Mechanical behaviour of tissue mimicking breast phantom materials

Abstract

The mechanical properties of soft tissue have long been of interest in biomedical research and 
\napplications, and increasingly for breast cancer imaging. In this paper, the mechanical 
\nproperties of three different materials used to emulate the mechanical behavior of real breast 
\ntissue are measured: agar, gelatine, and silicone, to assess their suitability for use in phantoms 
\nin systems assessing tissue mechanics for diagnostics. Two widely recognised measurement 
\nprocedures are used. Quasi-static uniaxial compression was performed under a strain rate of 
\n0.5 mm/min up to 15% strain with preloads of 0.05 N, 0.1 N, and 0.2 N, was used to measure 
\nthe elastic moduli. Dynamic testing over a frequency range of 0.1-50 Hz for agar and 0.1-100 
\nHz for gelatine and silicone with the same preload was used to measure the storage moduli. 
\nElastic and storage moduli were (5-81 kPa, 17-85 kPa, 5-112 kPa) and (3-128 kPa, 10-109 kPa, 
\n5-73 kPa) for agar, gelatine, and silicone, respectively at the three preloads. All materials can 
\nbe cast into arbitrary shapes and are suitable for tissue-mimicking phantoms. Silicone was the 
\nmost consistent across the different preloads and frequencies, and can provide a range of 
\nstiffness ratios of adipose to tumor tissue that match experimentally reported values. More 
\nspecifically, silicone samples for skin, adipose and tumour tissues show nonlinear stress–strain 
\ncharacteristics at 3 preloads characterized using hyperelastic parameters by fitting NeoHookean, 
\nMooney Rivlin and Ogden models. Silicone also does not contain water, so 
\nenvironmental influences do not affect its mechanical properties as much as the other materials, 
\nand is thus more durable for consistent re-use. Finally, breast shaped mimicking silicone 
\nphantoms were fabricated for in vitro trials of a Digital Image Elasto Tomography breast cancer 
\nscreening system assessing changes in mechanical properties.