Noninvasive magnetic resonance/photoacoustic imaging for photothermal therapy response monitoring.

In vivo assessment of vascular permeability and therapeutic response provides novel insights into photothermal therapy (PTT) that is currently under clinical investigation. We have developed noninvasive imaging strategies to improve the monitoring of nanoparticle-mediated PTT responses for personalized nanomedicine. Briefly, dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) and photoacoustic imaging (PAI) were applied to study the enhanced permeability and retention (EPR) effect in tumor models of different microvascular permeabilities (i.e., 4T1 mouse breast tumor model and HUH-7 human hepatoma model in nude mice). Magnetic resonance temperature imaging (MRTI) and diffusion-weighted MRI (DWI) showed that the 4T1 tumor model exhibits a higher PTT temperature response than that of the HUH-7 tumor model. Our findings demonstrate that the combined use of MRI and PAI techniques is useful in monitoring the vascular permeability and temperature status following PTT, promising to help guide PTT in future translational investigation.