Photoacoustic imaging of lacZ gene expression in vivo

In the postgenomic era, imaging techniques are playing an important role in visualizing gene expression in vivo. This work represents the first demonstration of photoacoustic tomography (PAT) for reporter gene imaging. Rats inoculated with 9L/lacZ gliosarcoma tumor cells are imaged with PAT before and after injection of X-gal, a colorimetric assay for the lacZ-encoded enzyme $β$-galactosidase. Using far-red optical illumination, the genetically tagged tumors in rats are clearly visualized by PAT following the assay. The spatial resolution is quantified to be less than $400μm$, while 500-nM-level sensitivity is demonstrated. With the future development of new absorption-based reporter gene systems, it is anticipated that photoacoustic technology will provide a valuable tool for molecular imaging research.