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Computational biology - modeling of primary blast effects on the central nervous system.

Defense and Veterans Brain Injury Center, Walter Reed Army Medical Center, Building 1, Room B207, 6900 Georgia Avenue NW, Washington DC 20309-5001, USA.
NeuroImage (Impact Factor: 6.13). 03/2009; 47 Suppl 2:T10-20. DOI: 10.1016/j.neuroimage.2009.02.019
Source: PubMed

ABSTRACT Recent military conflicts in Iraq and Afghanistan have highlighted the wartime effect of traumatic brain injury (TBI). The reason for the prominence of TBI in these particular conflicts as opposed to others is unclear but may result from the increased survivability of blast due to improvements in body armor. In the military context blunt, ballistic and blast effects may all contribute to CNS injury, however blast in particular, has been suggested as a primary cause of military TBI. While blast effects on some biological tissues, such as the lung, are documented in terms of injury thresholds, this is not the case for the CNS. We hypothesized that using bio-fidelic models, allowing for fluid-solid interaction and basic material properties available in the literature, a blast wave would interact with CNS tissue and cause a possible concussive effect.
The modeling approach employed for this investigation consisted of a computational framework suitable for simulating coupled fluid-solid dynamic interactions. The model included a complex finite element mesh of the head and intra-cranial contents. The effects of threshold and 50% lethal blast lung injury were compared with concussive impact injury using the full head model allowing upper and lower bounds of tissue injury to be applied using pulmonary injury as the reference tissue.
The effects of a 50% lethal dose blast lung injury (LD(50)) were comparable with concussive impact injury using the DVBIC-MIT full head model.
CNS blast concussive effects were found to be similar between impact mild TBI and the blast field associated with LD(50) lung blast injury sustained without personal protective equipment. With the ubiquitous use of personal protective equipment this suggests that blast concussive effects may more readily ascertained in personnel due to enhanced survivability in the current conflicts.

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    ABSTRACT: Primary blast wave induced traumatic brain injury and posttraumatic stress disorders have been observed in great number among military personnel in the recent Iraq and Afghanistan wars. Although combat helmets provide good protection against blunt/ballistic type threats, the current issue with military helmets is protection concerning the threats from primary blast wave. This study focused on investigating how combat helmets influence the blast-induced biomechanical loads in the human brain. Multi-Material Arbitrary Lagrangian Eulerian method was applied to simulate the wave propagation in the shock tube, the interaction of the shock wave with the human head, and the subsequent blast overpressure transformation through the head. The finite element model (FE) of Wayne State University shock wave generator (WSUSG) was developed and validated against experimentally measured side-on pressure time histories within the tube. Validated 3-D FE models of the human head and Advanced Combat Helmet (ACH) reported previously were used to predict the internal brain responses and assess the performance of the helmet in mitigating shock wave of various severities generated by WSUSG. Effectiveness of helmet with respect to various head orientations to oncoming shock waves was also evaluated. Biomechanical response parameters including the peak brain pressures and strains at various regions of the brain were calculated and compared between the heads with and without helmet. Wearing ACH was found to mitigate the intracranial pressures up to 33% at given blast loading conditions. The peak brain strain was reduced by 13-40% due to the use of helmet. In generally, ACH exhibited increased protective performance as the shock intensity increased. The current ACH helmet design offered superior protection to the brain in sideways blast than that in forward blast loading condition of same severity.

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