Com puter modeling is becom ing increasingly important in the realm of head injury with resulting traum atic brain injury (TBI). Com puter models, however, are only as good as the material property data that are used in creating them. Research done to date has determined the low frequency compression modulus, and the low frequency shear modulus of the tissue. Both have been found to vary with respect to frequency. Compression modulus has been measured at frequencies up to 350 Hz;​ however some of the data was generated from tissue that had been frozen, reducing the moduli of the tissue. Existing shear modulus data falls into two distinct categories:​ 1) shear modulus measured at less than 0.2% strain, and 2) shear modulus measured at greater than 1% strain. The low strain data are likely more realistic moduli, as it does not exceed the yield strain of the material. Im pact modeling requires use of frequency data at significantly higher frequencies than those that have been studied in the past.

The “wave-in-a-tube” method is a viable technique for determining the high frequency material properties of gel-like substances. Although the method is sound, care must be taken in selecting the tube material, tube size, and in ensuring the elimination of large air bubbles in the sample. This technique was applied to brain tissue to determine the properties of the tissue at frequencies between 100 kHz and 10 MHz. Of these properties, only bulk modulus is fairly invariant with respect to frequency. Shear and Young's moduli vary with frequency and appear to approach an asymptotic upper limit. There appears to be little difference between the properties of white and gray matter, but statistical testing did not com pletely rule out a difference in the tissue types.

A curve fit was established to estimate values for moduli in the frequency range that is inaccessible by either mechanical or ultrasonic techniques. These estimated values for Young's moduli range from 458 kPa at 1 kHz to 10.37 MPa at 10 kHz. For shear modulus the values range from 362 kPa at 1 kHz to 6.09 MPa at 10 kHz