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Results for “Optical imaging”

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At least 1,297 records · Page 72Linked to original sources
PubMed2000

Optical recording of membrane potential in dissociated mouse vestibular ganglion cells using a voltage-sensitive dye.

We investigated membrane electrophysiological features of dissociated vestibular ganglion neurons, using a voltage-sensitive dye and a multiple site optical imaging system. The neuronal nature of the cultured vestibular ganglion cells was confirmed by positive staining with the anti-neurofilament 200 kDa antibody, using immunocytochemical methods. Optical absorption of the dye which binds to the external surface of neuron membranes increased while the cells were depolarized during perfusion with 150 mM potassium solution. The relative ratio (deltaI/I) of optical absorption change was 0.23 +/- 0.08% (means +/- S.D., n = 16). These optical responses were wavelength dependent, therefore, the optical response apparently originated from the voltage-sensitive dye. Under our experimental conditions, photodynamic damage and pharmacological effects of the dye were either absent or insignificant. We therefore concluded that optical recording is a new, practical and non-invasive method to simultaneously monitor changes in membrane potential from cultured vestibular ganglion cells. Optical recording is expected to provide further insight into mechanisms of information processing by vestibular ganglion neurons.

Absorption↗
PubMed1998

Initiation of spontaneous epileptiform activity in the neocortical slice.

Cortical local circuitry is important in epileptogenesis. Voltage-sensitive dyes and fast imaging were used to visualize the initiation of spontaneous paroxysmal events in adult rat neocortical slices. Although spontaneous paroxysmal events could start from anywhere in the preparation, optical imaging revealed that all spontaneous events started at a few confined initiation foci and propagated to the whole preparation. Multielectrode recording over hundreds of spontaneous events revealed that often two or three initiation foci coexisted in each preparation (n = 10). These foci took turns being dominant; the dominant focus initiated the majority of the spontaneous paroxysmal events during that period. The dominant focus and dynamic rearrangement of foci suggest that the initiation of spontaneous epileptiform events involves a local multineuronal process, perhaps with potentiated synapses.

Action Potentials↗
PubMed2006

Blood volume and hemoglobin oxygenation response following electrical stimulation of human cortex.

Our understanding of perfusion-based human brain mapping techniques relies on a detailed knowledge of the relationship between neuronal activity and cerebrovascular hemodynamics. We performed optical imaging of intrinsic signals at wavelengths sensitive to total hemoglobin (Hbt; which correlate with cerebral blood volume (CBV)) and deoxygenated hemoglobin (Hbr) directly in humans during neurosurgical operations and investigated the optical signals associated with bipolar cortical stimulation at a range of amplitudes. Cortical stimulation elicited a rapid focal increase in Hbr (initial dip) in all subjects. An equally rapid increase in Hbt (<200 ms), with a slightly higher signal-to-noise ratio, was also highly localized for <2 s in spite of the non-columnar nature of the stimulus, after which the signal spread to adjacent gyri. A later decrease in Hbr (>3 s), which is relevant to the blood oxygen level dependent (BOLD) signal, was poorly localized. Increasing the stimulus amplitude elicited a linear increase in the area of the optical signal for Hbt and the initial dip but not the late decrease in Hbr, and a nonlinear increase in optical signal amplitude with a plateau effect for initial dip, Hbt and late decrease in Hbr.

Blood Volume↗
PubMed2001

Noninvasive functional optical spectroscopy of human breast tissue.

Near infrared diffuse optical spectroscopy and diffuse optical imaging are promising methods that eventually may enhance or replace existing technologies for breast cancer screening and diagnosis. These techniques are based on highly sensitive, quantitative measurements of optical and functional contrast between healthy and diseased tissue. In this study, we examine whether changes in breast physiology caused by exogenous hormones, aging, and fluctuations during the menstrual cycle result in significant alterations in breast tissue optical contrast. A noninvasive quantitative diffuse optical spectroscopy technique, frequency-domain photon migration, was used. Measurements were performed on 14 volunteer subjects by using a hand-held probe. Intrinsic tissue absorption and reduced scattering parameters were calculated from frequency-domain photon migration data. Wavelength-dependent absorption (at 674, 803, 849, and 956 nm) was used to determine tissue concentration of oxyhemoglobin, deoxyhemoglobin, total hemoglobin, tissue hemoglobin oxygen saturation, and bulk water content. Results show significant and dramatic differences in optical properties between menopausal states. Average premenopausal intrinsic tissue absorption and reduced scattering values at each wavelength are 2.5- to 3-fold higher and 16-28 % greater, respectively, than absorption and scattering for postmenopausal subjects. Absorption and scattering properties for women using hormone replacement therapy are intermediate between premenopausal and postmenopausal populations. Physiological properties show differences in mean total hemoglobin (7.0 microM, 11.8 microM, and 19.2 microM) and water concentration relative to pure water (10.9 %, 15.3 %, and 27.3 %) for postmenopausal, hormone replacement therapy, and premenopausal subjects, respectively. Because of their unique, quantitative information content, diffuse optical methods may play an important role in breast diagnostics and improving our understanding of breast disease.

Breast Neoplasms↗
PubMed1999

In vivo abnormal keratinazation in Darier-White's disease as viewed by real-time confocal imaging.

Darier-White's disease is a rare autosomal-dominant disorder of keratinization. The underlying pathology for the clinical presentation is acantholysis, and various types of dyskeratosis and acanthosis. In this study, we utilized a non-invasive optical imaging modality, confocal reflectance microscopy, to identify specific histologic features of Darier-White's disease in vivo. Micrographic findings in the confocal images were corps ronds, suprabasal clefts, acantholytic suprabasal keratinocytes, and villi. Real-time confocal images are illustrative and can be well correlated with known light microscopic phenomena, particularly in the case of keratinization abnormalities in Darier-White's disease.

Darier Disease↗
PubMedDate not supplied

In vivo absorption, scattering, and physiologic properties of 58 malignant breast tumors determined by broadband diffuse optical spectroscopy.

Diffuse optical imaging (DOI) may be a beneficial diagnostic method for women with mammographically dense breast tissue. In order to evaluate the utility of DOI, we are developing broadband diffuse optical spectroscopy (DOS) to characterize the functional origins of optical signals in breast cancer patients. Broadband DOS combines multifrequency intensity-modulated and continuous-wave near-infrared light to quantify tissue absorption and scattering spectra from 650 to 1000 nm. Values of intrinsic physiological properties (oxy- and deoxy-hemoglobin, water, lipid, and scatter power) derived from absorption and scattering spectra provide detailed information on breast physiology. We present the results of clinical studies of 58 stage II/III malignant breast tumors using a noninvasive, handheld, broadband DOS probe. On average, eight positions were scanned over tumor and contralateral normal breast for each subject. Intrinsic physiological properties were statistically significantly different for malignant vs. normal tissues for all subjects, without patient age or tumor size/type stratification. Breast tissues containing malignant tumors displayed reduced lipid content ( approximately 20%) and increased water, deoxy-, and oxy-hemoglobin (>50% each) compared to normal breast tissues. Functional perturbations by the tumor were significantly larger than functional variations in normal tissues. A tissue optical index (TOI) derived from intrinsic physiological properties yielded an average two-fold contrast difference between malignant tumors and intrinsic tissue properties. Our results demonstrate that intrinsic optical signals can be influenced by functional perturbations characteristic of malignant transformation; cellular metabolism, extracellular matrix composition, and angiogenesis. Our findings further underscore the importance of broadband measurements and patient age stratification in breast cancer DOI.

Adolescent↗
PubMed2005

Spectral and temporal near-infrared imaging of ex vivo cancerous and normal human breast tissues.

Cancerous and normal ex vivo human breast tissues were investigated using spectroscopic and time-sliced two-dimensional (2-D) transillumination imaging methods in order to demonstrate the importance and potential of spectral and temporal measurements in breast cancer detection and diagnosis. The experimental arrangement for time-sliced optical imaging used 120 fs, 1 kHz repetition-rate, 800 nm light pulses from a Ti:sapphire laser system for sample illumination, and a 80 ps resolution ultrafast gated intensified camera system for recording 2-D time-sliced images. The spectroscopic imaging arrangement used 1225-1300 nm tunable output of a Cr: forsterite laser for sample illumination, a Fourier space gate to discriminate against multiple-scattered light, and a near-infrared area camera to record 2-D images. Images recorded with earlier temporal slices of transmitted light highlighted tumors, while those recorded with later slices accentuated normal tissues. When light was tuned closer to the 1203 nm absorption resonance of adipose tissues, a marked enhancement in contrast between the images of adipose and fibrous tissues was observed. A similar wavelength-dependent difference between normal and cancerous tissues was observed. These results correlate well with pathology and nuclear magnetic resonance based analyses of the samples.

Adult↗
PubMed2000

Porcine coronary imaging in vivo by optical coherence tomography.

OBJECTIVE: A high-resolution coronary artery imaging modality has the potential to address important diagnostic and management problems in cardiology. Optical coherence tomography (OCT) is a promising new optical imaging technique with a resolution of approximately 10 microm. The purpose of this study was to use a new OCT catheter to demonstrate the feasibility of performing OCT imaging of normal coronary arteries, intimal dissections, and deployed stents in vivo. METHODS AND RESULTS: Normal coronary arteries, intimal dissections, and stents were imaged in five swine with OCT and compared with intravascular ultrasound (IVUS). In the normal coronary arteries, visualization of all of the layers of the vessel wall was achieved with a saline flush, including the intima which was not identified by IVUS. Following dissection, detailed layered structures including intimal flaps, intimal defects, and disruption of the medial wall were visualized by OCT. IVUS failed to show clear evidence of intimal and medial disruption. Finally, the microanatomic relationships between stents and the vessel walls were clearly identified only by OCT. CONCLUSIONS: In this preliminary experiment, we have demonstrated that in vivo OCT imaging of normal coronary arteries, intimal dissections, and deployed stents is feasible, and allows identification of clinically relevant coronary artery morphology with high-resolution and contrast.

Animals↗
PubMed1987

[Use of aspherical and atoric surfaces in the optics of eyeglasses].

As early as the beginning of this century, eyeglass lenses with aspherical surfaces were calculated at the behest of Gullstrand and M. von Rohr. There are considerable advantages in their use for the correction of hyperopic, aphakic, and myopic patients. The advantages lie not only in the better optical image produced by the lenses, but also in their lower weight and more pleasant appearance. The image quality of astigmatic lenses can be enhanced by means of atoric surfaces.

Astigmatism↗
PubMedDate not supplied

Transformation of a set of slices rotated on a common axis to a set of Z-slices: application to three-dimensional visualization of the in vivo human lens.

A technique that transforms a set of images acquired as a rotating frame about an axis (Z axis) into a set of images along the Z axis in presented. This technique is applied to the three-dimensional visualization of the in vivo human lens. A Scheimpfling slit camera acquired 60 optical images through the in vivo human lens. Between each image acquisition the plane containing the slit beam of light was sequentially rotated. This set of 60 images was transformed into a new stack of images on the Z axis. The transformed stack of Z images was visualized with volume rendering software.

Aged↗
PubMed2006

Surface-enhanced Raman scattering-based nanoprobe for high-resolution, non-scanning chemical imaging.

This work describes the development and demonstration of a non-scanning chemical imaging probe, capable of obtaining surface-enhanced Raman scattering (SERS) images of samples with which it is in direct contact. The SERS imaging arrays (i.e., nanoprobes) are used in a signal collection mode to obtain images by measuring as many as 30 000 individual sub-diffraction-limited locations on a sample's surface simultaneously. These SERS probes are fabricated from coherent fiber-optic imaging bundles, allowing for the formation of a highly ordered roughened metal surface, capable of providing uniform SERS enhancement (<2.0% relative standard deviation) across the entire imaging surface. These optimized SERS nanoprobes have potential application to a wide range of research fields from materials science to cellular biology.

Nanotechnology↗
PubMed2005

Frequency domain photon migration in the delta- P1 approximation: analysis of ballistic, transport, and diffuse regimes.

The standard diffusion approximation (SDA) to the Boltzmann transport equation (BTE) is commonly used to describe radiative transport for biomedical applications of frequency-domain diffuse optical imaging and spectroscopy. Unfortunately, the SDA is unable to provide accurate radiative transport predictions on spatial scales comparable to the transport mean free path and for media in which optical scattering is not dominant over absorption. Here, we develop and demonstrate the use of the delta- P1 approximation to provide improved radiative transport estimates in the frequency domain via the addition of a Dirac delta function to both radiance and phase function approximations. Specifically, we consider photon density wave propagation resulting from the illumination of an infinite turbid medium with an embedded, intensity-modulated, spherical light source. We examine the accuracy of the standard diffusion and delta- P1 approximations relative to Monte Carlo simulations that provide exact solutions to the BTE. This comparison establishes the superior accuracy of the delta- P1 approximation relative to the SDA that is most notable at distances less than 3 transport mean free paths from the source. In addition, we demonstrate that the differences in photon density wave propagation in a highly forward scattering medium (g1=0.95) vs an isotropically scattering medium (g1=0) provides a basis to define three spatial regimes where the light field is dominated by (a) unscattered/ballistic light, (b) minimally scattered light, and (c) diffusely scattered light. We examine the impact of optical properties, source modulation frequency, and numerical aperture of detection on the spatial extent and location of these regimes.

Biological Transport↗
PubMed2001

The effects of astigmatism and working distance on optic nerve head images using a Heidelberg Retina Tomograph scanning laser ophthalmoscope.

PURPOSE: To determine effects of astigmatism and working distance on optic nerve head images in normal patients using the Heidelberg Retina Tomograph. METHODS: The optic disks of 51 normal healthy subjects, aged 19 to 44 years, were imaged through dilated pupils. Subjects with 0.75 DC or less of astigmatism were imaged without correction at a working distance of 15 mm. They were then re-imaged with a cylindrical correction of +3.00 DC at 90 degrees axis (n = 20). Naturally astigmatic subjects with more than 1.00 DC were imaged without correction and then re-imaged once this was neutralized with their appropriate spectacle prescription (n = 15). The effects of working distance were studied using subjects with 0.75 DC or less (n = 16). Two working distances were used, 15 and 25 mm. At each session the means of three topographic images were taken from which standard deviations and parameters were recorded. Parameters analyzed included cup shape measure, rim area, and inferior temporal rim volume. Z-profile full width at half maximum was calculated from one image per subject for each condition. RESULTS: No significant difference was found in the measured parameters of the optic disk for any astigmatic condition or changes in working distance (P >.05), (paired t test). Both the standard deviation of the mean topographic images and the Z-profile half-maximum width of the axial intensity profile were significantly greater with induced astigmatism of +3.00 DC (P values 0.3 and.00, respectively). CONCLUSIONS: Optic disk parameters are not significantly affected by uncorrected astigmatism (up to 2.50 DC) or working distance. The algorithm used by the Heidelberg Retina Tomograph to generate topographic maps is sufficiently robust that astigmatism up to 2.50 DC does not require correction.

Adult↗
PubMed2005

High-resolution anatomic, diffusion tensor, and magnetization transfer magnetic resonance imaging of the optic chiasm at 3T.

PURPOSE: To evaluate techniques for anatomical and physiological imaging of the intracranial optic nerve (ON), optic chiasm (OC), and optic tract (OT) at 3T with the aim of visualizing axonal damage in multiple sclerosis (MS). MATERIALS AND METHODS: Imaging was performed on a 3T scanner employing a custom-designed head coil that consisted of a coil array with four coils (30 x 30 cm(2)). Oblique fast spin echo (FSE) images, magnetization transfer (MT)-enhanced 3D gradient-echo (GRE) time-of-flight (TOF) images, and line scan diffusion images (LSDI) were obtained. Full diffusion tensor (DT) analysis was performed, and apparent diffusion coefficient (ADC), fractional anisotropy (FA), and fiber direction maps were obtained. RESULTS: FSE anatomic images were obtained with an in-plane resolution of 0.39 x 0.52 mm(2). The in-plane resolution of the MT and LSDI images was 0.78 x 0.78 mm(2). The OC, intracranial ON, and OT can be seen on these images. The dominant fiber orientations in the OC, ON, and OT, as derived from the DT images, are displayed. CONCLUSION: This study shows that by using 3T and a custom-designed, four-channel head coil, it is possible to acquire high-resolution anatomical and physiological images of the OC, ON, and OT. The pilot results presented here pave the way for imaging the anterior visual pathway in patients with MS.

Adult↗
PubMed1990

Magnetic resonance imaging of radiation optic neuropathy.

Three patients with delayed radiation optic neuropathy after radiation therapy for parasellar neoplasms underwent magnetic resonance imaging. The affected optic nerves and chiasms showed enlargement and focal gadopentetate dimeglumine enhancement. The magnetic resonance imaging technique effectively detected and defined anterior visual pathway changes of radionecrosis and excluded the clinical possibility of visual loss because of tumor recurrence.

Adenoma↗
PubMed2005

Spatial specificity of the enhanced dip inherently induced by prolonged oxygen consumption in cat visual cortex: implication for columnar resolution functional MRI.

Since changes in oxygen consumption induced by active neurons are specific to cortical columns, the small and transient "dip" of deoxyhemoglobin signal, which indicates an increase in oxygen consumption, has been of great interest. In this study, we succeeded in enhancing and sustaining the dip in the deoxyhemoglobin-weighted 620-nm intrinsic optical imaging signals from a 10-s orientation-selective stimulation in cat visual cortex by reducing arterial blood pressure with sodium nitroprusside (a vasodilator) to mitigate the contribution of stimulus-induced blood supply. During this condition, intact spiking activity and a significant reduction of stimulus-induced blood volume changes (570-nm intrinsic signals) were confirmed. The deoxyhemoglobin signal from the prolonged dip was highly localized to iso-orientation domains only during the initial approximately 2 s; the signal specificity weakened over time although the domains were still resolvable after 2 s. The most plausible explanation for this time-dependent spatial specificity is that deoxyhemoglobin induced by oxygen consumption drains from active sites, where spiking activity occurs, to spatially non-specific downstream vessels over time. Our results suggest that the draining effect of pial and intracortical veins in dHb-based imaging techniques, such as blood oxygenation-level dependent (BOLD) functional MRI, is intrinsically unavoidable and reduces its spatial specificity of dHb signal regardless of whether the stimulus-induced blood supply is spatially specific.

Animals↗
PubMed2005

Correlation of endoscopic optical coherence tomography with histology in the lower-GI tract.

BACKGROUND: Optical coherence tomography (OCT), a noninvasive optical imaging technique, provides high-resolution cross-sectional images of tissue microstructure. We developed a system for real-time endoscopic OCT (EOCT) of the human GI tract. During clinical trials, the structure of mucosa and submucosa, glands, blood vessels, pits, villi, and crypts was observed in a range of GI organs. Although EOCT images are thought to accurately depict actual histologic features, there are few data to support this assumption. Therefore, the present study correlated images acquired with an EOCT imaging system in vitro to corresponding histologic sections. METHODS: EOCT images were obtained of fresh specimens of ileum, colon, and rectum that then were fixed in formalin and were processed for microscopic evaluation by using standard methods. The thickness of mucosa and of submucosa was determined for both EOCT images and histologic slides. RESULTS: The first hyper-reflective layer in the EOCT images was identified as mucosa. A close correlation (R 2=0.84) was observed between EOCT and histology. Furthermore, the submucosa and the muscularis propria could be identified as the next deepest hyporeflective band and a hyper-reflective layer, respectively, in EOCT images. The submucosa was found to be more compressible than mucosa, and its EOCT appearance was dependent on its content of adipose tissue. CONCLUSIONS: EOCT provides images that precisely correlate with the histologic structure of the mucosa and the submucosa of the GI tract.

Colon↗