Permanently Swollen Segmented Polyurethane Gel as a Robust Tissue-Mimicking Material for Ultrasound Diagnostic Phantoms

A novel tissue-mimicking material (TMM) based on permanently swollen segmented polyurethane gel (SPUG) was developed for use in diagnostic ultrasound phantoms. This TMM exhibits acoustic properties—sound velocity, attenuation, and acoustic impedance—that comply with International Electrotechnical Commission 61685 standards and closely mimic those of human soft tissue. Prototypes incorporating the TMM maintained high spatial resolution even after two years of storage under ambient conditions. Furthermore, compression tests demonstrated that the SPUG-based TMM is significantly softer and more resistant to mechanical failure than conventional agar-based materials. These findings suggest that the material is a promising candidate for fabricating robust, reusable ultrasound phantoms with long-term stability and consistent imaging performance.