Experimental validation of predicted application accuracies for computer-assisted (CAS) intraoperative navigation with paired-point registration

Open-source navigation system for tracking dissociated parts with multi-registration

PURPOSE

During reconstructive surgery, knee and hip replacements, and orthognathic surgery, small misalignments in the pose of prosthesis and bones can lead to severe complications. Hence, the translational and angular accuracies are critical. However, traditional image-based surgical navigation lacks orientation data between structures, and imageless systems are unsuitable for cases of deformed anatomy. We introduce an open-source navigation system using a multiple registration approach that can track instruments, implants, and bones to precisely guide the surgeon in emulating a preoperative plan.

METHODS

We derived the analytical error of our method and designed a set of phantom experiments to measure its precision and accuracy. Additionally, we trained two classification models to predict the system reliability from fiducial points and surface matching registration data. Finally, to demonstrate the procedure feasibility, we conducted a complete workflow for a real clinical case of a patient with fibrous dysplasia and anatomical misalignment of the right femur using plastic bones.

RESULTS

The system is able to track the dissociated fragments of the clinical case and average alignment errors in the anatomical phantoms of [Formula: see text]  mm and [Formula: see text]. While the fiducial-points registration showed satisfactory results given enough points and covered volume, we acknowledge that the surface refinement step is mandatory when attempting surface matching registrations.

CONCLUSION

We believe that our device could bring significant advantages for the personalized treatment of complex surgical cases and that its multi-registration attribute is convenient for intraoperative registration loosening cases.

Preliminary Study of the Treatment Strategy for Retaining Traumatic Foreign Bodies Involving the Carotid Artery

PURPOSE

Craniomaxillofacial trauma is usually accompanied by indwelling foreign bodies, and some of those are close to the carotid artery, which increases the risks and difficulties of surgical treatment. The introduction of interventional radiology combined with image-guided surgical navigation may be a good solution for precise surgery to remove foreign bodies.

PATIENTS AND METHODS

Four patients were included in the study. All patients underwent digital subtraction angiography and enhanced computed tomography before surgery. The patients were divided into 3 categories (A, B, and C) according to the presence of carotid artery damage and its positional relationship with the foreign body, and 3 corresponding treatment strategies were developed. Treatments were completed using interventional radiology and surgical navigation systems.

RESULTS

All foreign bodies were completely removed, except for 1 remaining in the jugular foramen in a patient. The prognosis of all patients was good, and no systemic complications occurred.

CONCLUSION

The combined interventional radiology and surgical navigation method proposed in this study is an effective method to improve the accuracy and safety of foreign body removal surgery.

Novel Multimodal, Multiscale Imaging System with Augmented Reality

A novel multimodal, multiscale imaging system with augmented reality capability were developed and characterized. The system offers 3D color reflectance imaging, 3D fluorescence imaging, and augmented reality in real time. Multiscale fluorescence imaging was enabled by developing and integrating an in vivo fiber-optic microscope. Real-time ultrasound-fluorescence multimodal imaging used optically tracked fiducial markers for registration. Tomographical data are also incorporated using optically tracked fiducial markers for registration. Furthermore, we characterized system performance and registration accuracy in a benchtop setting. The multiscale fluorescence imaging facilitated assessing the functional status of tissues, extending the minimal resolution of fluorescence imaging to ~17.5 µm. The system achieved a mean of Target Registration error of less than 2 mm for registering fluorescence images to ultrasound images and MRI-based 3D model, which is within clinically acceptable range. The low latency and high frame rate of the prototype system has shown the promise of applying the reported techniques in clinically relevant settings in the future.

Vector field analysis for surface registration in computer-assisted ENT surgery

Background

Manual paired‐point registration for navigated ENT‐surgery is prone to human errors; automatic surface registration is often caught in local minima.

Methods

Anatomical features of the human occiput are integrated into an algorithm for surface registration. A vector force field is defined between the patient and operating room datasets; registration is facilitated through gradient‐based vector field analysis optimization of an energy function. The method is validated exemplarily on patient surface data provided by a mechanically positioned A‐mode ultrasound sensor.

Results

Successful registrations were achieved within the entire parameter space, as well as from positions of local minima that were found by the Gaussian fields algorithm for surface registration. Sub‐millimetric registration error was measured in clinically relevant anatomical areas on the anterior skull and within the generally accepted margin of 1.5 mm for the entire head.

Conclusion

The satisfactory behavior of this approach potentially suggests a wider clinical integration.

Accuracy Validation of Neuronavigation Comparing Headholder-Based System with Head-Mounted Array-A Cadaveric Study

BACKGROUND

Neuronavigation is widely used for intracranial neurosurgical procedures and is commonly based on the standard reference array being fixed to the headholder. Some cases require the reference array to be attached directly to the head. The aim of this cadaveric study was to compare operational accuracy of a head-mounted reference array with the standard headholder-based system.

METHODS

Navigation accuracy was evaluated with 10 cadaveric specimens. Each specimen was prepared with 8 titanium microscrews that served as reference points on the external skull, and computed tomography was performed. Registration of all specimens was done using surface matching with infrared laser on three-dimensional reconstructed high-resolution computed tomography. In all 10 specimens, the head-mounted reference array and headholder-based system were compared by 10 repetitive measurements. The deviation was evaluated for each screw and compared using nonparametric Mann-Whitney U test between groups and screws. A Bland-Altman plot was generated for comparison.

RESULTS

A total of 1600 measurements were conducted. Mean deviation was 1.97 mm (95% confidence interval, 1.90-2.03 mm) with the head-mounted reference array and 2.10 mm (95% confidence interval, 2.04-2.18 mm) with the headholder based system. There was no significant difference between methods in 9 of 10 specimens. In 1 specimen, the head-mounted array was superior. The deviation in either method showed a significant correlation, indicating high pertinence for registration (P < 0.001).

CONCLUSIONS

Navigation with the head-mounted reference array demonstrated comparable accuracy to the headholder-based system and can be used without reduced accuracy. Careful registration is mandatory.

Probe versus microscope: a comparison of different methods for image-to-patient registration

PURPOSE

Computer-aided navigation is widely used in ENT surgery. The position of a surgical instrument is shown in the CT/MR images of the patient and can thus be a good support for the surgeon. The accuracy is highly dependent on the registration done prior to surgery. A microscope and a probe can both be used for registration and navigation, depending on the surgical intervention. A navigation system typically only reports the fiducial registration error after paired-point registration. However, the target registration error (TRE)-a measurement for the accuracy in the surgical area-is much more relevant. The aim of this work was to compare the performance of a microscope relative to a conventional probe-based approach with different registration methods.

METHODS

In this study, optical tracking was used to register a plastic skull to its preoperative CT images with paired-point registration. Anatomical landmarks and skin-affixed markers were used as fiducials and targets. With both microscope and probe, four different registration methods were evaluated based on their TREs at 10 targets. For half of the experiments, a surface registration and/or external fiducials were used additionally to paired-point registration to study their influence to accuracy.

RESULTS

Overall, probe registration leads to a smaller TRE ([Formula: see text]) than registration with a microscope ([Formula: see text]). Additional surface registration does not result in better accuracy of navigation for microscope and probe. The lowest mean TRE for both pointers can be achieved with paired-point registration only and radiolucent markers.

CONCLUSION

Our experiments showed that a probe used for registration and navigation achieves lower TREs compared using a microscope. Neither additional surface registration nor additional fiducials on an external reference element are necessary for improved accuracy of navigated ENT surgery on a plastic skull.