It is intended to provide a Magnetic Resonance Imaging (MRI) phantom for .sup.1H/.sup.19F signal detection that permits the stable and uniform dispersion of a vesicle and to accomplish the adjustment of a measurement parameter for a .sup.1H/.sup.19F signal and performance confirmation by use of the phantom. The present invention provides an MRI phantom having a gel comprising a vesicle comprising at least one of a perfluorocarbon and a superparamagnetic iron oxide particle and an MRI system having the phantom.