Biomedical imaging research opportunities workshop IV: a white paper

Multifunctional microbubbles and nanobubbles for photoacoustic imaging

Photoacoustic imaging is an emerging imaging modality for noninvasive detection of tissue structural and functional anomalies. Multifunctional microbubbles (MBs) and nanobubbles (NBs) are contrast agents integrating multiple disease-targeting, imaging and therapeutic functions. Multifunctional MBs and NBs represent an enabling technology for many potential applications in the field of photoacoustic imaging. Highly absorbing optical contrast agents, such as gold nanoparticles, India ink and Indocyanine Green, can be encapsulated in MBs and NBs for stable absorption properties and multimodal imaging contrasts. The surface of MBs and NBs can be modified for high disease-targeting affinity, reduced immunogenicity and prolonged circulation lifetime. Low boiling point perfluorocarbon compounds can be encapsulated in MBs and NBs for selective activation by external energy sources. The activation of these MBs and NBs may introduce significant contrast enhancement and facilitate a variety of potential clinical applications, such as image-guided drug delivery and therapeutic margin assessment. MB and NB enhanced photoacoustic imaging is still in its infancy. Further development and validation works are necessary for successful translation of the technology from the benchtop to the bedside.

Hybrid PET-optical imaging using targeted probes

Fusion imaging of radionuclide-based molecular (PET) and structural data [x-ray computed tomography (CT)] has been firmly established. Here we show that optical measurements [fluorescence-mediated tomography (FMT)] show exquisite congruence to radionuclide measurements and that information can be seamlessly integrated and visualized. Using biocompatible nanoparticles as a generic platform (containing a (18)F isotope and a far red fluorochrome), we show good correlations between FMT and PET in probe concentration (r(2) > 0.99) and spatial signal distribution (r(2) > 0.85). Using a mouse model of cancer and different imaging probes to measure tumoral proteases, macrophage content and integrin expression simultaneously, we demonstrate the distinct tumoral locations of probes in multiple channels in vivo. The findings also suggest that FMT can serve as a surrogate modality for the screening and development of radionuclide-based imaging agents.

Bioengineering and Imaging Research Opportunities Workshop V: a summary on Imaging and Characterizing Structure and Function in Native and Engineered Tissues

The Fifth Bioengineering and Imaging Research Opportunities Workshop (BIROW V) was held on January 18-19, 2008. As with previous BIROW meetings, the purpose of BIROW V was to identify and characterize research and engineering opportunities in biomedical engineering and imaging. The topic of this BIROW meeting was Imaging and Characterizing Structure and Function in Native and Engineered Tissues. Under this topic, four areas were explored in depth:1) Heterogeneous single-cell measurements and their integration into tissue and organism models;2) Functional, molecular, and structural imaging of engineered tissue in vitro and in vivo;3) New technologies for characterizing cells and tissues in situ;4) Imaging for targeted cell, gene, and drug delivery.