A group of researchers led by Thayer School of Engineering professor Brian Pogue introduced a new small animal imaging system last month in the Review of Scientific Instruments. The system may eventually aid in cancer therapy for humans.

Imaging fluorescence in vivo allows enhanced observations of drug uptake, diseased tissues, and molecular activity. Fluorescence tomography (FT) was developed based on this method. FT provides better fluorescence distribution maps in terms of depth as well as spatial resolution and sensitivity than near infrared red diffuse optical tomography, another noninvasive imaging technique.

However, the recently designed small animal FT imagers have drawbacks as well. FT imagers measure both fluorescence and transmission diffusion to reconstruct volumetric images. These two factors are sometimes measured as much as 30 minutes apart. During this interval the animal may move or the localized fluorescence may change due to drug uptake characteristics, resulting in poor resolution.

To target this problem in FT imaging, the research team employed x-ray microcomputed tomography (microCT), an anatomical imaging modality. The two systems complement each other: FT increasing the sensitivity of microCT to cancerous tissues thereby enhancing contrast, while microCT improves quantitative accuracy of the FT by reconstructing the volumetric images of interest.

In addition to merging FT and microCT techniques, the new FT imaging system counts single photons for maximum sensitivity. Moreover, five parallel detectors measured fluorescence and transmission simultaneously. As a result, the total imaging time was reduced to several minutes. All in all, the fluorescence distribution could be mapped out much more accurately using this new technique.

The researchers expect this microCT-coupled FT system, which provides more accurate small animal molecular imaging, to be applied in preclinical cancer research as well as cancer therapy.