The present invention relates to a phantom for periodical measurements of parameters allowing to ensure that performance of equipment for computed tomography and/or magnetic resonance tomography are compliant to established acceptability criteria, that is performance are constant in time. The main characteristic of such phantom is that the same phantom may be used for measurements of different physical parameters and for different machines, even of different type, such as machines for CT and/or MRT. The universal phantom described is made of a rectangular parallelepiped in PMMA made of different sections that may be filled with an appropriate liquid and/or contain different inserts according to the measurements to be performed, such as for example noise and uniformity, CT number linearity, high contrast spatial resolution, low contrast spatial resolution, layer thickness, etc.