Instrument Guidance Research Articles

Deformable registration of preoperative MR and intraoperative long-length tomosynthesis images for guidance of spine surgery via image synthesis

PurposeImproved integration and use of preoperative imaging during surgery hold significant potential for enhancing treatment planning and instrument guidance through surgical navigation. Despite its prevalent use in diagnostic settings, MR imaging is rarely used for navigation in spine surgery. This study aims to leverage MR imaging for intraoperative visualization of spine anatomy, particularly in cases where CT imaging is unavailable or when minimizing radiation exposure is essential, such as in pediatric surgery. MethodsThis work presents a method for deformable 3D-2D registration of preoperative MR images with a novel intraoperative long-length tomosynthesis imaging modality (viz., Long-Film [LF]). A conditional generative adversarial network is used to translate MR images to an intermediate bone image suitable for registration, followed by a model-based 3D-2D registration algorithm to deformably map the synthesized images to LF images. The algorithm’s performance was evaluated on cadaveric specimens with implanted markers and controlled deformation, and in clinical images of patients undergoing spine surgery as part of a large-scale clinical study on LF imaging. ResultsThe proposed method yielded a median 2D projection distance error of 2.0 mm (interquartile range [IQR]: 1.1–3.3 mm) and a 3D target registration error of 1.5 mm (IQR: 0.8–2.1 mm) in cadaver studies. Notably, the multi-scale approach exhibited significantly higher accuracy compared to rigid solutions and effectively managed the challenges posed by piecewise rigid spine deformation. The robustness and consistency of the method were evaluated on clinical images, yielding no outliers on vertebrae without surgical instrumentation and 3% outliers on vertebrae with instrumentation. ConclusionsThis work constitutes the first reported approach for deformable MR to LF registration based on deep image synthesis. The proposed framework provides access to the preoperative annotations and planning information during surgery and enables surgical navigation within the context of MR images and/or dual-plane LF images.

A Comparative Evaluation of Optical See-Through Augmented Reality in Surgical Guidance.

During traditional surgeries, planning and instrument guidance is displayed on an external screen. Recent developments of augmented reality (AR) techniques can overcome obstacles including hand-eye discoordination and heavy mental load. Among these AR technologies, optical see-through (OST) schemes with stereoscopic displays can provide depth perception and retain the physical scene for safety considerations. However, limitations still exist in certain AR systems and the influence of these factors on surgical performance is yet to explore. To this end, experiments of multi-scale surgical tasks were carried out to compare head-mounted display (HMD) AR and autostereoscopic image overlay (AIO) AR, concerning objective performance and subjective evaluation. To solely analyze effects brought by display techniques, the tracking system in each included display system was identical and similar tracking accuracy was proved by a preliminary experiment. Focus and context rendering was utilized to enhance in-situ visualization for surgical guidance. Latency values of all display systems were assessed and a delay experiment proved the latency differences had no significant impact on user performance. Results of multi-scale surgical tasks showed that HMD outperformed in detailed operations probably due to stable resolution along the depth axis, while AIO had better performance in larger-scale operations for better depth perception. This article helps point out the critical limitations of current OST AR techniques and potentially promotes the progress of AR applications in surgical guidance.

Risk of Injury to Retroperitoneal Structures in Prone and Lateral Decubitus Transpsoas Approaches to Lumbar Interbody Fusion: A Pilot Cadaveric Anatomical Study.

Introduction The retroperitoneal approach for lateral lumbar interbody fusion (LLIF) originally described an initial posterolateral fascial incision enabling finger dissection from behind the peritoneum and guidance of instruments through a second direct-lateral fascial incision. It has since become common for single direct-lateral incisional access to the retroperitoneum. This study attempted to quantify the distance of the peritoneum from posterior landmarks in the space, assess the risk of peritoneal violation in each access trajectory (i.e., posterolateral versus direct lateral retroperitoneal dissection), and determine whether there are differences based on patient position (prone versus lateral decubitus). Methods In three prone cadaveric torsos, Steinman pins were percutaneously placed mid-disc at each level L2-5 bilaterally (for a total of 18 prone approaches). Open dissections exposed the retroperitoneum including the quadratus lumborum and psoas muscles, maintaining the natural reflection of the peritoneum. Visual assessment qualified whether any pin violated any retroperitoneal structure. Distance from the anterior border of the quadratus lumborum to the posterior-most reflection of the peritoneum was measured. For comparison, three additional torsos were positioned in lateral decubitus, and the above steps were repeated, only unilaterally (for a total of nine lateral decubitus approaches). Results In prone, no pin violated the peritoneum; three (3/18 total approaches) violated the kidney, all at L2-3 (3/6 approaches at L2-3). In lateral decubitus, all three L2-3 pins violated the kidney (3/3 approaches at L2-3); five of the six remaining pins from L3-5 violated the peritoneum (totaling eight violations in the nine total approaches). The incidence of any violation was significantly greater in lateral decubitus vs. prone (8/9 vs. 3/18, p=0.0006). The structure at risk (kidney vs. peritoneum) was significantly associated with disc level (p=0.0041): all kidney violations occurred at L2-3 and all peritoneal violations occurred at L3-4 or L4-5. Distance from the quadratus lumborum to the posterior-most reflection of the peritoneum averaged 8.7 cm (range: 6-10) in prone, and 2.9 cm (range: 2.5-3.2) in lateral decubitus (p=0.0129). Conclusion A cadaveric study of retroperitoneal anatomy demonstrates that there is an increased distance from the quadratus lumborum to the peritoneum in prone versus lateral decubitus and that the trajectory of approach to the lumbar discs risks violation of the peritoneum more frequently when accessing directly laterally versus posterolaterally. In either approach, care should be taken to identify and release the peritoneal reflection to create a safe passage to the lumbar discs.

The use of robot-assisted surgery for the unstable traumatic spine: A retrospective cohort study

BackgroundRobotic assistance has been shown to increase instrumentation placement accuracy in open and minimally invasive spinal fusion. These gains have been achieved without increases in operative times, blood loss, or hospitalization duration. However, most work has been done in the degenerative population and little is known of the utility of robotic assistance when applied to spinal trauma. This is largely due to the uncertainty stemming from the disruption of normal anatomy by the traumatic injury. Since the robot depends upon registration for instrumentation guidance according to the fiducials it uses, trauma can introduce unique challenges. The present study sought to evaluate the safety and efficacy of robotic assistance in a consecutive cohort of spine trauma patients. MethodsAll patients with Thoracolumbar Injury Classification and Severity Scale (TLICS) >4 who underwent robot-assisted spinal fusion using the Globus ExcelsiusGPS at a single tertiary care center for trauma between 2020 and 2022 were identified. Demographic, clinical, and surgical data were collected and analyzed; the primary endpoints were operative time, fluoroscopy time, estimated blood loss, postoperative complications, admission time, and 90-day readmission rate. The paired t-test was used to compare differences between mean values when looking at the number of surgical levels. ResultsForty-two patients undergoing robot-assisted spinal surgery were included (mean age 61.3±17.1 year; 47% female. Patients were stratified by the number of operative levels, 2 (n = 10), 3-4 (n = 11), 5 to 6 (n = 13), or >6 (n = 8). There appeared to be a positive correlation between number of levels instrumented and odds of postoperative complications, admission duration, fluoroscopy time, and estimated blood loss. There were no instances of screw malposition or breach. ConclusionsThis initial experience suggests robotic assistance can be safely employed in the spine trauma population. Additional experiences in larger patient populations are necessary to delineate those traumatic pathologies most amenable to robotic assistance.

In situ guidance for MRI interventions using projected feedback.

To develop and evaluate an augmented reality instrument guidance system for MRI-guided needle placement procedures such as musculoskeletal biopsy and arthrography. Our system guides the physician to insert a needle toward a target while looking at the insertion site without requiring special headgear. The system is comprised of a pair of stereo cameras, a projector, and a computational unit with a touch screen. All components are designed to be used within the MRI suite (Zone 4). Multi-modality fiducial markers called VisiMARKERs, detectable in both MRI and camera images, facilitate automatic registration after the initial scan. The navigation feedback is projected directly onto the intervention site allowing the interventionalist to keep their focus on the insertion site instead of a secondary monitor which is often not in front of them. We evaluated the feasibility and accuracy of this system on custom-built shoulder phantoms. Two radiologists used the system to select targets and entry points on initial MRIs of these phantoms over three sessions. They performed 80 needle insertions following the projected guidance. The system targeting error was 1.09mm, and the overall error was 2.29mm. We demonstrated both feasibility and accuracy of this MRI navigation system. The system operated without any problems inside the MRI suite close to the MRI bore. The two radiologists were able to easily follow the guidance and place the needle close to the target without any intermediate imaging.

Development of a planned and monitoring robotic assistance and automation for application in orthopedics and trauma surgery

Robot-assisted surgery offers many advantages with respect to precision and facilitation in medicine, whereby the physician controls the system externally by guiding the movement of the robot during the operation. Despite training and experience, operating errors by the user cannot be excluded. In addition, for the established systems the precise guidance of instruments along complexly shaped surfaces, e.g. for milling or cutting, depends on the skills of the operator. This article presents an expansion of the established robotic assistance for smooth movement along randomly shaped surfaces and introduces a movement automation which goes beyond the assistance systems used so far. Both approaches aim to improve the accuracy in surface-dependent medical procedures and avoid operator errors. Special applications with these requirements are, for example the execution of precise incisions or removal of adhering tissue in cases of spinal stenosis. A segmented computed tomography (CT) or magnetic resonance imaging (MRI) scan serves as the basis for a precise implementation. For robotic assistance externally guided by the operator the commands given to the robot are tested and monitored without delay so that adaptation of the movement exactly corresponding to the surface can be carried out. In contrast, the automation for the established systems differs in that the movement along the desired surface is roughly planned by the surgeon preoperatively by marking prominent points on the CT or MRI scan. From this a suitable track, including the appropriate instrument orientation, is calculated and, after checking the results, the robot finally carries this out autonomously. Based on this procedure, which is planned by humans and carried out by robots, errors are minimized, respective advantages are maximized and costly training on correct steering of robots becomes obsolete. The evaluation is carried out both in simulation and also experimentally on a complexly shaped 3D-printed lumbar vertebra from a CT scan with a Stäubli TX2-60 manipulator (Stäubli Tec-Systems GmbH Robotics, Bayreuth, Germany); however, the procedures are also transferable to and applicable on every other robotic system that covers the necessary working space, such as the da Vinci system.

Spotlight-based 3D Instrument Guidance for Autonomous Task in Robot-assisted Retinal Surgery.

Retinal surgery is known to be a complicated and challenging task for an ophthalmologist even for retina specialists. Image guided robot-assisted intervention is among the novel and promising solutions that may enhance human capabilities during microsurgery. In this paper, a novel method is proposed for 3D navigation of a microsurgical instrument based on the projection of a spotlight during robot-assisted retinal surgery. To test the feasibility and effectiveness of the proposed method, a vessel tracking task in a phantom with a Remote Center of Motion (RCM) constraint is performed by the Steady-Hand Eye Robot (SHER). The results are compared to manual tracking, cooperative control tracking with the SHER and spotlight-based automatic tracking with SHER. The reported results are that the spotlight-based automatic tracking with SHER can reach an average tracking error of 0.013 mm and keeping distance error of 0.1 mm from the desired range demonstrating a significant improvement compared to manual or cooperative control methods alone.

Computer-Assisted Instrument Guidance to Improve Adductor Canal Block Performance for Total Knee Arthroplasty: A Pilot Randomized Controlled Trial.

BackgroundPostoperative pain associated with total knee arthroplasties (TKAs) is routinely managed with ultrasound-guided adductor canal blocks (ACBs). Computer-assisted instrument guidance (CAIG) systems can supplement the existing ultrasound machinery and block needles. CAIG systems allow the operator to navigate the needle in real time while displaying a projected trajectory of its path onto the ultrasound monitor. This study explored how ACBs performed with CAIG compare with conventional ultrasound-only ACBs in terms of block efficiency, success, and potential tissue damage for patients undergoing TKA.MethodologyA total of 26 patients undergoing TKA under spinal anesthesia with an ACB were randomized to ACB utilizing conventional real-time ultrasound or to ACB utilizing real-time ultrasound supplemented with CAIG. The primary outcome measure was time to block completion. The secondary outcome measures included number of needle insertions, postoperative pain scores until postoperative day three, postoperative muscle weakness, opioid requirements on postoperative day zero, length of stay, and patient satisfaction with pain management.ResultsThe time required to complete the block as well as the number of needle insertion attempts were similar between the CAIG and conventional ACB groups. Postoperative outcomes such as pain scores up to postoperative day three, postoperative muscle weakness, opioid requirements on postoperative day zero, length of stay, and patient satisfaction with perioperative pain management were comparable between the CAIG and conventional ACB groups.ConclusionsCAIG does not reduce ACB performance times or patient outcomes when performed by experienced anesthesiologists.

Concept description and accuracy evaluation of a moldable surgical targeting system

.Purpose: We explain our concept for customization of a guidance instrument, present a prototype, and describe a set of experiments to evaluate its positioning and drilling accuracy.Methods: Our concept is characterized by the use of bone cement, which enables fixation of a specific configuration for each individual surgical template. This well-established medical product was selected to ensure future intraoperative fabrication of the template under sterile conditions. For customization, a manually operated alignment device is proposed that temporary defines the planned trajectory until the bone cement is hardened. Experiments () with half-skull phantoms were performed. Analysis of accuracy comprises targeting validations and experiments including drilling in bone substitutes.Results: The resulting mean positioning error was found to be at the level of the target point whereas drilling was possible with a mean accuracy of .Conclusion: We proposed a cost-effective, easy-to-use approach for accurate instrument guidance that enables template fabrication under sterile conditions. The utilization of bone cement was proven to fulfill the demands of an easy, quick, and prospectively intraoperatively doable customization. We could demonstrate sufficient accuracy for many surgical applications, e.g., in neurosurgery. The system in this early development stage already outperforms conventional stereotactic frames and image-guided surgery systems in terms of targeting accuracy.

Significant improvement of laparoscopic knotting time in medical students through manual training with potential cost savings in laparoscopy - an observational study

Objective:Laparoscopy is a standard procedure in operative gynaecology, but laparoscopic simulator training for novices/junior surgeons is not currently well-established. The aims of this study were to demonstrate that a laparoscopic knot course for trainees can significantly shorten the knotting time and to perform a counter-value calculation for the clinic’s costs.Material and Methods:An observational study was performed with exercises on a laparoscopic box trainer as part of the practical clerkship in gynaecology and obstetrics between 07.10.2019-31.01.2020. At the beginning and at the end of the exercises, the participants made a laparoscopic knot and the difference in knotting time, Δt in seconds (s) was measured.Results:Eighty-eight medical students needed an average of 247.1 s for the first laparoscopic knot at the beginning of the course and an average of 45.43 s for the second at the end of the course. Mean shortening of the knotting time was 201.67 s or 81.6% (p=0.02). Calculating costs of an average of €40-50 for an operation minute would mean a cost saving of at least €120-150 for a partial node.Conclusion:Trainees can significantly improve their operative skills in a short time with the aid of surgical simulation training. Such training can be beneficial for clinics by reducing the operating time if the basics, such as sewing and instrument guidance, are learned on a simulator. We therefore suggest that operative simulation training should be mandatory in medical education.

The endonasal patient reference tracker: a novel solution for accurate noninvasive electromagnetic neuronavigation.

Electromagnetic (EM) navigation provides the advantages of continuous guidance and tip-tracking of instruments. The current solutions for patient reference trackers are suboptimal, as they are either invasively screwed to the bone or less accurate if attached to the skin. The authors present a novel EM reference method with the tracker rigidly but not invasively positioned inside the nasal cavity. The nasal tracker (NT) consists of the EM coil array of the AxiEM tracker plugged into a nasal tamponade, which is then inserted into the inferior nasal meatus. Initially, a proof-of-concept study was performed on two cadaveric skull bases. The stability of the NT was assessed in simulated surgical situations, for example, prone, supine, and lateral patient positioning and skin traction. A deviation ≤ 2 mm was judged sufficiently accurate for clinical trial. Thus, a feasibility study was performed in the clinical setting. Positional changes of the NT and a standard skin-adhesive tracker (ST) relative to a ground-truth reference tracker were recorded throughout routine surgical procedures. The accuracy of the NT and ST was compared at different stages of surgery. Ex vivo, the NT proved to be highly stable in all simulated surgical situations (median deviation 0.4 mm, range 0.0-2.0 mm). In 13 routine clinical cases, the NT was significantly more stable than the ST (median deviation at procedure end 1.3 mm, range 0.5-3.0 mm vs 4.0 mm, range 1.2-11.2 mm, p = 0.002). The loss of accuracy of the ST was highest during draping and flap fixation. Application of the EM endonasal patient tracker was found to be feasible with high procedural stability ex vivo as well as in the clinical setting. This innovation combines the advantages of high precision and noninvasiveness and may, in the future, enhance EM navigation for neurosurgery.

A Novel Augmented-Reality-Based Surgical Navigation System for Spine Surgery in a Hybrid Operating Room: Design, Workflow, and Clinical Applications.

Treatment of several spine disorders requires placement of pedicle screws. Detailed 3-dimensional (3D) anatomic information facilitates this process and improves accuracy. To present a workflow for a novel augmented-reality-based surgical navigation (ARSN) system installed in a hybrid operating room for anatomy visualization and instrument guidance during pedicle screw placement. The workflow includes surgical exposure, imaging, automatic creation of a 3D model, and pedicle screw path planning for instrument guidance during surgery as well as the actual screw placement, spinal fixation, and wound closure and intraoperative verification of the treatment results. Special focus was given to process integration and minimization of overhead time. Efforts were made to manage staff radiation exposure avoiding the need for lead aprons. Time was kept throughout the procedure and subdivided to reflect key steps. The navigation workflow was validated in a trial with 20 cases requiring pedicle screw placement (13/20 scoliosis). Navigated interventions were performed with a median total time of 379 min per procedure (range 232-548 min for 4-24 implanted pedicle screws).The total procedure time was subdivided into surgical exposure (28%), cone beam computed tomography imaging and 3D segmentation (2%), software planning (6%), navigated surgery for screw placement (17%) and non-navigated instrumentation, wound closure, etc (47%). Intraoperative imaging and preparation for surgical navigation totaled 8% of the surgical time. Consequently, ARSN can routinely be used to perform highly accurate surgery potentially decreasing the risk for complications and revision surgery while minimizing radiation exposure to the staff.

Robotic Spine Surgery and Augmented Reality Systems: A State of the Art.

Instrumented spine procedures have been performed for decades to treat a wide variety of spinal disorders. New technologies have been employed to obtain a high degree of precision, to minimize risks of damage to neurovascular structures and to diminish harmful exposure of patients and the operative team to ionizing radiations. Robotic spine surgery comprehends 3 major categories: telesurgical robotic systems, robotic-assisted navigation (RAN) and virtual augmented reality (AR) systems, including AR and virtual reality. Telesurgical systems encompass devices that can be operated from a remote command station, allowing to perform surgery via instruments being manipulated by the robot. On the other hand, RAN technologies are characterized by the robotic guidance of surgeon-operated instruments based on real-time imaging. Virtual AR systems are able to show images directly on special visors and screens allowing the surgeon to visualize information about the patient and the procedure (i.e., anatomical landmarks, screw direction and inclination, distance from neurological and vascular structures etc.). The aim of this review is to focus on the current state of the art of robotics and AR in spine surgery and perspectives of these emerging technologies that hold promises for future applications.

Evaluation of Adenoid Hypertrophy with Ultrasonography.

To determine the reliability of ultrasound in the diagnosis of adenoid hypertrophy in children. The subjects were divided into three groups: Group A: Pre-experiment group: 30 children who were hospitalized for adenoidal hypertrophy were selected, and preoperative ultrasound was used to measure adenoid thickness. Their re-confirmed Adenoidultrasound measurementthickness was obtained during surgeryunder the guidance of metal instruments; Group B: Ultrasound screening group: 1898 children aged 3-12 y were selected, and their adenoids were examined by ultrasonography to observe the size, shape, echo and blood flow of adenoids and the thickness of adenoids; Group C: Surgical resection group: 133 hospitalized patients were selected, and their adenoid ultrasound measurement thickness (AUT), the adenoid-nasopharynx (A/N) ratio was calculated based on nasopharyngeal lateral radiographs and obstruction ratio was obtained in electronic nasopharyngoscopy [extent of adenoid-posterior nostril occlusion (EANC)] were compared. In Group A, there was no statistical difference in the measurements of the adenoids between the preoperative ultrasound and the ultrasound measurements under the guidance of intraoperative metal instruments (P > 0.05). In Group B, the adenoids of 1898 children aged 3-12 y were measured and were found thickest at 6 y, with an average of 5.035 ± 0.0609mm. There was no statistical difference in adenoid thickness between boys and girls (P > 0.05). In Group C, there was a linear correlation between AUT and A/N ratio (r = 0.999, P = 0.01) and between AUT and EANC (r = 0.950, P = 0.000). In children between 3 and 12 y of age, AUT greater than 6mm may be considered for surgical resection of adenoid hypertrophy.

Intraoperative navigation: Current applications and future directions

This article will describe and characterize the variety of navigation options available to the spine surgeon and how they contribute to modern spine surgery. Current products generally involve preoperative 3D imaging, registration of the patient's anatomy in the operating room, intraoperative 3D visualization, and active stereotactic instrument guidance. Current navigation technology focuses most on accurate pedicle screw placement, but is showing increasing promise for guiding precise osseous resections. As technology improves alongside surgeon familiarity and lowering costs, future applications of this technology for decompression and instrumentation of spinal elements could offer substantial benefits and ultimately produce superior outcomes over traditional techniques.

Intraoperative ultrasound in visceral surgery

Intraoperative ultrasound is aroutine procedure in abdominal surgery. Not only detection of focal lesions but also perfusion and elasticity analyses using color-coded Doppler sonography, contrast-enhanced ultrasound and elastography enable highly sensitive and highly specific diagnostics, especially in oncological surgery. This article provides an overview on current techniques of intraoperative ultrasound and gives an outlook on future possibilities and applications. Literature-based presentation of evidence-based intraoperative ultrasound, discussion of current basic research and expert recommendations. Modern intraoperative ultrasound is ahighly efficient technique for detection and characterization of focal space-occupying lesions in surgery of benign and malignant diseases. Intraoperative ultrasound is ahighly sensitive and specific diagnostic tool, providing real-time diagnostics with a manageable amount of technical equipment. Thus, preoperative diagnostics can be refined, partly resulting in amodification of intraoperative treatment management. Future developments in the fields of digital image fusion with preoperative sectional imaging, optical guidance of surgical instruments and molecular targeted tumor therapy will increase the importance of intraoperative sonography even more.

Intraoperative Assessment of the Axial Rotational Positioning of a Modern Ankle Arthroplasty Tibial Component Using Preoperative Patient-Specific Instrumentation Guidance.

The use of patient-specific instrumentation (PSI) in modern total ankle replacement (TAR) has augmented positioning of the tibial component, eliminating the need for complex jigs. Coronal and sagittal alignment are intuitive with this design and have been studied, but axial rotation has not. The purpose of this study was to assess the relationship between the planned preoperative axial rotation as set by the PSI guide and the rotation determined intraoperatively with non-PSI instrumentation. This was a prospective cohort study of 22 consecutive cases. The axial rotation angle between the medial gutter and the tibial implant position on the preoperative CT-scan based plan was extracted. At the time of surgery, the medial gutter alignment instrument from the non-PSI instrumentation was inserted and an intraoperative axial photograph obtained to record the angle between the medial gutter and the axial rotation guide pins set by the PSI instrumentation. The 2 measurements were compared and further statistical analysis included Pearson correlation and paired Student t test. The average axial rotation angle between the medial gutter and the implant on the PSI preoperative plan was 5.4 ± 2.9 degrees, whereas the intraoperative photograph from the medial gutter alignment instrument to the pin was 5.9 ±3.8 degrees. This demonstrated a Pearson correlation of R = 0.54 and a P value of .53. The average difference between the two was -0.46 (95% CI: -2.04, 1.10), meaning that components were either slightly externally rotated or that the fork was aimed internally. Based on this group, 50% (11/22) were within 2 degrees of the target and 77% (17/22) were within 4 degrees of the target. Patient-specific guides allowed for reproducible rotational tibial component implantation in modern TAR. Further work is needed to better understand the biomechanical effects of the rotational profile and consequences on survivorship. Level IV, case series.

Low-Computational Cost Stitching Method in a Three-Eyed Endoscope.

Aortic valve replacement is the only definitive treatment for aortic stenosis, a highly prevalent condition in elderly population. Minimally invasive surgery brought numerous benefits to this intervention, and robotics recently provided additional improvements in terms of telemanipulation, motion scaling, and smaller incisions. Difficulties in obtaining a clear and wide field of vision is a major challenge in minimally invasive aortic valve surgery: surgeon orientates with difficulty because of lack of direct view and limited spaces. This work focuses on the development of a computer vision methodology, for a three-eyed endoscopic vision system, to ease minimally invasive instrument guidance during aortic valve surgery. Specifically, it presents an efficient image stitching method to improve spatial awareness and overcome the orientation problems which arise when cameras are decentralized with respect to the main axis of the aorta and are nonparallel oriented. The proposed approach was tested for the navigation of an innovative robotic system for minimally invasive valve surgery. Based on the specific geometry of the setup and the intrinsic parameters of the three cameras, we estimate the proper plane-induced homographic transformation that merges the views of the operatory site plane into a single stitched image. To evaluate the deviation from the image correct alignment, we performed quantitative tests by stitching a chessboard pattern. The tests showed a minimum error with respect to the image size of 0.46 ± 0.15% measured at the homography distance of 40 mm and a maximum error of 6.09 ± 0.23% at the maximum offset of 10 mm. Three experienced surgeons in aortic valve replacement by mini-sternotomy and mini-thoracotomy performed experimental tests based on the comparison of navigation and orientation capabilities in a silicone aorta with and without stitched image. The tests showed that the stitched image allows for good orientation and navigation within the aorta, and furthermore, it provides more safety while releasing the valve than driving from the three separate views. The average processing time for the stitching of three views into one image is 12.6 ms, proving that the method is not computationally expensive, thus leaving space for further real-time processing.

The impact of guided instrument insertion during laparoscopy: a randomized study with novices in an optical box trainer.

During laparoscopic operations, the trocars are often out of the viewing field of the laparoscope. Blind insertion of laparoscopic instruments is potentially dangerous especially when they are pointed or hot. A guidance of the instrument to the target point has the potential to improve the safety of instrument insertion. In this study, the effect of a mechanical and an optical tool for guided instrument insertion into the abdominal cave was evaluated. The controlled prospective randomized study measured safety and efficiency of instrument insertion by 60 novices in an inanimate standardized box trainer. A post-test questionnaire based on the NASA Task Load Index prompted for the subjective impressions of the subjects. Instrument insertion with optical guidance showed a shorter (p = 0.002) insertion time (median 87.5s for nine insertions) compared with blind insertion (median 112.0s for nine insertions). The error number with optical guidance (median 0.5) was lower (p = 0.064) compared with blind insertion (median 1.0). The mechanical guidance showed a shorter (p = 0.001) insertion time (median 89.0s for nine insertions) and less (p = 0.044) touch errors (median 0) compared with blind insertion. The results of the two guidance tools (mechanical vs. optical guidance) showed no significant difference. In the questionnaire, 89% of the novices subjectively judged the mechanical guidance tool better than blind insertion. The assessments of optical compared to mechanical guidance turned out quite similar. In the experimental setup, instrument insertion with a guidance tool performed faster and safer compared with blind insertion. The subjective assessments confirmed the benefit of instrument guidance.

EXPERIENCE OF THE DEVELOPMENT OF THE CONTROL SYSTEM OF MECHANISMS WITH PARALLEL STRUCTURE OF THE TYPE "HEXAPOD" FOR POSITIONING AND INTRODUCTION OF LARGE-SIZED OBJECTS OF INFORMATION SPACE PLATFORM

The problems of designing a hexapod control system - a mechanism with parallel kinematics, designed for guidance and positioning of instruments and antennas of orbiting satellite platforms are considered. Based on the solution of the extended kinematics problem, the algorithm for controlling linear drives with a kinematic pair of screw-nut and two two-axis hinges is specified. The hexapod control scheme with the spatial load position sensor is given, the feasibility of positional control algorithms is estimated on the basis of the modern domestic element base. The estimation is made by the method of mathematical modeling. An algorithm for adaptive neural network control of a hexapod is proposed. An artificial neural network has been developed, which together with a nonlinear controller regulates the force acting on linear actuators by control error. To assess the quality of hexapod control, a dynamic model of the hexapod control system was created in the simulation package SimMechanics of the MATLAB Simulink system. A description is given of the hardware part of the digital control system-the hexapod control unit).