Towards Photoswitchable Contrast Agents for Absolute 3D Temperature MR Imaging

Temperature can be used as clinical marker for tissue metabolism and the detection of inflammations or tumors. The use magnetic resonance imaging (MRI) monitoring physiological parameters like temperature noninvasively is steadily increasing. In this study, we present a proof-of-principle study MRI contrast agents (CA) absolute concentration independent imaging. These CAs are based on azoimidazole substituted NiII porphyrins, which undergo Light-Driven Coordination-Induced Spin State Switching (LD-CISSS) in solution. Monitoring fast first order kinetic back isomerisation (cis to trans) with standard MR sequences allows determination half-lives, that directly translated into temperatures. Different responsive were successfully tested prototypes methanol-based gels created maps gradient phantoms high spatial resolution (0.13×0.13×1.1 mm) low errors (<0.22 °C). method sufficiently record flow from heat source film.