# A Review of Validation Methods for the Intracranial Response of FEHM to Blunt Impacts
## 4 Further Research into Validation
### Investigation into Validation Protocol  
[PERSON] and [PERSON] [105] critically evaluated the validation data available from [PERSON] et al. [34], [PERSON] et al. [38] and [PERSON] et al. [35; 36] and [PERSON]'s PhD Thesis with the aim of creating a standardised validation protocol for FEHM. Experimental data for intracranial pressure response, relative brain displacement and brain deformation were judged according to selection criteria. Impact scenarios were selected if they were deemed to have sound experimental methodology (termed \"accuracy\"), complete kinematic data available (termed \"reproducibility\") and to represent unique impact conditions (termed \"redundancy\"). Cases were judged indepentdently for each validation metric. No cases from [PERSON] et al. [34] passed the reproducibility criterion as rotational kinematics, thought to be of high importance when considering TBI, and the cadavers used by [PERSON] et al. [38] were seen to have air within the intracranial space, thereby failing the accuracy criterion. Table 6 summarises the experiments suggested for use by [PERSON] and [PERSON] [105], excluding those within [PERSON]'s PhD Thesis. While the selection process is set to be unbiased, not every impact case within the assessed studies [34; 35; 36; 38] appears to have been considered and subjected to the selection criteria. For example, although C380-T4, -T5 and -T6 were deemed suitable for the complete set of validation metrics (ICP, relative brain displacement and brain deformation), C380-T1 and -T2 are not mentioned throughout the publication. The influence each scenario should hold when considering the overall performance of the model was then weighted (\(0<v_{i}<1.0\)) according to experimental limitations and data errors, as detailed by [PERSON] and [PERSON] [105]. The weighting that should be applied to each target (NDT or pressure transducer) within each test is similarly calculated and provided (\(0<w_{ij}<1.0\)). This is particularly pertinent for the brain deformation cases where the tests are all given equal weighting overall. However, the targets within each experiment have a range of weightings. For example, test C241-T5 negates (weighting = 0.0) seven of the 14 target points entirely, has five targets with 0.1 weighting and one each with 0.3 and 0.7. Table 6 also provides the overall test weighting for each validation criterion. bio-fidelity ratings between 5.80 and 6.43, deeming them \"fair\" representations of the human head, according to ISO/TR-9790 [102] (see Table 5). At the time of writing, no FEHM has been validated according to the above protocol. Caution and the need for further research into the sifting and weighting protocols has been raised [91; 111]. [PERSON] et al. [39] intended to ensure their cadaver experimentation procedures would pass all criteria laid out by [PERSON] and [PERSON] [105] to remove the need for case selection and to further standardise the validation process. Furthermore, despite [PERSON] and [PERSON] [105] proposing an unbiased selection criteria, some cases published within the assessed works [35; 36] are not mentioned and therefore, it is assumed, not subjected to the selection criteria. This includes cases C380-T2 and -T3 [36] which have previously been used in FEHM validation and present full sets of relative brain displacement and strain response data as well as partial pressure response data. The optimised CORA