Development of Ultrasound Phantom Made of Transparent Material: Feasibility of Optical Particle Image Velocimetry.

Objective: The need for ultrasound flow phantoms to validate ultrasound systems requires the development of materials that can clearly visualize the flow inside for measurement purposes.

Methods: A transparent ultrasound flow phantom material composed of poly(vinyl alcohol) hydrogel (PVA-H) with dimethyl sulfoxide (DMSO) and water solution manufactured using the freezing method and mixed with quartz glass powder to exhibit scattering effects is proposed. To achieve transparency of the hydrogel phantom, the refractive index (RI) was changed to match that of the glass by modifying the PVA concentration and the ratio of DMSO to water in the solvent. The feasibility of optical particle image velocimetry (PIV) was verified by comparing an acrylic rectangular cross-section channel with a rigid wall. After the feasibility tests, an ultrasound flow phantom was fabricated to conduct ultrasound B-mode visualization and Doppler-PIV comparison.

Discussion: The results revealed that the PIV measured through PVA-H material exhibited 0.8% error in the measured maximum velocity compared with PIV through the acrylic material. B-mode images are similar to real tissue visualization with a limitation of a higher sound velocity, when compared with human tissue, of 1792 m/s. Doppler measurement of the phantom revealed approximately 120% and 19% overestimation of maximum and mean velocities, respectively, compared with those from PIV.

Conclusion: The proposed material possesses the advantage of the single-phantom ability to improve the ultrasound flow phantom for validation of flow.