Comparison of magnetic tracking and optical tracking by simultaneous use of two independent frameless stereotactic systems

Computed tomography and structured light imaging guided orthopedic navigation puncture system: effective reduction of intraoperative image drift and mismatch

Background

Image-guided surgical navigation systems are widely regarded as the benchmark for computer-assisted surgical robotic platforms, yet a persistent challenge remains in addressing intraoperative image drift and mismatch. It can significantly impact the accuracy and precision of surgical procedures. Therefore, further research and development are necessary to mitigate this issue and enhance the overall performance of these advanced surgical platforms.

Objective

The primary objective is to improve the precision of image guided puncture navigation systems by developing a computed tomography (CT) and structured light imaging (SLI) based navigation system. Furthermore, we also aim to quantifying and visualize intraoperative image drift and mismatch in real time and provide feedback to surgeons, ensuring that surgical procedures are executed with accuracy and reliability.

Methods

A CT-SLI guided orthopedic navigation puncture system was developed. Polymer bandages are employed to pressurize, plasticize, immobilize and toughen the surface of a specimen for surgical operations. Preoperative CT images of the specimen are acquired, a 3D navigation map is reconstructed and a puncture path planned accordingly. During surgery, an SLI module captures and reconstructs the 3D surfaces of both the specimen and a guiding tube for the puncture needle. The SLI reconstructed 3D surface of the specimen is matched to the CT navigation map via two-step point cloud registrations, while the SLI reconstructed 3D surface of the guiding tube is fitted by a cylindrical model, which is in turn aligned with the planned puncture path. The proposed system has been tested and evaluated using 20 formalin-soaked lower limb cadaver specimens preserved at a local hospital.

Results

The proposed method achieved image registration RMS errors of 0.576 ± 0.146 mm and 0.407 ± 0.234 mm between preoperative CT and intraoperative SLI surface models and between preoperative and postoperative CT surface models. In addition, preoperative and postoperative specimen surface and skeletal drifts were 0.033 ± 0.272 mm and 0.235 ± 0.197 mm respectively.

Conclusion

The results indicate that the proposed method is effective in reducing intraoperative image drift and mismatch. The system also visualizes intraoperative image drift and mismatch, and provides real time visual feedback to surgeons.

Novel microscope-based visual display and nasopharyngeal registration for auditory brainstem implantation: a feasibility study in an ex vivo model

Purpose

An auditory brainstem implant (ABI) represents an alternative for patients with profound hearing loss who are constrained from receiving a cochlear implant. The positioning of the ABI electrode influences the patient’s auditory capacity and, therefore, quality of life and is challenging even with available intraoperative electrophysiological monitoring. This work aims to provide and assess the feasibility of visual-spatial assistance for ABI positioning.

Methods

The pose of the forceps instrument that grasps the electrode was electromagnetically navigated and interactively projected in the eyepieces of a surgical microscope with respect to a target point. Intraoperative navigation was established with an experimental technique for automated nasopharyngeal patient registration. Two ABI procedures were completed in a human specimen head.

Results

An intraoperative usability study demonstrated lower localization error when using the proposed visual display versus standard cross-sectional views. The postoperative evaluations of the preclinical study showed that the center of the electrode was misplaced to the planned position by 1.58 mm and 3.16 mm for the left and the right ear procedure, respectively.

Conclusion

The results indicate the potential to enhance intraoperative feedback during ABI positioning with the presented system. Further improvements consider estimating the pose of the electrode itself to allow for better orientation during placement.

Supplementary Information

The online version contains supplementary material available at 10.1007/s11548-021-02514-x.

Accurate Image-guided (Re)Placement of NIRS Probes

BACKGROUND AND OBJECTIVE

Functional near-infrared spectroscopy (fNIRS) has become an attractive choice to neuroscience because of its high temporal resolution, ease of use, non-invasiveness, and affordability. With the advent of wearable fNIRS technology, on-the-spot studies of brain function have become viable. However, the lack of within-subject reproducibility is one of the barriers to the full acceptability of fNIRS. To support the validation of the claim that within-subject reproducibility of fNIRS could benefit from accurate anatomical information, we present in this paper a method to develop an image-based system that improves the placement of the sensors on the scalp at interactive rates.

METHODS

The proposed solution consists of an electromagnetic digitizer and an interactive visualization system that allows monitoring the movements of the digitizer on a real head with respect to the underlying cerebral cortical structures. GPU-based volume raycasting rendering is applied to unveil these structures from the corresponding magnetic resonance imaging volume. Scalp and cortical surface are estimated from the scanned volume to improve depth perception. An alignment algorithm between the real and scanned heads is devised to visually feedback the position of the stylus of the digitizer. Off-screen rendering of the depthmaps of the visible surfaces makes spatial positioning of a 2D interaction pointer possible.

RESULTS

We evaluated the alignment accuracy using four to eight anatomical landmarks and found seven to be a good compromise between precision and efficiency. Next, we evaluated reproducibility in positioning five arbitrarily chosen points on three volunteers by four operators over five sessions. In every session, seven anatomical landmarks were applied in the alignment of the real and the scanned head. For the same volunteer, one-way analysis of variance (ANOVA) revealed no significant differences within the five points digitized by the same operator over five sessions (α = 0.05). In addition, preliminary study of motor cortex activation by right-hand finger tapping showed the potential of our approach to increase functional fNIRS reproducibility.

CONCLUSIONS

Results of experiments suggest that the enhancement of the visualization of the location of the probes on the scalp, relative to the underlying cortical structures, improves reproducibility of fNIRS measurements. As further work, we plan to study the fNIRS reproducibility in other cortical regions and in clinical settings using the proposed system.

The development of a novel grip motion analysis technique using the Dartfish movement analysis software to evaluate hand movements during activities of daily living

Individuals with hand osteoarthritis (OA) have impairments in grip strength and range of motion (ROM). Obtaining quantitative joint angle measures of the hand is difficult. Without a complete understanding of the kinematics of the hand, the assessment of hand OA when performing activities of daily living (ADL) and recreational activities is not fully understood. The objectives of this study were to establish a simple measurement technique (Grip Configuration Model) describing an individual's grip ROM using the Dartfish Movement Analysis Software, and compare the joint angle measures during maximum flexion/extension and five ADL in people with/without hand OA. Forty participants (20 without hand OA, 20 with hand OA) thumb CMC and MCP, and index MCP and PIP joint angles were evaluated for each activity using the Dartfish Software and Grip Configuration Model. Significant limitations of 17.2% (p < 0.001) and 12.7% (p = 0.01) were seen in the group with hand OA for maximum flexion/extension, respectively. The spray bottle task demonstrated a significant difference of 14.7% (p = 0.001) between the two test groups. Measurements using the Dartfish Software were compared against a manual goniometer and electromagnetic tracking system. This study demonstrated the weakened ROM in individuals with hand OA is translated to ADL and how the Grip Configuration Model simplifies the evaluation of how people grasp objects.

Optical and Electromagnetic Tracking Systems for Biomedical Applications: A Critical Review on Potentialities and Limitations

Optical and electromagnetic tracking systems represent the two main technologies integrated into commercially-available surgical navigators for computer-assisted image-guided surgery so far. Optical Tracking Systems (OTSs) work within the optical spectrum to track the position and orientation, i.e., pose of target surgical instruments. OTSs are characterized by high accuracy and robustness to environmental conditions. The main limitation of OTSs is the need of a direct line-of-sight between the optical markers and the camera sensor, rigidly fixed into the operating theatre. Electromagnetic Tracking Systems (EMTSs) use electromagnetic field generator to detect the pose of electromagnetic sensors. EMTSs do not require such a direct line-of-sight, however the presence of metal or ferromagnetic sources in the operating workspace can significantly affect the measurement accuracy. The aim of the proposed review is to provide a complete and detailed overview of optical and electromagnetic tracking systems, including working principles, source of error and validation protocols. Moreover, commercial and research-oriented solutions, as well as clinical applications, are described for both technologies. Finally, a critical comparative analysis of the state of the art which highlights the potentialities and the limitations of each tracking system for a medical use is provided.

Recent technological advances in pediatric brain tumor surgery

X-rays and ventriculograms were the first imaging modalities used to localize intracranial lesions including brain tumors as far back as the 1880s. Subsequent advances in preoperative radiological localization included computed tomography (CT; 1971) and MRI (1977). Since then, other imaging modalities have been developed for clinical application although none as pivotal as CT and MRI. Intraoperative technological advances include the microscope, which has allowed precise surgery under magnification and improved lighting, and the endoscope, which has improved the treatment of hydrocephalus and allowed biopsy and complete resection of intraventricular, pituitary and pineal region tumors through a minimally invasive approach. Neuronavigation, intraoperative MRI, CT and ultrasound have increased the ability of the neurosurgeon to perform safe and maximal tumor resection. This may be facilitated by the use of fluorescing agents, which help define the tumor margin, and intraoperative neurophysiological monitoring, which helps identify and protect eloquent brain.

Smart stylet: the development and use of a bedside external ventricular drain image-guidance system

BACKGROUND

Placement accuracy of ventriculostomy catheters is reported in a wide and variable range. Development of an efficient image-guidance system may improve physician performance and patient safety.

OBJECTIVE

We evaluate the prototype of Smart Stylet, a new electromagnetic image-guidance system for use during bedside ventriculostomy.

METHODS

Accuracy of the Smart Stylet system was assessed. System operators were evaluated for their ability to successfully target the ipsilateral frontal horn in a phantom model.

RESULTS

Target registration error across 15 intracranial targets ranged from 1.3 to 4.6 mm (mean 3.1 mm). Using Smart Stylet guidance, a test operator successfully passed a ventriculostomy catheter to a shifted ipsilateral frontal horn 20/20 (100%) times from the frontal approach in a skull phantom. Without Smart Stylet guidance, the operator was successful 4/10 (40%) times from the right frontal approach and 6/10 (60%) times from the left frontal approach. In a separate experiment, resident operators were successful 2/4 (50%) times when targeting the shifted ipsilateral frontal horn with Smart Stylet guidance and 0/4 (0%) times without image guidance using a skull phantom.

CONCLUSIONS

Smart Stylet may improve the ability to successfully target the ventricles during frontal ventriculostomy.

Optical Flow-Based Tracking of Needles and Needle-Tip Localization Using Circular Hough Transform in Ultrasound Images

Image-guided interventions have become the standard of care for needle-based procedures. The success of the image-guided procedures depends on the ability to precisely locate and track the needle. This work is primarily focused on 2D ultrasound-based tracking of a hollow needle (cannula) that is composed of straight segments connected by shape memory alloy actuators. An in-plane tracking algorithm based on optical flow was proposed to track the cannula configuration in real-time. Optical flow is a robust tracking algorithm that can easily run on a CPU. However, the algorithm does not perform well when it is applied to the ultrasound images directly due to the intensity variation in the images. The method presented in this work enables using the optical flow algorithm on ultrasound images to track features of the needle. By taking advantage of the bevel tip, Circular Hough transform was used to accurately locate the needle tip when the imaging is out-of-plane. Through experiments inside tissue phantom and ex-vivo experiments in bovine kidney, the success of the proposed tracking methods were demonstrated. Using the methods presented in this work, quantitative information about the needle configuration is obtained in real-time which is crucial for generating control inputs for the needle and automating the needle insertion.

Neuronavigation in the surgical management of brain tumors: current and future trends

Neuronavigation has become an ubiquitous tool in the surgical management of brain tumors. This review describes the use and limitations of current neuronavigational systems for brain tumor biopsy and resection. Methods for integrating intraoperative imaging into neuronavigational datasets developed to address the diminishing accuracy of positional information that occurs over the course of brain tumor resection are discussed. In addition, the process of integration of functional MRI and tractography into navigational models is reviewed. Finally, emerging concepts and future challenges relating to the development and implementation of experimental imaging technologies in the navigational environment are explored.

The usefulness of electromagnetic neuronavigation in the pediatric neuroendoscopic surgery

OBJECTIVE

Neuroendoscopy is applied to various intracranial pathologic conditions. But this technique needs informations for the anatomy, critically. Neuronavigation makes the operation more safe, exact and lesser invasive procedures. But classical neuronavigation systems with rigid pinning fixations were difficult to apply to pediatric populations because of their thin and immature skull. Electromagnetic neuronavigation has used in the very young patients because it does not need rigid pinning fixations. The usefulness of electromagnetic neuronavigation is described through our experiences of neuroendoscopy for pediatric groups and reviews for several literatures.

METHODS

Between January 2007 and July 2011, nine pediatric patients were managed with endoscopic surgery using electromagnetic neuronavigation (AxiEM, Medtronics, USA). The patients were 4.0 years of mean age (4 months-12 years) and consisted of 8 boys and 1 girl. Totally, 11 endoscopic procedures were performed. The cases involving surgical outcomes were reviewed.

RESULTS

The goal of surgery was achieved successfully at the time of surgery, as confirmed by postoperative imaging. In 2 patients, each patient underwent re-operations due to the aggravation of the previous lesion. And one had transient mild third nerve palsy due to intraoperative manipulation and the others had no surgery related complication.

CONCLUSION

By using electromagnetic neuronavigation, neuroendoscopy was found to be a safe and effective technique. In conclusion, electromagnetic neuronavigation is a useful adjunct to neuroendoscopy in very young pediatric patients and an alternative to classical optical neuronavigation.

Technical accuracy of optical and the electromagnetic tracking systems

Thousands of operations are annually guided with computer assisted surgery (CAS) technologies. As the use of these devices is rapidly increasing, the reliability of the devices becomes ever more critical. The problem of accuracy assessment of the devices has thus become relevant. During the past five years, over 200 hazardous situations have been documented in the MAUDE database during operations using these devices in the field of neurosurgery alone. Had the accuracy of these devices been periodically assessed pre-operatively, many of them might have been prevented.

The technical accuracy of a commercial navigator enabling the use of both optical (OTS) and electromagnetic (EMTS) tracking systems was assessed in the hospital setting using accuracy assessment tools and methods developed by the authors of this paper. The technical accuracy was obtained by comparing the positions of the navigated tool tip with the phantom accuracy assessment points. Each assessment contained a total of 51 points and a region of surgical interest (ROSI) volume of 120x120x100 mm roughly mimicking the size of the human head.

The error analysis provided a comprehensive understanding of the trend of accuracy of the surgical navigator modalities. This study showed that the technical accuracies of OTS and EMTS over the pre-determined ROSI were nearly equal. However, the placement of the particular modality hardware needs to be optimized for the surgical procedure. New applications of EMTS, which does not require rigid immobilization of the surgical area, are suggested.

Towards unified electromagnetic tracking system assessment-static errors

Recent advances in Image-Guided Surgery allows physicians to incorporate up-to-date, high quality patient data in the surgical decision making, and sometimes to directly perform operations based on pre- or intra-operatively acquired patient images. Electromagnetic tracking is the fastest growing area within, where the position and orientation of tiny sensors can be determined with sub-millimeter accuracy in the field created by a generator. One of the major barriers to the wider spread of electromagnetic tracking solutions is their susceptibility to ferromagnetic materials and external electromagnetic sources. The research community has long been engaged with the topic to find engineering solutions to increase measurement reliability and accuracy. This article gives an overview of related experiments, and presents our recommendation towards a robust method to collect representative data about electromagnetic trackers.

Application of electromagnetic technology to neuronavigation: a revolution in image-guided neurosurgery

Object

The authors investigated the practicality of electromagnetic neuronavigation in routine clinical use, and determined the applications for which it is at the advantage compared with other systems.

Methods

A magnetic field is generated encompassing the surgical volume. Devices containing miniaturized coils can be located within the field. The authors report on their experience in 150 cases performed with this technology.

Results

Electromagnetic neuronavigation was performed in 44 endoscopies, 42 ventriculoperitoneal shunt insertions for slit ventricles, 21 routine shunt insertions, 6 complex shunt insertions, 14 external ventricular drain placements for traumatic brain injury, 5 awake craniotomies, 5 Ommaya reservoir placements, and for 13 other indications. Satisfactory positioning of ventricular catheters was achieved in all cases. No particular changes to the operating theater set-up were required, and no significant interference from ferromagnetic instruments was experienced. Neurophysiological monitoring was not affected, nor did it affect electromagnetic guidance.

Conclusions

Neuronavigation enables safe, accurate surgery, and may ultimately reduce complications and improve outcome. Electromagnetic technology allows frameless, pinless, image-guided surgery, and can be used in all procedures for which neuronavigation is appropriate. This technology was found to be particularly advantageous compared with other technologies in cases in which freedom of head movement was helpful. Electromagnetic neuronavigation was therefore well suited to CSF diversion procedures, awake craniotomies, and cases in which rigid head fixation was undesirable, such as in neonates. This technology extends the application of neuronavigation to routine shunt placement and ventricular catheter placement in patients with traumatic brain injury.

The effect of surface area digitizations on the prediction of spherical anatomical geometries for computer-assisted applications

Intraoperative digitization of osseous structures is an integral component of computer-assisted orthopaedic surgery. This study determined the repeatability and accuracy of predicting known radii and center locations of spherical objects for different proportions of digitized surface areas and various sphere sizes. Also, we investigated these accuracies for some relevant near-spherical osseous structures where results from full area digitizations were considered to be true. Digitizations were performed using an electromagnetic tracker with a stylus on the total and fractional surfaces of 10 hemispheres, ranging from 10 to 28mm in radius. Repeatability was quantified by digitizing five trials of the entire surface and various fractional areas of selected hemisphere sizes. Similar trials were conducted on models of a humeral and femoral head, using the full head area as baseline and digitizing 15 and 30mm diameter areas of the full head. Mean error for the predicted radii and center positions of the hemispheres ranged from 0.39+/-0.29 to 0.14+/-0.07mm and 0.52+/-0.31 to 0.22+/-0.12mm, respectively. Repeatability for the predicted radii and centers produced maximum standard deviations of 0.31 and 0.42mm, respectively. All errors decreased as fractional area (40%, 60%, 80% and 100%) increased (p<0.05). Radius of curvature and center position errors for the humeral head model were 1.51+/-2.11 and 2.28+/-1.51mm, respectively. These errors for the femoral head model were 3.37+/-4.14 and 4.25+/-4.14mm, respectively. Errors resulting from the prediction of radius and center indicate that non-spherical anatomical structures are more sensitive to the digitized area, and hence digitization of the largest surface possible seems warranted.

Quantification of true in vivo (application) accuracy in cranial image-guided surgery: influence of mode of patient registration

OBJECTIVE

Very few studies have attempted to quantify the true (application) accuracy of image-guidance systems during craniotomy. This is, in part, because of the lack of millimetric intraoperative targets to allow such measurements. Few in vivo studies have compared the influence of mode of patient registration on subsequent true accuracy.

METHODS

Seven modes of patient registration (anatomic landmarks, 5 or 10 adhesive fiducials, bone-implanted fiducials [Stryker-Leibinger], surface matching using 45 or 100 points over scalp convexity or nose/auditory meatus contours) were compared. Thirty patients were involved in the study. Millimetric targets (bone drill holes or deep 1-mm titanium hemoclips) were placed then localized and saved at surgery. These targets were then identified on postoperative volumetric computed tomography fused with operative data sets. Localization errors of the targets were measured for each registration on an optical image-guidance system (StealthStation).

RESULTS

Only implanted cranial fiducials had a statistically significant accuracy advantage (1.7 +/- 0.7 mm). All other registrations had similar accuracies (approximately 4.0 +/- 1.7 mm) except anatomic landmarks, which were worse (4.8 +/- 1.9 mm). Calculated accuracies (root mean squared) had no predictive value for true (application) accuracies.

CONCLUSION

Not surprisingly, application accuracy of image-guidance is worse without implanted cranial markers. Unexpectedly, there was no major difference in localization of deep targets between the other registrations tested in this study. Care must be taken when using image-guidance tools to consider error introduced by registration. Cranium-implanted fiducials should be considered when high accuracy and reproducibility are needed.