Tissue mimicking material and image artifacts in intravascular elastography

Intravascular ultrasound is being investigated as a tool for imaging the local elasticity of atherosclerotic vessels: obtaining images of the compression modulus is the ultimate goal. In practice, radial strain is used to depict local hardness: this simplification causes artifacts that must be understood or corrected. Phantoms mimicking vessels with atherosclerotic lesions were constructed using agar-gelatin gels. The mechanical properties of these gels were investigated. Gels with varying compression moduli were made using a gelatin solution (8% by weight) with a variable amount of agar (1%-3% by weight). The modulus is determined using a dynamic mechanical analyser. The modulus is strongly dependent on the age and the actual temperature of the samples. By varying the agar concentration, compression moduli spanning a useful range for vascular phantom construction can be achieved. Phantom studies and finite element modelling were used to describe and characterise artifacts. In simple morphologies compensation for the artifacts may be possible, but complex morphologies require complex compensations. In these cases, the finite element method can assist in a correct interpretation of local tissue hardness from strain images