Enhancing Video-Rate Fluorescence Imagery Collected in the Second Near-Infrared Optical Window for Diagnostic Real-Time Surgical and Post-Surgical Applications

Technology

This technology enables the intraoperative detection of tumors using both reflectance imaging at the edge of the NIR-I band and fluorescence imaging in the NIR-II band. In this system, the target tissue is irradiated by two NIR light sources emitting light at two different wavelengths - both of which are shorter than 1000 nm. An ordinary LED surgical illuminator can also be used during fluorescence imaging, allowing the surgical team to view the surgical field throughout the entire surgical procedure.The first light source can be an LED which emits around 970nm, where tissue reflectance is high due to the strong water absorption at 960nm. The NIR detector senses the reflected 970nm light and creates a “visible-like” image on the display screen which closely emulates a monochrome visible image. This anatomically co-registers the surgical field with the brightly fluorescing tumors, to facilitate resection, and to give the surgeon the spatial orientation they need when locating small tumors embedded just beneath the tissue surface.The second light source can be an 808 nm diode laser that excites functionalized fluorescent molecules which localize the tumors. These unique fluorescent molecules can be excited by 808nm light and then emit light in the NIR-II spectral band. Both the reflected light and the fluorescent light irradiated from the tissue are captured by a single imaging camera operating in the NIR-II spectral window. Importantly, this single camera can detect both reflected light and fluorescent NIR light. Since the intensities of both NIR light sources can be adjusted independently of each other, the users can select a “visible-like” tissue view, a sharp tumor-only view, or a blended combination of both views which provides excellent tumor registration together with an adjustable level of tissue imaging. This allows the surgeon to quickly locate and resect each tumor in turn. Flashing the 808nm NIR source means only the fluorescing tumors themselves “flash,” making even pinhead-sized tumors or sub-surface tumors clearly noticeable within the visible-like context image.  The NIR camera is only sensitive to light with wavelengths greater than ~950 nm, which minimizes the effect of daylight and ambient room light - especially with modern high-efficiency LED lamps.   

Problem Addressed

Near-infrared (NIR) fluorescence-based imaging has the potential to detect tumors with high sensitivity and high specificity in real time. Current approaches employ fluorescent dyes and operate mostly in the first NIR window (NIR-I, 700 - 900 nm) for image-guided use. To image tissue, visible light and fluorescence images are either taken with the same detector or with multiple cameras in different spectral ranges simultaneously or sequentially. Systems that can detect both visible and fluorescent imaging simultaneously use silicon-based detectors that are sensitive to visible and NIR-I spectral bands. However, to properly separate these narrowly-spaced passbands, expensive spectral filters with narrow fields-of-view are required. Other systems which instead use multiple cameras to detect visible light, NIR-I, and/or the second NIR window (NIR-II, 1000 - 1700 nm), must fuse the images from all these detectors to create the combined image via post processing. This image fusion requires precise optical alignment and positioning, which ultimately increases the size, weight, and cost of the imaging system. This fluorescence-based imaging technology overcomes the limitations of these two approaches. Moreover, NIR-II imaging technology can offer better tissue penetration, reduced light scattering, and lower tissue autofluorescence.The present invention is an improved method for image acquisition in both the NIR-I and NIR-II spectral windows using a single image detection system.  It is also compatible with nearly all LED surgical illuminators.  

Advantages

• Achieves intraoperative fluorescence imaging of tumors
• One camera performs fluorescence and reflective “visible-like” imaging with perfect image registration
• Does not require costly spectral filters