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Characterization of Closed Head Impact Injury in Rat.

Hua Y, Akula P, Kelso M, Gu L - Biomed Res Int (2015)

Bottom Line: Results revealed that impact depth and impactor shape were the two leading factors affecting intracranial responses.An indentation depth instead of impact depth would be appropriate to characterize the influence of a large deformed rubber impactor.This work could be used to better design or compare CHI experiments.

View Article: PubMed Central - PubMed

Affiliation: Department of Mechanical and Materials Engineering, University of Nebraska-Lincoln, Lincoln, NE 68588-0656, USA.

ABSTRACT
The closed head impact (CHI) rat models are commonly used for studying the traumatic brain injury. The impact parameters vary considerably among different laboratories, making the comparison of research findings difficult. In this work, numerical CHI experiments were conducted to investigate the sensitivities of intracranial responses to various impact parameters (e.g., impact depth, velocity, and position; impactor diameter, material, and shape). A three-dimensional finite element rat head model with anatomical details was subjected to impact loadings. Results revealed that impact depth and impactor shape were the two leading factors affecting intracranial responses. The influence of impactor diameter was region-specific and an increase in impactor diameter could substantially increase tissue strains in the region which located directly beneath the impactor. The lateral impact could induce higher strains in the brain than the central impact. An indentation depth instead of impact depth would be appropriate to characterize the influence of a large deformed rubber impactor. The experimentally observed velocity-dependent injury severity could be attributed to the "overshoot" phenomenon. This work could be used to better design or compare CHI experiments.

No MeSH data available.


Related in: MedlinePlus

Pareto chart of region-specific biomechanical responses to external impact parameters. A: impact depth; B: impact velocity; C: impact position; D: impactor diameter; E: impactor material; F: impactor shape.
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fig4: Pareto chart of region-specific biomechanical responses to external impact parameters. A: impact depth; B: impact velocity; C: impact position; D: impactor diameter; E: impactor material; F: impactor shape.

Mentions: The predicted MPS was used to characterize the brain responses. The peak MPS in the cerebrum, hippocampus, and cerebellum for all eight cases are listed in Table 2. The range analysis, which assumes that the influence of other factors on the result is balanced when analyzing the impact of a specific factor, was performed to quantify the significance level of each factor as shown in Table 3. The Ki value of a factor was the average of four values of peak MPS for level i listed in Table 2, and the range value R for each factor was the difference between Ki values of the two levels. A larger R indicates that the corresponding factor plays a more important role in the brain responses. The Pareto chart (Figure 4), based on the magnitude of range value R, has shown that impact depth and impactor shape were the two leading factors affecting biomechanical responses of the brain regardless of regions. For example, varying the impact depth from 1 mm to 2 mm produced an increase of peak MPS in the cerebrum of 0.1941, in the hippocampus of 0.1514, and in the cerebellum of 0.1595. As a flat impactor was changed to a convex one, the peak MPS decreased by 0.1473, 0.1102, and 0.1386 in the cerebrum, hippocampus, and cerebellum, respectively. Moreover, the high strains induced by the flat impactor were approximately parallel to the bottom rim of the impactor, while those induced by the convex one were concentrated along the axial line (Figure 5, Cases  1 and 7).


Characterization of Closed Head Impact Injury in Rat.

Hua Y, Akula P, Kelso M, Gu L - Biomed Res Int (2015)

Pareto chart of region-specific biomechanical responses to external impact parameters. A: impact depth; B: impact velocity; C: impact position; D: impactor diameter; E: impactor material; F: impactor shape.
© Copyright Policy - open-access
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4588353&req=5

fig4: Pareto chart of region-specific biomechanical responses to external impact parameters. A: impact depth; B: impact velocity; C: impact position; D: impactor diameter; E: impactor material; F: impactor shape.
Mentions: The predicted MPS was used to characterize the brain responses. The peak MPS in the cerebrum, hippocampus, and cerebellum for all eight cases are listed in Table 2. The range analysis, which assumes that the influence of other factors on the result is balanced when analyzing the impact of a specific factor, was performed to quantify the significance level of each factor as shown in Table 3. The Ki value of a factor was the average of four values of peak MPS for level i listed in Table 2, and the range value R for each factor was the difference between Ki values of the two levels. A larger R indicates that the corresponding factor plays a more important role in the brain responses. The Pareto chart (Figure 4), based on the magnitude of range value R, has shown that impact depth and impactor shape were the two leading factors affecting biomechanical responses of the brain regardless of regions. For example, varying the impact depth from 1 mm to 2 mm produced an increase of peak MPS in the cerebrum of 0.1941, in the hippocampus of 0.1514, and in the cerebellum of 0.1595. As a flat impactor was changed to a convex one, the peak MPS decreased by 0.1473, 0.1102, and 0.1386 in the cerebrum, hippocampus, and cerebellum, respectively. Moreover, the high strains induced by the flat impactor were approximately parallel to the bottom rim of the impactor, while those induced by the convex one were concentrated along the axial line (Figure 5, Cases  1 and 7).

Bottom Line: Results revealed that impact depth and impactor shape were the two leading factors affecting intracranial responses.An indentation depth instead of impact depth would be appropriate to characterize the influence of a large deformed rubber impactor.This work could be used to better design or compare CHI experiments.

View Article: PubMed Central - PubMed

Affiliation: Department of Mechanical and Materials Engineering, University of Nebraska-Lincoln, Lincoln, NE 68588-0656, USA.

ABSTRACT
The closed head impact (CHI) rat models are commonly used for studying the traumatic brain injury. The impact parameters vary considerably among different laboratories, making the comparison of research findings difficult. In this work, numerical CHI experiments were conducted to investigate the sensitivities of intracranial responses to various impact parameters (e.g., impact depth, velocity, and position; impactor diameter, material, and shape). A three-dimensional finite element rat head model with anatomical details was subjected to impact loadings. Results revealed that impact depth and impactor shape were the two leading factors affecting intracranial responses. The influence of impactor diameter was region-specific and an increase in impactor diameter could substantially increase tissue strains in the region which located directly beneath the impactor. The lateral impact could induce higher strains in the brain than the central impact. An indentation depth instead of impact depth would be appropriate to characterize the influence of a large deformed rubber impactor. The experimentally observed velocity-dependent injury severity could be attributed to the "overshoot" phenomenon. This work could be used to better design or compare CHI experiments.

No MeSH data available.


Related in: MedlinePlus