Purpose: Fluorescence-enhanced optical imaging using near-infrared (NIR) light developed for in-vivo molecular targeting and reporting of cancer provides promising opportunities for diagnostic imaging. In this study, we demonstrated fluorescence-enhanced optical tomography using fluorescent contrast agents in large tissue-mimicking breast phantoms in order to facilitate clinical translation.
Methods and Materials: Frequency-domain fluorescence measurements were performed using a gain-modulated ICCD (intensified charge-coupled device) detection system for rapid data acquisition and was operated at 100MHz. Micromolar concentrations of fluorescent contrast agent (indocyanine green, ICG) were used in order to enhance the optical contrast between the target and the background.
Results: Targets of 0.5 to 1 cc volume located up to 2 cm deep from the phantom surface, and under target:background contrast ratios of 1:0 and 100:1 were tomographically reconstructed. A 1 cc target located 1 cm from the phantom surface was also differentiated from its background phantom based on the lifetime of the fluorescing contrast agents present in the target and background. While nuclear imaging provides diagnostic imaging opportunities, molecular targeting of tumors using low dosages of fluorescent contrast agents could possibly become an alternate approach and more sensitive.
Conclusion: An optical imager with a rapid data acquisition system provides robust and accurate measurements, which when combined with tomography may provide clinical application for targeting early stage tumors using fluorescent contrast agents, based on the absorption contrast or lifetime contrast between the target and the background.
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