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PubMed2006

In vivo imaging of integrin alpha v beta 3 expression using fluorescence-mediated tomography.

PURPOSE: Optical imaging would be desirable for cancer diagnostics since it can potentially resolve relevant oncological target structures in vivo. We therefore synthesised an alpha v beta(3) targeted fluorochrome and imaged tumour xenografts with different alpha v beta(3) expression levels using both planar and tomographic optical imaging methods. METHODS: An alpha v beta(3)-targeted RGD peptide was labelled with a cyanine dye (Cy 5.5). Binding of the optical tracer was tested on M21 melanoma (n=5), HT-1080 fibrosarcoma (n=6) and MCF-7 adenocarcinoma (n=5) cells and their tumour xenografts. All optical imaging studies were performed using two-dimensional planar fluorescence reflectance imaging (FRI) technology and three-dimensional fluorescence-mediated tomography (FMT). RESULTS: In vitro, the peptide-dye conjugate showed a clear binding affinity to alpha v beta(3)-positive M21 and HT-1080 cells while alpha v beta(3)-negative MCF-7 cells and pre-dosing with the free RGD peptide revealed little to no fluorescence. In vivo, tumour xenografts were clearly visualised by FRI and FMT up to 24 h post injection. FMT allowed quantification of the fluorochrome distribution in deeper tissue sections showing an average fluorochrome concentration of 417.61 +/- 105.82 nM Cy 5.5 (M21), 353.68 +/- 54.02 nM Cy 5.5 (HT-1080) and 262.83 +/- 155.36 nM Cy 5.5 (MCF-7) in the target tissue 60 min after tracer administration. Competition with the free RGD peptide resulted in a reduction in the fluorochrome concentration in M21 tumour tissue (294.35 +/- 84.27 nM). CONCLUSION: RGD-Cy 5.5 combined with novel tomographic optical imaging methods allows non-invasive imaging of tumour-associated alpha v beta(3) expression and may thus be a promising strategy for sensitive evaluation of tumour target expression.

Animals↗

PubMed2006

Paired-angle-rotation scanning optical coherence tomography forward-imaging probe.

We report a novel forward-imaging optical coherence tomography (OCT), needle-probe paired-angle-rotation scanning OCT (PARS-OCT) probe. The probe uses two rotating angled gradient-index lenses to scan the output OCT probe beam over a wide angular arc (approximately 19 degrees half-angle) of the region forward of the probe. Among other advantages, this probe design is readily amenable to miniaturization and is capable of a variety of scan modes, including volumetric scans. To demonstrate the advantages of the probe design, we have constructed a prototype probe with an outer diameter of 1.65 mm and employed it to acquire four OCT images, with a 45 degrees angle between adjacent images, of the gill structure of a Xenopus laevis tadpole. The system sensitivity was measured to be 93 dB by using the prototype probe with an illumination power of 450 microW on the sample. Moreover, the axial and the lateral resolutions of the probe are 9.3 and 10.3-12.5 microm, respectively.

Computer-Aided Design↗

PubMed2000

Comparability of three-dimensional optic disc imaging with different techniques. A study with confocal scanning laser tomography and raster tomography.

PURPOSE: We wanted to compare optic nerve head topography measurements and discrimination between normal and glaucomatous eyes with two entirely different three-dimensional optic disc imaging techniques, confocal scanning laser tomography (Heidelberg Retina Tomograph, Heidelberg Engineering) and raster tomography (Glaucoma-Scope, Ophthalmic Imaging Systems). METHODS: Both eyes of 225 normal subjects and 229 eyes of 166 patients with glaucoma at different stages were imaged with the Heidelberg Retina Tomograph and the Glaucoma-Scope. Optics discs were analysed in 15 degrees sectors around the circumference. Depth measurements were calibrated on objects with known dimensions. RESULTS: We observed no significant differences in absolute measurements of maximum cup depth and cup area between the two instruments. We observed small differences in absolute measurements of disc anti rim area between the two instruments. Discrimination between normal and glaucomatous eyes was close to identical for the two instruments. Both instruments had the same ability to distinguish glaucomatous regional alterations of optic nerve head topography from normal disc configuration. CONCLUSION: Both instruments while using entirely different principles for three-dimensional optic disc imaging gave very similar results. This correspondence of results implies that the same optic disc parameters can be analysed, and the results interpreted similarly for both methods, and probably with other three-dimensional imaging instruments. It may also indicate that results of studies with one of the instruments have general validity.

Adult↗

PubMed1987

Morphological optics.

Image analysis methods are first classified into four groups of theories related to optics, after which the associate hypotheses, the structures, the laboratory equipment and the mathematical framework for one of them, better known by the term of morphological optics, are studied in detail. Conclusions are drawn as to the role played by hypotheses in image analysis.

Animals↗

PubMed2000

Comparison of optic disc image assessment methods when examining serial photographs for glaucomatous progression.

AIM: To assess serial, simultaneous stereo optic disc images by four methods for glaucomatous progression. METHODS: Using varying techniques, two ophthalmologists assessed serial optic disc images of 52 eyes from 27 patients with a mean duration between images of 18 months. The neuroretinal rim width was qualitatively assessed by four assessment methods and compared with quantitative rim measurements made using PC based software. RESULTS: The highest sensitivity of 83% was achieved using computerised stereo chronoscopy. CONCLUSION: Stereo chronoscopy improved the detection of subtle optic disc changes when compared with simpler assessment techniques.

Disease Progression↗

PubMed2001

Information content of volume holographic imaging.

We discuss the general properties of optical imaging in three-dimensional object domains from an information-theoretic standpoint, expressing system performance in terms of imaging mutual information (IMI). We use IMI to characterize volume holographic imaging, a new optical imaging method with depth discrimination capability. The performance of this holographic method in imaging a simple discrete, axial fluorescent object is compared with that of two alternatives: a pinhole-based system and a combined system that uses both a pinhole and a hologram in parallel.

Holography↗

PubMedDate not supplied

Non-invasive image acquisition and advanced processing in optical bioimaging.

Light is a most versatile tool for investigating biological systems and phenomena; the range, non-destructiveness, spatial discrimination and speed of optical imaging are all important for investigating structure and function at the cellular, tissue or even whole organism level. In live biological imaging, where the technological requirements are heightened, other features of light, such as coherence and wavelength, are used to generate the additional contrast and resolution needed. We report here recent improvements in our ability to image biological specimens optically, focusing on (a) spectral resolution and the related image processing issues, and (b) tomographic three-dimensional fluorescence imaging in vivo.

Fluorescence↗

PubMed2005

Quantitative thickness measurement of retinal layers imaged by optical coherence tomography.

PURPOSE: To report an image analysis algorithm that was developed to provide quantitative thickness measurement of retinal layers on optical coherence tomography (OCT) images. DESIGN: Prospective cross-sectional study. METHODS: Imaging was performed with an OCT3 commercial instrument in 10 visually normal healthy subjects. A dedicated software algorithm was developed to process the raw OCT images and detect the depth location of peaks from intensity profiles. Quantitative thickness measurements of three retinal layers, in addition to total retinal thickness, were derived. Total retinal thickness measurements obtained by the algorithm were compared with measurements provided by the standard OCT3 software. RESULTS: The total retinal thickness profile demonstrated foveal depression, corresponding to normal anatomy, with a thickness range of 160 to 291 microm. Retinal thickness measured by the algorithm and by the standard OCT3 software were highly correlated (R = 0.98). The inner retinal thickness profile predictably demonstrated a minimum thickness at the fovea, ranging between 58 to 217 microm along the 6-mm scan. The outer retinal thickness profile displayed a maximum thickness at the fovea, ranging between 66 to 107 microm along the 6-mm scan. The photoreceptor outer segment thickness profile was relatively constant along the 6-mm scan through the fovea, ranging between 42 to 50 microm. The intrasubject variabilities of the inner retina, outer retina, and photoreceptor outer segment thickness was 14, 10, and 6 microm, respectively. CONCLUSIONS: Thickness measurements of retinal layers derived from OCT images have potential value for objectively documenting disease-related retinal thickness abnormalities and monitoring progressive changes over time.

Adult↗

PubMed1995

Anthropometric optical surface imaging system repeatability, precision, and validation.

Disciplines using human body surface dimensions require accurate, repeatable measurements. This study presents a design for the analysis of repeatability, precision, and validation of a new anthropometric device. This model enables estimation of the proportion of the total variation attributable to each level of data collection. This model is applied to an analysis of repeatability, precision, and validation of the Cencit Imaging System, a new optical surface scanner. Twenty-seven facial landmarks were marked on 10 men and 10 women at two measurement sessions. Two images were scanned during each session, and each image was digitized twice. The Cencit Imaging System results were compared with a previously validated digitizer. The Cencit Imaging System was found to produce accurate, highly repeatable images. Much of the error in this study is attributable to human error in marking landmarks on the subjects. The new imaging system will prove useful in a variety of anthropometric applications.

Anthropometry↗

PubMed2001

Near-field mapping of surface polariton fields.

Using the general approach to image formation in collection near-field optical microscopy, I derive the symmetry relations for the amplitude coupling coefficients in the case of a weakly guiding single-mode fibre terminated with a probe tip possessing axial symmetry. It is shown that, for the symmetrical detection configuration, six elements of the coupling matrix can be expressed by using only three independent coupling coefficients. The obtained relations are further applied to describe near-field mapping of surface plasmon polariton (SPP) fields. I demonstrate that, for the symmetrical detection configuration, the near-field optical image reflects the intensity distribution of the SPP field components parallel to the surface plane, even though the strong perpendicular component is also being detected. This conclusion is supported with numerical simulations that elucidate the influence of symmetry of the fibre probe on the resulting near-field optical image. The near-field optical images simulated for scattering systems typical for SPP microoptics and localization are presented. It is found that the presence of asymmetry in the detection configuration increases the contribution of the perpendicular field component and results in the images approaching the corresponding SPP intensity distributions.

Journal Article↗

PubMed2005

Cy5.5-DTPA-galactosyl-dextran: a fluorescent probe for in vivo measurement of receptor biochemistry.

The high sensitivity of fluorescent reporters offers an opportunity to analytically probe the biochemistry of in vivo receptor systems with low target tissue concentration. We investigated the ability of an optical imaging system to acquire adequate signal for in vivo measurement of receptor biochemistry. The imaging system consisted of a small animal optical imager operating in the time domain (TD) and a fluorescent-labeled diagnostic probe of known receptor-binding properties. Optical imaging of mice (n = 4) using the targeted probe, Cy5.5-DTPA-galactosyl-dextran (2.2 Cy5.5, 4 DTPA, 68 galactose units per dextran, 124 kDa, 24 nmol/kg), demonstrated blood clearance and hepatic uptake. The mean and standard deviation for the time to reach 90% of the peak liver intensity were 15.4 +/- 1.6 min. Typical fluorescent intensities within a 10-pixel region-of-interest from a 30-s image acquired 30 min postinjection were in excess of 2.5 million counts. The nontargeted agent (Cy5.5-DTPA-dextran) did not demonstrate (n = 4) hepatic uptake. This uptake pattern was duplicated by nuclear imaging of rabbits using (99m)Tc-labeled Cy5.5-DTPA-galactosyl-dextran and Cy5.5-DTPA-dextran. This study demonstrated the feasibility of optically labeling a receptor-binding diagnostic probe and imaging in the TD with sufficient sensitivity and temporal resolution for pharmacokinetic analysis.

Animals↗

PubMed2002

Image fiber optic space-CDMA parallel transmission experiment using 8 x 8 VCSEL/PD arrays.

We experimentally demonstrate space-code-division multiple access (space-CDMA) based twodimensional (2-D) parallel optical interconnections by using image fibers and 8 x 8 vertical-cavity surface-emitting laser (VCSEL)/photo diode (PD) arrays. Two spatially encoded four-bit (2 x 2) parallel optical signals were emitted fiom 2-D VCSEL arrays and transmitted through image fibers. The encoded signals were multiplexed by an image-fiber coupler and detected by a 2-D PD array on the receiver side. The receiver recovered the intended parallel signal by decoding the signal. The transmission speed was 64 Mbps/ch (total throughput: 512 Mbps). Bit-error-rate (BER) measurement with a laterally misaligned PD array showed the array had a misalignment tolerance of 25 microm for a BER performance of 10(-9).

Journal Article↗

PubMed2004

Clinical considerations in rodent bioimaging.

Imaging modalities such as micro-computed tomography (micro-CT), micro-positron emission tomography (micro-PET), high-resolution magnetic resonance imaging (MRI), optical imaging, and high-resolution ultrasound are rapidly becoming invaluable research tools. These advanced imaging technologies are now commonly used to investigate rodent biology, metabolism, pharmacokinetics, and disease in vivo. Choosing an appropriate anesthetic regimen as well as monitoring and supporting the animal's physiologic balance is key to obtaining images that truly represent the biologic process or disease state of interest. However, there are many challenges in rodent bioimaging such as limited animal access, small sample volumes, anesthetic complications, strain and gender variability, and the introduction of image artifacts. Because each imaging study presents unique challenges, a thorough understanding of the imaging modality used, the animal's health status, and the research data desired is required. This article addresses these issues along with other common laboratory animal clinical considerations such as biosecurity and radiation safety in in vivo rodent bioimaging.

Anesthesia↗

PubMed2005

Lasers in cancer detection and diagnosis research: enabling characteristics with illustrative examples.

The salient properties of laser light and the way light interacts with biological tissues and molecular constituents of tissues offer possibilities for detection and diagnosis of cancer. In particular, the wavelength selectivity of tunable lasers, narrow bandwidth around the selected wavelength, and spectral brightness enable probing of key molecular constituents of tissues, and endow laser-based techniques with much desired diagnostic potential. This article presents an overview of some recent developments in optical imaging and optical biopsy of different types of cancers, and illustrates the diagnostic role of the color of light.

Biopsy↗

PubMed2006

Double-clad photonic crystal fiber coupler for compact nonlinear optical microscopy imaging.

A 1 x 2 double-clad photonic crystal fiber coupler is fabricated by the fused tapered method, showing a low excess loss of 1.1 dB and a splitting ratio of 97/3 over the entire visible and near-infrared wavelength range. In addition to the property of splitting the laser power, the double-clad feature of the coupler facilitates the separation of a near-infrared single-mode beam from a visible multimode beam, which is ideal for nonlinear optical microscopy imaging. In conjunction with a gradient-index lens, this coupler is used to construct a miniaturized microscope based on two-photon fluorescence and second-harmonic generation. Three-dimensional nonlinear optical images demonstrate potential applications of the coupler to compact all-fiber and nonlinear optical microscopy and endoscopy.

Journal Article↗

PubMed2002

Optical scatter imaging detects mitochondrial swelling in living tissue slices.

Mitochondrial swelling is observed in neuronal injury and is a key event in many pathways to cell death. Currently, there is no technique for directly measuring mitochondrial size changes within living tissue slices with a field of view of several millimeters. In this paper, we test our hypothesis that Mie light-scatter theory can be used to study mitochondrial swelling in living tissue sections. Using a unique dual-angle scatter ratio (DASR) optical imaging system previously demonstrated to be sensitive to latex particle size changes and N-methyl-D-aspartate (NMDA) treatment of hippocampal slices, we studied mitochondrial swelling induced by 500 microM NMDA treatment of hippocampal slices. We observed a strong (R(2) = 0.73) and significant (P < 0.000005) correlation between the electron microscopy-determined diameters of swollen, intact mitochondria and the DASR imaging. We examined the robustness of the technique by evaluating the correlation between the dual-angle scatter ratio and the diameter of the dendrites, observed to swell, in NMDA-treated slices and found no correlation (R(2) = 0.06). The advantage of DASR imaging over electron microscopy or other methods of studying mitochondrial swelling is the sensitivity of DASR imaging to mitochondrial swelling over a large field of view (>9 mm(2)) in an intact tissue slice. This novel technique may allow for the study of regional changes in mitochondrial swelling and recovery as sequential events within a single specimen. This technique will eventually be useful in studying the efficacy of stroke and other disease therapies targeting mitochondrial swelling.

Animals↗

PubMed1994

Fibre optic confocal imaging (FOCI) for subsurface microscopy of the colon in vivo.

Fibre optic confocal imaging (FOCI) is a new type of microscopy which has been recently developed (Delaney et al. 1993). In contrast to conventional light microscopy, FOCI and other confocal techniques allow clear imaging of subsurface structures within translucent objects. However, unlike conventional confocal microscopes which are bulky (because of a need for accurate alignment of large components) FOCI allows the imaging end to be miniaturised and relatively mobile. FOCI is thus particularly suited for clear subsurface imaging of structures within living animals or subjects. The aim of the present study was to assess the suitability of using FOCI for imaging of subsurface structures within the colon, both in vitro (human and rat biopsies) and in vivo (in rats). Images were obtained in fluorescence mode (excitation 488 nm, detection above 515 nm) following topical application of fluorescein. By this technique the glandular structure of the colon was imaged. FOCI is thus suitable for subsurface imaging of the colon in vivo.

Animals↗

PubMed1990

[Magnetic resonance imaging in optic nerve lesions with multiple sclerosis].

Magnetic resonance imaging (MRI) of the optic nerves was performed in 10 patients with multiple sclerosis (MS) using short inversion time inversion recovery (STIR) pulse sequences, and the results were compared with the visual evoked potentials (VEP). The 10 patients had optic neuritis in the chronic or remitting phase together with additional symptoms or signs allowing a diagnosis of clinically definite or probable MS. Sixteen optic nerves were clinically affected and 4 were unaffected. MRI was performed using a 0.5 tesla superconducting unit, and multiple continuous 5 mm coronal and axial STIR images were obtained. A lesion was judged to be present if a focal or diffuse area of increased signal intensity was detected in the optic nerve. In VEP, a delay in peak latency or no P 100 component was judged to be abnormal. With regard to the clinically affected optic nerves, MRI revealed a region of increased signal intensity in 14/16 (88%) and the VEP was abnormal in 16/16 (100%). In the clinically unaffected optic nerves, MRI revealed an increased signal intensity in 2/4 (50%). One of these nerves had an abnormal VEP and the other had a VEP latency at the upper limit of normal. The VEP was abnormal in 1/4 (25%). In the clinically affected optic nerves, the degree of loss of visual acuity was not associated with the longitudinal extent of the lesions shown by MRI. The mean length was 17.5 mm in optic nerves with a slight disturbance of visual acuity and 15.0 mm in nerves with severe visual loss.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗