This PDF file contains the front matter associated with SPIE Proceedings Volume 10057, including the Title Page, Copyright information, Table of Contents, and Conference Committee listing.

Optical coherence tomography (OCT) provides high resolution and cross-sectional images of biological tissue and is widely used for diagnosis of ocular diseases. However, OCT images suffer from speckle noise, which typically considered as multiplicative noise in nature, reducing the image resolution and contrast. In this study, we propose a two-step iteration (TSI) method to suppress those noises. We first utilize augmented Lagrange method to recover a low-rank OCT image and remove additive Gaussian noise, and then employ the simple and efficient split Bregman method to solve the Total-Variation Denoising model. We validated such proposed method using images of swine, rabbit and human retina. Results demonstrate that our TSI method outperforms the other popular methods in achieving higher peak signal-to-noise ratio (PSNR) and structure similarity (SSIM) while preserving important structural details, such as tiny capillaries and thin layers in retinal OCT images. In addition, the results of our TSI method show clearer boundaries and maintains high image contrast, which facilitates better image interpretations and analyses.

Optical non-contact measurements in general, and chromophore concentration estimation in particular, have been identified to be useful tools for skin assessment. Spectral estimation using a low cost hand held device has not been studied adequately as a basis for skin assessment. Spectral measurements on the one hand, which require bulky, expensive and complex devices and direct channel approaches on the other hand, which operate with simple optical devices have been considered and applied for skin assessment. In this study, we analyse the capabilities of spectral estimation for skin assessment in form of chromophore concentration estimation using a prototypical low cost optical non-contact device. A spectral estimation work flow is implemented and combined with pre-simulated Monte Carlo spectra to use estimated spectra based on conventional image sensors for chromophore concentrations estimation and obtain health metrics. To evaluate the proposed approach, we performed a series of occlusion experiments and examined the capabilities of the proposed process. Additionally, the method has been applied to more general skin assessment tasks. The proposed process provides a more general representation in form of a spectral image cube which can be used for more advanced analysis and the comparisons show good agreement with expectations and conventional skin assessment methods. Utilising spectral estimation in conjunction with Monte Carlo simulation could lead to low cost, easy to use, hand held and multifunctional optical skin assessment with the possibility to improve skin assessment and the diagnosis of diseases.

Super fine collimated x-ray beam based x-ray luminescence computed tomography (XLCT) has the potential to reconstruct the deeply embedded targets with a spatial resolution of hundreds of micrometers. However, due to the low x-ray photon utilization efficiency and low optical signal sensitivity of the electron multiplying charge coupled device (EMCCD) camera, XLCT usually requires a long measurement time. To overcome this limitation, we propose a fiber based, fast XLCT design, in which optical fiber bundles are applied to collect the emitted optical photons on the phantom surface. Highly sensitive photomultiplier tubes (PMT) with a cooling unit and pre-amplifier are used to measure the photons from the fiber bundles. The PMT outputs are collected by a high-speed data acquisition board. A linear scan is estimated to take about 130 seconds, thus for an XLCT scan with 6 projections, we require 13 minutes for each section, which makes it feasible to have a whole body scan of XLCT. To validate our design, numerical simulations and phantom experiments have been performed. In numerical simulation studies, we have investigated the effect of the number of optical fiber bundle on the XLCT reconstruction. We found that one optical fiber bundle is sufficient to reconstruct the deeply embedded targets if measurements from 6 projections are used. Phantom experiments with multiple targets have been performed to validate the proposed fast XLCT imaging.

Burns are thermal injuries that can completely damage or at least compromise the protective function of skin, and affect the ability of tissues to manage moisture. Burn-damaged tissues exhibit lower elasticity than healthy tissues, due to significantly reduced water concentrations and plasma retention. Current methods for determining burn intensity are limited to visual inspection, and potential hospital x-ray examination. We present a unique confocal microscope capable of measuring Raman and Brillouin spectra simultaneously, with concurrent fluorescence investigation from a single spatial location, and demonstrate application by investigating and characterizing the properties of burn-afflicted tissue on chicken skin model. Raman and Brillouin scattering offer complementary information about a material's chemical and mechanical structure, while fluorescence can serve as a useful diagnostic indicator and imaging tool. The developed instrument has the potential for very diverse analytical applications in basic biomedical science and biomedical diagnostics and imaging.

In this proceeding we demonstrate a system combining optical coherence tomography (OCT) and hyper-spectral imaging (HSI) into a single dual-clad fiber (DCF). Combining these modalities gives access to the sample morphology through OCT and to its molecular content through HSI. Both modalities have their illumination through the fiber core. The OCT is then collected through the core while the HSI is collected through the inner cladding of the DCF. A double-clad fiber coupler (DCFC) is used to address both channels separately. A scanning spectral filter was developed to successively inject narrow spectral bands of visible light into the fiber core and sweep across the entire visible spectrum. This allows for rapid HSI acquisition and high miniaturization potential.

In this paper a multimodal optical resolution microscope in frequency domain is introduced. Fluorescence and photoacoustic signals are generated simultaneously using an amplitude modulated diode laser. The resulting signals are recorded by a lock-in amplifier. By scanning the sample, two-dimensional plots of the fluorescence and photoacoustic signals can be generated. In this paper, the signal-to-noise ratios of amplitude modulated signals are compared to those expected for pulsed excitation under the assumption that the maximum permissible exposure limits are fulfilled. Furthermore, it is described how to determine the excited state life-times from the measured frequency responses of the fluorescence or photoacoustic signals, respectively.

Multispectral imaging has the potential to improve sensitivity and specificity in biomedical imaging through simultaneous acquisition of both morphological (spatial) and chemical (spectral) information. Performing multispectral imaging in real time with spectrally resolved detector arrays (SRDAs), for example in endoscopy or intraoperative imaging, requires a direct trade off between spatial and spectral resolution. We sought to quantitatively assess the impact of spectral band selection on contrast agent detection in fluorescence endoscopic imaging. As a proof of concept, we measured the ‘ground truth’ spectra from a dilution series of a single near-infrared fluorescent contrast agent using a spectrometer incorporated into the detection path of our endoscope. We then modeled the influence of an SRDA on these spectra and calculated the theoretical endmembers associated with reflectance and fluorescence signals from the pure contrast agent. To test the accuracy of our model, we incorporated into the same endoscope an off-the-shelf SRDA with a 3x3 filter deposition pattern of 9 spectral bands. After spectral unmixing using the modeled endmembers, the amplitude of the fluorescence recorded with the SRDA compared favorably with the amplitude of fluorescence derived from the ‘ground truth’ spectra recorded with the spectrometer. In the future, this approach could be used to minimize the number of spectral bands required in a given imaging system and hence maximize the spatial resolution of the multispectral camera.

Moving towards label-free techniques for cell identification is essential for many clinical and research applications. Raman spectroscopy and digital holographic microscopy (DHM) are both label-free, non-destructive optical techniques capable of providing complimentary information. We demonstrate a multi-modal system which may simultaneously take Raman spectra and DHM images to provide both a molecular and a morphological description of our sample. In this study we use Raman spectroscopy and DHM to discriminate between three immune cell populations CD4+ T cells, B cells, and monocytes, which together comprise key functional immune cell subsets in immune responses to invading pathogens. Various parameters that may be used to describe the phase images are also examined such as pixel value histograms or texture analysis. Using our system it is possible to consider each technique individually or in combination. Principal component analysis is used on the data set to discriminate between cell types and leave-one-out cross-validation is used to estimate the efficiency of our method. Raman spectroscopy provides specific chemical information but requires relatively long acquisition times, combining this with a faster modality such as DHM could help achieve faster throughput rates. The combination of these two complimentary optical techniques provides a wealth of information for cell characterisation which is a step towards achieving label free technology for the identification of human immune cells.

Early detection is the key to the prevention of cervical cancer. There is an urgent need for a portable, affordable, and easy-to-use device for cervical pre-cancer detection, especially in low-resource settings. We have developed a dual-modality fiber-optic endoscope system (SmartME) that integrates high-resolution fluorescence imaging (FLI) and quantitative diffuse reflectance spectroscopy (DRS) onto a smartphone platform. The SmartME consists of a smartphone, a miniature fiber-optic endoscope, a phone attachment containing imaging optics, and a smartphone application (app). FLI is obtained by painting the tissue with a contrast agent (e.g., proflavine), illuminating the tissue and collecting its fluorescence images through an imaging bundle that is coupled to the phone camera. DRS is achieved by using a white LED, attaching additional source and detection fibers to the imaging bundle, and converting the phone camera into a spectrometer. The app collects images/spectra and transmits them to a remote server for analysis to extract the tissue parameters, including nuclear-to-cytoplasm ratio (calculated from FLI), concentrations of oxyhemoglobin (HbO2) and deoxyhemoglobin (Hb) as well as scattering (measured by DRS). These parameters can be used to detect cervical dysplasia. Our preliminary studies have demonstrated that the SmartME can clearly visualize the nuclei in living cells and in vivo biological samples, with a high spatial resolution of ~3.1μm. The device can also measure tissue absorption and scattering properties with comparable accuracy to those of a benchtop DRS system. The SmartME has great potential to provide a compact, affordable, and ‘smart’ solution for early detection of neoplastic changes in cervix.

Multimodal endoscopy, with fluorescence-labeled probes binding to overexpressed molecular targets, is a promising technology to visualize early-stage cancer. T/B ratio is the quantitative analysis used to correlate fluorescence regions to cancer. Currently, T/B ratio calculation is post-processing and does not provide real-time feedback to the endoscopist. To achieve real-time computer assisted diagnosis (CAD), we establish image processing protocols for calculating T/B ratio and locating high-risk fluorescence regions for guiding biopsy and therapy in Barrett’s esophagus (BE) patients.

Methods: Chan-Vese algorithm, an active contour model, is used to segment high-risk regions in fluorescence videos. A semi-implicit gradient descent method was applied to minimize the energy function of this algorithm and evolve the segmentation. The surrounding background was then identified using morphology operation. The average T/B ratio was computed and regions of interest were highlighted based on user-selected thresholding. Evaluation was conducted on 50 fluorescence videos acquired from clinical video recordings using a custom multimodal endoscope.

Results: With a processing speed of 2 fps on a laptop computer, we obtained accurate segmentation of high-risk regions examined by experts. For each case, the clinical user could optimize target boundary by changing the penalty on area inside the contour.

Conclusion: Automatic and real-time procedure of calculating T/B ratio and identifying high-risk regions of early esophageal cancer was developed. Future work will increase processing speed to <5 fps, refine the clinical interface, and apply to additional GI cancers and fluorescence peptides.

We present high spatial density, multi-modal, parallel-plate Diffuse Optical Tomography (DOT) imaging systems for the purpose of breast tumor detection. One hybrid instrument provides time domain (TD) and continuous wave (CW) DOT at 64 source fiber positions. The TD diffuse optical spectroscopy with PMT- detection produces low-resolution images of absolute tissue scattering and absorption while the spatially dense array of CCD-coupled detector fibers (108 detectors) provides higher-resolution CW images of relative tissue optical properties. Reconstruction of the tissue optical properties, along with total hemoglobin concentration and tissue oxygen saturation, is performed using the TOAST software suite. Comparison of the spatially-dense DOT images and MR images allows for a robust validation of DOT against an accepted clinical modality. Additionally, the structural information from co-registered MR images is used as a spatial prior to improve the quality of the functional optical images and provide more accurate quantification of the optical and hemodynamic properties of tumors. We also present an optical-only imaging system that provides frequency domain (FD) DOT at 209 source positions with full CCD detection and incorporates optical fringe projection profilometry to determine the breast boundary. This profilometry serves as a spatial constraint, improving the quality of the DOT reconstructions while retaining the benefits of an optical-only device. We present initial images from both human subjects and phantoms to display the utility of high spatial density data and multi-modal information in DOT reconstruction with the two systems.

Sepsis is a potentially fatal disease with mortality rate as high as 50% in patients with septic shock; mortality rate can increase by 7.6% per hour if appropriate treatment is not started. Internationally accepted guidelines for diagnosis of sepsis rely on vital sign monitoring and laboratory tests in order to recognize organ failure. This pilot study aims to explore the potential of hyperspectral and thermal imaging techniques to identify and quantify early alterations in skin oxygenation and perfusion induced by sepsis. The study comprises both physiological model experiments on healthy volunteers in a laboratory environment, as well as screening case series of patients with septic shock in the intensive care department. Hyperspectral imaging is used to determine one of the main characteristic visual signs of skin oxygenation abnormalities - skin mottling, whereas changes in peripheral perfusion have been visualized by thermal imaging as heterogeneous skin temperature areas. In order to mimic septic skin mottling in a reproducible way in laboratory environment, arterial occlusion provocation test was utilized on healthy volunteers. Visualization of oxygen saturation by hyperspectral imaging allows diagnosing microcirculatory alterations induced by sepsis earlier than visual assessment of mottling. Thermal images of sepsis patients in the clinic clearly reveal hotspots produced by perforating arteries, as well as cold regions of low blood supply. The results of this pilot study show that thermal imaging in combination with hyperspectral imaging allows the determination of oxygen supply and utilization in critically ill septic patients.

There is a dire clinical need for surgical margin guidance in breast conserving therapy (BCT). We present a multispectral spatial frequency domain imaging (SFDI) system, spanning the visible and near-infrared (NIR) wavelengths, combined with a shielded X-ray computed tomography (CT) system, designed for intraoperative breast tumor margin assessment. While the CT can provide a volumetric visualization of the tumor core and its spiculations, the co-registered SFDI can provide superficial and quantitative information about localized changes tissue morphology from light scattering parameters. These light scattering parameters include both model-based parameters of sub-diffusive light scattering related to the particle size scale distribution and also textural information of the high spatial frequency reflectance. Because the SFDI and CT components are rigidly fixed, a simple transformation can be used to simultaneously display the SFDI and CT data in the same coordinate system. This is achieved through the Visualization Toolkit (vtk) file format in the open-source Slicer medical imaging software package. In this manuscript, the instrumentation, data processing, and preliminary human specimen data will be presented. The ultimate goal of this work is to evaluate this technology in a prospective clinical trial, and the current limitations and engineering solutions to meet this goal will also be discussed.

We present a multimodal optical setup, allowing non-contact photoacoustic imaging (PAI) and optical coherence tomography (OCT). Optical coherence tomography is sensitive to changes in the specimen’s refractive index, thereby offering complementary information to photoacoustic signals which are induced by light absorption. A multimodal setup, allowing OCT and photoacoustic measurements, should ideally not rely on any physical contact to a specimen and, thus, commonly used transducers for photoacoustic signal detection which require acoustic coupling to the specimen should be avoided. In this work photoacoustic signals are acquired by measuring the surface displacement of a specimen using a fiber-optic Mach-Zehnder interferometer. Photoacoustic signals are excited with a Nd:YAG pulse laser. The interferometer for non-contact photoacoustic detection and the OCT system are realized in the same fiber-optic network. Light from the PAI detection laser and the OCT source are multiplexed into a single optical fiber and the same objective is used for both imaging modalities. Light reflected from specimens is demultiplexed and guided to the respective imaging systems. To allow fast non-contact PAI and OCT imaging the detection spot is scanned across the specimens’ surface using a galvanometer scanner. As the same fiber-network and optical components are used for photoacoustic and OCT imaging the obtained, images are co-registered intrinsically. Imaging is demonstrated on a tissue mimicking sample.

The complementary contrast of the optoacoustic (OA) and pulse-echo ultrasound (US) modalities makes the combined usage of these imaging technologies highly advantageous. Due to the different physical contrast mechanisms development of a detector array optimally suited for both modalities is one of the challenges to efficient implementation of a single OA-US imaging device. We demonstrate imaging performance of the first hybrid detector array whose novel design, incorporating array segments of linear and concave geometry, optimally supports image acquisition in both reflection-mode ultrasonography and optoacoustic tomography modes. Hybrid detector array has a total number of 256 elements and three segments of different geometry and variable pitch size: a central 128-element linear segment with pitch of 0.25mm, ideally suited for pulse-echo US imaging, and two external 64-elements segments with concave geometry and 0.6mm pitch optimized for OA image acquisition. Interleaved OA and US image acquisition with up to 25 fps is facilitated through a custom-made multiplexer unit. Spatial resolution of the transducer was characterized in numerical simulations and validated in phantom experiments and comprises 230 and 300 μm in the respective OA and US imaging modes. Imaging performance of the multi-segment detector array was experimentally shown in a series of imaging sessions with healthy volunteers. Employing mixed array geometries allows at the same time achieving excellent OA contrast with a large field of view, and US contrast for complementary structural features with reduced side-lobes and improved resolution. The newly designed hybrid detector array that comprises segments of linear and concave geometries optimally fulfills requirements for efficient US and OA imaging and may expand the applicability of the developed hybrid OPUS imaging technology and accelerate its clinical translation.

Due to its penetrating power, fine resolution, unique contrast, high-speed, and cost-effectiveness, x-ray imaging is one of the earliest and most popular imaging modalities in biomedical applications. Current x-ray radiographs and CT images are mostly on gray-scale, since they reflect overall energy attenuation. Recent advances in x-ray detection, contrast agent, and image reconstruction technologies have changed our perception and expectation of x-ray imaging capabilities, and generated an increasing interest in imaging biological soft tissues in terms of energy-sensitive material decomposition, phase-contrast, small angle scattering (also referred to as dark-field), x-ray fluorescence and luminescence properties. These are especially relevant to preclinical and mesoscopic studies, and potentially mendable for hybridization with optical molecular tomography. In this article, we review new x-ray imaging techniques as related to optical imaging, suggest some combined x-ray and optical imaging schemes, and discuss our ideas on micro-modulated x-ray luminescence tomography (MXLT) and x-ray modulated opto-genetics (X-Optogenetics).

With global trends in population aging, the need to decrease and prevent the onset of cardiovascular disease has drawn a great attention. The traditional cuff-based upper arm sphygmomanometer is still the standard method to retrieve blood pressure information for diagnostics. However, this method is not easy to be adapted by patients and is not comfortable enough to perform a long term monitoring process. In order to correlate the beating profile of the arterial pulse on the wrist skin, an Advanced Vibrometer Interferometer Device (AVID) is adopted in this study to measure the vibration amplitude of skin and compare it with blood pressure measured from the upper arm. The AVID system can measure vibration and remove the directional ambiguity by using circular polarization interferometer technique with two orthogonal polarized light beams. The displacement resolution of the system is nearly 1.0 nm and the accuracy is experimentally verified. Using an optical method to quantify wrist pule, it provides a means to perform cuff-less, noninvasive and continuous measurement. In this paper, the correlations between the amplitude of skin vibration and the actual blood pressure is studied. The success of this method could potentially set the foundation of blood pressure monitor system based on optical approaches.

There are several ophthalmic devices to image the retina, from fundus cameras capable to image the whole fundus to scanning ophthalmoscopes with photoreceptor resolution. Unfortunately, these devices are prone to a variety of ocular conditions like defocus and media opacities, which usually degrade the quality of the image. Here, we demonstrate a novel approach to image the retina in real-time using a single pixel camera, which has the potential to circumvent those optical restrictions. The imaging procedure is as follows: a set of spatially coded patterns is projected rapidly onto the retina using a digital micro mirror device. At the same time, the inner product’s intensity is measured for each pattern with a photomultiplier module. Subsequently, an image of the retina is reconstructed computationally. Obtained image resolution is up to 128 x 128 px with a varying real-time video framerate up to 11 fps. Experimental results obtained in an artificial eye confirm the tolerance against defocus compared to a conventional multi-pixel array based system. Furthermore, the use of a multiplexed illumination offers a SNR improvement leading to a lower illumination of the eye and hence an increase in patient’s comfort. In addition, the proposed system could enable imaging in wavelength ranges where cameras are not available.

Reconstruction of fluorescence molecular tomography (FMT) is an ill-posed inverse problem. Anatomical guidance in the FMT reconstruction can improve FMT reconstruction efficiently. We have developed a kernel method to introduce the anatomical guidance into FMT robustly and easily. The kernel method is from machine learning for pattern analysis and is an efficient way to represent anatomical features. For the finite element method based FMT reconstruction, we calculate a kernel function for each finite element node from an anatomical image, such as a micro-CT image. Then the fluorophore concentration at each node is represented by a kernel coefficient vector and the corresponding kernel function. In the FMT forward model, we have a new system matrix by multiplying the sensitivity matrix with the kernel matrix. Thus, the kernel coefficient vector is the unknown to be reconstructed following a standard iterative reconstruction process. We convert the FMT reconstruction problem into the kernel coefficient reconstruction problem. The desired fluorophore concentration at each node can be calculated accordingly. Numerical simulation studies have demonstrated that the proposed kernel-based algorithm can improve the spatial resolution of the reconstructed FMT images. In the proposed kernel method, the anatomical guidance can be obtained directly from the anatomical image and is included in the forward modeling. One of the advantages is that we do not need to segment the anatomical image for the targets and background.

Fever screening based on infrared thermographs (IRTs) is a viable mass screening approach during infectious disease pandemics, such as Ebola and Severe Acute Respiratory Syndrome (SARS), for temperature monitoring in public places like hospitals and airports. IRTs have been found to be powerful, quick and non-invasive methods for detecting elevated temperatures. Moreover, regions medially adjacent to the inner canthi (called the canthi regions in this paper) are preferred sites for fever screening. Accurate localization of the canthi regions can be achieved through multi-modality registration of infrared (IR) and white-light images. Here we propose a registration method through a coarse-fine registration strategy using different registration models based on landmarks and edge detection on eye contours. We have evaluated the registration accuracy to be within ± 2.7 mm, which enables accurate localization of the canthi regions.