Harnessing Rare-Earth Materials as Exogenous Contrast Agents for Enhanced Photoacoustic Imaging.

Photoacoustic imaging (PAI) has emerged as a promising noninvasive biomedical imaging modality with high spatial resolution and soft tissue contrast. Exogenous contrast agents play a crucial role in enhancing the sensitivity and specificity of PAI. Among these contrast agents, the rare earth materials (REM) have garnered a lot of interest due to their near-infrared (NIR) absorption properties. REM established itself as a well-known entity in the field of bioimaging and therapy due to their optical, magnetic, and photothermal characteristics. The photoacoustic phenomenon of REM has the potential to emerge as a promising feature alongside its existing properties. The integration of the various REM as PAI exogenous contrast agents offers the potential for targeted imaging of specific biological structures or pathological conditions. In the present study, mechanisms behind the generation of acoustic signals are elucidated in detail, providing insights into the underlying principles of acoustic enhancements, in relation to the properties of contrast agents. The integration of rare earth contrast agents in various studies is highlighted, showcasing their potential for acoustic detection, multimodal imaging, and therapy. This review provides a comprehensive overview of recent advancements in utilizing rare earth contrast agents for enhancing PAI.