Acoustical properties of selected tissue phantom materials for ultrasound imaging

Abstract

This note summarizes the characterization of the acoustic properties of four materials intended for the development of tissue, and especially breast tissue, phantoms for the use in photoacoustic and ultrasound imaging. The materials are agar, silicone, polyvinyl alcohol gel (PVA) and polyacrylamide gel (PAA). The acoustical properties, i.e., the speed of sound, impedance and acoustic attenuation, are determined by transmission measurements of sound waves at room temperature under controlled conditions. Although the materials are tested for application such as photoacoustic phantoms, we focus here on the acoustic properties, while the optical properties will be discussed elsewhere. To obtain the acoustic attenuation in a frequency range from 4 MHz to 14 MHz, two ultrasound sources of 5 MHz and 10 MHz core frequencies are used. For preparation, each sample is cast into blocks of three different thicknesses. Agar, PVA and PAA show similar acoustic properties as water. Within silicone polymer, a significantly lower speed of sound and higher acoustical attenuation than in water and human tissue were found. All materials can be cast into arbitrary shapes and are suitable for tissue-mimicking phantoms. Due to its lower speed of sound, silicone is generally less suitable than the other presented materials.

High-resolution imaging in a deep turbid medium based on an ultrasound-switchable fluorescence technique

“…The amplified signal was input into an impedance matching network to drive the HIFU transducer (H-108, Sonic Concepts, Washington; central frequency: 2.5 MHz; active diameter: 60 mm; focal length: 50 mm). The HIFU transducer was focused on a silicone sample (VST-50, Factor II, Inc, Lakeside, AZ) that functioned as an acoustic absorber 19 and was located at the HIFU focal zone. A small silicone tube (Instech Lab, BSIL-T031, PA) that was filled with the thermo-sensitive fluorescent polymer solution (10 mg/ml) and inserted into the silicone phantom along Y direction was used to simulate a small blood vessel.…”

Acoustic characterization of Thiel liver for magnetic resonance-guided focused ultrasound treatment

“…where Z is the acoustic impedance (N × s / m 3 ; rayls) ρ is the density of the organ (Kg / mm 3 ) and c is the speed of sound (m / s) in the Thiel embalmed tissue [8]. To measure the density the following equation was used:…”

“…8 The calculation of the reflection coefficient on the liver-water interface was based on the following formula:…”

Ultrasound assisted particle and cell manipulation on-chip

“…However, care must be taken to avoid local hot-spots which may occur near the transducer because of excess heating from the ultrasound generation process or in relatively lossy media. For example, the acoustic attenuation (approximately equivalent to heating) in PDMS and other plastics is much higher than in glass and silicon [59].…”