MRI is likely to play an important role in the development and implementation of gene therapy, as it is growing its slow translation from the pre-clinical setting, to its application to many forms of disease in humans. Imaging techniques such as MRI and positron emission tomography (PET) may greatly benefit from the gene targeting modalities being developed in gene therapy, making it a reality to be able to combine therapy with targeted contrast agents, thus enhancing the specificity and capability of both MRI and MRS technologies. Genetically modified cells may be tagged with MR contrast agents for imaging in medical applications. One of the major advantage of MRI is its potential for high resolution compared to mm resolution for radionuclide and optical based methods. Basic strategies for imaging therapeutic gene expression by MR-based methods can be categorized into direct and indirect imaging methods.