Compression-dependent viscoelastic behavior of human cervix tissue.

We have characterized the viscoelastic properties of human cervical tissue through a range of precompressional loads and testing frequencies. Mechanical testing is necessary to develop robust elasticity-based techniques for the diagnosis of cervical abnormalities. The storage modulus (E') and material damping (tan 6) were measured in 13 patients, 40 to 76 years old. Our results showed that E' increased monotonically from approximately 4.7 to 6.3 kPa over the precompression range (1-6%) for a testing frequency of 1 Hz. Increases in precompressions of 4% or greater significantly increased E' obtained after dynamic compression testing when data were normalized to 1% precompression. Tan delta remained fairly constant (approximately 0.35) and was not significantly affected by changes in precompression. E' and tan delta increased significantly with frequency. E 'monotonically increased from 4.7 to 7.9 kPa for the 1-3% compression range (lowest precompression for 2% amplitude) and from 6.3 to 10.3 kPa for the 6-8% range (highest precompression for 2% amplitude) when increasing frequency from 1 to 30 Hz. Tan delta increased montonically from 0.35 to 0.45 for 2% amplitude compressions from 1 to 30 Hz regardless of initial precompression. Our results show that precompression and testing frequency must be taken into account in order to obtain consistent measurements in mechanical diagnostic tests developed for cervical abnormalities.