Abstract. Anesthetic nerve blocks are a common therapy performed in hospitals around the world to alleviate acute and chronic pain. Tracking systems have shown considerable promise in other forms of therapy, but little has been done to apply this technology in the field of anesthesia. We are developing a guidance system for combining tracked needles with non-invasive ultrasound (US) and patient-specific geometric models. In experiments with phantoms two augmented reality (AR) guidance systems were compared to the exclusive use of US for lumbar facet injection therapy. Anesthetists and anesthesia residents were able to place needles within 0.57mm of the intended targets using our AR systems compared to 5.77mm using US alone. A preliminary cadaver study demonstrated the system was able to accurately place radio opaque dye on targets. The combination of real time US with tracked tools and AR guidance has the potential to replace CT and fluoroscopic guidance, thus reducing radiation dose to patients and clinicians, as well as reducing health care costs.
Abstract.A new augmented reality apparatus was evaluated. The device uses scanned infrared and visible lasers to project computer generated information such as surgical plans, entry pints for probes etc, directly onto the patient. In addition to projecting the plan, the device can be integrated with a 3D camera and is capable of measuring the location of projected infrared laser spots. This can be used to ensure that the display is accurate, apply corrections to the projection path and to assist in registration. The projection system has its own Application Programmer's Interface (API) and is a stand-alone add-on unit to any host computer system. Tests were conducted to evaluate the accuracy and repeatability of the system. We compared the locations of points projected on a flat surface with the measurements obtained from a tracked probe. The surface was rotated through 60 degrees in 5 degree increments and locations measured from the two devices agreed to within 2mm. An initial host application was also developed to demonstrate the new unit. Fiducials representing vertices along a proposed craniotomy were embedded into a plastic skull and a projection path defining the craniotomy was calculated. A feedback-based optimization of the plan was performed by comparing the measurement taken by the camera of these coordinates. The optimized plan was projected onto the skull. On average, the projection deviated by approximately 1mm from the plan. Applications include identification of critical anatomical structures, visualization of preplanned paths and targets, and telesurgery or teleconsultation.
Clinical research has been rapidly evolving towards the development of less invasive surgical procedures. We recently embarked on a project to improve intracardiac beating heart interventions. Our novel approach employs new surgical technologies and support from image-guidance via pre-operative and intra-operative imaging (i.e. two-dimensional echocardiography) to substitute for direct vision. Our goal was to develop a versatile system that allowed for safe cardiac port access, and provide sufficient image-guidance with the aid of a virtual reality environment to substitute for the absence of direct vision, while delivering quality therapy to the target. Specific targets included the repair and replacement of heart valves and the repair of septal defects. The ultimate objective was to duplicate the success rate of conventional open-heart surgery, but to do so via a small incision, and to evaluate the efficacy of the procedure as it is performed. This paper describes the software and hardware components, along with the methodology for performing mitral valve replacement as one example of this approach, using ultrasound and virtual tool models to position and fasten the valve in place.
Surgical guidance in the absence of direct vision and with no exposure to ionizing radiation was achieved, so our virtual environment constitutes a feasible candidate for performing various off-pump intracardiac interventions.
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