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Intraoperative resection of tumors currently relies upon the surgeon’s ability to visually locate and palpate tumor
nodules. Undetected residual malignant tissue often results in the need for additional treatment or surgical
intervention. The Solaris platform is a multispectral open-air fluorescence imaging system designed for
translational fluorescence-guided surgery. Solaris supports video-rate imaging in four fixed fluorescence channels
ranging from visible to near infrared, and a multispectral channel equipped with a liquid crystal tunable filter
(LCTF) for multispectral image acquisition (520-620 nm). Identification of tumor margins using reagents emitting in
the visible spectrum (400-650 nm), such as fluorescein isothiocyanate (FITC), present challenges considering the
presence of auto-fluorescence from tissue and food in the gastrointestinal (GI) tract. To overcome this, Solaris
acquires LCTF-based multispectral images, and by applying an automated spectral unmixing algorithm to the data,
separates reagent fluorescence from tissue and food auto-fluorescence. The unmixing algorithm uses vertex
component analysis to automatically extract the primary pure spectra, and resolves the reagent fluorescent signal
using non-negative least squares. For validation, intraoperative in vivo studies were carried out in tumor-bearing
rodents injected with FITC-dextran reagent that is primarily residing in malignant tissue 24 hours post injection. In
the absence of unmixing, fluorescence from tumors is not distinguishable from that of surrounding tissue. Upon
spectral unmixing, the FITC-labeled malignant regions become well defined and detectable. The results of these
studies substantiate the multispectral power of Solaris in resolving FITC-based agent signal in deep tumor masses,
under ambient and surgical light, and enhancing the ability to surgically resect them.
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