Iranian researchers investigated properties of gold nanorods as the carrier of radiodrugs. The nanorods are coated with polyethylene glycol (PEG) and are labeled with iodine-131 isotope, and they have applications in medical industries, specially for in vivo imaging and in the treatment of diseases like tumors. Gold nanoparticles have various applications in molecular imaging and carrying medications due to their unique physicochemical properties such as ease of production and surface modification and biocompatibility. Among various shapes, gold nanorods have significant optical properties and their known biocompatibility is higher than that of other shapes of gold nanoparticles. The use of isotopes has recently increased in studying the distribution of nanoparticles inside the body. The reason is the availability of highly sensitive methods to detect radioisotope coated with nanoparticles inside the body. Therefore, it is expected that the combination of nanorods with iodine-131 isotope, which is mostly used in imaging and in the treatment of diseases, would result in the creation and development of imaging methods combined with nuclear imaging. A two-functional group is used in most of nanoparticles labeling methods by using radionuclides to be connected with the nanoparticles, and then a radioactive metal is added to it. However, in this research, the modified nanoparticles were labeled with iodine-131 without using any type of functional group. The reason is high affinity of iodine in connection with the surface of gold nanorods. The researchers are currently trying to synthesize gold nanoparticles in various shapes and sizes, to label them with other radionuclides, and to investigate the distribution of labeled nanoparticles. Results of the research, carried out by Dr. Sajjadi et al, have been published in details in December 2012 in Journal of Labelled Compounds and Radiopharmaceuticals, vol. 56, pp. 12-16.