IEC/TS 62558:2011(E) specifies essential characteristics of a phantom and method for the measurement of void-detectability ratio for medical ultrasound systems and related transducers. It is restricted to the aspect of long-term reproducibility of testing results. Medical diagnostic ultrasound systems and related transducers need periodic testing as the quality of medical decisions based on ultrasonic images may decrease over time due to progressive degradation of essential systems characteristics. The TMM (Tissue Mimicking Material) phantom is intended to be used to measure and to enable documentation of changes in void-detectability ratio in periodic tests over years of use. This technical specification establishes: - Important characteristics and requirements for a TMM 3D artificial cyst phantom using anechoic voids - A design example of a 3D artificial cyst phantom, the necessary test equipment and use of relevant computer software algorithms. This technical specification is currently applicable for linear array transducers. A uniformity test prior to void-detectability ratio (VDR) measurement is recommended.