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Issue No. 04 - April (2012 vol. 18)
ISSN: 1077-2626
pp: 617-625
S. Ullrich , Virtual Reality Group, RWTH Aachen Univ., Aachen, Germany
T. Kuhlen , Virtual Reality Group, RWTH Aachen Univ., Aachen, Germany
Palpation is a physical examination technique where objects, e.g., organs or body parts, are touched with fingers to determine their size, shape, consistency and location. Many medical procedures utilize palpation as a supplementary interaction technique and it can be therefore considered as an essential basic method. However, palpation is mostly neglected in medical training simulators, with the exception of very specialized simulators that solely focus on palpation, e.g., for manual cancer detection. In this article we propose a novel approach to enable haptic palpation interaction for virtual reality-based medical simulators. The main contribution is an extensive user study conducted with a large group of medical experts. To provide a plausible simulation framework for this user study, we contribute a novel and detailed interaction algorithm for palpation with tissue dragging, which utilizes a multi-object force algorithm to support multiple layers of anatomy and a pulse force algorithm for simulation of an arterial pulse. Furthermore, we propose a modification for an off-the-shelf haptic device by adding a lightweight palpation pad to support a more realistic finger grip configuration for palpation tasks. The user study itself has been conducted on a medical training simulator prototype with a specific procedure from regional anesthesia, which strongly depends on palpation. The prototype utilizes a co-rotational finite-element approach for soft tissue simulation and provides bimanual interaction by combining the aforementioned techniques with needle insertion for the other hand. The results of the user study suggest reasonable face validity of the simulator prototype and in particular validate medical plausibility of the proposed palpation interaction algorithm.
virtual reality, computer based training, finite element analysis, haptic interfaces, medical computing, user interfaces, needle insertion, haptic palpation, medical simulation, virtual environment, palpation examination technique, medical procedure, supplementary interaction technique, medical training simulator, manual cancer detection, virtual reality-based medical simulator, user study, tissue dragging, multiobject force algorithm, pulse force algorithm, arterial pulse simulation, anatomy layer support, haptic device, finger grip configuration, regional anesthesia, corotational finite-element approach, soft tissue simulation, bimanual interaction, Haptic interfaces, Force, Skin, Rendering (computer graphics), Bismuth, Visualization, Phantoms, user studies., Medicine, physically-based simulation, haptics

S. Ullrich and T. Kuhlen, "Haptic Palpation for Medical Simulation in Virtual Environments," in IEEE Transactions on Visualization & Computer Graphics, vol. 18, no. , pp. 617-625, 2012.
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