The invention relates to a contrast agent particle comprising a carrier particle having a particle size of between 5 and 200 nm and at least one quadrupolar compound comprising at least one bismuth as a quadrupolar nucleus, wherein the at least one quadrupolar compound is bound to the carrier particle via at least one linker. The invention also relates to a Magnetic Resonance Imaging contrast medium (MRI contrast medium) comprising a contrast agent particle according to the invention. Furthermore, the invention relates to the use of contrast agent particles and Magnetic Resonance Imaging media according to the invention in Quadrupole Relaxation Enhancement (QRE)-based Magnetic Resonance Imaging.
