Multispectral Imaging Leads to Advances in Eye Tracking

Multispectral imaging allows for the identification, classification, and segregation of objects and areas in scenes based on their spectral signatures. In her doctoral dissertation, at the University of Eastern Finland, Ana Gebejes, used the FluxData 1665-MS7, in a novel application. She created spectral videos for use in eye analysis and tracking. In addition to the proof of concept, she created a publicly available database of spectral images and videos, the Spectral Eye vidEo Database (SPEED). This database can be used by researchers for creating and testing new methods of dynamic eye analysis. The database contains both still images and videos of eyes performing different eye-tracking tasks under different conditions, such as wearing corrective lenses or sunglasses and different lighting conditions.

Due to recent technological advances in optics and electronics, spectral-video sensors are now able to capture spectral information at video rates. Dr. Gebejes carefully analyzed the spectral, temporal and spatial characteristics of the FD 1665-MS7, a seven-channel spectral video system, and found it was uniquely suited for eye tracking. Not only were the spatial and temporal resolution high enough capture high resolution images of the fast-moving eye, but the spectral characteristics of the camera allowed excellent spectral classification of the different parts of the scene. Using spectral segmentation algorithms, she could identify features in the image such as the pupil, iris, blood vessels, sclera, skin and eyebrows.  

In spectral videos, each frame of the video contains a spectral image cube, allowing spectral video systems to capture spatial, spectral, and temporal information simultaneously.  In the figure, below, each column represents an image cube. Each row shows the response for one of the seven channels for five frames of a video arranged in columns. For each pixel in the image, a spectral signature can be calculated. With knowledge of the scene illumination, identification and segmentation of the scene can be achieved.

Pictured above is five selected frames from one standard video taken from FluxData's 1665-MS7

Compared to traditional eye-tracking methods that use near-IR imaging mounted on a wearable camera system, spectral imaging using the FD 1665-MS7 makes it possible to use a remote camera system. This can allow for use in many more applications from the operating room to security and surveillance.  Traditional eye-tracking relies on spatial scene analysis to locate the pupil. However, spectral analysis of the scene allows for better segmentation of the pupil under harsh conditions, for example, when the subject is wearing glasses, where traditional pupil-detection algorithms fail.

Dr. Gebejes describes her research as a first step in creating the new eye-tracking technologies of the future. She believes that her results provide evidence for the utility of using spectral data for eye-tracking. The FD 1665-MS7 can provide for real-time scene analysis and future work may focus on the most efficient methods to accomplish this for eye-tracking. The data in the SPEED database has the potential to be used in other areas of eye-related research including medicine, biometric, and vision research.

To read the full dissertation by Ana Gebejes, click here.


FluxData’s FD-1665 Used to Assess Rheumatoid Flare

Rheumatoid arthritis (RA) is a chronic, debilitating disease affecting over 1 million people in the United States. RA is characterized by the draining of lymphatic vessels coupled with dynamic changes in lymph node volume and flow. Impaired lymph egress from inflamed synovium is associated with joint flare in murine models of inflammatory-erosive arthritis. Unfortunately, advancements in understanding lymphatic changes have been slow, due to the lack of technology to measure and quantify lymphatic function in vivo. Lymphoscintigraphy is the current standard used in assessing lymphedema and sentinel lymph nodes in cancer patients, but is not adequate to study lymphatics in RA.
High-resolution MRI, power Doppler ultrasound, and near-infrared imaging that permits real-time quantification of lymphatic function have been the largest advancements thus far, and have produced a new paradigm of altered lymphatic function that underlies both accute arthritic flare and chronic inflammation. In accute flare, lymphatic drainage increases several fold, whereas no lymphatic contractions are detected in lymph vessels draining chronic arthritic joints.
In a study done by Homaira Rahimi, Richard Bell, Echoe M. Bouta, Ronald W. Wood, Lianping Xing, Christopher T. Ritchlin and Edward M. Schwarz, they explained the knowledge to date on lymphatics in RA, new in-vivo imaging modalities that have elucidated how lymphatics modulate acute versus chronic joint inflammation, and how these preclinical outcome measures are being translated to study RA inflammation and how effective RA therapies alter lymphatic flow and lymph nodes draining flaring joints. The discoveries were facilitated by novel imaging methods, one being the use of a custom NIR imaging system; FluxData’s FD-1665.
For the purpose of this study, FluxData’s FD-1665 was used to quantify lymphatic flow in the upper extremity. The custom NIR imaging system was used to assess lymphatic contraction frequency in a healthy human subject after ICG injection in the second, third, and fourth web spaces of both hands. The NIR excitation was monitored with a Thorlabs PM16-121 power meter adjacent to the first web space. After the injections, the upper extremities were imaged for 10 minutes to observe lymphatic flow. Visible and NIR images were collected simultaneously. Dysfunctional contractions, or no contractions, could indicate that the arthritic episode is the result of a drainage issue rather than synovial disturbances. The treatment would then be tailored accordingly.
The rationale for using NIR-ICG to evaluate lymphatic contractions is justified because it provides real-time information for the clinician. Using this sytem to test such has been approved by the FDA, therefore there is no major health limitations of the given technique.
The importance of this study is three-fold. The role of lympthatics in RA can now be examined with the advent of in-vivo imaging modalities that quantify lymphatic flow and contraction frequency. Such technical advances can empower investigators to promote understanding in three areas: redefinition of patterns of lymphatic flow anatomically, discovery of the cellular, molecular, and structural mechanisms that regulate lymphatic function and that are closely integrated with local biomechanics, inflammation, and parasympathetic innervation. Lastly, the goal is to identify novel molecular targets that will give rise to new interventions for RA flare. The advancement of noninvasive technologies was a critical first step.
To read the full article from the National Center for Biotechnology Information, click here.