Enrique Campos-Náñez

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We present three image-guided navigation systems developed for needle-based interventional radiology procedures, using the open source image-guided surgery toolkit (IGSTK). The clinical procedures we address are vertebroplasty, RF ablation of large lung tumors, and lung biopsy. In vertebroplasty, our system replaces the use of fluoroscopy, reducing(More)
Wireless sensor networks pose numerous fundamental coordination problems. For instance, in a number of application domains including homeland security, environmental monitoring and surveillance for military operations, a network's ability to efficiently manage power consumption is extremely critical as direct user intervention after initial deployment is(More)
PURPOSE To develop an image guidance system that incorporates volumetric planning of spherical ablations and electromagnetic tracking of radiofrequency (RF) electrodes during insertion. MATERIALS AND METHODS Simulated tumors were created in three live swine by percutaneously injecting agar nodules into the lung. A treatment plan was devised for each tumor(More)
Recent research on pricing multiclass loss networks [19] has shown that the performance of optimal static pricing approaches that of optimal dynamic (congestion-dependent) pricing in the many small sources limit. In our own work with similar models, we have found it difficult to obtain large gains over static pricing in realistic settings, even when the(More)
This article addresses the two key challenges in computer-assisted percutaneous tumor ablation: planning multiple overlapping ablations for large tumors while avoiding critical structures, and executing the prescribed plan. Toward semiautomatic treatment planning for image-guided surgical interventions, we develop a systematic approach to the needle-based(More)
Motivated by the September 11 attacks, we are addressing the problem of policy analysis of supply-chain security. Considering the potential economic and operational impacts of inspection together with the inherent difficulty of assigning a reasonable cost to an inspection failure call for a policy analysis methodology in which stakeholders can understand(More)
We address performance issues associated with simulation-based algorithms for optimizing Markov reward processes. Specifically, we are concerned with algorithms that exploit the regenerative structure of the process in estimating the gradient of the objective function with the respect to control parameters. In many applications, states which initially have(More)
Simulation-based algorithms for maximizing the average reward of a parameterized Markov chain often rely upon the existence of a state which is recurrent for all choices of parameter values. For example, in the " batch " simulation-based algorithm of Marbach and Tsitsiklis [28], a given recurrent state i * is used to mark the onset of regenerative cycles(More)