title: An animal-to-human scaling law for blast-induced traumatic brain injury risk assessment.
abstract: Despite recent efforts to understand blast effects on the human brain, there are still no widely accepted injury criteria for humans. Recent animal studies have resulted in important advances in the understanding of brain injury due to intense dynamic loads. However, the applicability of animal brain injury results to humans remains uncertain. Here, we use advanced computational models to derive a scaling law relating blast wave intensity to the mechanical response of brain tissue across species. Detailed simulations of blast effects on the brain are conducted for different mammals using image-based biofidelic models. The intensity of the stress waves computed for different external blast conditions is compared across species. It is found that mass scaling, which successfully estimates blast tolerance of the thorax, fails to capture the brain mechanical response to blast across mammals. Instead, we show that an appropriate scaling variable must account for the mass of protective tissues relative to the brain, as well as their acoustic impedance. Peak stresses transmitted to the brain tissue by the blast are then shown to be a power function of the scaling parameter for a range of blast conditions relevant to TBI. In particular, it is found that human brain vulnerability to blast is higher than for any other mammalian species, which is in distinct contrast to previously proposed scaling laws based on body or brain mass. An application of the scaling law to recent experiments on rabbits furnishes the first physics-based injury estimate for blast-induced TBI in humans.
authors.affiliation: Institute for Soldier Nanotechnologies, Department of Aeronautics and Astronautics, and ajean@mit.edu joannop@mit.edu.
authors.forename: Aurélie
authors.initials: A
authors.lastname: Jean
authors.affiliation: Institute for Soldier Nanotechnologies, Department of Aeronautics and Astronautics, and.
authors.forename: Michelle K
authors.initials: MK
authors.lastname: Nyein
authors.affiliation: Soldier Protection and Individual Equipment, Program Executive Office Soldier, US Army, Fort Belvoir, VA 22060.
authors.forename: James Q
authors.initials: JQ
authors.lastname: Zheng
authors.affiliation: Institute for Soldier Nanotechnologies.
authors.forename: David F
authors.initials: DF
authors.lastname: Moore
authors.affiliation: Institute for Soldier Nanotechnologies, Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139; and ajean@mit.edu joannop@mit.edu.
authors.forename: John D
authors.initials: JD
authors.lastname: Joannopoulos
authors.affiliation: Institute for Soldier Nanotechnologies, Department of Aeronautics and Astronautics, and.
authors.forename: Raúl
authors.initials: R
authors.lastname: Radovitzky
mesh_terms: D000818:Animals; D001753:Blast Injuries / Q000150:complications* / Q000473:pathology* / Q000503:physiopathology; D001835:Body Weight; D001930:Brain Injuries / Q000209:etiology* / Q000473:pathology* / Q000503:physiopathology; D004548:Elasticity; D020342:Finite Element Analysis; D006801:Humans; D007427:Intracranial Pressure; D051379:Mice; D008954:Models, Biological; D009929:Organ Size; D011817:Rabbits; D018570:Risk Assessment; D013045:Species Specificity; D034421:Sus scrofa; D014783:Viscosity
keywords: TBI; injury risk criteria; interspecies scaling; transfer function