A Novel Method for the Mechanical Testing of Human Cerebrovascular Tissue: A Validation Study

Abstract

This study describes and validates a novel mechanical testing apparatus capable of generating a viscoelastic response from which the time-dependent behavior of human cerebrovascular tissue can be derived to inform vessel wall failure prediction and therapeutic device design. Testing involved vascular specimen cannulation, pressurization, and recording dynamic changes in vessel diameter using a three-axis laser micrometer. Device validity and versatility were evaluated via two synthetic microvessel specimen experiments: (I) comparison to an Instron stress-relaxation protocol, and (II) vessel segment length parametric analysis. A standard linear solid (SLS) model was chosen to fit the experimental results, from which the model coefficients (E1, E2, and ) and equilibrium modulus (Ge) were computed. Ge comparisons were made using Bland-Altman analysis and Welchs F-test for experiment I and II, respectively. Device feasibility was evaluated through testing human cadaveric cerebrovascular tissue. The SLS model provided accurate experimental data fits, with overall mean R2 value of 0.99 (SD= 2.4E-3). Ge for inflation-creep and Instron stress-relaxation experiments were statistically comparable, with Bland-Altman mean bias of 1.9% (95% CI: -0.9% - 4.6%, p=.18). Holistically, the vessel segment length parametric analysis revealed inconsistent values for Ge across the complete range of testing lengths, where ad hoc family-wise comparison indicated that the 0.5 cm length cohort was the singular outlier (p < .05). Our device successfully recorded a viscoelastic response from human cadaveric middle cerebral artery tissue (n=12). This study demonstrated that our novel device was both versatile and capable of eliciting an accurate viscoelastic response.