Extrinsic Contrast Agents Research Articles

Image reconstruction in non-reciprocal broken-ray tomography.

Optical methods of biomedical tomographic imaging are of considerable interest due to their non-invasive nature and sensitivity to physiologically important markers. Similarly to other imaging modalities, optical methods can be enhanced by utilizing extrinsic contrast agents. Typically, these are fluorescent molecules, which can aggregate in regions of interest due to various mechanisms. In the current approaches to imaging, the intrinsic (related to the tissue) and extrinsic (related to the contrast agent) optical parameters are determined separately. This can result in errors, in particular, due to using simplified heuristic models for the spectral dependence of the optical parameters. Recently, we have developed the theory of non-reciprocal broken-ray tomography (NRBRT) for fluorescence imaging of weakly scattering systems. NRBRT enables simultaneous reconstruction of the fluorophore concentration as well as of the intrinsic optical attenuation coefficient at both the excitation and the emission wavelengths. Importantly, no assumption about the spectral dependence of the tissue optical properties is made in NRBRT. In this study, we perform numerical validation of NRBRT under realistic conditions using the Monte Carlo method to generate forward data. We demonstrate that NRBRT can be used for tomographic imaging of samples of up to four scattering lengths in size. The effects of physical characteristics of the detectors such as the area and the acceptance angle are also investigated.

Advances in micro-CT imaging of small animals.

Micron-scale computed tomography (micro-CT) imaging is a ubiquitous, cost-effective, and non-invasive three-dimensional imaging modality. We review recent developments and applications of micro-CT for preclinical research. Based on a comprehensive review of recent micro-CT literature, we summarize features of state-of-the-art hardware and ongoing challenges and promising research directions in the field. Representative features of commercially available micro-CT scanners and some new applications for both in vivo and ex vivo imaging are described. New advancements include spectral scanning using dual-energy micro-CT based on energy-integrating detectors or a new generation of photon-counting x-ray detectors (PCDs). Beyond two-material discrimination, PCDs enable quantitative differentiation of intrinsic tissues from one or more extrinsic contrast agents. When these extrinsic contrast agents are incorporated into a nanoparticle platform (e.g. liposomes), novel micro-CT imaging applications are possible such as combined therapy and diagnostic imaging in the field of cancer theranostics. Another major area of research in micro-CT is in x-ray phase contrast (XPC) imaging. XPC imaging opens CT to many new imaging applications because phase changes are more sensitive to density variations in soft tissues than standard absorption imaging. We further review the impact of deep learning on micro-CT. We feature several recent works which have successfully applied deep learning to micro-CT data, and we outline several challenges specific to micro-CT. All of these advancements establish micro-CT imaging at the forefront of preclinical research, able to provide anatomical, functional, and even molecular information while serving as a testbench for translational research.

Imaging to assist fertility-sparing surgery.

Cytological screening and human papilloma virus testing has led to diagnosis of cervical cancer in young women at an earlier stage. Defining the full extent of the disease within the cervix with imaging aids the decision on feasibility of fertility-sparing surgical options, such as extended cone biopsy or trachelectomy. High spatial resolution images with maximal contrast between tumour and surrounding background are achieved with T2-weighted and diffusion-weighted (DW) magnetic resonance imaging (MRI) obtained using an endovaginal receiver coil. Tumour size and volume demonstrated in this way correlates between observers and with histology and differences between MRI and histology estimates of normal endocervical canal length are not significant. For planning fertility-sparing surgery, this imaging technique facilitates the best oncological outcome while minimising subsequent obstetric risks. Parametrial invasion may be assessed on large field of view T2-weighted MRI. The fat content of the parametrium limits the utility of DW imaging in this context, because fat typically shows diffusion restriction. The use of contrast-enhanced MRI for assessing the parametrium does not provide additional benefits to the T2-weighted images and the need for an extrinsic contrast agent merely adds additional complexity and cost. For nodal assessment, 18fluorodeoxyglucose positron emission tomography-computerised tomography (18FDG PET-CT) remains the gold standard.

Reproductive outcomes predicted by phase imaging with computational specificity of spermatozoon ultrastructure

The ability to evaluate sperm at the microscopic level, at high-throughput, would be useful for assisted reproductive technologies (ARTs), as it can allow specific selection of sperm cells for in vitro fertilization (IVF). The tradeoff between intrinsic imaging and external contrast agents is particularly acute in reproductive medicine. The use of fluorescence labels has enabled new cell-sorting strategies and given new insights into developmental biology. Nevertheless, using extrinsic contrast agents is often too invasive for routine clinical operation. Raising questions about cell viability, especially for single-cell selection, clinicians prefer intrinsic contrast in the form of phase-contrast, differential-interference contrast, or Hoffman modulation contrast. While such instruments are nondestructive, the resulting image suffers from a lack of specificity. In this work, we provide a template to circumvent the tradeoff between cell viability and specificity by combining high-sensitivity phase imaging with deep learning. In order to introduce specificity to label-free images, we trained a deep-convolutional neural network to perform semantic segmentation on quantitative phase maps. This approach, a form of phase imaging with computational specificity (PICS), allowed us to efficiently analyze thousands of sperm cells and identify correlations between dry-mass content and artificial-reproduction outcomes. Specifically, we found that the dry-mass content ratios between the head, midpiece, and tail of the cells can predict the percentages of success for zygote cleavage and embryo blastocyst formation.

Low-cost embedded system for optical imaging of intrinsic signals

This paper describes the proof-of-concept evaluation of a low-cost imaging system for obtaining functional connectivity maps of in vivo murine models. This non-contact system is based on the Raspberry Pi 3 and its V2 camera and offers a method for obtaining resting-state images of brain activity without the use of extrinsic contrast agents. The system was fully characterized in terms of dark signal, linearity, sensor noise resolution and spatial frequency response. One mouse was observed in vivo and functional connectivity maps were obtained by combining resting-state analysis and optical intrinsic signals imaging. Intra-mouse variations in functional connectivity remain consistent across multiple imaging sessions. In principle, inexpensive optical imaging of intrinsic signals allows the study of the mechanisms underlying human brain disorders in well-controlled murine models.

Dynamic optical coherence tomography imaging of the lacrimal passage with an extrinsic contrast agent.

Recently, in vivo trans-conjunctiva optical coherence tomography (OCT) imaging of the lacrimal passage was demonstrated using a turbid commercial eye drop as an extrinsic contrast agent. However, static OCT images are not sufficient to unambiguously delineate the lumen boundary to render 3D lumen images of the lacrimal passage by segmentation. The turbid eye drop is expected to include small particles that flow and undergo Brownian motion and can be used as an extrinsic contrast agent for dynamic OCT. We conducted dynamic OCT measurements of the lacrimal passage using a swept source OCT system. Firstly, characterization of the dynamic OCT properties of the eye drop was performed. For improved delineation of the lumen boundary, we calculated the sum of the squared differences of intensities with two different normalization parameters. By making composite color images from OCT images and these two dynamic OCT images, we could execute unambiguous segmentation of the lumen of the lacrimal passage. Three-dimensional volumetric images of parts of the lacrimal passage, i.e., lacrimal canaliculus and lacrimal punctum, are demonstrated.

Multispectral Optoacoustic Tomography: Intra- and Interobserver Variability Using a Clinical Hybrid Approach.

Multispectral optoacoustic tomography (MSOT) represents a new imaging approach revealing functional tissue information without extrinsic contrast agents. Using a clinical combined ultrasound (US)/MSOT device, we investigated the interindividual robustness and impact of intra- and interobserver variability of MSOT values in soft tissue (muscle and subcutaneous fat) of healthy volunteers. Semiquantitative MSOT values for deoxygenated (Hb), oxygenated (HbO2) and total hemoglobin (HbT), as well as oxygen saturation (sO2), were calculated for both forearms in transversal and longitudinal probe orientation (n = 3, 8 measurements per subject). For intraobserver reproducibility, the same examiner investigated three subjects twice. Mean values of left vs. right forearm and transversal vs. longitudinal probe orientation were compared using an unpaired Student’s t test. Bland Altmann plots with 95% limits of agreement for absolute averages and differences were calculated. Intraclass correlation coefficients (ICC 2,k) were computed for three different examiners. We obtained reproducible and consistent MSOT values with small-to-moderate deviation for muscle and subcutaneous fat tissue. Probe orientation and body side had no impact on calculated MSOT values (p > 0.05 each). Intraobserver reproducibility revealed equable mean values with small-to-moderate deviation. For muscular tissue, good ICC was obtained for sO2. Measurements of subcutaneous tissue revealed good-to-excellent ICCs for all calculated values. Thus, in this preliminary study on healthy individuals, clinical MSOT provided consistent and reproducible functional soft tissue characterization, independent on the investigating personnel.

Enhanced resolution and speckle-free three-dimensional printing of macular optical coherence tomography angiography.

Enhanced resolution and speckle-free three-dimensional printing of macular optical coherence tomography angiography.

Label-Free Imaging of Single Microtubule Dynamics Using Spatial Light Interference Microscopy.

Due to their diameter, of only 24 nm, single microtubules are extremely challenging to image without the use of extrinsic contrast agents. As a result, fluorescence tagging is the common method to visualize their motility. However, such investigation is limited by photobleaching and phototoxicity. We experimentally demonstrate the capability of combining label-free spatial light interference microscopy (SLIM) with numerical processing for imaging single microtubules in a gliding assay. SLIM combines four different intensity images to obtain the optical path length map associated with the sample. Because of the use of broadband fields, the sensitivity to path length is better than 1 nm without (temporal) averaging and better than 0.1 nm upon averaging. Our results indicate that SLIM can image the dynamics of microtubules in a full field of view, of 200 × 200 μm2, over many hours. Modeling the microtubule transport via the diffusion-advection equation, we found that the dispersion relation yields the standard deviation of the velocity distribution, without the need for tracking individual tubes. Interestingly, during a 2 h window, the microtubules begin to decelerate, at 100 pm/s2 over a 20 min period. Thus, SLIM is likely to serve as a useful tool for understanding molecular motor activity, especially over large time scales, where fluorescence methods are of limited utility.

Review of optical breast imaging and spectroscopy.

Diffuse optical imaging and spectroscopy of the female breast is an area of active research. We review the present status of this field and discuss the broad range of methodologies and applications. Starting with a brief overview on breast physiology, the remodeling of vasculature and extracellular matrix caused by solid tumors is highlighted that is relevant for contrast in optical imaging. Then, the various instrumental techniques and the related methods of data analysis and image generation are described and compared including multimodality instrumentation, fluorescence mammography, broadband spectroscopy, and diffuse correlation spectroscopy. We review the clinical results on functional properties of malignant and benign breast lesions compared to host tissue and discuss the various methods to improve contrast between healthy and diseased tissue, such as enhanced spectroscopic information, dynamic variations of functional properties, pharmacokinetics of extrinsic contrast agents, including the enhanced permeability and retention effect. We discuss research on monitoring neoadjuvant chemotherapy and on breast cancer risk assessment as potential clinical applications of optical breast imaging and spectroscopy. Moreover, we consider new experimental approaches, such as photoacoustic imaging and long-wavelength tissue spectroscopy.

Near-Infrared Spectroscopy Technology in Typically Fluent Speakers and Persons who Stutter

Near-infrared spectroscopy (NIRS) is a biomedical optical imaging technique that is used to measure real-time functional brain activity. NIRS uses non-invasive infrared light to measure oxy-, de-oxy, and total hemoglobin concentration at the surface of the cerebral cortex. Hemoglobin concentration is monitored through the use of light scattering and tissue absorption. NIRS is advantageous over other techniques (e.g., EEG, MRI, PET etc.) because it does not utilize harmful radiation or an extrinsic contrast agent. It is also portable and is a low cost technology to administer. NIRS can also be used with infants, young children, and adults. Since its discovery, NIRS has been used to study Alzheimer's disease, verbal fluency, language processing, epilepsy, frontal lateralization in speech tasks, cerebral hemodynamics, visual stimulation, odor stimulation, chronic schizophrenia, and other conditions. We have used NIRS to measure hemoglobin changes in typically fluent speakers (TFS) and persons who stutter (PWS). Our NIRS device has 16 sources and 24 detectors to measure haemoglobin concentration changes during speech and non-speech tasks for TFS and PWS. Our participants ranged in age from 10 to young adulthood. Measurements were taken during three conditions: Speakers were asked to read out loud, to engage in spontaneous speech, and to sit for a rest period. The purpose of this study was to determine whether there were haemoglobin concentration changes in TFS and PWS while they engaged in speech and non-speech tasks. Initial results indicate that speech tasks caused hemoglobin concentration changes. A more in-depth analysis of our technology and pilot data will be presented.

Imaging translucent cell bodies in the living mouse retina without contrast agents

The transparency of most retinal cell classes typically precludes imaging them in the living eye; unless invasive methods are used that deploy extrinsic contrast agents. Using an adaptive optics scanning light ophthalmoscope (AOSLO) and capitalizing on the large numerical aperture of the mouse eye, we enhanced the contrast from otherwise transparent cells by subtracting the left from the right half of the light distribution in the detector plane. With this approach, it is possible to image the distal processes of photoreceptors, their more proximal cell bodies and the mosaic of horizontal cells in the living mouse retina.

High-throughput measurements of the optical redox ratio using a commercial microplate reader.

There is a need for accurate, high-throughput, functional measures to gauge the efficacy of potential drugs in living cells. As an early marker of drug response in cells, cellular metabolism provides an attractive platform for high-throughput drug testing. Optical techniques can noninvasively monitor NADH and FAD, two autofluorescent metabolic coenzymes. The autofluorescent redox ratio, defined as the autofluorescence intensity of NADH divided by that of FAD, quantifies relative rates of cellular glycolysis and oxidative phosphorylation. However, current microscopy methods for redox ratio quantification are time-intensive and low-throughput, limiting their practicality in drug screening. Alternatively, high-throughput commercial microplate readers quickly measure fluorescence intensities for hundreds of wells. This study found that a commercial microplate reader can differentiate the receptor status of breast cancer cell lines (p < 0.05) based on redox ratio measurements without extrinsic contrast agents. Furthermore, microplate reader redox ratio measurements resolve response (p < 0.05) and lack of response (p > 0.05) in cell lines that are responsive and nonresponsive, respectively, to the breast cancer drug trastuzumab. These studies indicate that the microplate readers can be used to measure the redox ratio in a high-throughput manner and are sensitive enough to detect differences in cellular metabolism that are consistent with microscopy results.

Su2002 Nonmyeloablative Stem Cell Therapy for Perianal Fistulizing Crohn's Disease: A Systematic Review of Safety and Efficacy

BODY: BACKGROUND/AIMS: Three-dimensional endomicroscopy using optical coherence tomography (3D-OCT) provides volumetric images of tissue microstructure without requiring extrinsic contrast agents. Commercially available OCT systems have limited frame rates and typically use proximal rotation and pullback mechanisms to scan the imaging beam across the tissue. These two factors limit the ability to generate high quality en face images of aberrant mucosal surface patterns, which correlate with the presence and grade of dysplasias. In this study, we present a prototype ultrahigh speed 3D-OCT system with an advanced imaging probe using distal micromotor scanning. This system enables en face 3D-OCT images that visualize the mucosal surface patterns in a variety of GI structures in vivo. METHODS: The study was performed at the VA Boston Healthcare System (VABHS) under a study protocol approved by the VABHS, Harvard Medical School and M.I.T. We used a prototype 3D-OCT system that has an imaging speed (axial scan rate) of 600 kHz, which is ~10 times faster than commercially available 3D-OCT imaging systems. Scanning of the imaging beam is performed using a micromotor at the distal end of the OCT probe. The probe was passed through the accessory channel of an Olympus double channel endoscope (GIF-2TH180) to allow coregistration of images with biopsies. RESULTS: The combined advantages of ultrahigh speed and distal scanning of the new 3D-OCT system and probe enables visualization of mucosal surface patterns with unprecedented clarity. Fig. 1(A) demonstrates a volumetric reconstruction of a 3D-OCT dataset acquired in the gastric body of a patient. While cross sectional images give information on the layered architecture of the tissue, gastric folds and pit pattern can be visualized in the en face direction. Fig. 1(C) shows the squamocolumnar junction (SCJ) of a patient with Barrett's esophagus (BE), where the squamous epithelium (SE) appears as a smooth layer, whereas the area with BE has a well-defined pit pattern architecture. Fig. 1(D) shows a region of the esophagus a BE patient immediately after radiofrequency ablation (RFA), where residual BE that is missed by the RFA application can be observed. CONCLUSIONS: This study demonstrates that ultrahigh speed 3D-OCT system with a distal scanning micromotor probe can generate cross-sectional and en face images from the same dataset, yielding a more comprehensive evaluation of tissue architecture. Moreover, imaging can be performed even after biopsies or ablations, and can survey margins of endoscopic resections which is not possible with confocal endomicroscopy using exogenous contrast agents. Therefore, this novel imaging system has the potential to greatly improve the clinical utility of 3D-OCT. ACKNOWLEDGEMENT: NIH 5R01-CA075289-16, R44-CA101067-06, AFOSR FA9550-12-1-0499, and FA9550-10-10551. Figure 1: (A) Volumetric reconstruction of a 3D-OCT dataset acquired in the gastric body of a patient showing cross sectional as well as en face visualization of the gastric folds and pit patterns. (B) Zoomed view of the en face image shown in (A). (C) Squamocolumnar junction (SCJ) of a patient with Barrett's esophagus (BE) showing a region with smooth squamous epithelium and the BE region with well-defined pit patterns. (D) A region of a patient with BE immediately after radiofrequency ablation (RFA), where the encircled area shows BE glands that are likely missed by the RFA. Scale bars: 500um.

Su2001 The Role of the Histone Methyltransferase EZH2 in the Mouse Intestinal Epithelium

BODY: BACKGROUND/AIMS: Three-dimensional endomicroscopy using optical coherence tomography (3D-OCT) provides volumetric images of tissue microstructure without requiring extrinsic contrast agents. Commercially available OCT systems have limited frame rates and typically use proximal rotation and pullback mechanisms to scan the imaging beam across the tissue. These two factors limit the ability to generate high quality en face images of aberrant mucosal surface patterns, which correlate with the presence and grade of dysplasias. In this study, we present a prototype ultrahigh speed 3D-OCT system with an advanced imaging probe using distal micromotor scanning. This system enables en face 3D-OCT images that visualize the mucosal surface patterns in a variety of GI structures in vivo. METHODS: The study was performed at the VA Boston Healthcare System (VABHS) under a study protocol approved by the VABHS, Harvard Medical School and M.I.T. We used a prototype 3D-OCT system that has an imaging speed (axial scan rate) of 600 kHz, which is ~10 times faster than commercially available 3D-OCT imaging systems. Scanning of the imaging beam is performed using a micromotor at the distal end of the OCT probe. The probe was passed through the accessory channel of an Olympus double channel endoscope (GIF-2TH180) to allow coregistration of images with biopsies. RESULTS: The combined advantages of ultrahigh speed and distal scanning of the new 3D-OCT system and probe enables visualization of mucosal surface patterns with unprecedented clarity. Fig. 1(A) demonstrates a volumetric reconstruction of a 3D-OCT dataset acquired in the gastric body of a patient. While cross sectional images give information on the layered architecture of the tissue, gastric folds and pit pattern can be visualized in the en face direction. Fig. 1(C) shows the squamocolumnar junction (SCJ) of a patient with Barrett's esophagus (BE), where the squamous epithelium (SE) appears as a smooth layer, whereas the area with BE has a well-defined pit pattern architecture. Fig. 1(D) shows a region of the esophagus a BE patient immediately after radiofrequency ablation (RFA), where residual BE that is missed by the RFA application can be observed. CONCLUSIONS: This study demonstrates that ultrahigh speed 3D-OCT system with a distal scanning micromotor probe can generate cross-sectional and en face images from the same dataset, yielding a more comprehensive evaluation of tissue architecture. Moreover, imaging can be performed even after biopsies or ablations, and can survey margins of endoscopic resections which is not possible with confocal endomicroscopy using exogenous contrast agents. Therefore, this novel imaging system has the potential to greatly improve the clinical utility of 3D-OCT. ACKNOWLEDGEMENT: NIH 5R01-CA075289-16, R44-CA101067-06, AFOSR FA9550-12-1-0499, and FA9550-10-10551. Figure 1: (A) Volumetric reconstruction of a 3D-OCT dataset acquired in the gastric body of a patient showing cross sectional as well as en face visualization of the gastric folds and pit patterns. (B) Zoomed view of the en face image shown in (A). (C) Squamocolumnar junction (SCJ) of a patient with Barrett's esophagus (BE) showing a region with smooth squamous epithelium and the BE region with well-defined pit patterns. (D) A region of a patient with BE immediately after radiofrequency ablation (RFA), where the encircled area shows BE glands that are likely missed by the RFA. Scale bars: 500um.

Tu1965 Polarization Gating Spectroscopy to Detect Pancreas Cancer - Final Results of the Pilot Study

BACKGROUND/AIMS: Three-dimensional endomicroscopy using optical coherence tomography (3D-OCT) provides cross sectional and volumetric images of tissue microstructure without requiring extrinsic contrast agents. We recently described "buried" Barrett's esophagus (BE) glands and ability to predict the efficacy of radio frequency ablation (RFA) using this uniquely suited imaging modality. In this study, we demonstrate a processing method that provides enhanced contrast to 3D-OCT images by analysing the variations in the intensity profile of the structural images. The processed 3D-OCT images improve the identification and classification of subsurface tissue architectures. METHODS: The study was performed at the VA Boston Healthcare System (VABHS) with the study protocol approved by the VABHS, Harvard Medical School and M.I.T. The analysis method calculates the normalized gradient of the local intensity profile of 3D-OCT images and overlays the processing result onto the original intensity image in a Hue-Saturation-Value (HSV) color space. Images acquired from upper esophagus of normal and BE patients undergoing endoscopic surveillance are analysed with the new processing method. RESULTS: 3D-OCT intensity images (Fig. 1(A, C), and the overlay images derived from the intensity analysis (Fig. 1(B, D)) from endoscopically normal-appearing (A and B) and Barrett's (C and D) esophagus demonstrate the ability of the new analysis method to enhance the contrast of the 3D-OCT images. Consistent with characteristic features of normal esophagus, intensity image in Fig. 1(A) shows squamous epithelium (SE) and lamina propria/muscularis mucosa (LP/MM) layers. These two layers are better delineated in the enhanced HSV image shown in Fig. 1(B), where the SE layer appears with the tones blue and the LP/MM layers appears with the tones of green and red. Application of this method for 3D-OCT images taken from the BE patient showed disruption of this layered architecture (Fig. 1(D)). Moreover, images taken from BE patients immediately after RFA showed enhanced contrast for the residual burned tissue and the underlying subsurface structures, showing that the enhanced contrast might also be useful in assessing RFA treatment response and efficacy. CONCLUSIONS: This study demonstrates that by analysing the variations of the local intensity profile it is possible to enhance the contrast of conventional 3D-OCT images without the use of extrinsic contrast agents. The application of this method should aid the identification of fine subsurface structures and possibly improve the diagnostic capability of the 3D-OCT. ACKNOWLEDGEMENT: NIH 5R01-CA075289-14, K99-EB010071-01A1, AFOSR FA9550-07-1-0101, and FA9550-10-1-0551.

Tu1963 Contrast Enhancement for Three-Dimensional Optical Coherence Tomography Images for Improved Delineation of Subsurface Structures

BACKGROUND/AIMS: Three-dimensional endomicroscopy using optical coherence tomography (3D-OCT) provides cross sectional and volumetric images of tissue microstructure without requiring extrinsic contrast agents. We recently described buried Barrett's esophagus (BE) glands and ability to predict the efficacy of radio frequency ablation (RFA) using this uniquely suited imaging modality. In this study, we demonstrate a processing method that provides enhanced contrast to 3D-OCT images by analysing the variations in the intensity profile of the structural images. The processed 3D-OCT images improve the identification and classification of subsurface tissue architectures. METHODS: The study was performed at the VA Boston Healthcare System (VABHS) with the study protocol approved by the VABHS, Harvard Medical School and M.I.T. The analysis method calculates the normalized gradient of the local intensity profile of 3D-OCT images and overlays the processing result onto the original intensity image in a Hue-Saturation-Value (HSV) color space. Images acquired from upper esophagus of normal and BE patients undergoing endoscopic surveillance are analysed with the new processing method. RESULTS: 3D-OCT intensity images (Fig. 1(A, C), and the overlay images derived from the intensity analysis (Fig. 1(B, D)) from endoscopically normal-appearing (A and B) and Barrett's (C and D) esophagus demonstrate the ability of the new analysis method to enhance the contrast of the 3D-OCT images. Consistent with characteristic features of normal esophagus, intensity image in Fig. 1(A) shows squamous epithelium (SE) and lamina propria/muscularis mucosa (LP/MM) layers. These two layers are better delineated in the enhanced HSV image shown in Fig. 1(B), where the SE layer appears with the tones blue and the LP/MM layers appears with the tones of green and red. Application of this method for 3D-OCT images taken from the BE patient showed disruption of this layered architecture (Fig. 1(D)). Moreover, images taken from BE patients immediately after RFA showed enhanced contrast for the residual burned tissue and the underlying subsurface structures, showing that the enhanced contrast might also be useful in assessing RFA treatment response and efficacy. CONCLUSIONS: This study demonstrates that by analysing the variations of the local intensity profile it is possible to enhance the contrast of conventional 3D-OCT images without the use of extrinsic contrast agents. The application of this method should aid the identification of fine subsurface structures and possibly improve the diagnostic capability of the 3D-OCT. ACKNOWLEDGEMENT: NIH 5R01-CA075289-14, K99-EB010071-01A1, AFOSR FA9550-07-1-0101, and FA9550-10-1-0551.

Near‐infrared imaging of breast cancer using optical contrast agents

Breast cancer is the most common malignancy in women worldwide and the second leading cause of cancer death. On the basis of three studies performed by our group, this article reviews the current status of optical breast imaging using extrinsic contrast agents. To date, only two contrast agents have been applied in human studies, indocyanine green (ICG) and omocianine. Both contrast media were used for absorption and fluorescence imaging. Generally speaking, malignant breast lesions exhibited higher absorption contrast as well as higher fluorescence contrast compared to benign lesions or non-diseased breast tissue. Some groups consider early enhancement characteristics helpful for differentiation between malignant and benign lesions. Late fluorescence ICG imaging - capitalizing on the extravasation of the dye through the wall of tumorous vessels - seems to be a promising technique to distinguish malignant from benign breast lesions.

Nichtinvasive Messung des relativen zerebralen Blutflusses mit der MR-Blutbolusmarkierungstechnik (arterial-spin-labeling): Physikalische Grundlagen und klinische Anwendungen

Knowledge of tumor blood flow is important for diagnosis and follow-up of brain tumors after therapy, especially to discriminate necrosis from tumor recurrence after radiation or chemotherapy. Meanwhile, perfusion and diffusion MRI, besides MR-angiography, are state of the art in stroke imaging. Until now, perfusion imaging was mostly performed using the first-pass dynamic susceptibility-weighted contrast-enhanced (DSC) MRI. The MRI-based arterial spin labeling technique (ASL) is a novel approach for measuring relative cerebral blood flow (rCBF) without using extrinsic contrast agents, by labeling spins of flowing arterial blood as intrinsic contrast agent. This article describes physical basics of ASL and shows clinical examples in neuroimaging such as in meningeoma, glioblastoma, oligodendroglioma, and cerebral ischemia, using the Q2TIPS ASL technique. Gray matter is clearly visible, while the observed white matter signal obtained by Q2TIPS is only slightly higher than background noise. Venous blood causes artefacts in the sagittal sinus and other large superficial veins in the subarachnoid space. Meningeoma and glioblastoma show elevated rCBF, whereas oligodendroglioma and cerebral ischemia have reduced rCBF values. Arterial-spin-labeling techniques are noninvasive tools for measuring rCBF within 5 min, using a standard MRI scanner.

High-resolution three-dimensional scanning optical image system for intrinsic and extrinsic contrast agents in tissue

This article presents the theory and development of a three-dimensional (3D) imaging instrument capable of determining the biochemical properties of tissue by measuring the absorption or fluorescence of different intrinsic and extrinsic agents simultaneously. A bifurcated optical fiber bundle, serving to deliver the excitation light and collect the emission or reflection light, scans over the flat tissue surface retrieving optical signals in each pixel. Two-dimensional (2D) images of a series of subsequent sections are obtained after signal conversion and processing to yield a 3D image. Manipulation of the scanning step and diameter size of the fibers within the bundle, the spatial resolution of the instrument attains a maximum of 40 × 40 × 10 μm3. The wavelength range is extended from ultraviolet to the near infrared (NIR) through specialized optical design, typically employed for the NIR extrinsic contrast agents study. The instrument is most applicable in situations involving the measurement of fluorescence or absorption at any specific wavelength within the spectrum range. Flavoprotein and nicotinamide adeine dinucleotide are the two typical intrinsic agents indicating the oxidization and reduction status of the tissue sample, with their fluorescence detected at wavelengths of 540 and 440 nm, respectively. Oxy and deoxy hemoglobin are two other significant intrinsic agents for evaluating the blood oxygenation saturation by recording their absorptions at two different wavelengths of 577 and 546 nm. These intrinsic agents were measured in this study for comparison of biochemical properties of rat liver in different gas inhalation treatments. Indocyanine green, a NIR extrinsic contrast agent measured at wavelengths of 780 nm/830 nm as excitation/emission can indicate blood pooling by displaying the distribution of blood vessels within a 9 L tumor. The advantage of high sensitivity, spatial resolution, and broad applied potentiality were demonstrated by the instrument during these experiments.