Acoustic and Elastic Properties of Glycerol in Oil-Based Gel Phantoms

Phantoms are important tools for image quality control and medical training. Many phantom materials have been proposed for ultrasound; most of them use water as the solvent, but these materials have disadvantages such as dehydration and low temporal stability if not properly stored. To overcome these difficulties, copolymer-in-oil gel was proposed as an inert and stable material; however, speed of sound for these materials is still lower than what is described for most biological tissues. Here, we propose the glycerol dispersion in oil-based gels to modify the acoustic and elastic properties of copolymer-in-oil phantoms. We manufactured copolymer-in-oil gels using styrene-ethylene/butylene-styrene (SEBS) in concentrations 8%-15%. We used 2 types of mineral oils with different viscosities. Glycerol was added in a volume fraction 0%-30% of the total amount of liquid. The acoustic (i.e., speed of sound, attenuation and backscattering) and the mechanical (i.e., density and Young's modulus) properties of the samples were within the range of values observed for soft tissues. The acoustic parameters of the samples were dependent on oil viscosity and glycerol concentration. The speed of sound ranged 1423 m/s - 1502 m/s, while the acoustic attenuation and the ultrasonic backscattering increased by adding glycerol. The density and the Young's moduli were less affected by the presence of glycerol. We conclude that glycerol can be used to control the acoustic parameters of copolymer-in-oil gels. Additionally, it opens the possibility of incorporating other oil-insoluble substances to control further properties of the phantom.