Evaluation of a curved surgical prototype in a human larynx.

PURPOSE: It is not always possible to create linear access to the larynx using a rigid operating laryngoscope for microlaryngoscopy. In this study, we evaluate the usability of a novel curved surgical prototype with flexible instruments for the larynx (sMAC) in a simulation dummy and human body donor. METHODS: In a user study (n = 6), head and neck surgeons as well as medical students tested the system for visualization quality and accessibility of laryngeal landmarks on an intubation dummy and human cadaver. A biopsy of the epiglottis was taken from the body donor. Photographic and time documentation was carried out. RESULTS: The sMAC system demonstrated general feasibility for laryngeal surgery. Unlike conventional microlaryngoscopy, all landmarks could be visualized and manipulated in both setups. Biopsy removal was possible. Visibility of the surgical field remained largely unobstructed even with an endotracheal tube in place. Overall handling of the sMAC prototype was satisfactorily feasible at all times. CONCLUSION: The sMAC system could offer an alternative for patients, where microlaryngoscopy is not applicable. A clinical trial has to clarify if the system benefits in clinical routine.

[Measurement of tissue-shift for head neck rotation]. / Messung von Strukturverschiebungen bei Kopf-Hals-Rotation.

BACKGROUND: During neck surgery the head of the patient is located in such a position that the neck-tissue is deformed compared to the normal head-position. The consideration of this tissue deformation of the neck during head rotation is the first step to using preoperative image data for medical navigation. MATERIAL AND METHODS: The tissue shift was measured and analyzed based on MRT-image data of a subject group of 5 patients. RESULTS: The big vessels, lying contralateral to the rotation, demonstrated a larger shift than those vessels, lying ipsilateral. The shift was nonlinear to the head rotation and the shift of the V. jugularis interna was less pronounced than the shift of the A. carotis communis even though they both run in the same adventitia. In the cranial neck section, the movement of the tissue was larger than in the caudal neck section. CONCLUSION: The knowledge about tissue shifts in different head positions should promote intraoperative, minimally invasive procedures. The expectation is that such examinations facilitate the navigation in neck surgery with online calculation of tissue shifts.

Preclinical Performance Evaluation of a Robotic Endoscope for Non-Contact Laser Surgery.

Despite great efforts, transoral robotic laser surgery has not been established clinically. Patient benefits are yet to be proven to accept shortcomings of robotic systems. In particular, laryngeal reachability and transition from microscope to accurate endoscopic laser ablation have not been achieved. We have addressed those challenges with a highly integrated robotic endoscope for non-contact endolaryngeal laser surgery. The current performance status has been assessed in multi-level user studies. In addition, the system was deployed to an ex vivo porcine larynx. The robotic design comprises an extensible continuum manipulator with multifunctional tip. The latter features laser optics, stereo vision, and illumination. Vision-based performance assessment is derived from depth estimation and scene tracking. Novices and experts (n = 20) conducted teleoperated delineation tasks to mimic laser ablation of delicate anatomy. Delineation with motion-compensated and raw endoscopic visualisation was carried out on planar and non-planar nominal patterns. Root mean square tracing errors of less than 0.75 mm were feasible with task completion times below 45 s. Relevant anatomy in the porcine larynx was exposed successfully. Accuracy and usability of the integrated platform bear potential for dexterous laser manipulation in clinical settings. Cadaver and in vivo animal studies may translate ex vivo findings.

Droplet applicator module for reproducible and controlled endoscopic laryngeal adductor reflex stimulation.

This work presents a droplet applicator module to generate stable droplets with different muzzle energies for the reproducible endoscopic stimulation of the laryngeal adductor reflex (LAR). The LAR is a protective reflex of the human larynx; an abnormal LAR performance may cause aspiration pneumonia. A pathological LAR can be detected by evaluating its onset latency. The reflex can be triggered by shooting a droplet onto the laryngeal mucosa, which is referred to as Microdroplet Impulse Testing of the LAR (MIT-LAR). Stimulation intensity variation is desired as the reflex threshold may vary inter-individually. The kinetic energy of a droplet after detachment from the nozzle, i.e., its muzzle energy, is considered an appropriate metric for the LAR stimulation intensity. In this work, a suitable nozzle channel geometry is identified based on the experimental evaluation of droplet formation using three different nozzle channel geometries. Two nontoxic additives are evaluated regarding their effect on fluid properties and droplet formation. The range of achievable droplet muzzle energies is determined by high-speed cinematography in association with a physically motivated model of the macroscopic droplet motion. The experimental results show that sodium chloride is a suitable additive to enhance droplet stability in the studied parameter range with the proposed system. Droplet muzzle energy variation from 0.02 µ J to 1.37 µ J was achieved while preserving the formation of a single stimulation droplet. These results are an important prerequisite for a safe and reproducible LAR stimulation by MIT-LAR, which could also help to further elucidate the physiological mechanisms underlying this laryngeal reflex.

New augmented reality and robotic based methods for head-surgery.

Within the framework of the collaborative research centre "Information Technology in Medicine--Computer and Sensor-Aided Surgery" (SFB414) new methods for intraoperative computer assistance of surgical procedures are being developed. The developed tools will be controlled by an intraoperative host which provides interfaces to the electronic health record (EHR) and intraoperative computer assisted instruments.The interaction is based on standardised communication protocols. Plug & work functions will allow easy integration and configuration of new components. Intraoperative systems currently under development are intraoperative augmented reality (AR) using a projector and via a microscope, a planning system for definition of complex trajectories and a surgical robot system. The developed systems are under clinical evaluation and showing promising results in their application.