Earlier detection of diseases reduces the mortality rate. So the development of better screening techniques could be considered as a main topic of interest. In non-invasive medical imaging, specifically in MAGNETIC Resonance Imaging (MRI), conventional contrast agents do not have a good performance in imaging of some fine parts. The prosperity of preclinical researches in oncology that purpose at developing and evaluating curative strategies on samples, requires effective new functionalized contrast agents for portrayal tumor growth, monitoring the trace of a treatment and/or inducing the demolition of cancerous tumors. This study was performed by searching Nanotechnology, Molecular imaging, MAGNETIC NANOPARTICLES, and contrast agent NANOPARTICLES keywords in Google scholar, Science direct, PubMed and Scopus websites in terms of content. We reviewed the recent studies about development of NANOPARTICLES as contrast agents for medical imaging because they have a longer vascular half-life than molecular contrast agents. It could be indicate that NANOPARTICLES are important items in increasing the contrast of the images so that even reducing the size of the MAGNETIC NANOPARTICLES escalates the contrast and half-life of the particles. Particles with a diameter of 10 nm have a greater half-life than particles with a diameter of 30 nm or larger. It was also found that to removing material defects or improve their biocompatibility; particles should be covered with other materials or doped with metals.