Radiofrequency-Sensitive Longitudinal Relaxation Tuning Strategy Enabling the Visualization of Radiofrequency Ablation Intensified by Magnetic Composite

As a minimally invasive heat source, radiofrequency (RF) ablation still encounters potential damages to the surrounding normal tissues because of heat diffusion, high power, and long time. With a comprehensive understanding of the current state of the art on RF ablation, a magnetic composite using porous hollow iron oxide nanoparticles (HIONs) as carriers to load dl-menthol (DLM) has been engineered. This composite involves two protocols for enhancing RF ablation, that is, HION-mediated magnetothermal conversion in RF field and RF solidoid vaporation (RSV)-augmented inertial cavitation, respectively. A combined effect based on two protocols is found to improve energy transformation, and further, along with hydrophobic DLM-impeded heat diffusion, improve the energy utilization efficiency and significantly facilitate ex vivo and in vivo RF ablation. More significantly, in vitro and in vivo RSV processes and RSV-augmented inertial cavitation for RF ablation can be monitored by T₁-weighted magnetic resonance imaging (MRI) via an RF-sensitive longitudinal relaxation tuning strategy because the RSV process can deplete DLM and make HION carriers permeable to water molecules, consequently improving the longitudinal relaxation rate of HIONs and enhancing T₁-weighted MRI. Therefore, this RF-sensitive magnetic composite holds a great potential in lowering the power and time of RF ablation and improving its therapeutic safety.