Across the world cancer is a leading cause of illness and death for millions of people. As a result, the development of new medicines, treatments and technologies to combat this disease are critical. Optical-based technologies are playing an increasingly important role in the detection, diagnosis and resection of a large variety of cancers. Current surgical microscopy utilizes white light imaging to visualize cancerous tumors within the host body. New developments however, have merged fluorescence imaging with conventional white-light modalities. This new approach is commonly known as fluorescence-image guided surgery (FIGS), or fluorescence-assisted resection and exploration (FLARE)  and can be employed in either an open-cavity or minimally invasive endomicroscopy modality, depending on the location of a particular cancer. The major advantage provided by incorporating fluorescence imaging is the ability to provide the surgeon with a clear, high-contrast view resulting in improved identification and delineation of tumor masses during surgery.
Central to the success of the FIGS approach to cancer surgery is the utilization of non-toxic contrast agents, such as indocyanine green (ICG) that allow the surgeon to easily identify the tumor mass before and during resection. Contrast agents that emit in the NIR are preferred since tissue autofluorescence is reduced over the spectral region 600-1000nm. Light scatter and absorption are also reduced at these wavelengths, allowing for deeper light penetration. Preoperative administration of the contrast agent is followed by illumination of the surgical field during resection. The detection of fluorescence emission from the stained tumor mass allows the surgeon to accurately distinguish between cancerous and non-cancerous tissue, something that is difficult to achieve with white-light illumination and detection alone. Given the nature of the surgical procedure it is critical to use optical filters that offer the maximum brightness and contrast to aid the surgeon in removing as much cancerous and as little non-cancerous tissue as possible.
Semrock is at the forefront of developments in fluorescence-image guided surgery. Due to the critical nature of FIGS it is essential to have filters that offer the maximum contrast and light sensitivity while eliminating stray excitation light and undesired autofluorescence that can contaminate and prevent high-fidelity imaging. Several companies across the United States and Europe have placed their trust in Semrock to develop and deliver the right filters for their FIGS instrumentation as they enter clinical trials.
|Dye||Abs / Em (nm)||Filter Options|
||649 / 666
|Cy5.5 / AlexaFluor 6802
||678 / 703 or 679 / 702
||749 / 775
|Indocyanine Green (ICG)
||775 / 820
||785 / 810
Table 1: List of commonly used fluorescent probes in fluorescence image-guided surgery and the right filter options for instrument prototyping.
1 See Ref 2.
2 See Ref 3.
3 Developed by Li-Cor Biosciences (www.licor.com).
 S. Keereweer, et al., Optical Image-Guided surgery – Where Do We Stand?, Molecular Imaging and Biology, Review Article, July 2010.
 Q. T. Nguyen, et al., Surgery with molecular fluorescence imaging using activatable cell-penetrating peptides decreases residual cancer and improves survival, PNAS, 107, (2010), 4317.
 S. Foersch, et al., Molecular imaging of VEGF in gastrointestinal cancer in vivo using confocal laser endomicroscopy, Gut, 59, (2010), 1046.
Learn more about FIGS:
Quantitative and Depth-Resolved Fluorescence Techniques for Intraoperative Guidance of Brain Tumor Resection Surgery
Surgery with molecular fluorescence imaging using activatable cell-penetrating peptides decreases residual cancer and improves survival
Prof. Brian Wilson, University of Toronto