Magnetic Resonance Imaging (MRI) Contrast Agents for Tumor Diagnosis

This review focuses on MRI contrast agents for tumor diagnosis. Several types of low molecular weight Gd3+-based complexes and dextran-coated superparamagnetic iron oxide (SPIO) nanoparticles have been used for clinical tumor diagnosis as longitudinal relaxation time (T-1) and transverse relaxation time (T-2) MRI contrast agents, respectively. To further improve the sensitivity of MRI, new types of chelates for T-1 MRI contrast agents and combination of low molecular weight T-1 MRI contrast agents with different types of carriers have been investigated. Different types of materials for forming secure coating layers of SPIO and novel superparamagnetic particles with higher relaxivity values have been explored. Various types of ligands were applied to improve the capability to target tumor for both T-1 and T-2 contrast agents. Furthermore, MRI contrast agents for detection of tumor metabolism were also pursued.