title: Temporal cavity and pressure distribution in a brain simulant following ballistic penetration.
abstract: To study ballistic brain injury biomechanics, two common civilian full metal jacket handgun projectiles (25-caliber and 9-mm) were discharged into a transparent brain simulant (Sylgard gel). Five pressure transducers were placed at the entry (two), exit (two) and center (one) of the simulant. High-speed digital video photography (20,000 frames/second) was used to capture the temporal cavity pulsation. Pressure histories and high-speed video images were synchronized with a common trigger. Pressure data were sampled at 308 kHz. The 25-caliber projectile had an entry velocity of 238 m/s and exit velocity of 170 m/s. The 9-mm projectile had an entry velocity of 379 m/s and exit velocity of 259 m/s. Kinetic energies lost during penetration were 45.2 J for the 25-caliber projectile and 283.7 J for the 9-mm. Size of temporary cavities and pressures were dependent on projectile size and velocity. The 9-mm projectile created temporary cavities 1.5 times larger in size and lasted 1.5 times longer than the 25-caliber projectile. The 9-mm projectile had pressures three times higher than the 25-caliber projectile. Pressure differences between the center location and surrounding regions were approximately 1.4 times higher and lasted about 1.6 times longer in the 9- mm projectile than the 25-caliber projectile. Collapsing of the temporary cavity drew the brain simulant toward the center of the temporary cavity and created negative pressures of approximately -0.5 atmospheric pressure in the surrounding region. Pressures reached approximately +2 atmospheric pressure when temporary cavities collapsed. These quantified data may assist in understanding injury biomechanics and management of penetration brain trauma.
authors.affiliation: Department of Veterans Affairs Medical Center, Milwaukee, Wisconsin, USA. jy-zhang@mcw.edu
authors.forename: Jiangyue
authors.initials: J
authors.lastname: Zhang
authors.forename: Narayan
authors.initials: N
authors.lastname: Yoganandan
authors.forename: Frank A
authors.initials: FA
authors.lastname: Pintar
authors.forename: Thomas A
authors.initials: TA
authors.lastname: Gennarelli
mesh_terms: D001696:Biomechanical Phenomena; D044709:Forensic Ballistics; D005782:Gels; D020197:Head Injuries, Penetrating / Q000503:physiopathology*; D006801:Humans; D008953:Models, Anatomic; D014160:Transducers, Pressure; D014741:Video Recording; D014948:Wounds, Gunshot / Q000503:physiopathology*
chemical_list: D005782:Gels