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A Human Body Model for Computational Assessment of Blast Injury and Protection


OBJECTIVE: Formulate, develop and demonstrate anatomically consistent, articulated human body model for computational assessment of explosion blast injury loads, body responses and casualty estimation and for analysis of personal protective equipment. DESCRIPTION: Blasts from improvised explosive devices (IEDs) are the most common cause of wounded-in-action injuries and death in recent military operations [De Palma 2005]. US and coalition military personnel are engaged in unconventional warfare with continuously evolving terrorist threats (IEDs, road side bombs, car-borne bombs, suicide bombers and others). The primary goal of the Department of Defense (DoD) Blast Injury Research Program is to understand and predict the threat scenarios, injury potentials and to develop improved protective measures. Current body armor has been designed primarily to protect against ballistic and fragment impact threats and to a lesser degree to protect against explosion blasts, partly because of limited understanding of blast injury pathways. Moreover, experimental evaluation of protective armor against ballistic and impact loads, which have a localized focus, can be conducted using well established human body surrogates [Roberts 2007]. Explosion blast loads engulf the entire human body, are much more complex and involve loads induced by shock waves, debris, shrapnel, thermal flash and toxic gases. The biomechanical injury may be caused by the direct effects of pressures penetrating the body, flying debris, body translocation in air and impact on hard objects [Elsayed and Atkins 2008]. The types of injuries caused by blasts also depend on whether the blast occurs in an open field or within a building. In the last few years the DoD has made substantial research investments in understanding blast wave traumatic brain injury (TBI). The majority of these efforts use an experimental approach and shock tube tests using human physical surrogates (dummies), cadavers and animal models [Chavko 2007], which are useful and necessary but are slow, expensive, lack injury scaling and prediction capability. Anatomically consistent, articulated human body model and computational tools for modeling blast physics coupled to body biodynamics and biomechanics will help in better understanding of blast injury threats, interpret experimental data and in the development of improved protective armor and medical treatment procedures. Existing articulated human body models and associated computational tools have been developed for studying impact injury [Cheng 1998], lack required anatomical biofidelity and do not allow coupled blast-biodynamics-injury biomechanics simulation capability. Several teams have recently developed anatomical geometry model of a human head/brain to study TBI mechanisms [Moore 2009] but they lack the capability of modeling head/neck/body biodynamics, whole body responses, and other injury mechanisms. The goal of this project is to 1) establish a prototype database of body tissue material properties relevant to human response to blast environment using open literature data and identify missing but required data , 2) develop a human body anatomic model including skin, skeletal, head/neck and internal organs susceptible to blast injury (brain, spine, lungs, etc), 3) develop geometry and computational meshes to enable blast wave loads, body biodynamic responses and the biomechanics of pressure waves within the body, 4) conduct parametric simulations using selected computational tools of blast wave physics and body biomechanics and model validation against existing human/cadaver test data, and 5) demonstrate the capability to simulate the performance of personal protective equipment (PPE) in various explosion blast scenarios. PHASE I: Conduct thorough review of existing anatomical models of a human body and evaluate their capabilities and limitations for simulations of blast injury. Formulate specifications of a modeling framework integrating the anatomical data (skin, skeletal, major organs), geometric modeling tools for human body articulation (size, shape, posture), blast scene generation, material property data needed for biodynamic and biomechanic simulations. Evaluate and select existing software tools for modeling explosion blast events, blast body interaction, and assessment of injury/casualty estimation. Formulate a plan for model validation to be executed in Phase II and III. Develop prototype components of such a framework and demonstrate their capability to generate anatomical geometries of articulated human bodies and to simulate blast-body interaction including: blast loading, body biodynamics, and biomechanics and initial analysis of injury pathways to a selected organ e.g. brain, lung, spine, groin, extremity. The results of Phase I should be documented in a final report describing details of the proposed simulation framework, availability of existing data, results of relevant demonstration/validation simulations and rationale for further model development and validation. PHASE II: Implement the software tools for generation of anatomic geometry models of a human body and for generation of computational models for both high fidelity and reduced order simulations. Establish a database of human body models (e.g. based on body scans), develop software tools for articulation of a human body (e.g. upright standing, seating, leaning) and for generation of internal organs/tissues including skeletal, muscular, brain, lung, vascular, abdominal, etc. Develop a simulation framework integrating blast wave physics and human body biodynamics/biomechanics using existing software tools and evaluate its capabilities and limitations in modeling blast wave injury events. It is desirable that such a framework should enable both high fidelity and reduced order (fast running) simulations. Conduct model validation on existing published data of human (cadaver, dummy) body response to inertial, impact, shock tube and blast wave response. Demonstrate the capability to generate human body models wearing personal protective armor (helmet, vest, boots) and equipment. Conduct computational analysis of the role of PPE in protection against blast injury. Using the simulation results and available experimental data develop and demonstrate the capability to generate blast injury assessment and criteria to selected organs including: brain, lung, neck, groin, vascular and others. PHASE III DUAL USE APPLICATIONS: The data, software tools and results of this project will have immense potential application in military and civilian medicine. The US military will use such tools for development and evaluation of protective armor and equipment, for forensic analysis of blast events, development of blast dosimeters, diagnostics, and treatment of blast injury casualties. It will be also applicable for ergonomic evaluation of military equipment (cockpits, seats, vehicle safety, egress, etc.) and as a personal aid of soldier training. The technology developed in this SBIR project could also support various commercial applications such as automotive safety, sport medicine, rehabilitation after injury or surgery, and others. REFERENCES: 1. DePalma R., Burris DG., Champion HR., Hodgson MJ., (2005), Blast Injuries, N. Engl. J. Med, 352(13), 1335-1342, 2. Roberts, JC., Merkle AC., Biermann PJ., Ward EE. Carkuff BG., Cain RP., O'Connor JV., (2007), Computational and experimental models of the human torso for non-penetrating ballistic impact, J Biomechnaics, v40, 1, 125-136, 3. Elsayed N.M., and Atkins J.L., (2008), Explosion and Blast-Related Injuries: Effects of Explosion and Blast from Military Operations and Acts of Terrorism, Elsevier Academic Press 2008 4. Chavko M., Koller WA., Prusaczyk WK., McCarron RM., (2007), Measurement of blast wave by a miniature fiber optic pressure transducer in the rat brain, J. Neurosci. Meth., 159(2):277-81 5. Cheng, H., Rizer, A. L., and Obergefell, L. A., (1998), Articular Total Body Model Version V: User"s Manual, Human Effectiveness Directorate, Crew Survivability and Logistics Division, Wright-Patterson AFB, Dayton, OH, Report No. AFRL-HE-WP-TR-1998-0015. 6. Moore DF., Jerusalem A., Nyein M., Noels L., Jaffee MS., Radovitzky RA., (2009), Computational biology modeling of primary blast effects on the central nervous system. NeuroImage v47(S2):T1020, 2009.
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