Development of polyvinyl alcohol cyrogel based anatomically realistic vessels for use in Doppler ultrasound flow phantoms

Abstract

Polyvinyl alcohol cyrogel (PVA-C) is commonly utilised in ultrasound flow phantoms due to its variable Young’s modulus, which can be manipulated through successive freeze-thaw cycles. Vessel mimicking material (VMM) was prepared using PVA-C with varying concentrations of Aluminium Oxide (Al2O3) to optimise the production. These samples were characterised acoustically and mechanically to determine the optimum concentrations of constituent chemicals to adequately mimic the properties of healthy and diseased vessels found in vivo. The optimised mixture was determined using a PVA-C sample prepared after two freeze-thaw cycles, with a speed of sound of 1530 ± 5 m/s and an attenuation of 0.521 ± 0.02 dB cm−1 MHz−1. In addition, this material was used in a series of experiments to test a new approach to the production of anatomically realistic soft plaques in flow phantoms. Current research into plaque characteristics in Doppler flow phantoms has been limited to the use of wedges of PVA-C which are subjected to more (hard plaques) or fewer (soft plaques) freeze thaw cycles than the surrounding vessel [1] . A novel approach to the production of soft plaques is presented where cod liver oil capsules are embedded in the tissue. Following the production of the flow phantom, the gelatine capsules can be breached and liquefied by placing the entire phantom in a heated water bath; this leaves the cod liver oil encased in the vessel by a thin layer of PVA-C. By replacing the cod liver oil with a soft lipid mimicking fluid, anatomically realistic plaques can be constructed.