Traditional cochlear implant (CI) surgery is typically performed without tool tracking or detailed preoperative planning using monocular surgical microscopy. We introduce a novel computer vision-based tool tracking method to facilitate augmented reality CI surgery. Meta's Segment Anything Model 2 (SAM 2) is used for 2D segmentation of the CI insertion tool, which is subsequently used in a 3D to 2D registration method that registers a 3D model of the CI insertion tool with video frames using a gradient descent optimization strategy that leverages differentiable rendering. This registration facilitates accurate pose estimation. A validation study was performed on both synthetic ground truth datasets and real surgical datasets. Results show that the method achieves a mean absolute rotation error of less than 1 degree and a translation error of less than 1 mm. These findings demonstrate the method's potential for accurately localizing and estimating the pose of the surgical tool for augmented reality-assisted CI surgery.

This article presents the design and performance of a small-scale magnetorheological (MR) brake, with the fastest time constant and highest torque-to-mass ratio among small-scale MR brakes (i.e., those with a diameter less than 40 mm and a thickness less than 30 mm), which are typically designed for use in small haptic or robotic devices. By combining disk- and drum-type designs and incorporating the current-carrying coils into the rotor, this brake uses all three shear surfaces of the rotor to generate large braking torque. Additionally, a serpentine magnetic flux path that crosses the MR fluid shear surfaces a total of six times is used to achieve this torque in a small form factor. An FEM model is used to inform the dimensions of the brake components to increase the magnetic flux density within the MR fluid gap. This enables us to increase the shear force of the MR fluid, and thus, increase braking torque. To characterize brake performance and dynamic response, we measure the relationship between current and braking torque. We then compare the brake’s performance to various types of similarly sized commercial brakes and other small-scale MR brakes found in the literature.

OBJECTIVE:Minimally invasive, image-guided cochlear implantation (CI) surgery consists of drilling a precise tunnel from the surface of the mastoid cortex through the facial recess to target the scala tympani. In the first set of clinical trials of this technique, heat-induced facial nerve paresis (House-Brackmann II/VI) occurred on a patient on the last day of the initial trial which was scheduled to be halted secondary to a change in the regulatory requirements dictated by the 2012 the Food and Drug Administration Safety and Innovation Act requiring Investigational Device Exemption approval for previously exempted customized medical device testing. To address this adverse event, extensive changes were made to the drilling protocol; additionally, a custom insertion tool was developed. To address the Food and Drug Administration Safety and Innovation Act, an Investigational Device Exemption was submitted and, subsequently approved. Herein is described our first clinical implementation of the modified technique.PATIENT:Seventy-year-old with profound, postlingual sensorineural hearing loss who had previously undergone right CI via traditional approach in 2015.INTERVENTION:Minimally invasive image-guided left CI.MAIN OUTCOME MEASURE:Time of intervention, final location of CI electrode array within cochlea.RESULTS:Surgery took 155 minutes of which the largest components (in descending order) were soft tissue work, closure, and drilling. Full scala tympani insertion with angular insertion depth of 557 degrees of the electrode array was achieved. There were no complications, and the patient had an uneventful recovery and activation.CONCLUSIONS:Minimally invasive, image-guided CI surgery is achievable and reduces the mastoid depression associated with traditional CI surgery.CLINICALTRIALSGOV INFORMATION:Study NCT03101917, Microtable Microstereotactic Frame and Drill Press and Associated Method for Cochlear Implantation.LEVEL OF EVIDENCE:Case Report.

Steerable needles are capable of curved paths through soft tissues, which is useful for steering around obstacles and compensating for deviations from the intended needle path. However, the ability to reach a desired target still depends on setting the initial needle launch pose such that the desired target is within the needle’s workspace. Thus, it is desirable to have a means of adjusting the needle’s launch orientation locally at the tissue entry point. In this paper we present a new aiming device for steerable needles that locally adjusts needle launch orientation. It consists of a tendon-actuated, notched tube design, which enables adjustment of the needle’s initial orientation.

The maximum curvature of a steerable needle in soft tissue is highly sensitive to needle shaft stiffness, which has motivated use of small diameter needles in the past. However, desired needle payloads constrain minimum shaft diameters, and shearing along the needle shaft can occur at small diameters and high curvatures. We provide a new way to adjust needle shaft stiffness (thereby enhancing maximum curvature, i.e. "steerability") at diameters selected based on needle payload requirements. We propose helical dovetail laser patterning to increase needle steerability without reducing shaft diameter. Experiments in phantoms and ex vivo animal muscle, brain, liver, and inflated lung tissues demonstrate high steerability in soft tissues. These experiments use needle diameters suitable for various clinical scenarios, and which have been previously limited by steering challenges without helical dovetail patterning. We show that steerable needle targeting remains accurate with established controllers and demonstrate interventional payload delivery (brachytherapy seeds and radiofrequency ablation) through the needle. Helical dovetail patterning decouples steerability from diameter in needle design. It enables diameter to be selected based on clinical requirements rather than being carefully tuned to tissue properties. These results pave the way for new sensors and interventional tools to be integrated into high-curvature steerable needles.

Current surgical approaches to radical prostatectomy are associated with high rates of erectile dysfunction and incontinence. These complications occur secondary to the disruption of surrounding healthy tissue, which is required to expose the prostate. The urethra offers the least invasive access to the prostate, and feasibility has been demonstrated of enucleating the prostate with an endoscope using Holmium laser, which can itself be aimed by concentric tube robots. However, the transurethral approach to radical prostatectomy has thus far been limited by the lack of a suitable means to perform an anastomosis of the urethra to the bladder after prostate removal. Only a few intraluminal anastomotic devices currently exist, and none are small enough to pass through the urethra. In this article we describe a new way to perform an anastomosis in the small luminal space of the urethra, harnessing the dexterity and customizability of concentric tube manipulators. We demonstrate a successful initial proof-of-concept anastomosis in an anthropomorphic phantom of the urethra and bladder.

Lung cancer is one of the most prevalent and deadly forms of cancer, claiming more than 154,000 lives in the USA per year. Accurate targeting and biopsy of pulmonary abnormalities is key for early diagnosis and successful treatment. Many cancerous lesions originate in the peripheral regions of the lung which are not directly accessible from the bronchial tree, thereby requiring percutaneous approaches to collect biopsies, which carry a higher risk of pneumothorax, hemorrhage, and death in extreme cases. In prior work, our group proposed a concept for accessing the peripheral lung through the airways, via a bronchscope deployed steerable needle. In this paper, we present a more compact, modular, multi-stage robot, designed to deploy a steerable needle through a standard flexible bronchoscope, to retrieve biopsies from lesions in the peripheral regions of the lung. The robot has several stages that can control a steerable biopsy needle, as well as concentric tubes, which act as an aiming conduit. The functionality of this robot is demonstrated via closed-loop lesion targeting in a CT scanner. The steerable needle is controlled using a previously proposed sliding mode controller, based on feedback from a magnetic tracker embedded in the steerable needle's tip. Towards developing a clinically viable platform, this system builds on prior work through its modular, compact form factor, and workflow-conscious design that provides precise homing and the ability to interchange tools as needed.

Image-guided, minimally-invasive cochlear implant surgery is a novel "keyhole" surgical approach for placing a cochlear implant electrode array eliminating the need for a wide-field mastoidectomy approach. Image guidance is used for path planning which is followed by the construction of a customized micro-stereotactic frame to drill a narrow channel from the skull surface to the cochlea. Herein, we present an insertion tool that uses roller wheels to advance the electrode array through the narrow tunnel and into the cochlea. Testing in a phantom revealed that when compared to insertions with surgical forceps, the new insertion tool was on average 26s faster, produced complete insertions more often (i.e. in 6/6 trials, vs. 1/6), and reduced array buckling (0/6 trials vs. 5/6). The tool provides a viable solution to complete the last step of this novel, minimally-invasive procedure. It also provides the advantage over previously developed manual insertion tools of enabling the surgeon to blindly actuate the roller wheel tool to advance the electrode into the tunnel. This allows the surgeon to visualize and guide insertion into the cochlea from a more advantageous visual perspective.

Cochlear implant surgery typically requires a wide-field mastoidectomy to access the cochlea. This portion of the surgery can leave a visible and palpable depression behind the patient's ear, which can be cosmetically displeasing to the patient. For the surgeon, a wide-field mastoidectomy is challenging to perform because bone must be gradually removed by freehand drilling guided primarily by visual feedback in an effort to detect, yet avoid, vital anatomy including the facial nerve which controls motion of the face. Toward overcoming these issues and standardizing surgery, imaged-guided, minimally invasive approaches have been developed in which the cochlea is accessed using a single pre-planned drill trajectory. This approach promises decreased invasiveness, but the limited surgical view and long narrow opening to the cochlea present significant challenges for inserting electrode arrays. This paper describes the first cadaver experiments using a new manual insertion tool which provides a roller mechanism to enable the physician to deploy a cochlear implant electrode array through the narrow drilled hole created by this minimally invasive, image-guided access technique. Results demonstrate that the new tool enables consistent and successful insertions similar to insertions with the traditional tool while increasing the ease of the insertion and freeing the surgeon to monitor progress and make fine adjustments as needed.

This article presents the development and experimental validation of a methodology to reduce the risk of thermal injury to the facial nerve during minimally invasive cochlear implantation surgery. The first step in this methodology is a pre-operative screening process, in which medical imaging is used to identify those patients that present a significant risk of developing high temperatures at the facial nerve during the drilling phase of the procedure. Such a risk is calculated based on the density of the bone along the drilling path and the thermal conductance between the drilling path and the nerve, and provides a criterion to exclude high-risk patients from receiving the minimally invasive procedure. The second component of the methodology is a drilling strategy for manually-guided drilling near the facial nerve. The strategy utilizes interval drilling and mechanical constraints to enable better control over the procedure and the resulting generation of heat. The approach is tested in fresh cadaver temporal bones using a thermal camera to monitor temperature near the facial nerve. Results indicate that pre-operative screening may successfully exclude high-risk patients and that the proposed drilling strategy enables safe drilling for low-to-moderate risk patients.

Safe and effective planning for robotic surgery that involves cutting or ablation of tissue must consider all potential sources of error when determining how close the tool may come to vital anatomy. A pre-operative plan that does not adequately consider potential deviations from ideal system behavior may lead to patient injury. Conversely, a plan that is overly conservative may result in ineffective or incomplete performance of the task. Thus, enforcing simple, uniform-thickness safety margins around vital anatomy is insufficient in the presence of spatially varying, anisotropic error. Prior work has used registration error to determine a variable-thickness safety margin around vital structures that must be approached during mastoidectomy but ultimately preserved. In this paper, these methods are extended to incorporate image distortion and physical robot errors, including kinematic errors and deflections of the robot. These additional sources of error are discussed and stochastic models for a bone-attached robot for otologic surgery are developed. An algorithm for generating appropriate safety margins based on a desired probability of preserving the underlying anatomical structure is presented. Simulations are performed on a CT scan of a cadaver head and safety margins are calculated around several critical structures for planning of a robotic mastoidectomy.

Cochlear implants (CIs) can restore the perception of sound to individuals with severe to profound sensorineural hearing loss. The implanted component of a CI system is an electrode array inserted into the cochlea where it electrically stimulates the intracochlear nerve. Sound is picked up from the environment by an external microphone, filtered, processed, and then converted to electrical signals which are sent to the electrode array. The traditional surgical approach is invasive. A mastoidectomy is performed, in which a fairly large volume of the mastoid region of the temporal bone (approximately 40 mm × 30 mm × 25 mm) is milled away with a high-speed surgical drill to gain access to the cochlea. Vital anatomical structures such as the facial nerve and chorda tympani are embedded within the bone in this region and must be carefully avoided, making the surgery slow and challenging. Due to the invasiveness, risk, and expense of the procedure, many CI candidates do not receive an implant.An alternative less invasive approach to CI surgery has been investigated by several research groups (e.g., Refs. [1] and [2]) in which a narrow hole is drilled from the skull surface directly to the cochlea, obviating the mastoidectomy. In addition to decreasing the invasiveness of the procedure, this approach has the potential to reduce costs, decrease operating room time, and allow less specialized surgeons to perform the surgery, enabling additional CI candidates to receive the implant.The less invasive system discussed in this paper uses a patient-specific microstereotactic frame, called a microtable, to align the surgical drill along the desired drilling trajectory (see Fig. 1). Pre-operative imaging enables planning of a safe drill path to the cochlea that avoids the vital anatomy. Bone-implanted fiducial markers, which also serve as microtable mounting points, are inserted around the mastoid region in the operating room. The microtable is manufactured in several minutes based on an intraoperative computed tomography (CT) scan and the pre-operative planning. It is then assembled, sterilized, and mounted to fiducial markers on the patient. A custom drill guide is attached to the microtable and the surgeon manually moves the drill downward into the skull (see Ref. [1] for further system details). After the cochlea is accessed, the implant is inserted using specialized tools [3,4].A challenge in this approach is to minimize the temperature rise associated with drilling through the mastoid bone. The drill path must pass very close to the facial nerve and chorda tympani (0.5 mm between the nerve and drill surface for some patients) so a large spike in temperature has the potential to damage these nearby nerves [5]. During earlier clinical trials using this system, one patient experienced temporary facial paralysis, believed to be caused by excessive heat at the facial nerve [6]. Like any material, the temperature rise in drilling through bone is related to the drilling parameters (spindle speed, feed rate, etc.) and material properties. Considering all of these factors such that the heat generation is kept at a safe level while manually drilling can be difficult. Thus, we hypothesize that an automated drill guide and trajectory can decrease the temperature rise, and thus the likelihood of heat-related trauma to the patient. Additionally, results from testing various drilling strategies can be used to guide the surgeons when performing the surgery manually with the current system.The objective of this design was to develop an automatic drill guide that fits within the current minimally invasive CI surgical system used at Vanderbilt as well as a method for measuring the temperature rise at the facial nerve during the procedure. The motivation is twofold: first, the automatic guide can be used to test a variety of drilling strategies to help inform the surgeons when performing the drilling manually, and second, the automatic drill press may be integrated easily into the existing surgical protocol if there is a clear benefit over the manual approach.The drill guide design is a simple lead screw driven slide that holds the surgical drill (see Fig. 2). A brushless motor drives the slide and the guide mounts to the microtable using a coupling that aligns the drill along the target axis. The drill trajectory parameters, e.g., continuous versus peck drilling, plunge speed, retraction speed and distance, etc., can be selected easily by the surgeon in software. A computer interface allows the surgeon to control when the drilling starts and pause/stop the drilling at any time.To evaluate the heat rise near the facial nerve for various drilling strategies, an experimental setup using ex vivo temporal bone specimens was developed. Bone anchors and fiducial markers were attached to the temporal bone specimen, a CT scan was acquired, and the standard trajectory planning and microtable manufacturing processes were completed. Using the mounted microtable as a reference, the temporal bone was cut perpendicular to the planned trajectory at the middle ear where the facial nerve is closest to the drill path (plane location measured in CT scan). The temporal bone was clamped to a table and a thermal imaging camera (FLIR A655sc with 50 μm close-up lens) was positioned such that it could monitor the temperature of the plane containing the facial nerve throughout the procedure (see Fig. 3).Several trials were performed to evaluate the system and the experimental setup. Fresh human cadaveric temporal bones were used and different drilling strategies were employed, including constant velocity drilling at various rates and peck drilling. No irrigation was used in these trials, which represents a worst-case scenario and the bones were initially at 20 °C. For each bone, two trials were performed: one directed at the cochlea and another parallel to the first trajectory offset by 7 mm. The data were exported to matlab and the temperature distributions throughout the trajectories were analyzed.The initial experimental results indicate that high temperatures can arise near the facial nerve during this procedure when irrigation is not used. Figure 4 shows a plot of the temperature rise at a distance of 0.5 mm from the edge of the drill path on the cut plane. It is clear that the temperature rise can be high for certain drilling strategies. Comparing the temperature distributions to the bone density (via image intensity values), higher temperatures are observed when drilling through denser bone. In particular, the 1 mm/s continuous velocity trajectory through the offset path (dashed line with peak at approximately 40 °C in Fig. 4) contained highly porous bone near the facial nerve and resulted in the lowest recorded temperatures at the cut plane in the middle ear.The design developed is a very simple device that fits within the current framework of the minimally invasive surgical system and provides the ability to plan a variety of drilling trajectories. Currently, the automatic drill press is being used to test a range of drilling parameters in the laboratory to develop a surgical protocol for the manual drilling approach. Eventually, it may be incorporated into the clinical system. Initial experiments indicated that high temperatures are possible at the facial nerve with nonoptimized drilling parameters and no irrigation. Many more trials must be performed before any meaningful conclusion can be reached regarding the optimal drilling parameters, and various irrigation strategies must be explored to improve cooling at the drill tip. Additionally, it is likely that a patient-specific drill trajectory should be employed based on a thermal model that incorporates bone density information from the CT scan.

This paper describes a transhumeral prosthesis prototype intended for the purpose of experimentally investigating design features and control strategies for the control of transhumeral prostheses. This paper specifically focuses on the design and performance characterization of a powered wrist rotator and powered elbow joint, in addition to the embedded system that controls them. In addition to outlining design objectives associated with the wrist and elbow joints, this paper describes the design of both joints, and the embedded system that provides control of them and the arm system. Experimental data are presented that characterizes the performance characteristics of both joints, including data associated with electrical power consumption and audible noise. The arm prosthesis described here is intended to be used with a multigrasp hand prosthesis, previously published by the authors.

This paper describes the design of a powered elbow prosthesis, which incorporates a belt and cable drive transmission with a brushless DC motor to achieve an output torque of approximately 18.4 Nm, a backdrive torque of 1.5 Nm, and a speed of up to 360 deg/s while remaining within the anthropomorphic envelope with regard to mass and size. The measured torque and speed of the prosthesis is commensurate with nominal capability of the natural limb (for purposes of performing activities of daily living).

This paper describes a walking controller implemented on a powered ankle prosthesis prototype and assessed by a below-knee amputee subject on a treadmill at three speeds. The walking controller is a finite state machine which emulates a series of passive impedance functions at the joint in order to reproduce the behavior of a healthy joint. The assessments performed demonstrate the ability of the powered prosthesis prototype and walking controller to reproduce essential biomechanical aspects (i.e. joint angle, torque, and power profiles) of the healthy joint, especially relative to a passive prosthesis.

This article describes the design and control of a powered knee and ankle prosthesis for transfemoral amputees. Following a description of the design hardware, a hybrid control approach that provides coordination for level walking is described. The hybrid control approach combines a piecewise-passive impedance-based component during the stance phase of gait with a high impedance trajectory-tracking component during the terminal stance and swing. To validate the design, the controller was implemented on the powered prosthesis prototype, and its ability to provide level walking functionality was evaluated on three transfemoral amputee subjects. The data presented from these experimental trials indicate that the prosthesis and control approach reproduce knee and ankle joint kinematic and kinetic features that are highly representative of corresponding healthy joint biomechanics.

Deep brain stimulation (DBS) surgery utilizes image guidance via bone-implanted fiducial markers to achieve the desired submillimetric accuracy and to provide means for attaching microstereotactic frames. For maximal benefit, the markers must be inserted to the correct depth since over-insertion leads to stripping and under-insertion leads to instability.