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.
In this paper, beam-shifting optical coherence tomography (BSOCT) is presented for speckle reduction and flow rate measurement. The sample beam is rotated about the optical axis of the objective lens to modulate the incident angle on sample; 17 and 3 incident angles are respectively performed for speckle reduction and flow rate measurement. The performance of the proposed technique is investigated on both phantom and in vivo experiments. By combining a 2D micro-electro-mechanical system (MEMS) and a zigzag scanning protocol, the frame rates of 45.2 Hz for speckle reduction and 25.6 Hz for flow rate measurement are achieved. With beam-shifting angle of 4.76º, the speckle noise reduction of 91% and the flow rate measurement precision of 0.0019 μl/s are achieved.
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.
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.
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.
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.
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.
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.
Surgical navigation has been more actively deployed in open spinal surgeries due to the need for improved precision during procedures. This is increasingly difficult in minimally invasive surgeries due to the lack of visual cues caused by smaller exposure sites, and increases a surgeon’s dependence on their knowledge of anatomical landmarks as well as the CT or MRI images.
The use of augmented reality (AR) systems and registration technologies in spinal surgeries could allow for improvements to techniques by overlaying a 3D reconstruction of patient anatomy in the surgeon’s field of view, creating a mixed reality visualization. The AR system will be capable of projecting the 3D reconstruction onto a field and preliminary object tracking on a phantom. Dimensional accuracy of the mixed media will also be quantified to account for distortions in tracking.
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.
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.
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.
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.
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.
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 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.
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