  Objective: Realistic tissue-mimicking phantoms are essential for the
development, the investigation and the calibration of medical imaging
techniques and protocols. Because it requires taking both mechanical and
imaging properties into account, the development of robust, calibrated phantoms
is a major challenge in elastography. Soft polyvinyl chloride gels in a liquid
plasticizer (plastisol or PVCP) have been proposed as soft tissue-mimicking
phantoms (TMP) for elasticity imaging. PVCP phantoms are relatively low-cost
and can be easily stored over long time periods without any specific
requirements. In this work, the preparation of a PVCP gel phantom for both MR
and ultrasoundelastography is proposed and its acoustic, NMR and mechanical
properties are studied.Material and methods: The acoustic and magnetic
resonance imaging properties of PVCP are measured for different mass ratios
between ultrasound speckle particles and PVCP solution, and between resin and
plasticizer. The linear mechanical properties of plastisol samples are then
investigated over time using not only indentation tests, but also MR and
ultrasound-elastography clinical protocols. These properties are compared to
typical values reported for biological soft tissues and to the values found in
the literature for PVCP gels.Results and conclusions: After a period of two
weeks, the mechanical properties of the plastisol samples measured with
indentation testing are stable for at least the following 4 weeks (end of
follow-up period 43 days after gelation-fusion). Neither the mechanical nor the
NMR properties of plastisol gels were found to be affected by the addition of
cellulose as acoustic speckle. Mechanical properties of the proposed gels were
successfully characterized by clinical, commercially-available MR Elastography
and sonoelastography protocols. PVCP with a mass ratio of ultrasound speckle
particles of 0.6% to 0.8% and a mass ratio between resin and plasticizer
between 50 and 70% appears as a good TMP candidate that can be used with both
MR and ultrasound-based elastography methods.
