In vivo molecular imaging techniques for the pathological features of Alzheimer’s disease in the brain, such as senile plaques (amyloid β aggregates) and neurofibrillary tangles (tau pathology), are being developed. One of the most promising techniques is positron emission tomography (PET) imaging; however, it is high-cost and internal radiation exposure is not ruled out due to the use of radioisotopes. To replace or complement PET imaging, we focus on magnetic resonance imaging (MRI), an imaging technique using nuclear magnetic resonance (NMR) of certain atomic nuclei. In particular, we focus on 19F MRI because 19F is a relatively high-sensitive, cost-effective NMR atom with a very low level in the body. We previously developed 19F probes for amyloid β aggregates and tau pathology, which bind to the target molecules in the brain following systemic administration. In our study MRI successfully detected the NMR of the 19F probes, providing an image that reflects the formation of pathological changes in the brain. Furthermore, we have recently developed a 19F probe (named Shiga-Y51) for amyloid β oligomers, which are soluble, high-toxic species of amyloid β aggregates, and succeeded in the in vivo imaging of Shiga-Y51 using 19F MRI.