Currently there is a radiopharmaceutical product for research purposes available (99mTc-EC20, EtarfolatideTM, Endocyte Inc.) which can be used for Single Photon Emission Computed Tomography (SPECT) imaging. SPECT, however, has multiple limitations compared to PET, such as inferior spatial resolution, soft tissue attenuation, lack of dynamic acquisition etc. Therefore, a PET-compound for FR imaging has been shown to image FR-positive tumors in experimental animals .