Non-invasive MR thermometry monitoring in plasmonic photothermal therapy using gold nanorods

This study used magnetic resonance (MR) thermometry to investigate the temperature increases and thermal diffusion that occur during plasmonic photothermal therapy (PTT) with gold nanorods (GNRs). An artificial tumor phantom made of agarose gel containing GNRs was heated by irradiation with an 808 nm laser. The MR thermometer visualized the conditions: a well-localized temperature distribution with suppressed thermal diffusion that depended on laser power and irradiation time. A tumor phantom model was implanted in mice, and MR thermometry evaluated the temperature change in the presence and absence of GNRs and the thermal diffusion into the surrounding tissues. That experiment showed that MR thermometry can be a useful tool for monitoring PTT. These results suggest that MR temperature measurement could help to establish ideal laser irradiation conditions in GNR-mediated PTT, and that it has great potential for visualizing local photothermal induction and evaluating therapeutic effects.