Missael Garcia

Trimodal color-fluorescence-polarization endoscopy aided by a tumor selective molecular probe accurately detects flat lesions in colitis-associated cancer

Abstract. Colitis-associated cancer (CAC) arises from premalignant flat lesions of the colon, which are difficult to detect with current endoscopic screening approaches. We have developed a complementary fluorescence and polarization reporting strategy that combines the unique biochemical and physical properties of dysplasia and cancer for real-time detection of these lesions. Using azoxymethane-dextran sodium sulfate (AOM-DSS) treated mice, which recapitulates human CAC and dysplasia, we show that an octapeptide labeled with a near-infrared (NIR) fluorescent dye selectively identified all precancerous and cancerous lesions. A new thermoresponsive sol-gel formulation allowed topical application of the molecular probe during endoscopy. This method yielded high contrast-to-noise ratios (CNR) between adenomatous tumors (20.6±1.65) and flat lesions (12.1±1.03) and surrounding uninvolved colon tissue versus CNR of inflamed tissues (1.62±0.41). Incorporation of nanowire-filtered polarization imaging into NIR fluorescence endoscopy shows a high depolarization contrast in both adenomatous tumors and flat lesions in CAC, reflecting compromised structural integrity of these tissues. Together, the real-time polarization imaging provides real-time validation of suspicious colon tissue highlighted by molecular fluorescence endoscopy.

Bio-inspired imager improves sensitivity in near-infrared fluorescence image-guided surgery

Image-guided surgery can enhance cancer treatment by decreasing, and ideally eliminating, positive tumor margins and iatrogenic damage to healthy tissue. Current state-of-the-art near-infrared fluorescence imaging systems are bulky and costly, lack sensitivity under surgical illumination, and lack co-registration accuracy between multimodal images. As a result, an overwhelming majority of physicians still rely on their unaided eyes and palpation as the primary sensing modalities for distinguishing cancerous from healthy tissue. Here we introduce an innovative design, comprising an artificial multispectral sensor inspired by the Morpho butterflys compound eye, which can significantly improve image-guided surgery. By monolithically integrating spectral tapetal filters with photodetectors, we have realized a single-chip multispectral imager with 1000 × higher sensitivity and 7 × better spatial co-registration accuracy compared to clinical imaging systems in current use. Preclinical and clinical data demonstrate that this technology seamlessly integrates into the surgical workflow while providing surgeons with real-time information on the location of cancerous tissue and sentinel lymph nodes. Due to its low manufacturing cost, our bio-inspired sensor will provide resource-limited hospitals with much-needed technology to enable more accurate value-based health care.

A 4-Megapixel Cooled CCD Division of Focal Plane Polarimeter for Celestial Imaging

The field of astronomy relies on spectral and polarization imagery recorded across a wide range of spectra to make inferences about imaged objects from nearby and distant galaxies. One of the challenges in recording celestial polarization information is recording multiple images filtered with various polarization optics, such as linear polarization filters or retarders, and with low-noise, low-dark-current sensors. In this paper, we present a division of focal plane polarimeter that can operate at room temperature down to −20 °C. When the imaging sensor operates at −20 °C, the dark currents is reduced by two orders of magnitude, which improves the polarization extinction ratio by ~5-fold. Comprehensive optoelectronic tests are presented with data recorded with the polarimeter.

A 1300 × 800, 700 mW, 30 fps spectral polarization imager

We have designed, fabricated, and tested a division-of-focal-plane polarimeter capable of simultaneously imaging both spectral and polarization information at 30 frames per second. The imaging sensor, composed of 1300 by 800 imaging elements, each containing three vertically stacked photodetectors, is covered by pixelated nanowire polarization filters at four different orientations offset by 45°. The polarimeter has a dynamic range of 62 dB and captures intensity, angle, and degree of linear polarization in three visible spectrum bands while consuming 700 mW of power.

Biologically inspired imaging sensors for multi-spectral and polarization imagery

Multi-spectral and polarization imaging have enabled and exploited a wide range of applications, from remote sensing to biomedical applications such as early cancer detection for image-guided surgery. However, state-of-the-art multispectral and polarization cameras are still based on conventional advances in optics and integrated circuits, yielding bulky form factors and poor signal reconstruction. Thus, these technologies have failed to be adopted as research or clinical imaging tools. Nature is full of examples of animals that take advantage of multi-spectral and polarization phenomena to gain an evolutionary advantage. For example, elegant low-power and compact biological visual systems, capable of multispectral and polarization imaging surpassing any man-made imaging system, can be found in the compound eyes of many arthropods. Here, we demonstrate radically novel, multi-spectral and polarization imaging sensors that function on the same fundamental principles as do the ommatidia of the mantis shrimp. Our bio-inspired imaging systems combine vertically stacked photodiodes, for single-pixel trichromatic vision, with an array of pixelated polarization filters, resulting in compact and low-power architectures. Our single-chip imager comprises of 1280-by-720 pixels, yielding a 62 dB and 48 dB dynamic range and signal-to-noise ratio, respectively, and operates at a maximum frame rate of 24 fps. This topology inherently co-registers in time and space the different spectral and polarization channels. This novel and ergonomic technology is enabling real-time in situ underwater polarization imaging as well as applications in biomedical fields.

Bio-inspired near infrared fluorescence sensors: from the ocean to the operating room (Conference Presentation)

Surgery is the primary curative option for patients with cancer, with the overall objective of complete resection of all cancerous tissue while avoiding iatrogenic damage to healthy tissue. Simultaneous imaging of weak fluorescence signals from multiple targeted molecular markers under bright surgical illumination is an unmet goal with current intra operating instrument. In this talk, I will describe our recent efforts in solving this intraoperative challenge by drawing inspiration from the visual system of the mantis shrimp – a compact biological system optimized for multispectral imaging. We have successfully designed, tested and clinically translated our bio-inspired imagers by monolithically integrating vertically stacked photodetectors with pixelated interference filters. The sensor is capable of recording color and NIR fluorescence from three different molecular markers and display this information using augmented reality goggles. The sensor resolution is 1280 by 720 and operates at 30 frames per second and has been used to simultaneously image tumor targeted dye IR800 and nerve targeted dye, Oxazine-4. Displaying this information in the operating room is a challenging feat. We have used variety of augmented reality displays and will provide overview of both pre-clinical and clinical translation of this technology.

Hexachromatic imager for near-infrared fluorescence image-guided surgery (Conference Presentation)

Image-guided surgery (IGS) can improve the patient’s outcome by providing meaningful real-time information about the location of cancerous tumors and surrounding tissue, aiding in the elimination of positive tumor margins and reducing iatrogenic damage. However, the clinical need for imaging systems that can provide real-time feedback under real operating room settings remains unmet. State-of-the-art imaging systems for near-infrared fluorescence IGS rely on a series of complex optics and several imaging sensors. As a result, these systems are bulky and expensive, and their architecture lacks the versatility to simultaneously image multiple fluorophores, effectively making them cumbersome when merged into the current surgical workflow. To address these shortcomings, we have designed a multi-spectral imager capable of spatially co-registered hexachromatic vision: three spectral channels in the visible spectrum for the identification of anatomical features in color and three spectral channels in the near-infrared spectrum for the simultaneous identification of multiple near-infrared fluorescence dyes used in IGS. Our single-chip imaging sensor combines the vertically stacked photodetectors technology with pixelated interference filters to create a multi-spectral imager that can help surgeons make clinically relevant decisions in real time, with an effective resolution of 1280x720x3 photodiodes and a frame rate of 24 FPS. Our imager has the ability to identify different shades of near-infrared fluorescent light, allowing the surgeon to use and differentiate multiple fluorophores as molecular probes with high sensitivity. Pre-clinical data is shown where simultaneous imaging of anatomical features in color, and identification of nerves and cancerous tumors, are achieved using multiple near-infrared fluorescent agents.

Live demonstration: A 1600 by 1200, 300 mW, 40 fps multi-spectral imager for near-infrared fluorescence image-guided surgery

We have designed, fabricated, and tested a multi-spectral imager for near-infrared fluorescence image-guided surgery capable of simultaneously imaging both color and near-infrared fluorescence information with high sensitivity at 40 frames per second. The imaging sensor is composed of 1600 by 1200 imaging elements covered by pixelated spectral interference filters. The imaging sensor was successfully used in a preclinical study to assess and compare altered dynamic arterial perfusion in a murine model.

A 1600 by 1200, 300 mW, 40 fps multi-spectral imager for near-infrared fluorescence image-guided surgery

We have designed, fabricated, and tested a multi-spectral imager for near-infrared fluorescence image-guided surgery capable of simultaneously imaging both color and near-infrared fluorescence information with high sensitivity at 40 frames per second. The imaging sensor is composed of 1600 by 1200 imaging elements covered by pixelated spectral interference filters. The imaging sensor was successfully used in a preclinical study to assess and compare altered dynamic arterial perfusion in a murine model.

Optical characterization and polarization calibration for rigid endoscopes

Polarization measurements give orthogonal information to spectral images making them a great tool in the characterization of environmental parameters in nature. Thus, polarization imagery has proven to be remarkably useful in a vast range of biomedical applications. One such application is the early diagnosis of flat cancerous lesions in murine colorectal tumor models, where polarization data complements NIR fluorescence analysis. Advances in nanotechnology have led to compact and precise bio-inspired imaging sensors capable of accurately co-registering multidimensional spectral and polarization information. As more applications emerge for these imagers, the optics used in these instruments get very complex and can potentially compromise the original polarization state of the incident light. Here we present a complete optical and polarization characterization of three rigid endoscopes of size 1.9mm x 10cm (Karl Storz, Germany), 5mm x 30cm, and 10mm x 33cm (Olympus, Germany), used in colonoscopy for the prevention of colitis-associated cancer. Characterization results show that the telescope optics act as retarders and effectively depolarize the linear component. These incorrect readings can cause false-positives or false-negatives leading to an improper diagnosis. In this paper, we offer a polarization calibration scheme for these endoscopes based on Mueller calculus. By modeling the optical properties from training data as real-valued Mueller matrices, we are able to successfully reconstruct the initial polarization state acquired by the imaging system.