Development of an Endoscopic Navigation System Based on Digital Image Processing

[Display technologies for augmented reality in medical applications]

BACKGROUND

One of the main challenges for modern surgery is the effective use of the many available imaging modalities and diagnostic methods. Augmented reality systems can be used in the future to blend patient and planning information into the view of surgeons, which can improve the efficiency and safety of interventions.

OBJECTIVE

In this article we present five visualization methods to integrate augmented reality displays into medical procedures and the advantages and disadvantages are explained.

MATERIAL AND METHODS

Based on an extensive literature review the various existing approaches for integration of augmented reality displays into medical procedures are divided into five categories and the most important research results for each approach are presented.

RESULTS

A large number of mixed and augmented reality solutions for medical interventions have been developed as research prototypes; however, only very few systems have been tested on patients.

CONCLUSION

In order to integrate mixed and augmented reality displays into medical practice, highly specialized solutions need to be developed. Such systems must comply with the requirements with respect to accuracy, fidelity, ergonomics and seamless integration into the surgical workflow.

The Influence of Different Segmentation Methods on the Extraction of Imaging Histological Features of Hepatocellular Carcinoma CT

In order to analyze the influence of different segmentation techniques on hepatocellular carcinoma (HCC) CT (Computed Tomography) imaging histological feature extraction, Grow Cut method and Graph Cut method are used to segment hepatocellular carcinoma from arterial CT images of HCC patients, and the stability and repeatability of imaging histological features are studied. Meanwhile, hierarchical clustering method is used to reduce the redundancy of features. The results show that the repeatability and redundancy mainly depend on the method of tumor segmentation. Semi-automatic segmentation method can improve the repeatability of image features, and hierarchical clustering can reduce the redundancy of features. Different segmentation techniques have different effects on the extraction of histological features of CT images of HCC.

Robust Motion Estimation and Structure Recovery from Endoscopic Image Sequences With an Adaptive Scale Kernel Consensus Estimator

To correctly estimate the camera motion parameters and reconstruct the structure of the surrounding tissues from endoscopic image sequences, we need not only to deal with outliers (e.g., mismatches), which may involve more than 50% of the data, but also to accurately distinguish inliers (correct matches) from outliers. In this paper, we propose a new robust estimator, Adaptive Scale Kernel Consensus (ASKC), which can tolerate more than 50 percent outliers while automatically estimating the scale of inliers. With ASKC, we develop a reliable feature tracking algorithm. This, in turn, allows us to develop a complete system for estimating endoscopic camera motion and reconstructing anatomical structures from endoscopic image sequences. Preliminary experiments on endoscopic sinus imagery have achieved promising results.

Image-guided minimally invasive surgical access to the temporomandibular joint: A preliminary report

PURPOSE

To establish a protocol for image-guided minimally invasive surgical access to the temporomandibular joint (TMJ).

MATERIALS AND METHODS

This study involved 2 patients with TMJ pain and mandibular motion dysfunction. Axial magnetic resonance imaging (MRI) of the TMJ was obtained and loaded into an intra-operative navigation system to guide joint space injection. With a navigated syringe, 1 mL synvisc Hylan G-F 20 was directly injected into the superior and inferior joint spaces under navigation guidance.

RESULTS

With the assistance of an intraoperative navigational system, the TMJ MRI images were visualized in 3 dimensions and enabled guiding a needle into the superior and inferior joint spaces for therapeutic injection. The treatment outcome for both patients was satisfactory with improvement in pain score and mandibular motion.

CONCLUSIONS

A protocol for image-guided minimally invasive surgical access to the TMJ was established. This could provide the technical basis for evaluation of accurate joint space intervention as a form of treatment of appropriate TMJ disorders.

Markerless Endoscopic Registration and Referencing

Accurate patient registration and referencing is a key element in navigated surgery. Unfortunately all existing methods are either invasive or very time consuming. We propose a fully non-invasive optical approach using a tracked monocular endoscope to reconstruct the surgical scene in 3D using photogrammetric methods. The 3D reconstruction can then be used for matching the pre-operative data to the intra-operative scene. In order to cope with the near real-time requirements for referencing, we use a novel, efficient 3D point management method during 3D model reconstruction. The presented prototype system provides a reconstruction accuracy of 0.1 mm and a tracking accuracy of 0.5 mm on phantom data. The ability to cope with real data is demonstrated by cadaver experiments.

Scale-invariant registration of monocular endoscopic images to CT-scans for sinus surgery

In this paper, we present a novel method for intra-operative registration directly from monocular endoscopic images. This technique has the potential to provide a more accurate surface registration at the surgical site than existing methods. It can operate autonomously from as few as two images and can be particularly useful in revision cases where surgical landmarks may be absent. A by-product of video registration is an estimate of the local surface structure of the anatomy, thus providing the opportunity to dynamically update anatomical models as the surgery progresses. Our approach is based on a previously presented method [Burschka, D., Hager, G.D., 2004. V-GPS (SLAM):--Vision-based inertial system for mobile robots. In: Proceedings of ICRA, 409-415] for reconstruction of a scaled 3D model of the environment from unknown camera motion. We use this scaled reconstruction as input to a PCA-based algorithm that registers the reconstructed data to the CT data and recovers the scale and pose parameters of the camera in the coordinate frame of the CT scan. The result is used in an ICP registration step to refine the registration estimates. The details of our approach and the experimental results with a phantom of a human skull and a head of a pig cadaver are presented in this paper.

Virtual image navigation: a new method to control intraoperative bleeding in neuroendoscopic surgery. Technical note

In this neuroendoscopic study the authors tested the newly developed "red-out module" of their visual navigation system that enables the neurosurgeon to achieve hemostasis if total visualization is lost due to hemorrhage ("red out") within the visual field. An optical position measurement system connected to the endoscope guarantees that digitized endoscopic images are coupled with the accurate endoscopic position. Computerized images are simultaneously stored with their respective position data, and this creates a virtual anatomical landscape. The system was tested in in vivo bleeding conditions in a rat model. Artificial endoscopic cavities were created in the inguinal, pelvic, and jugular regions in rats to imitate the conditions of the human ventricular system. Two experimental settings were tested: Technique I, in which a computer landmark has been previously determined at the point where the vessel will be lesioned; and Technique II, in which a landmark has been previously set in the surrounding area of the vessel. Immediately after hemorrhage obscures the visual field (red out), the computer automatically displays the virtual images on a separate monitor. The previously set landmarks and the graphic overlay of the coagulation fiber enable the surgeon to navigate within the operative field based on the virtual images and to perform coagulation at the site of the lesion. A total of 175 vessels were coagulated: 43 arteries and 132 veins. In using Technique I, 130 (90.9%) of 143 vessels and in using Technique II, 26 (81.2%) of 32 arteries were successfully coagulated. The authors' data revealed that virtual image guidance has the potential to be a helpful tool in neuroendoscopy.