Ubiquitous Tracking in the Medical Environment

Abstract

Computer-Integrated Surgery and intra-operative navigation opened a new era in interventional medicine. With the use of surgical navigation systems it has become possible to track tools and visualize the patient's preoperative records in real-time in the desired region, or overlay patient information and critical data. Navigation, as an enabling technology, has facilitated surgical simulation and training of medical students. In the future, we expect the rise of the concept of “ubiquitous tracking”, where all major parts of the medical working environment are tracked and modeled real-time in a virtual environment according to their physical state and position.One of the emerging modalities, electromagnetic tracking's (EMT) main advantage is that it does not required the continuous line-of-sight between the marker and the receiver, while this remains a serious limitation for optical tracking. EMT makes it possible to assist complex interventions, such as bronchoscopy, radiosurgery, heart ablation and beyond 0. In the future, tracking technology should get embedded in the entire operating theater through the combination of EMT sensors and RF ID tags. A fully sensorized operating room (OR) would allow for the better understanding of the procedures, the motion of the tools and the devices, track every movement of the patient, or the posture and the gestures of the surgeon—all without constraining the intervention. This will lead to an enormous improvement in interventional simulation and workflow analysis, and will result in the dramatic improvement of assistive surgical technologies.However, current EMT systems are highly susceptible to the presence of other electronic devices and metallic distortions 0. Ferromagnetic items, such as the surgical tool and instruments (laparoscopic forceps, cutlery, trays, etc.) alter the EM field, therefore the tracking accuracy is highly reduced, and measurements become less reliable. Due to recent advancement in system design, certain materials (e.g., titanium) do not cause significant error any more, but there is still no general solution for metallic sensitivity 0. Further weakness is lower accuracy compared to optical modality and the working volume being significantly limited.In the near future, the research community will be able to overcome most of the technical difficulties, given the right approach and methodology. A few years from now, the primary issues will be solved, including static error correction and susceptibility reduction. Our group is currently focusing on the development of a unified method—a quick calibration protocol—that can assess EM distortions in a given workspace rapidly, and based on what compensation for static distortions of the EM field becomes possible. Next, dynamic distortions have to be measured, modeled and simulated, enabling device-specific tracking in the medical environment 0. Furthermore, all active and passive devices in the OR should be modeled and tracked to support the concept of ubiquitous tracking. Reliable simulation programs will be available for modeling the field and the distortion caused by the individual instruments. The further development of systems will include the support of multi-sensor applications, significant extension of the work space and innovative types of sensors.Within a few decades, we will have accurate soft tissue models available, beyond the current model of the surgical tools. Therefore it will be possible to immediately determine how the magnetic field was affected by the surgical tools. The compensation will be feasible in real time, thus the position of sensors will be highly trusted, and all environmental variables fully tracked and followed.Ultimately, wireless power transmission technologies will overcome cabled ones in these applications 0. The sensors will also be used to transmit and receive power for their functioning; however it will severely influence the EM field, requiring dynamic compensation for distortions. This would leave more space for the physicians, while allowing complete tracking and control of the operating theater.Our paper presents the concept of “ubiquitous tracking” in the medical environment. We enlist the advantages and hinder falls of the technology that will enable complete EMT in the OR. We began to work on the currently most pressing issue, the susceptibility of the EMT systems to the environmental effects. Thorough measurements within the entire workspace have been taken, and we started to develop a model for error assessment and a compact tool for rapid calibration. This shall be a plexiglass calibration bracket that was designed to best measure the possible distortions in a given field. CT breeds and MR fiducials will be incorporated allowing a gold standard calibration to the CAD model.Eventually, the field is advancing towards the concept of fully controlled operating room, where the optical and electromagnetic tracking-based interventions can be done with reasonably high accuracy. Compensating the electromagnetic fields distortions in real-time, tracking can be used to improve minimally invasive procedures and serve as an enabling technology for various medical procedures.