Prof. Jinwoo Cheon (Yonsei University) and Prof. Jungsoo You(Kyungpook University) has introduced a hybrid PET-MRI probe A new type of nanotechnology-based probes for PET (positron emission tomography) and MRI (magnetic resonance imaging) diagnostics has been developed with a promising possibility for false-free disease diagnosis. According to the report in the recent issue of Angewante Chemie, a team lead by Prof. Jinwoo Cheon (Chemistry Department, Yonsei University) and Prof. Jungsoo You (Molecular and Nuclear Medicine Department, Kyungpook University) has introduced a hybrid PET-MRI probe which has merits from both imaging systems such as high sensitivity and accurate anatomical information of disease. In the modern medicine, increment of the diagnostic accuracy is one of the most important issues for the treatment and prevention of the diseases including cancer. However, single modality diagnostic tools have not been fully satisfactory yet. For example, PET has the highest detection sensitivity among various imaging tools but its anatomical information has been very poor. On the other hand, MRI can provide nice anatomical information but has comparably much lower signal intensity. Therefore, researches for combining multiple imaging tools have been very important. The research team has successfully developed a novel hybrid PET-MRI contrast agent which is an ideal candidate for the highly accurate disease diagnosis, having comprehensive merits of individual imaging techniques. The contrast agent is constituted of radioisotpe (124I) and magnetic nanoparticle (figure 1). By using the hybrid nanoparticle probe, accurate detection of lymph nodes which are important sites for malignant cancer metastasis and biological immunological defense has been successfully accomplished. As seen in figure 2, a targeted lymph node is clearly located in a PET-MRI fusion image without any ambiguity, while it is difficult to locate it from the images of PET and MRI, respectively. (Figure 2) Such hybrid contrast agents would be also beneficial for non-invasive and highly sensitive real-time imaging of various biological events such as cell migration as well as the diagnosis of various disease including stroke, myocardial infarction, sclerosis of the arteries, etc. Figure 1. PET-MRI hybrid contrast agent is developed by combining PET signal generating ratio isotope (124I) and MRI signal generating magnetic nanoparticle. PET-MRI hybrid contrast agent provides excellent dual PET and MRI signals (image on the right). Figure 2. PET and MRI images of a mouse are taken after the intravenous injection of PET-MRI hybrid contrast agent. Exact position of targeted lymph node is accurately identified by PET-MRI fusion image. (Dotted circle: target lymph nodes)