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Mastoidectomy involves drilling the temporal bone while avoiding the facial nerve, semicircular canals, sigmoid sinus, and tegmen. Optical topographic imaging (OTI) is a novel registration technique that allows rapid registration with minimal navigational error. To date, no studies have examined the use of OTI in skull-base procedures.In this cadaveric study, 8 mastoidectomies were performed in 2 groups-4 free-hand (FH) and 4 OTI-assisted mastoidectomies. Registration accuracy for OTI navigation was quantified with root mean square (RMS) and target registration error (TRE). Procedural time, percent of mastoid resected, and the proximity of the mastoidectomy cavity to critical structures were determined.The average RMS and TRE associated with OTI-based registration were 1.44 mm (±0.83 mm) and 2.17 mm (±0.89 mm), respectively. The volume removed, expressed as a percentage of the total mastoid volume, was 37.5% (±10.2%) versus 31.2% (±2.3%), P = 0.31, for FH and OTI-assisted mastoidectomy. There were no statistically significant differences between FH and OTI-assisted mastoidectomies with respect to proximity to critical structures or procedural time.This work is the first examining the application of OTI neuronavigation in lateral skull-base procedures. This pilot study revealed the RMS and TRE for OTI-based navigation in the lateral skull base are 1.44 mm (±0.83 mm) and 2.17 mm (±0.89 mm), respectively. This pilot study demonstrates that an OTI-based system is sufficiently accurate and may address barriers to widespread adoption of navigation for lateral skull-base procedures.

Many biomimetic legged robots exist, but their leg designs appear to be arbitrarily chosen. Here, we examine the performance difference between a canine-inspired rear leg in its normal configuration versus the same leg in a transverse-mirrored configuration. A quadrupedal robot was built to test this hypothesis; the robot was successfully able to walk in with both rear-leg configurations. Successful telemetry of energy and localization data was also demonstrated. Both experimental and simulation results confirm that the transverse-mirrored configuration is faster and more efficient. In experiment the robot achieved speeds of up to 0.4 m/s versus 0.33 m/s, and specific resistances of 3.9 versus 5.1 in transverse and normal experiments, respectively. It is suggested here that the transverse-mirrored configuration, which engages the knee spring more than the normal configuration, be used in designs which require higher speeds and greater efficiencies.

Repetitive transcranial magnetic stimulation (rTMS) is a non-invasive brain stimulation tool with potential for broad application in individuals with neuropsychiatric conditions. As in adults, most rTMS research in youth has focused on treatment-resistant depression. A limited number of rTMS studies have also been conducted in children and youth with primary diagnoses of Autism Spectrum Disorder (ASD), Attention-Deficit/Hyperactivity Disorder (ADHD) or Tourette's syndrome. Across the available rTMS literature, rTMS appears to be well tolerated with few adverse effects reported when applied to child and youth research samples. However, the potential efficacy of rTMS treatment for a variety of targets in children and youth remains unclear, due in part to limitations of the current literature, including studies using diverse protocols, potential for bias in existing clinical trial designs, variability in the research samples, and the use of heterogenous outcome measures. While rTMS is unlikely to take the place of more accessible treatments (e.g., psychopharmacological, psychosocial, psychotherapeutic), rTMS may provide a valuable alternative treatment option, particularly for those individuals where conventional treatments are inaccessible, poorly tolerated, or ineffective. A more robust body of well-designed, controlled trials, is needed in order to clarify rTMS treatment efficacy across relevant neuropsychiatric conditions, optimize treatment protocols, and meet the critical need for novel mental health interventions in children and youth.La Stimulation magnétique transcrânienne répétitive (SMTr) est un instrument de stimulation du cerveau non invasif qui a le potentiel d’une application élargie chez les personnes souffrant de conditions neuropsychiatriques. Comme chez les adultes, la majorité de la recherche sur la SMTr chez les jeunes a porté sur la dépression réfractaire au traitement. Un nombre limité d’études sur la SMTr ont aussi été menées chez les enfants et les jeunes ayant des diagnostics primaires du trouble du spectre de l’autisme (TSA), du trouble de déficit de l’attention avec hyperactivité (TDAH) ou du syndrome de la Tourette. Dans la littérature disponible sur la SMTr, celle-ci semble bien tolérée et peu d’effets indésirables sont signalés lorsqu’elle est appliquée aux enfants et aux jeunes des échantillons de recherche. Cependant, l’efficacité potentielle d’un traitement par SMTr pour une variété d’objectifs chez les enfants et les jeunes demeure imprécise, partiellement en raison des limitations de la littérature actuelle, notamment des études utilisant divers protocoles, le potentiel de biais dans les méthodes d’essais cliniques existants, la variabilité des échantillons de recherche, et l’usage de mesures de résultats hétérogènes. Même si la SMTr ne prendra probablement pas la place de traitements plus accessibles (p. ex., psychopharmacologiques, psychosociaux, psychothérapeutiques), la SMTr peut procurer une option de traitement parallèle valable, chez les personnes pour qui les traitements conventionnels sont inaccessible, mal tolérés ou inefficaces. Un ensemble plus robuste d’essais contrôlés mieux conçus est nécessaire afin de clarifier l’efficacité du traitement par SMTr dans toutes les conditions neuropsychiatriques, optimiser les protocoles de traitement et répondre au besoin critique de nouvelles interventions de santé mentale chez les enfants et les jeunes.

Bone cutting in surgery is currently done using un-intelligent tools that depend on the proficiency of the surgeon to prevent damage to underlying critical structures. As one can imagine, damage isn’t always prevented. Iatrogenic damage to dura and sub-dural neural structures during osteotomical procedures such as a craniotomy can result in increased patient morbidity. This dissertation proposes the development of a robot-guided laser osteotome (bone cutter) with the use of inline optical coherence tomography (OCT) to precisely control the cutting depth in real-time. The all-fiber system design integrates a high peak-power pulsed Yb-doped fiber laser (1064nm) coupled directly into the sample arm of a swept-source OCT system (λc = 1310nm) with a fourth-order power disparity between the OCT system and fiber laser. Sub-millimeter accuracy was achieved in percussion drilling of phantom and porcine bone. Through the use of optical topographic imaging (OTI), this work presents a novel method for the surgeon to identify arbitrary trajectories for desired cuts. A surgical pencil is used to demarcate cutting trajectories for the robot to follow directly onto the boney surface. OTI imaging combined with a novel algorithm developed through this work allows the penscribed line to be isolated and translated into spatial attitude information for the robot to guide the end effector-mounted laser along. Sub-millimeter trajectory following accuracy was achieved. This work also demonstrates the first use of OCT in continuous, real-time refocusing of the optical end-effector in order to maintain cut quality. The focus of the laser was able to be maintained within the Rayleigh length of the focused Gaussian beam for linear feed rates up to 1mm/s at a 45◦ surface incline. Finally, optimization of bone ablation is explored in this dissertation. The use of graphite as a high-absorption topical chromophore and the use of nitrogen as an assist gas in the form of a coaxial jet are both analyzed to determine how to achieve the highest etch rate in bone. The results in this dissertation show that the topical application of graphite was able to significantly reduce the mean and variance of etching performance; an improvement by at least two orders of magnitude in the time to 0.5mm etch depth is demonstrated. It is also demonstrated that etch rate during ablation can be optimized for coaxial nitrogen flow (30SCFH out of a nozzle with 3mm output diameter); higher and lower flow rates showed slower etch rates. It is hypothesized that a system such as the one developed in this dissertation will increase the precision of bone cutting, decrease the amount of time needed to make cuts into sensitive structures and also address certain issues of unsuccessful uptake of lasers in modern medicine.

Background: Robotics is currently being adopted across the spectrum of neurosurgery from deep brain stimulation to spine surgery instrumentation. Mastoidectomy is a cognitively demanding procedure that involves careful removal of bone around the critical structures of the temporal bone. Herein, we report a pilot study that serves as a proof of concept for real-time, multiparameter recording during mastoidectomy. Methods: This pilot study involved the iterative development of a platform for the real time recording of video, 3D position, velocity, acceleration, and force data during the performance of mastoidectomy using cadaveric specimens. Results: Across all 8 replicates, the average distance traveled by the drill tip in the x, y, and z axes was 39.88 mm (±11.98 mm), 38.52 mm (±8.24 mm), 31.40 mm (±7.89 mm), respectively. The overall average ranges for velocity and acceleration of the drill tip in the x axis were 412.81 mm/s (±91.12 mm/s) and 6383.05 mm/s2 (±941.05 mm/s2). The range of forces recorded was 8.52 N (±2.90 N), 40.94 N (±9.81 N), and 35.42 N (±11.06 N) in the x-, y-, and z-axis, respectively. Conclusions: This study represents a proof-of-concept that the mechanical parameters associated with surgeon-performed mastoidectomy can be recorded in real-time. This represents a crucial step in understanding the human drilling process which incorporates visual and haptic sensory input with experiential and explicit knowledge using fuzzy logic feedback. Ultimately, data collected using this methodology may provide the groundwork for the development of an algorithm for robotic mastoidectomy.

The development of improved Augmented Reality (AR) Head-Mounted Devices (HMDs) have led to increasing use cases for AR applications. In the case of surgery, an HMD can be used as an assistive tool to help surgeons operate. With a triplanar surgical navigation system as an industry standard, the use of an HMD can improve the surgeon’s comfort, and overall experience. An HMD can offer the surgeon a consistent flow of information in front of their eyes with medically relevant images, such as craniospinal computed tomography (CT) data that can be displayed as they operate. This paper aims to bring an HMD-based overlay framework that can be used in the operating room. With a combination of Android Studio, OpenCV, and OpenGL, an inside-out localization method with Aruco Markers is demonstrated. The framework estimates the head pose of the user and subsequently renders a patient specific CT scan that will be spatially anchored to the real world. The CT reconstruction can then be virtually superimposed onto the physical patient. The HMD’s (ODG R9) fisheye lens will also be used to enhance and enable a larger field of view for better object detection. This paper also introduces a “focus mode” that improves the localization accuracy. The framework will be evaluated in each of the 3-axes for translational and rotational movement error. It will be evaluated on the detection accuracy of different numbers of markers and at different distances. It will also be evaluated using an ultra-high definition (UHD) camera.

Intraoperative image-guided surgical navigation for craniospinal procedures has significantly improved accuracy by providing an avenue for the surgeon to visualize underlying internal structures corresponding to the exposed surface anatomy. Despite the obvious benefits of surgical navigation, surgeon adoption remains relatively low due to long setup and registration times, steep learning curves, and workflow disruptions. We introduce an experimental navigation system utilizing optical topographical imaging (OTI) to acquire the 3D surface anatomy of the surgical cavity, enabling visualization of internal structures relative to exposed surface anatomy from registered preoperative images. Our OTI approach includes near instantaneous and accurate optical measurement of >250,000 surface points, computed at >52,000 points-per-second for considerably faster patient registration than commercially available benchmark systems without compromising spatial accuracy. Our experience of 171 human craniospinal surgical procedures, demonstrated significant workflow improvement (41 s vs. 258 s and 794 s, p

Laser ablation of bone for the purposes of osteotomy is not as well understood as ablation of homogeneous, non-biological materials such as metals and plastics. Ignition times and etch rate can vary during ablation of cortical bone. In this study, we propose the use of two techniques to optimize bone ablation at 1064nm using a coaxial nitrogen jet as an assist gas and topical application of graphite as a highly absorbing chromophore. We show a two order of magnitude reduction in mean time to ignition and variance by using the graphite topical chromophore. We also show that an increase in volumetric flow rate of the assist gas jet does show an initial increase in etch rate, but increased pressure beyond a certain point shows decreased return. This study also demonstrates a 2(nd) order relationship between exposure time, volumetric flow rate of nitrogen, and etch rate of cortical bone. The results of this study can be used to optimize the performance of laser ablation systems for osteotomy. This is a companion study to an earlier one carried out by Wong et al. [Biomedical Opt. Express 6, 1 (2015)].

Planning osteotomies is a task that surgeons do as part of standard surgical workflow. This task, however, becomes more difficult and less intuitive when a robot is tasked with performing the osteotomy. In this study, we aim to provide a new method for surgeons to allow for highly intuitive trajectory planning, similar to the way an attending surgeon would instruct a junior. Planning an osteotomy, especially during a craniotomy, is performed intraoperatively using a sterile surgical pen or pencil directly on the exposed bone surface. This paper presents a new method for generating osteotomy trajectories for a multi-DOF robotic manipulator using the same method and relaying the penscribed cut path to the manipulator as a three-dimensional trajectory. The penscribed cut path is acquired using structured light imaging, and detection, segmentation, optimization and orientation generation of the Cartesian trajectory are done autonomously after minimal user input. A 7-DOF manipulator (KUKA IIWA) is able to follow fully penscribed trajectories with sub-millimeter accuracy in the target plane and perpendicular to it (0.46 mm and 0.36 mm absolute mean error, respectively). The robot is able to precisely follow cut paths drawn by the surgeon directly onto the exposed boney surface of the skull. We demonstrate through this study that current surgical workflow does not have to be drastically modified to introduce robotic technology in the operating room. We show that it is possible to guide a robot to perform an osteotomy in much the same way a senior surgeon would show a trainee by using a simple surgical pen or pencil.

This review provides an examination of contemporary neurosurgical robots and the developments that led to them. Improvements in localization, microsurgery and minimally invasive surgery have made robotic neurosurgery viable, as seen by the success of platforms such as the CyberKnife and neuromate. Neurosurgical robots can now perform specific surgical tasks such as skull-base drilling and craniotomies, as well as pedicle screw and cochlear electrode insertions. Growth trends in neurosurgical robotics are likely to continue but may be tempered by concerns over recent surgical robot recalls, commercially-driven surgeon training, and studies that show operational costs for surgical robotic procedures are often higher than traditional surgical methods. We point out that addressing performance issues related to navigation-related registration is an active area of research and will aid in improving overall robot neurosurgery performance and associated costs.

Biomimetic leg designs often appear to be arbitrarily chosen. To make a more objective choice regarding biomimetic leg configuration for small canine-inspired robots, we compare one hind leg to the same leg arranged in a different orientation, and show that the less biomimetic leg provides better performance. This differently-oriented leg design, which we call “transverse-mirrored” was more efficient and faster, both in simulation and experiment even though both leg configurations used the same passive and active components, rest angles, and monoarticular knee spring. In experiments the normal configuration had a maximum speed of 0.33 m·s−1 and a specific resistance of 5.1. Conversely, the less biomimetic transverse-mirrored configuration had a maximum speed of 0.4 m·s−1 and specific resistance of 3.9. Therefore the transverse-mirrored leg's best performance yields a 21% increase in speed and 24% decrease in specific resistance when compared to the best performance achieved in the normal biomimetic leg. The major underlying reason is that the knee spring engages more readily in the transverse-mirrored configuration, resulting in this faster and more efficient locomotion. The conclusion is that simply copying from nature does not lead to optimal performance and that insight into the role played by passive design components on natural locomotory dynamics is important.

Intracranial aneurysms affect a large number of individuals every year. Changes to hemodynamics are thought to be a crucial factor in the initial formation and enlargement of intracranial aneurysms. Previously, surgical clipping – an open an invasive procedure, was the standard of care. More recently, minimally invasive, catheter based therapies, specifically stenting and coiling, has been employed for treatment as it is less invasive and poses fewer overall risks. However, these treatments can further alter hemodynamic patterns of patients, affecting efficacy and prognosis. Doppler optical coherence tomography (DOCT) has shown to be useful for the evaluation of changes to hemodynamic patterns in various vascular pathologies, and intravascular DOCT may provide useful insight in the evaluation and changes to hemodynamic patterns before and during the treatment of aneurysms. In this study, we present preliminary results of DOCT imaging used in three patient-specific aneurysm phantoms located within the Circle of Willis both pre and post-treatment. These results are compared with computational fluid dynamics (CFD) simulations and high-speed camera imaging for further interpretation and validation of results.

When using surgical loupes and other head mounted surgical instruments for an extended period of time, many surgeons experience fatigue during the procedure, which results in a lot of pain in the neck and upper back. This is primarily due to the surgeon being subjected to long periods of uncomfortable positions, due to the design of the surgical instrument. To combat this issue, the surgeon is required to have a larger freedom of movement, which will reduce the fatigue in the affected areas, and allow the surgeon to comfortably operate for longer periods of time. The proposed design will incorporate an optical magnification system on a surgical head mounted display that will allow the surgeon to freely move their head and neck during the operation, while the optics are focused on the area of interest. The design will also include an infrared tracking system in order to acquire the field of view data, which will be used to control the optics. The reduction in neck pain will also be quantified using a clinically standardized numeric pain rating scale.

Endovascular Optical Coherence Tomography (OCT) has previously been used in both bench-top and clinical environments to produce vascular images, and can be helpful in characterizing, among other pathologies, plaque build-up and impedances to normal blood flow. The raw data produced can also be processed to yield high-resolution blood velocity information, but this computation is expensive and has previously only been available a posteriori using post-processing software. Real-time Doppler OCT (DOCT) imaging has been demonstrated before in the skin and eye, but this capability has not been available to vascular surgeons. Graphics Processing Units (GPUs) can be used to dramatically accelerate this type of distributed computation. In this paper we present a software package capable of real-time DOCT processing and circular image display using GPU acceleration designed to operate with catheter-based clinical OCT systems. This image data is overlayed onto structural images providing clinicians with live, high-resolution blood velocity information to complement anatomical data. Further, we validated flow data obtained in real time using a carotid flow phantom -- constructed using 3D structural OCT data -- and controlled flow from an external pump.

Inline optical coherence tomography (OCT) has proven to be an ideal feedback mechanism for real-time depth control of high-power ablation lasers. This has found use in industrial laser ablation applications, but it has the potential to truly change the use of laser ablation in medicine. Previously, we have presented a novel design that is able to place the OCT beam ( λc = 1310nm) coaxially with the beam of a high-powered fiber laser (λ = 1064nm, Pavg=10W, Ppeak = 1kW) without the need of a dichroic mirror on the output stage. This design successfully demonstrated real-time ablation depth feedback. Development of this design was continued and further refinements have been made to improve performance and form factor, with the ultimate goal being to create a compact, low-cost, high-precision laser scalpel to be used for various surgical osteotomies. We present an improved design that, unlike before, removes the need for bulk optics in the entire system other than a single collimator and doublet lens on the output. Strategies for dispersion mismatch compensation will be discussed to optimize resolution of OCT feedback. Initial results for depth-controlled ablation of tissue is presented.

Tissue removal using electrocautery is standard practice in neurosurgery since tissue can be cut and cauterized simultaneously. Thermally mediated tissue ablation using lasers can potentially possess the same benefits but with increased precision. However, given the critical nature of the spine, brain, and nerves, the effects of direct photo-thermal interaction on neural tissue needs to be known, yielding not only high precision of tissue removal but also increased control of peripheral heat damage. The proposed use of lasers as a neurosurgical tool requires that a common ground is found between ablation rates and resulting peripheral heat damage. Most surgical laser systems rely on the conversion of light energy into heat resulting in both desirable and undesirable thermal damage to the targeted tissue. Classifying the distribution of thermal energy in neural tissue, and thus characterizing the extent of undesirable thermal damage, can prove to be exceptionally challenging considering its highly inhomogenous composition when compared to other tissues such as muscle and bone. Here we present the characterization of neural tissue ablation rate and heat affected zone of a 1.94 micron thulium doped fiber laser for neural tissue ablation. In-Vivo ablation of porcine cerebral cortex is performed. Ablation volumes are studied in association with laser parameters. Histological samples are taken and examined to characterize the extent of peripheral heat damage.

Optical Coherence Tomography (OCT) provides a high-resolution imaging technique with limited depth penetration. The current use of OCT is limited to relatively small areas of tissue for anatomical structure diagnosis or minimally invasive guided surgery. In this study, we propose to image a large area of the surface of the cerebral cortex. This experiment aims to evaluate the potential difficulties encountered when applying OCT imaging to large and irregular surface areas. The current state-of-the-art OCT imaging technology uses scanning systems with at most 3 degrees-of-freedom (DOF) to obtain a 3D image representation of the sample tissue. We propose the use of a 7 DOF industrial robotic arm to increase the scanning capabilities of our OCT. Such system will be capable of acquiring data from large samples of tissue that are too irregular for conventional methods. Advantages and disadvantages of our system are discussed.

In this paper, a multi-beam optical coherence tomography (OCT) was used to reconstruct the microvascular image of human skin in vivo with phase resolved Doppler OCT (PRDOCT), phase resolved Doppler variance (PRDV) and speckle variance OCT (svOCT), in which the blood flow image was calculated by averaging the four blood flow images obtained by the four beams. In PRDOCT method, it is difficult to detect the blood flow perpendicular to optical axis of the probe beam for single beam OCT, but the multi-beam scanning method can solve this because the input angles of the four probe beams are slightly different from each other. The proposed method can further improve the signal-to-noise ratio (SNR) of the blood flow signals extracted by the three methods mentioned above.

Endovascular Optical Coherence Tomography (OCT) has previously been used in both bench-top and clinical environments to produce vascular images, and can be helpful in characterizing, among other pathologies, plaque build-up and impedances to normal blood ow. The raw data produced can also be processed to yield high- resolution blood velocity information, but this computation is expensive and has previously only been available a posteriori using post-processing software. Real-time Doppler OCT (DOCT) imaging has been demonstrated before in the skin and eye, but this capability has not been available to vascular surgeons. Graphics Processing Units (GPUs) can be used to dramatically accelerate this type of distributed computation. In this paper we present a software package capable of real-time DOCT processing and circular image display using GPU acceleration designed to operate with catheter-based clinical OCT systems. This image data is overlayed onto structural images providing clinicians with live, high-resolution blood velocity information to complement anatomical data.

Participatory research aims to increase the relevance and broaden the implementation of health research by involving those affected by the outcomes of health studies. Few studies within the field of neurodevelopmental disorders, particularly autism spectrum disorders, have involved autistic individuals as partners. This study sought to identify and characterize published participatory research partnerships between researchers and individuals with autism spectrum disorder or other neurodevelopmental disorders and examine the influence of participatory research partnerships on the research process and reported study outcomes. A search of databases and review of gray literature identified seven studies that described participatory research partnerships between academic researchers and individuals with autism spectrum disorder or other neurodevelopmental disorders. A comparative analysis of the studies revealed two key themes: (1) variations in the participatory research design and (2) limitations during the reporting of the depth of the partner’s involvement. Both themes potentially limit the application and generalizability of the findings. The results of the review are discussed in relation to the use of evaluative frameworks for such participatory research studies to determine the potential benefits of participatory research partnerships within the neurodevelopmental and autism spectrum disorder populations.

Background: Adaptive approaches to the introduction of drugs and medical devices involve the use of an evolving evidence base rather than conventional single-point-in-time evaluations as a proposed means to promote patient access to innovation, reduce clinical uncertainty, ensure effectiveness, and improve the health technology development process.Methods: This report summarizes a Health Technology Assessment International (HTAi) Policy Forum discussion, drawing on presentations from invited experts, discussions among attendees about real-world case examples, and background paper.Results: For adaptive approaches to be understood, accepted, and implemented, the Forum identified several key issues that must be addressed. These include the need to define the goals of and to set priorities for adaptive approaches; to examine evidence collection approaches; to clarify the roles and responsibilities of stakeholders; to understand the implications of adaptive approaches on current legal and ethical standards; to determine costs of such approaches and how they will be met; and to identify differences in applying adaptive approaches to drugs versus medical devices. The Forum also explored the different implications of adaptive approaches for various stakeholders, including patients, regulators, HTA/coverage bodies, health systems, clinicians, and industry.Conclusions: A key outcome of the meeting was a clearer understanding of the opportunities and challenges adaptive approaches present. Furthermore, the Forum brought to light the critical importance of recognizing and including a full range of stakeholders as contributors to a shared decision-making model implicit in adaptive pathways in future discussions on, and implementation of, adaptive approaches.

Robot-guided laser ablation for surgical applications potentially offers many advantages compared to by-hand mechanical tissue cutting. However, given that tissue can be rough and/or uneven, ablation quality can be compromised if the beam waist deviates significantly from the target tissue surface. Therefore, we present a method that uses optical coherence tomography (OCT) for dynamic refocusing of robot-guided surgical laser ablation. A 7-DOF robotic manipulator with an OCT-equipped optical payload was used to simulate robotic guided laser osteotomy. M-mode OCT feedback is used for continuous surface detection to correct for axial deviations along the ablation path due to surface nonuniformity. We were able to show that such a correction scheme could maintain the beam waist within the depth of focus for surface variation as aggressive as 45 deg with feed rates up to 1 mm / s. Strategies for implementation in surgical and nonsurgical applications are examined.

Real-time depth metrology during material removal via laser ablation is useful in many forms of laser machining. Until now, coaxial optical coherence tomography (OCT) metrology was achieved by the coupling of an OCT imaging beam and ablating beams using a dichroic filter. We present an alternative design with all fiber delivery that is more suitable for surgical laser ablation applications. The novel system design integrates a high peak-power pulsed Yb-doped fiber laser (1064nm) coupled directly into the sample arm of a swept-source OCT system (λ(c) = 1310nm). We measured the OCT signal degradation due to dispersion and attenuation through the ablation fiber laser cavity. Ablation progression is measured in real-time using M-mode OCT. The mean depth targeting error was found to range from 10µm to 80µm in phantom ablation experiments and 21µm to 60µm in bone ablation. A number of issues have been solved, including point-spread function (PSF) peak broadening due to signal delay and dispersion, high bending loss due to dissimilar fiber used throughout the design, and problems due to the extremely high ablation power to swept-source power ratio (> 2×10(4) peak to average power). To our knowledge, this is the first demonstration of thermal-mediated laser ablation drilling integrated with coaxial OCT imaging through a single-mode, single-cladded output fiber, without using dichroic beam splitters or free-space optic filters anywhere in the optical path and with this high ablation laser power to OCT source power ratio. The removal of bulk optics compared to existing designs opens a new path for compact integration of the entire system. Also, since the ablation laser and OCT feedback system exist along the same fiber path, the need for maintenance and repair are greatly reduced since spatial beam alignment and the potential open-air contamination of optical surfaces are virtually eliminated. We believe that this integrated system is a great candidate for adoption in depth-controlled surgical ablation applications.

A surgical laser soft tissue ablation system based on an adjustable 1942 nm single-mode all-fiber Tm-doped fiber laser operating in pulsed or CW mode with nitrogen assistance is demonstrated. Ex vivo ablation on soft tissue targets such as muscle (chicken breast) and spinal cord (porcine) with intact dura are performed at different ablation conditions to examine the relationship between the system parameters and ablation outcomes. The maximum laser average power is 14.4 W, and its maximum peak power is 133.1 W with 21.3 μJ pulse energy. The maximum CW power density is 2.33 × 10sup6/supW/cmsup2/supand the maximum pulsed peak power density is 2.16 × 10sup7/supW/cmsup2/sup. The system parameters examined include the average laser power in CW or pulsed operation mode, gain-switching frequency, total ablation exposure time, and the input gas flow rate. The ablation effects were measured by microscopy and optical coherence tomography (OCT) to evaluate the ablation depth, superficial heat-affected zone diameter (HAZD) and charring diameter (CD). Our results conclude that the system parameters can be tailored to meet different clinical requirements such as ablation for soft tissue cutting or thermal coagulation for future applications of hemostasis.

This narrative review captures a subset of recent advances in imaging of the central nervous system. First, we focus on improvements in the spatial and temporal profile afforded by optical coherence tomography, fluorescence-guided surgery, and Coherent Anti-Stokes Raman Scattering Microscopy. Next, we highlight advances in the generation and uses of imaging-based atlases and discuss how this will be applied to specific clinical situations. To conclude, we discuss how these and other imaging tools will be combined with neuronavigation techniques to guide surgeons in the operating room. Collectively, this work aims to highlight emerging biomedical imaging strategies that hold potential to be a valuable tool for both clinicians and researchers in the years to come.

Optical Coherence Tomography (OCT) has extensive potential for producing clinical impact in the field of neurological diseases. A neurosurgical OCT hand-held forward viewing probe in Bayonet shape has been developed. In this study, we test the feasibility of integrating this imaging probe with modern navigation technology for guidance and monitoring of skull base surgery. Cadaver heads were used to simulate relevant surgical approaches for treatment of sellar, parasellar and skull base pathology. A high-resolution 3D CT scan was performed on the cadaver head to provide baseline data for navigation. The cadaver head was mounted on existing 3- or 4-point fixation systems. Tracking markers were attached to the OCT probe and the surgeon-probe-OCT interface was calibrated. 2D OCT images were shown in real time together with the optical tracking images to the surgeon during surgery. The intraoperative video and multimodality imaging data set, consisting of real time OCT images, OCT probe location registered to neurosurgical navigation were assessed. The integration of intraoperative OCT imaging with navigation technology provides the surgeon with updated image information, which is important to deal with tissue shifts and deformations during surgery. Preliminary results demonstrate that the clinical neurosurgical navigation system can provide the hand held OCT probe gross anatomical localization. The near-histological imaging resolution of intraoperative OCT can improve the identification of microstructural/morphology differences. The OCT imaging data, combined with the neurosurgical navigation tracking has the potential to improve image interpretation, precision and accuracy of the therapeutic procedure.

The use of gas assistance in laser machining hard materials is well established in manufacturing but not in the context of surgery. Laser cutting of osseous tissue in the context of neurosurgery can benefit from gas-assist but requires an understanding of flow and pressure effects to minimize neural tissue damage. In this study we acquire volumetric flow rates through a gas nozzle on the spinal cord, with dura and without dura.

Carotid atherosclerosis is a critical medical concern that can lead to ischemic stroke. Local hemodynamic patterns have also been associated with the development of atherosclerosis, particularly in regions with disturbed flow patterns such as bifurcations. Traditionally, this disease was treated using carotid endarterectomy, however recently there is an increasing trend of carotid artery stenting due to its minimally invasive nature. It is well known that this interventional technique creates changes in vasculature geometry and hemodynamic patterns due to the interaction of stent struts with arterial lumen, and is associated with complications such as distal emboli and restenosis. Currently, there is no standard imaging technique to evaluate regional hemodynamic patterns found in stented vessels. Doppler optical coherence tomography (DOCT) provides an opportunity to identify in vivo hemodynamic changes in vasculature using high-resolution imaging. In this study, blood flow profiles were examined at the bifurcation junction in the internal carotid artery (ICA) in a porcine model following stent deployment. Doppler imaging was further conducted using pulsatile flow in a phantom model, and then compared to computational fluid dynamics (CFD) simulation of a virtual bifurcation to assist with the interpretation of emphin vivo results.

This study presents the design of a system used to monitor laser ablation in real-time using Optical Coherence Tomography (OCT). The design of the system involves a high-powered fiber laser (wavelength of 1064nm, 1kW peak power) being built directly into the sample arm of the OCT system (center wavelength 1310). It is shown that the OCT laser light and subsequent backscatter pass relatively unaffected through the fiber laser. Initial results are presented showing monitoring of the ablation process at a single point in real time using m-mode imaging.

This paper presents the development of a compact, desktop laser-cutting system capable of cutting materials such as wood, metal and plastic. A re-commissioned beheaded MakerBot ® Replicator 2X is turned into a 3-DOF laser cutter by way of integration with 800W (peak power) fiber laser. Special attention is paid to tear-down, modification and integration of the objective lens in place of the print head. Example cuts in wood and metal will be presented, as well as design of an exhaust system.

This narrative review captures a subset of recent advances in imaging of the central nervous system. First, we focus on improvements in the spatial and temporal profile afforded by optical coherence tomography, fluorescence-guided surgery, and Coherent Anti-Stokes Raman Scattering Microscopy. Next, we highlight advances in the generation and uses of imaging-based atlases and discuss how this will be applied to specific clinical situations. To conclude, we discuss how these and other imaging tools will be combined with neuronavigation techniques to guide surgeons in the operating room. Collectively, this work aims to highlight emerging biomedical imaging strategies that hold potential to be a valuable tool for both clinicians and researchers in the years to come.

In this paper, a multi-beam scanning technique is proposed to optimize the microvascular images of human skin obtained with Doppler effect based methods and speckle variance processing. Flow phantom experiments were performed to investigate the suitability for combining multi-beam data to achieve enhanced microvascular imaging. To our surprise, the highly variable spot sizes (ranging from 13 to 77 μm) encountered in high numerical aperture multi-beam OCT system imaging the same target provided reasonably uniform Doppler variance and speckle variance responses as functions of flow velocity, which formed the basis for combining them to obtain better microvascular imaging without scanning penalty. In vivo 2D and 3D imaging of human skin was then performed to further demonstrate the benefit of combining multi-beam scanning to obtain improved signal-to-noise ratio (SNR) in microvascular imaging. Such SNR improvement can be as high as 10 dB. To our knowledge, this is the first demonstration of combining different spot size, staggered multiple optical foci scanning, to achieve enhanced SNR for blood flow OCT imaging.

Hemodynamics plays a critical role in the development of atherosclerosis, specifically in regions of curved vasculature such as bifurcations exhibiting irregular blood flow profiles. Carotid atherosclerotic disease can be intervened by stent implantation, but this may result in greater alterations to local blood flow and consequently further complications. This study demonstrates the use of a variant of Doppler optical coherence tomography (DOCT) known as split spectrum DOCT (ssDOCT) to evaluate hemodynamic patterns both before and after stent implantation in the bifurcation junction in the internal carotid artery (ICA). Computational fluid dynamics (CFD) models were constructed to simulate blood velocity profiles and compared to the findings achieved through ssDOCT images. Both methods demonstrated noticeable alterations in hemodynamic patterns following stent implantation, with features such as slow velocity regions at the neck of the bifurcation and recirculation zones at the stent struts. Strong correlation between CFD models and ssDOCT images demonstrate the potential of ssDOCT imaging in the optimization of stent implantation in the clinical setting.

RE Objective: This study sought to identify the point prevalence of depressive symptoms, quality-of-life (QOL) impairment, and demographic parameters associated with depression in patients with age-related macular degeneration (AMD) attending a retina clinic in Edmonton, Alberta. Design: A cross-sectional design was used. Methods: Consecutive patients with AMD were invited to participate in the study. Demographic data, as well as ophthalmic, medical, and psychiatric histories, were collected. Participants completed the Center for Epidemiological Studies Depression Scale (CES-D) and the Visual Function Questionnaire (VFQ-25) scales to quantify the burden of depressive symptoms and vision-related QOL impairment. Results: The study enrolled 101 patients, of whom 7 (6.9%) had a previous history of depression. Twenty (21.3%) of the remaining patients endorsed severe symptoms of depression that had not yet been diagnosed. Significant differences in vision-related QOL between depressed and not depressed patients were identified. Depressed patients were also found to have worse visual acuity (p ¼ 0.047) and were less likely to live with others (p ¼ 0.020) than those who were not depressed. Conclusions: After excluding patients with a history of diagnosed depression, 20 (21.3%) patients demonstrated severe symptoms of depression. Development of depression screening protocols for patients with AMD would improve identification and referral of patients at risk. The finding that patients who lived with others had a lower prevalence of depressive symptoms suggests that further research into the relationship between mood symptoms and environmental supports is merited. Objet : Cette etude cherche a identifier la prevalence ponctuelle des symptomes de depression, des pertes de qualite de vie et des parametres demographiques associes a la depression des patients ayant une degenerescence maculaire liee a l'âge (DMLA), en attente dans une clinique de la retine d'Edmonton, Alberta. Nature : Analyse transversale. Methodes : Des patients consecutifs ayant une DMA ont ete invites a participer a cette etude. Les donnees demographiques ainsi que les antecedents ophtalmiques, medicaux et psychiatriques ont ete colliges. Les patients ont complete les echelles du Center for Epidemiologic Studies Depression Scale (CES-D) et du Visual Function Questionnaire (VFQ-25) pour evaluer l'ampleur du poids des symptomes de depression et la qualite de vie quant a la vision. Resultats : 101 patients ont participe a l'etude et sept d'entre eux (6,9 %) avaient des antecedents de depression. Vingt (21,3 %) des autres patients ont confirme de graves symptomes de depression qui n'avaient pas encore ete diagnostiques. Des ecarts significatifs de qualite de vie quant a la vision entre les patients deprimes et non deprimes ont ete identifies. L'on a aussi constate que les patients deprimes avaient la pire acuite visuelle (p = 0,047) et etaient moins enclins a vivre avec ceux (p = 0,020) qui n'etaient pas deprimes. Conclusions : Apres l'exclusion des patients avec antecedents de depression diagnostiquee, vingt (21,3 %) en ont demontre des symptomes severes. Le developpement de protocoles de depistage de depression chez les patients atteints de DMLA ameliorerait l'identification et l'orientation des patients a risque. La decouverte de patients qui, vivant avec d'autres personnes, manifestaient moins de symptomes de depression indique qu'il vaut la peine de poursuivre les recherches sur le rapport entre les symptomes d'humeur et le soutien environnemental.

Gas assisted laser machining of materials is a common practice in the manufacturing industry. Advantages in using gas assistance include reducing the likelihood of flare-ups in flammable materials and clearing away ablated material in the cutting path. Current surgical procedures and research do not take advantage of this and in the case for resecting osseous tissue, gas assisted ablation can help minimize charring and clear away debris from the surgical site. In the context of neurosurgery, the objective is to cut through osseous tissue without damaging the underlying neural structures. Different inert gas flow rates used in laser machining could cause deformations in compliant materials. Complications may arise during surgical procedures if the dura and spinal cord are damaged by these deformations. We present preliminary spinal deformation findings for various gas flow rates by using optical coherence tomography to measure the depression depth at the site of gas delivery.