Automated medical avatar animation for warfighter mission simulation.

BACKGROUND: Virtual representations of human internal anatomy are important for military applications such as protective equipment design, injury severity prediction, thermal analysis, and physiological simulations. High-fidelity volumetric models based on imaging data are typically in static postures and difficult to use in simulations of realistic mission scenarios. This study aimed to investigate a hybrid approach to reposition medical avatars that preserves internal anatomy but allows rapid repositioning of full three-dimensional (3D) meshes. METHODS: A software framework that accepts a medical avatar in a 3D tetrahedral mesh format representing 72 organs and tissues with an articulated skeleton was developed. The skeleton is automatically resized and associated to the avatar using rigging and skinning algorithms inspired by computer animation techniques. Military relevant motions were used for animations. A motion retargeting algorithm was implemented to apply animation to avatars of various sizes, and a motion blending algorithm was implemented to smoothly transition between movements. These algorithms were incorporated into a path generation tool that accepts initial, intermediate, and final coordinates of a multisegment action along with the specific motion for each segment to synthesize a realistic compound set of movements comprising the animation. RESULTS: The developed pipeline for dynamic repositioning of medical avatars was demonstrated. Various complex motions were automatically animated. Retargeting was demonstrated on models of varying sizes. Movements along a path were animated to demonstrate smooth motion transitions. Animation of the full 3D avatar mesh ran in real time on a standard desktop personal computer. The repositioning algorithm successfully preserved the shape and volume of rigid structures such as bone. CONCLUSION: The developed software leverages techniques from various disciplines to create a hybrid approach enabling real-time 3D mesh repositioning appropriate for use in simulated military missions using avatars containing a complete anatomy representation. The workflow is largely automated, enabling rapid evaluation of new mission scenarios.

Biomechanics of Blast TBI With Time-Resolved Consecutive Primary, Secondary, and Tertiary Loads.

Blast-induced traumatic brain injury (bTBI) has become a signature casualty of recent military operations. In spite of significant clinical and preclinical TBI research, current understanding of injury mechanisms and short- and long-term outcomes is limited. Mathematical models of bTBI biomechanics may help in better understanding of injury mechanisms and in the development of improved neuroprotective strategies. Until present, bTBI has been analyzed as a single event of a blast pressure wave propagating through the brain. In many bTBI events, the loads on the body and the head are spatially and temporarily distributed, involving the primary intracranial pressure wave, followed by the head rotation and then by head impact on the ground. In such cases, the brain microstructures may experience time/space distributed (consecutive) damage and recovery events. The paper presents a novel multiscale simulation framework that couples the body/brain scale biomechanics with micro-scale mechanobiology to study the effects of micro-damage to neuro-axonal structures. Our results show that the micro-mechanical responses of neuro-axonal structures occur sequentially in time with "damage" and "relaxation" periods in different parts of the brain. A new integrated computational framework is described coupling the brain-scale biomechanics with micro-mechanical damage to axonal and synaptic structures.

Intranasal Deposition of Accuspray™ Aerosol in Anatomically Correct Models of 2-, 5-, and 12-Year-Old Children.

BACKGROUND: To our knowledge, quantification of intranasal deposition of aerosol generated by Accuspray(™) (AS) in children has never been published. We hypothesized that deposition would vary significantly with age and with placement of the device within, or outside, of the nostril. METHODS: We tested these hypotheses in anatomically-correct physical models based on CT scans of 2-, 5-, and 12-year-old children with normal, intranasal airways. Models included a removable anterior nose (AN) with exterior facial features and interior nasal vestibule and nasal valve area and a main nasal airway (MNA), subdivided into upper (superior turbinates and olfactory area), middle (middle turbinates), and lower (inferior turbinates and nasopharynx) thirds. Aerosol was generated from distilled water admixed with (99m)technetium pertechnetate and administered during static airflow by AS inserted inside the right nostril (eight runs/model), or outside the right nostril (six runs/model). Mean aerosol Dv(50) ± standard deviation was 67.8 ± 24.7 µm. Deposition was quantified by 2D gamma scintigraphy and expressed as percentage of the emitted dose. RESULTS: When placed inside the nostril, mean (± standard deviation) deposition within the MNA was significantly less in the 2-year-old, compared to the 5- and 12-year-old, averaging 46.8 ± 33.8% (AN:55.4 ± 29.9%), 75.4 ± 26.7% (AN:23.3 ± 13.6%), and 72.1 ± 18.5% (AN:25.8 ± 18.5%), respectively (p<0.05). When placed outside the nostril, MNA was significantly less in the 2- and 5-year-old compared to the 12-year-old, with 1.4 ± 2.5% (AN:69.7 ± 40.7%), 7.4 ± 9.0% (AN:77.8 ± 32.8%), and 21.1 ± 29.1% (AN:29.2 ± 19.3%), respectively (p<0.05). Deposition in the MNA of all age models was highest when AS was placed inside the nostril (p<0.05). Deposition in the lower third was significantly increased for the 5- and 12-year-old and in the middle third of the 5-year-old when AS was placed inside the nostril. CONCLUSIONS: These results indicate that age and device placement play important roles in terms of intranasal deposition, when administering aerosol with Accuspray(™) to children.