status (positive/negative), whole-brain volume and white matter hyperintensity volume. We compared preclinical Alzheimer’s groups against controls cross-sectionally (mutation carriers versus non-carriers; amyloid-positive versus amyloid-negative) on speed and accuracy of circle-tracing and subtraction. Mutation carriers (mean 7 years before expected onset) and amyloid-positive older adults traced disproportionately less accurately than controls when visual feedback was indirect, and were slower at dual-task subtraction. In the older adults, the same pattern of associations was found when considering amyloid burden as a continuous variable (Standardized Uptake Value Ratio). The effect of amyloid was independent of white matter hyperintensity and brain volumes, which themselves were associated with different aspects of performance: greater white matter hyperintensity volume was also associated with disproportionately poorer tracing accuracy when visual feedback was indirect, whereas larger brain volume was associated with faster tracing and faster subtraction. Mutation carriers also showed evidence of poorer tracing accuracy when visual feedback was direct. This study provides the first evidence of visuomotor integration deficits common to familial and sporadic preclinical Alzheimer’s disease, which may precede the onset of clinical symptoms by several years.

Controllable fabrication of solid state nanopores array by electron beam shrinking

Electron beam shrinking is a technique for manufacturing solid-state nanopores with direct visual feedback for better control. The electron beam in scanning electron microscopy (SEM) offers the high-resolution geometry information of nanostructure during the nanopore manufacturing processes. However, the mechanism of electron beam shrinkage is still unclear, which hinders the fabrication of solid-state nanopores array as well as their applications. In this study, Si3N4 nanopores were used as examples to explore the mechanism of electron beam shrinking. The morphology and composition characterization of the Si3N4 nanopores before and after shrinking revealed that the deposition of hydrocarbons dominates the shrinking process, accompanied by some decomposition of Si3N4. Based on this model, the controlled shrinking of nanopores was achieved, which were assembled into solid state nanopores array. The size of the nanopores can be accurately tuned by adjusting the electron beam accelerating voltage, beam current, and magnification. Under the optimal conditions, the smallest diameter of nanopore of 5.3 nm and the fastest shrinkage rate of 2.51 nm/s were obtained. Meanwhile, solid-state nanopores array, including an axisymmetric nanopore array structure, were also created for detecting translocated AuNPs-DNA through the shrunken nanopores. This study demonstrated a facile technique for fine control of the shape and size of nanopores with designed array patterns, which have great applications in producing nanogap electrodes, complex nanostructure, and surface modification or nanostructure repairing on different materials with desired geometries.

Direct tumor visual feedback during free breathing in 0.35T MRgRT.

To present a tumor motion control system during free breathing using direct tumor visual feedback to patients in 0.35 T magnetic resonance‐guided radiotherapy (MRgRT). We present direct tumor visualization to patients by projecting real‐time cine MR images on an MR‐compatible display system inside a 0.35 T MRgRT bore. The direct tumor visualization included anatomical images with a target contour and an auto‐segmented gating contour. In addition, a beam‐status sign was added for patient guidance. The feasibility was investigated with a six‐patient clinical evaluation of the system in terms of tumor motion range and beam‐on time. Seven patients without visual guidance were used for comparison. Positions of the tumor and the auto‐segmented gating contour from the cine MR images were used in probability analysis to evaluate tumor motion control. In addition, beam‐on time was recorded to assess the efficacy of the visual feedback system. The direct tumor visualization system was developed and implemented in our clinic. The target contour extended 3 mm outside of the gating contour for 33.6 ± 24.9% of the time without visual guidance, and 37.2 ± 26.4% of the time with visual guidance. The average maximum motion outside of the gating contour was 14.4 ± 11.1 mm without and 13.0 ± 7.9 mm with visual guidance. Beam‐on time as a percentage was 43.9 ± 15.3% without visual guidance, and 48.0 ± 21.2% with visual guidance, but was not significantly different (P = 0.34). We demonstrated the clinical feasibility and potential benefits of presenting direct tumor visual feedback to patients in MRgRT. The visual feedback allows patients to visualize and attempt to minimize tumor motion in free breathing. The proposed system and associated clinical workflow can be easily adapted for any type of MRgRT.

The benefits of a Bayesian analysis for the characterization of magnetic nanoparticles

Magnetic nanoparticles offer a unique potential for various biomedical applications, but prior to commercial usage a standardized characterization of their structural and magnetic properties is required. For a thorough characterization, the combination of conventional magnetometry and advanced scattering techniques has shown great potential. In the present work, we characterize a powder sample of high-quality iron oxide nanoparticles that are surrounded with a homogeneous thick silica shell by DC magnetometry and magnetic small-angle neutron scattering (SANS). To retrieve the particle parameters such as their size distribution and saturation magnetization from the data, we apply standard model fits of individual data sets as well as global fits of multiple curves, including a combination of the magnetometry and SANS measurements. We show that by combining a standard least-squares fit with a subsequent Bayesian approach for the data refinement, the probability distributions of the model parameters and their cross correlations can be readily extracted, which enables a direct visual feedback regarding the quality of the fit. This prevents an overfitting of data in case of highly correlated parameters and renders the Bayesian method as an ideal component for a standardized data analysis of magnetic nanoparticle samples.

Cathodal Cerebellar tDCS Combined with Visual Feedback Improves Balance Control

Balance control is essential to maintain a stable body position and to prevent falls. The aim of this study was to determine whether balance control could be improved by using cerebellar transcranial direct current stimulation (tDCS) and visual feedback in a combined approach. A total of 90 healthy volunteers were randomly assigned to six groups defined by the delivery of tDCS (cathodal or anodal or sham) and the provision or not of visual feedback on balance during the acquisition phase. tDCS was delivered over the cerebellar hemisphere ipsilateral to the dominant leg for 20 min at 2 mA during a unipedal stance task. Body sway (i.e., ankle angle and hip position) was measured as an overall maximal unit in anteroposterior and mediolateral direction, together with participant rating of perception of stability, before (baseline), during (acquisition), and after (final) the intervention. We found a reduction in body sway during the acquisition session when visual feedback alone was provided. When the visual feedback was removed (final session), however, body sway increased above baseline. Differently, the reduction in overall maximal body sway was maintained during the final session when the delivery of cathodal tDCS and visual feedback was combined. These findings suggest that cathodal tDCS may support the short-term maintenance of the positive effects of visual feedback on balance and provide the basis for a new approach to optimize balance control, with potential translational implications for the elderly and patients with impaired posture control.

Influence of visual biofeedback and inherent stability on trunk postural control

BackgroundFor individuals who never achieve independent standing, rehabilitation is focused on trunk posture and balance control. Visual biofeedback has the potential to augment sitting balance training, however previous work in this area has been limited to standing. Research questionTo what extent do different types of visual biofeedback influence trunk sway in sitting? MethodsTwelve healthy young adults sat on an articulating bench. During ‘sway referencing’ trials, the bench tilted up and down in proportion to trunk sway in the frontal plane. This paradigm increased difficulty of the balance task and required participants to rely on visual and vestibular cues. Participants were provided different visual biofeedback through a rotating needle-gage display. Trials lasted 165 s, were ordered randomly, and included either direct feedback (needle rotated in proportion to body sway), inverted feedback (needle rotated in the opposite direction of sway), time delayed feedback (0.5 s), random feedback, eyes closed, or control (eyes open with screen off). To explore the impact of inherent stability, trials were repeated with and without external trunk support. ResultsBody sway depended on feedback type. Specifically, direct and inverted feedback reduced root-mean-squared (RMS) sway the most, time delayed feedback had a smaller effect, and random visual feedback increased participants’ RMS sway compared to control. Frequency domain analyses demonstrated direct and inverted visual feedback reduced sway amplitude at the lower frequencies while having minimal effect on (or increasing) sway amplitude at higher frequencies. SignificanceThis study extends previous work by showing that visual biofeedback can have powerful effects on sitting balance, even with external support. Results from the different types of feedback conditions further our understanding of how the brain interprets visual biofeedback. Frequency-based results were similar to previous studies using different modalities and suggest participants interpret biofeedback through sensory addition as opposed to sensory substitution.

Muscle strength is a major determinant of the blood pressure response to isometric stress testing: the Asklepios population study.

Maximal handgrip strength is a strong predictor of cardiovascular mortality in economically and socioculturally diverse countries, yet the main determinants of cardiovascular response to change in afterload during handgrip are not well known. We examined the blood pressure (BP) responses during submaximal handgrip (at 25% of grip strength) and the determinants of grip strength. We studied 2215 participants from a population-based random sample without overt clinical disease (Asklepios Study; mean age 56.2 years). Handgrip testing was performed using a modified Jamar dynamometer with direct visual feedback. Simultaneously, a validated finger plethysmographic device measured continuous BP and heart rate. During handgrip, SBP and DBP rose by, respectively, 20 ± 13 and 10 ± 6 mmHg. These changes were normally distributed and consistently higher in men. The main independent determinants of mean arterial pressure response during handgrip were: grip strength (F = 191.4; P < 0.001), baseline pulse pressure (F = 32.0; P < 0.001), height (F = 16.4; P < 0.001) and age (F = 12.8; P < 0.001). Grip strength was associated with muscle mass, better metabolic health, but also with higher baseline DBP. There was a significant graded increase in maximum pressure achieved and in the magnitude of pressure change during handgrip with increasing BP categories (P for trend <0.001). The population BP response to handgrip is variable and its predominant determinant turned out to be grip strength itself, which should be accounted for in future analyses. Higher baseline BP, even within the normotensive range, acted as an independent and graded predictor of BP increase during handgrip.

1836 The Bougie Cap: A Novel Device for Treatment of Esophageal Strictures

INTRODUCTION: Treatment of high cervical esophageal strictures can be technically challenging. Placement of endoscopic balloons across the stricture may not be feasible due to their proximal location. Serial dilation with the use of Savary-Gilliard dilators is a well-established method for treatment of these strictures. However, this technique does not allow for direct optical feedback during dilation. We present a case of benign cervical esophageal stricture treated with a novel method utilizing the BougieCap (Ovesco Endoscopy AG). CASE DESCRIPTION/METHODS: A 62-year-old male presented with dysphagia. He had a prior history of peptic stricture at the gastroesophageal junction, treated with multiple balloon dilations that was complicated by an esophageal perforation. Patient underwent an emergent thoracotomy, esophagectomy, and gastric pull-up with placement of a feeding jejunostomy. Four months after surgery, he noted recurrence of dysphagia, with food getting lodged in the area below his throat and upper chest. Barium swallow revealed a tight stricture at the anastomosis that narrowed the lumen down to 5 mm in size. Upper endoscopy confirmed a stricture located 18 cm from the incisors. Using an endoscopic BougieCap the stricture was dilated serially from 7 to 12 mm in size with good results. Expected mucosal disruption was identified at the end of the procedure. On follow up, patient reported significant improvement in his symptoms without any complications. DISCUSSION: Use of Savary-Gilliard Dilators for stricture dilation provides only haptic control and often requires the use of fluoroscopic guidance. Our case highlights the use of a novel device - the BougieCap - for treatment of esophageal strictures which allows for direct visual control and optical feedback during the procedure. Ability to visualize the tension on the tissue while passing the stricture with the cap avoids overstretching and may help reduce the risk of complications, allowing for a more effective procedure. Moreover, by eliminating the need to switch instruments, the use of BougieCap can reduce procedure times. Additional prospective studies with a larger number of patients and long-term follow-up are necessary to determine its safety and long-term efficacy.

CIGuide: in situ augmented reality laser guidance

Purpose A robotic intraoperative laser guidance system with hybrid optic-magnetic tracking for skull base surgery is presented. It provides in situ augmented reality guidance for microscopic interventions at the lateral skull base with minimal mental and workload overhead on surgeons working without a monitor and dedicated pointing tools.Methods Three components were developed: a registration tool (Rhinospider), a hybrid magneto-optic-tracked robotic feedback control scheme and a modified robotic end-effector. Rhinospider optimizes registration of patient and preoperative CT data by excluding user errors in fiducial localization with magnetic tracking. The hybrid controller uses an integrated microscope HD camera for robotic control with a guidance beam shining on a dual plate setup avoiding magnetic field distortions. A robotic needle insertion platform (iSYS Medizintechnik GmbH, Austria) was modified to position a laser beam with high precision in a surgical scene compatible to microscopic surgery.Results System accuracy was evaluated quantitatively at various target positions on a phantom. The accuracy found is 1.2 mm ± 0.5 mm. Errors are primarily due to magnetic tracking. This application accuracy seems suitable for most surgical procedures in the lateral skull base. The system was evaluated quantitatively during a mastoidectomy of an anatomic head specimen and was judged useful by the surgeon.Conclusion A hybrid robotic laser guidance system with direct visual feedback is proposed for navigated drilling and intraoperative structure localization. The system provides visual cues directly on/in the patient anatomy, reducing the standard limitations of AR visualizations like depth perception. The custom- built end-effector for the iSYS robot is transparent to using surgical microscopes and compatible with magnetic tracking. The cadaver experiment showed that guidance was accurate and that the end-effector is unobtrusive. This laser guidance has potential to aid the surgeon in finding the optimal mastoidectomy trajectory in more difficult interventions.

Controlled size reduction and its underlying mechanism to form solid-state nanopores via electron beam induced carbon deposition

Solid-state nanopores have drawn considerable attention for their potential applications in DNA sequencing and nanoparticle analysis. However, fabrication of nanopores, especially those of diameter below 30 nm, requires sophisticated techniques. Here, a versatile method to controllably reduce the diameter of prefabricated large-size pores down to sub-30 nm without greatly increasing the effective pore depth from the original membrane thickness is shown. This method exploits carbon deposition achieved via hydrocarbon evaporation, induced by an incident beam of electrons, and subsequent dissociation of hydrocarbon to solid carbon deposits. The carbon deposition employs a conventional scanning electron microscope equipped with direct visual feedback, along with a stable hydrocarbon source nearby the sample. This work systematically studies how electron beam accelerating voltage, imaging magnification, initial pore size and membrane composition affect the process of pore size reduction. Secondary electrons generated in the membrane material are confirmed to be the main cause of the dissociation of hydrocarbon. Thicker carbon deposited on one side than on the other of the membrane results in an asymmetric nanopore shape and a rectifying ionic transport. A physico-phenomenological model combined with Monte Carlo simulations is proposed to account for the observed carbon deposition behaviors.