Inducing hypothermia to brain tissue after brain ischemia or head injury has been demonstrated beneficial to the patients. Clinical studies have shown that even 1 or 2°C temperature reduction in brain tissue can be protective [Dietrich 1992]. On the contrary, fever-induced hyperthermia can worsen the neurological outcome in an animal model after cerebral ischemia. It is of clinical importance to understand the temperature distribution in brain during brain hypothermia.
The delivery of therapeutic agents into the brain is impeded by the blood-brain barrier, preventing adequate treatment of diseases of the central nervous system. Convection enhanced delivery was developed as a means to deliver therapeutic agents directly into brain tissue and to transport the drugs in the extracellular space using convective flow. Poroelastic or biphasic models have been used to study the concomitant fluid transport and tissue deformation that occurs during infusion, however previous studies have been limited by the assumption of linear elasticity of the solid phase [1].
IntroductionLoss of consciousness (LOC) occurs with approximately 8 percent of concussions in professional American football and has been associated with severity of injury (1, 2). However it is unknown how LOC relates to severity of head impact responses. The purpose of this study was to compare the head accelerations and brain tissue deformation between cases of concussions with and without LOC in elite American football to inform prevention strategies.MethodsConcussive injuries with and without LOC from helmet-to-helmet and shoulder collisions as well as falls in elite American football were reconstructed in laboratory using hybrid III headform to obtain peak linear and rotational acceleration and maximum principal strain, cumulative strain damage at 10%, and strain rate metrics in 5 brain regions associated with loss of consciousness.ResultsImpact velocity, peak linear and rotational acceleration were greater in the LOC group than the no LOC group. The brain tissue deformation metrics were greater in the LOC group than the no LOC group. Linear acceleration was most predictive for cases of helmet-to-helmet collisions whereas shoulder collisions were best predicted by rotational acceleration. The best overall predictor was impact velocity.Discussion/conclusionThe presence of a loss of consciousness in concussive impacts is a result of greater magnitude of brain tissue trauma. This was primarily caused by greater impact velocities in head impacts leading to LOC. Rules aiming at mitigating this aspect of the game would decrease the risk of a loss of consciousness in this sport. Each type of events resulted in different values of kinematic data and brain tissue deformation, which suggests that studies evaluating risk of concussions based 1 type of event cannot be generalized.
Strain Tensor Imaging: Cardiac-induced brain tissue deformation in humans quantified with high-field MRI