Seeing life in a new light NuanceTM and MaestroTM Imaging Systems

Increasing sophistication in the design and interrogation of biological models, and the advent of novel fluorescent probes have led to new demands on molecular imaging systems to deliver enhanced sensitivity, reliable quantitation, and the ability to resolve multiple simultaneous signals. Sensitivity is limited, especially in the visible spectral range, by the presence of ubiquitous autofluorescence signals (mostly arising from skin and gut), which need to be separated from those of targeted fluorophores. Fluorescence-based imaging is also affected by absorbing and scattering properties of tissue in the visible and to a lesser extent in the near-infrared (NIR). However, the small size of typical animal models (usually mice) often permit the detection of enough light arising even from relatively deep locations to allow capture of signals with acceptable signal-to-noise. Multispectral imaging, through its ability to separate autofluorescence from the label fluorescence, can increase sensitivity by as much as 300 fold compared to conventional approaches, and concomitantly improves quantitative accuracy. In the NIR region, autofluorescence, while still significant, poses less of a problem. However, the task of disentangling signals from multiple fluorophores remains. Multispectral imaging allows the separation of five or more fluorophores, with each signal quantitated and visualized separately. Preclinical small-animal imaging is often accompanied by microscopic analysis, both before and after the in-vivo phase. This can involve tissueculture manipulations and/or histological examination of fixed or frozen tissue. Due to the same advantages already discussed with respect to sensitivity, quantitation and multiplexing, microscopy-based multispectral techniques form an excellent complement to in-vivo imaging.