Iranian researchers in association with their Australian and Belgian colleagues successfully produced a new nanoprobe to diagnose cancerous cells. The main characteristic of the nanoprobe is to diagnosis the disease before it causes physiological changes in the body. Among the applicable properties of the results of this research in the field of medicine, mention can be made of imaging, separation of cancerous cells from healthy ones, hyperthermia, and studying the amount of gene expression. Taking into account the advantages and wide applications of MRI in different cancer treatment stages, the need for paying attention to new imaging methods is increasing day by day to converge and improve the sensitivity of imaging method, specially magnetic resonance molecular imaging (MRMI). In this research, a magnetic nanoprobe was designed and tested to increase the sensitivity and make more specialized MRI method to specifically detect prostate cancer cells. In this research, PSMA antigen, which is a specific antigen for prostate cancer with high expression on the surface of cancerous cells but with no expression on the surface of prostate natural cells, was characterized and determined as an ideal target agent. Next, J591 antibody was chosen as targeting agent due to its unique properties. The antibody was attached to the magnetic iron nanoparticle with a coating of polyethylene glycol and –NH2 surfactants after activation and preparation of particles by using a specific cross linker entitled Sulfo-SMCC. Finally and after the production of the nanoprobe, its physical and chemical properties and its performance were investigated in in-vitro and in-vivo applications. The difference in this research with the similar researches is in introducing and developing the contrast agent that is able to detect prostate cancer cells among the healthy ones, which can result in early diagnosis of the disease before it causes physiological changes on the surface of cells before changing the anatomy. Results of the research have been published in details in Contrast Media & Molecular Imaging, vol. 8, September 2012, pp. 175-184.