Laboratory test of Single Landmark registration method for ultrasound-based navigation in laparoscopy using an open-source platform.

PURPOSE: Test the feasibility of the novel Single Landmark image-to-patient registration method for use in the operating room for future clinical trials. The algorithm is implemented in the open-source platform CustusX, a computer-aided intervention research platform dedicated to intraoperative navigation and ultrasound, with an interface for laparoscopic ultrasound probes. METHODS: The Single Landmark method is compared to fiducial landmark on an IOUSFAN (Kyoto Kagaku Co., Ltd., Japan) soft tissue abdominal phantom and T2 magnetic resonance scans of it. RESULTS: The experiments show that the accuracy of the Single Landmark registration is good close to the registered point, increasing with the distance from this point (12.4 mm error at 60 mm away from the registered point). In this point, the registration accuracy is mainly dominated by the accuracy of the user when clicking on the ultrasound image. In the presented set-up, the time required to perform the Single Landmark registration is 40% less than for the FLRM. CONCLUSION: The Single Landmark registration is suitable for being integrated in a laparoscopic workflow. The statistical analysis shows robustness against translational displacements of the patient and improvements in terms of time. The proposed method allows the clinician to accurately register lesions intraoperatively by clicking on these in the ultrasound image provided by the ultrasound transducer. The Single Landmark registration method can be further combined with other more accurate registration approaches improving the registration at relevant points defined by the clinicians.

Anthropomorphic liver phantom with flow for multimodal image-guided liver therapy research and training.

PURPOSE: The objective of this study was to develop a multimodal, permanent liver phantom displaying functional vasculature and common pathologies, for teaching, training and equipment development in laparoscopic ultrasound and navigation. METHODS: Molten wax was injected simultaneously into the portal and hepatic veins of a human liver. Upon solidification of the wax, the surrounding liver tissue was dissolved, leaving a cast of the vessels. A connection was established between the two vascular trees by manually manipulating the wax. The cast was placed, along with different multimodal tumor models, in a liver shaped mold, which was subsequently filled with a polymer. After curing, the wax was melted and flushed out of the model, thereby establishing a system of interconnected channels, replicating the major vasculature of the original liver. Thus, a liquid can be circulated through the model in a way that closely mimics the natural blood flow. RESULTS: Both the tumor models, i.e., the metastatic tumors, hepatocellular carcinoma and benign cyst, and the vessels inside the liver model, were clearly visualized by all the three imaging modalities: CT, MR and ultrasound. Doppler ultrasound images of the vessels proved the blood flow functionality of the phantom. CONCLUSION: By a two-step casting procedure, we produced a multimodal liver phantom, with open vascular channels, and tumor models, that is the next best thing to practicing imaging and guidance procedures in animals or humans. The technique is in principle applicable to any organ of the body.

Navigated bronchoscopy: a technical review.

BACKGROUND: Navigated bronchoscopy uses virtual 3-dimensional lung model visualizations created from preoperative computed tomography images often in synchronization with the video bronchoscope to guide a tool to peripheral lesions. Navigated bronchoscopy has developed fast since the introduction of virtual bronchoscopy with integrated electromagnetic sensors in the late 1990s. The purposes of the review are to give an overview and update of the technological components of navigated bronchoscopy, an assessment of its clinical usefulness, and a brief assessment of the commercial platforms for navigated bronchoscopy. METHODS: We performed a literature search with relevant keywords to navigation and bronchoscopy and iterated on the reference lists of relevant papers, with emphasis on the last 5 years. RESULTS: The paper presents an overview of the components necessary for performing navigated bronchoscopy, assessment of the diagnostic accuracy of different approaches, and an analysis of the commercial systems. We were able to identify 4 commercial platforms and 9 research and development groups with considerable activity in the field. Finally, on the basis of our findings and our own experience, we provide a discussion on navigated bronchoscopy with focus on the next steps of development. CONCLUSIONS: The literature review showed that the peripheral diagnostic accuracy has improved using navigated bronchoscopy compared with traditional bronchoscopy. We believe that there is room for improvement in the diagnostic success rate by further refinement of methods, approaches, and tools used in navigated bronchoscopy.

Bronchoscope-induced displacement of lung targets: first in vivo demonstration of effect from wedging maneuver in navigated bronchoscopy.

BACKGROUND: The accuracy of navigated bronchoscopy relies on a best possible correlation between the preoperative computed tomography images used for planning and the actual tumor position during bronchoscopy. Change in lung structure during the procedure may reduce success rate. The size of the lung changes during breathing, which may be predicted and at least partly compensated by a navigation system. We have studied the effect of the bronchoscopy itself, to see if and how the procedure causes further distortions, which might be harder to predict and compensate. METHODS: Using newly developed lung tracking sensors, we have measured the movement of individual lung segments during a bronchoscopy session in pigs. The bronchoscope was moved stepwise forward, ending in a wedge position, where it is often positioned when collecting peripheral biopsy specimens during conventional bronchoscopy. RESULTS: The influence of the bronchoscope on lung segment movement was minimal while positioned in the trachea, main bronchus, or lobe bronchus. However, in the wedge position, it displaced the lung targets and reduced the natural respiratory motion. CONCLUSIONS: A bronchoscope placed in a wedge position displaces lung targets and affects their respiratory behavior. As an image navigation system guides the operator towards a position dictated by the preoperative computed tomography, the displacement found in this study may cause the operator to miss the target. This may be part of the explanation for the limited success rates reported in the literature for navigated bronchoscopy.