Biosensor Imaging of Redundant Deviation of Shifts (BIRDS) represents another alternative to CEST imaging, using resonances from paramagnetic lanthanide-based contrast agents (CAs). Although spatial resolution is high, CEST data are qualitative because the signal attenuation remains relative unless the CA concentration, temperature and pH are known. A typical BIRDS experiment uses high-speed CSI because of favorable relaxation times for CAs. A europium-based CA, EuDOTA-(gly) 4-, exhibits enhanced CEST characteristics while still retaining high sensitivity to temperature variations specific to BIRDS. Here, we illustrate the principles of combining CEST and BIRDS to obtain optimal temperature measurements with improved spatial resolution.
