Acoustic Characterization of a Modified IEC Agar-Based Tissue-Mimicking Material Across the 3.5-50 MHz Frequency...

The Edinburgh Pipe Phantom (EPP) is a test-object developed to measure the imaging performance of ultrasound scanners. It is manufactured from the International Electrotechnical Commission (IEC) agar-based tissue-mimicking material (TMM) into which a range of fluid-filled pipes are molded. In this study we investigated the impact of increasing freeze-thaw (F/T) cycles on the acoustic properties of the IEC TMM to explore whether F/T modifications to the material allow for multimaterial phantom design.

This study aims to acoustically characterize the IEC TMM over the frequency range 3.5 to 50 MHz, after undergoing 0-3 freeze-thaw cycles.

Samples of the IEC agar-based TMM were manufactured and subjected to 0-3 F/T cycles, with a cycle consisting of 12 hours at -18°C followed by controlled thawing for a further 12 hours. The acoustic properties were measured using an acoustic macroscope, across the 3.5-50 MHz frequency range and samples were later observed using an optical microscope. Statistical significance was assessed at the 95% confidence level.

The acoustic attenuation across F/T cycles remained unchanged within experimental error, with a mean value of 0.54 ± 0.04 dB·cm^-1·MHz^-1. The speed of sound of the samples however significantly increased with each cycle, from 1502.6 ± 14.7 ms^-1 (0 cycle) to 1554.8 ± 10.3 ms^-1 (3 cycles). Microscopic analysis revealed cracks throughout the samples.

This study suggests that despite freeze-thaw induced changes in its structure and speed of sound, the acoustic attenuation of the IEC agar-based TMM remained stable for up to 3 F/T cycles, suggesting potential for multimaterial phantom development, although further work is required to assess imaging performance and stability.